Phytochemistry, 2004 Jun, 65(11), 1651 - 9 Impact of sewage sludges on Medicago truncatula symbiotic proteome; Bestel-Corre G et al.; The effects of sewage sludges were investigated on the symbiotic interactions between the model plant Medicago truncatula and the arbuscular mycorrhizal fungus Glomus mosseae or the rhizobial bacteria Sinorhizobium meliloti . By comparison to a control sludge showing positive effects on plant growth and root symbioses, sludges enriched with polycylic aromatic hydrocarbons or heavy metals were deleterious . Symbiosis-related proteins were detected and identified by two-dimensional electrophoresis and matrix-assisted laser desorption ionization mass spectrometry, and image analysis was used to study the effects of sewage sludges on M . truncatula symbiotic proteome. Plant J, 2004 Aug, 39(4), 587 - 98 From pollen tubes to infection threads: recruitment of Medicago floral pectic genes for symbiosis; Rodriguez-Llorente ID et al.; While the biology of nitrogen-fixing root nodules has been extensively studied, little is known about the evolutionary events that predisposed legume plants to form symbiosis with rhizobia . We have studied the presence and the expression of two pectic gene families in Medicago, polygalacturonases (PGs) and pectin methyl esterases (PMEs) during the early steps of the Sinorhizobium meliloti-Medicago interaction and compared them with related pollen-specific genes . First, we have compared the expression of MsPG3, a PG gene specifically expressed during the symbiotic interaction, with the expression of MsPG11, a highly homologous pollen-specific gene, using promoter-gus fusions in transgenic M . truncatula and tobacco plants . These results demonstrated that the symbiotic promoter functions as a pollen-specific promoter in the non-legume host . Second, we have identified the presence of a gene family of at least eight differentially expressed PMEs in Medicago . One subfamily is represented by one symbiotic gene (MtPER) and two pollen-expressed genes (MtPEF1 and MtPEF2) that are clustered in the M . truncatula genome . The promoter-gus studies presented in this work and the homology between plant PGs, together with the analysis of the PME locus structure and MtPER expression studies, suggest that the symbiotic MsPG3 and MtPER could have as ancestors pollen-expressed genes involved in polar tip growth processes during pollen tube elongation . Moreover, they could have been recruited after gene duplication in the symbiotic interaction to facilitate polar tip growth during infection thread formation. J Environ Sci (China), 2004, 16(3), 458 - 61 Effect of inoculation with arbuscular mycorrhizal fungi on the degradation of DEHP in soil; Wang SG et al.; The effect of inoculation with arbuscular mycorrhizal (AM) fungi (Acaulospora lavis) on the degradation of di(2-ethylhexyl) phthalate (DEHP) in soil was studies . Cowpea plants (Pigna sinensis) were used as host plants and grown in a specially designed rhizobox . The experimental results indicated that, both in sterile and non-sterile soil, mycorrhizal colonization rates were much higher in the mycorrhizal plants than in the non-mycorrhizal plants . Addition of 4 mg/kg DEHP slightly affected mycorrhizal colonization, but the addition of 100 mg/kg DEHP significantly decreased mycorrhizal colonization . DEHP degradation in the mycorrhizosphere (Ms) and hyphosphere (Hs), especially in the Hs, increased after inoculation with Acaulospora lavis . It is concluded that mycorrhizal hyphae play an important role in the plant uptake, degradation and translocation of DEHP . The mechanism might be attributed to increased numbers of bacteria and actinomycetes and activity of dehydrogenase, urease and acid phosphatase in the Ms and Hs by mycorrhizal fungi. Chemosphere, 2004 Sep, 56(10), 957 - 65 Implications of rhizospheric heavy metals and nutrients for the growth of alfalfa in sludge amended soil; Su DC et al.; Rhizospheric distribution of nutrients and heavy metals in sludge amended soil was investigated using the rhizobag technique to give an indication of the release of metals from wastewater sludge . DTPA-extractable Zn, Cd, Ni and Mn, and available P, K and NH4+-N in the rhizosphere were markedly depleted when soil was amended with sludge . There was no conspicuous depletion or accumulation of DTPA-extractable Cu in the rhizosphere when the soil was amended with sewage sludge but DTPA-extractable Fe accumulated in the rhizosphere when the soil was amended with increasing amounts of sludge . The pH value in the rhizosphere increased with distance from the roots when soil was amended with larger amounts of sludge . The exchangeable fraction of Cu in the rhizosphere was depleted whether or not the soil was treated with sludge . Carbonate, oxide, organic and residual fractions of Cu and Zn were depleted in the rhizosphere at a distance of 0-2 mm from the roots when soil was amended with 50% sludge . Application of sewage sludge had a positive effect on alfalfa growth . With an increase in sludge amounts, the concentrations of Fe, Cu and Zn in alfalfa shoots did not change . Soil amendments with less than 25% sludge did not increase the availability or mobility of heavy metals . The depletion in rhizospheric DTPA-extractable Zn, Cd and Ni indicates that with the sole exception of Cu, release of metals from sludge amended soil was very limited. Indian J Exp Biol, 2003 Jun, 41(6), 627 - 31 Rhizoctonia wilt suppression of brinjal (Solanum melongena L) and plant growth activity by Bacillus BS2; Boruah HP et al.; An antibiotic-producing and hydrogen-cyanide-producing rhizobacteria strain Bacillus BS2 showed a wide range of antifungal activity against many Fusarium sp . and brinjal wilt disease pathogen Rhizoctonia solani . Seed bacterization with the strain BS2 promoted seed germination and plant growth in leguminous plants Phaseolus vulgaris and non-leguminous plants Solanum melongena L, Brassica oleracea var . capitata, B . oleraceae var . gongylodes and Lycopersicon esculentum Mill in terms of relative growth rate, shoot height, root length, total biomass production and total chlorophyll content of leaves . Yield of bacterized plants were increased by 10 to 49% compared to uninoculated control plants . Brinjal sapling raised through seed bacterization by the strain BS2 showed a significantly reduced wilt syndrome of brinjal caused by Rhizoctonia solani . Control of wilt disease by the bacterium was clue to the production of antibiotic-like substances, whereas plant growth-promotion was due to the activity of hydrogen cyanide . Root colonization study confirmed that the introduced bacteria colonized the roots and occupied 23-25% of total aerobic bacteria, which was confirmed using dual antibiotic (nalidixic acid and streptomycin sulphate) resistant mutant strain . The results obtained through this investigation suggested the potentiality of the strain BS2 to be used as a plant growth promoter and suppressor of wilt pathogen. J Mol Microbiol Biotechnol, 2004, 7(3), 133 - 9 Probing for pH-regulated genes in Sinorhizobium medicae using transcriptional analysis; Tiwari RP et al.; The low pH sensitivity of Sinorhizobium species is one of the major causes of reduced productivity of Medicago species (such as lucerne) sown in acidic soils . To investigate the pH response of an acid-tolerant Sinorhizobium medicae strain, a pool of random promoter fusions to gusA was created using minitransposon insertional mutagenesis . Acid-activated expression was identified in 11 mutants; rhizobial DNA flanking insertions in 10 mutants could be cloned and the DNA sequences obtained were used to interrogate the genome database of Sinorhizobium meliloti strain 1021 . Acid activated expression was detected for fixNO, kdpC, lpiA, and phrR and for genes encoding a putative lipoprotein, two ABC-transporter components, a putative DNA ligase and a MPA1-family protein . These findings implicate cytochrome synthesis, potassium ion cycling, lipid biosynthesis and transport processes as key components of pH response in S . medicae . Indian J Exp Biol, 2004 Jun, 42(6), 611 - 5 Nodulation competitiveness between contrasting phage phenotypes of pigeonpea rhizobial strains; Mishra A et al.; Competitiveness between (I) lysogenic vs . phage-indicator strains, (II) phage-resistant vs phage-sensitive strains, and (III) large plaque vs . small plaque developing strains was examined under laboratory and field conditions in order to study the involvement of these crucial phage sensitivity patterns in the competition for nodule occupancy of pigeonpea rhizobia . The phage-indicator strain (A039) exhibited higher competitiveness over the lysogenic strain (A025 Sm(r)); the phage sensitive strain (IHP-195) over the phage resistant strain (IHP 195 Sm(r)V(r)); and the large plaque developing strain (A059) over the small plaque developing strain (IHP195 Sm(r)) in association with pigeonpea cv . bahar both under laboratory and field conditions . Dual inoculation of A025 Sm(r) + A039 and A059 + IHP195 Sm(r) (mixed in equal proportion just before treatment) improved the nodule occupancy by inoculant strains against native rhizobia and resulted into higher plant dry weight and yield as compared to their application as single inoculum . The phage-resistant mutant IHP195 Sm(r)V(r) showed reduced competitiveness against native rhizobia, compared to its parental strain . The dual inoculation of parental strain and phage-resistant mutant gave the same result as the inoculation of parental strain alone. Biometals, 2004 Aug, 17(4), 457 - 66 Monitoring of cobalt(II) uptake and transformation in cells of the plant-associated soil bacterium Azospirillum brasilense using emission Mössbauer spectroscopy; Kamnev AA et al.; Interaction of cobalt(II) at micromolar concentrations with live cells of the plant-growth-promoting rhizobacterium Azospirillum brasilense (strain Sp245) and further transformations of the metal cation were monitored using 57Co emission Mossbauer spectroscopy (EMS) . Cell suspensions of the bacterial culture (2.4 x 10(8) cells ml(-1)) were doped with radioactive 57CoCl2 (1 mCi; final concentration 2 x 10(-6) M 57Co2+), kept under physiological conditions for various periods of time (from 2 min up to 1 hour) and then rapidly frozen in liquid nitrogen . Analysis of emission Mossbauer spectra of the frozen aqueous suspensions of the bacterial cell samples shows that the primary absorption of cobalt(II) at micromolar concentrations by the bacterial cells is rapid and virtually complete, giving at least two major forms of cobalt(II) species bound to the cells . Within an hour, the metal is involved in further metabolic transformations reflected by changes occurring in the spectra . The Mossbauer parameters calculated from the EMS data by statistical treatment were different for suspensions of live and dead (thermally killed) bacterial cells that had been in contact with 57Co2+ for 1 h, as well as for the cell-free culture medium containing the same concentration of 57Co2+ . Chemical after-effects of the nuclear transition (57Co --> 5 7Fe), which provide additional information on the chemical environment of metal ions, are also considered . The data presented demonstrate that EMS is a valuable tool for monitoring the chemical state of cobalt species in biological matter providing information at the atomic level in the course of its uptake and/or metabolic transformations. Microbiology, 2004 Jul, 150(Pt 7), 2237 - 46 The nitrogen-fixing gene (nifH) of Rhodopseudomonas palustris: a case of lateral gene transfer? Cantera JJ, Kawasaki H, Seki T. Nitrogen fixation is catalysed by some photosynthetic bacteria . This paper presents a phylogenetic comparison of a nitrogen fixation gene (nifH) with the aim of elucidating the processes underlying the evolutionary history of Rhodopseudomonas palustris . In the NifH phylogeny, strains of Rps . palustris were placed in close association with Rhodobacter spp . and other phototrophic purple non-sulfur bacteria belonging to the alpha-Proteobacteria, separated from its close relatives Bradyrhizobium japonicum and the phototrophic rhizobia (Bradyrhizobium spp . IRBG 2, IRBG 228, IRBG 230 and BTAi 1) as deduced from the 16S rRNA phylogeny . The close association of the strains of Rps . palustris with those of Rhodobacter and Rhodovulum, as well as Rhodospirillum rubrum, was supported by the mol% G+C of their nifH gene and by the signature sequences found in the sequence alignment . In contrast, comparison of a number of informational and operational genes common to Rps . palustris CGA009, B . japonicum USDA 110 and Rhodobacter sphaeroides 2.4.1 suggested that the genome of Rps . palustris is more related to that of B . japonicum than to the Rba . sphaeroides genome . These results strongly suggest that the nifH of Rps . palustris is highly related to those of the phototrophic purple non-sulfur bacteria included in this study, and might have come from an ancestral gene common to these phototrophic species through lateral gene transfer . Although this finding complicates the use of nifH to infer the phylogenetic relationships among the phototrophic bacteria in molecular diversity studies, it establishes a framework to resolve the origins and diversification of nitrogen fixation among the phototrophic bacteria in the alpha-Proteobacteria. Plant J, 2004 Aug, 39(3), 381 - 92 Plant growth-promoting rhizobacteria systemically protect Arabidopsis thaliana against Cucumber mosaic virus by a salicylic acid and NPR1-independent and jasmonic acid-dependent signaling pathway; Ryu CM et al.; Arabidopsis thaliana ecotype Columbia plants (Col-0) treated with plant growth-promoting rhizobacteria (PGPR) Serattia marcescens strain 90-166 and Bacillus pumilus strain SE34 had significantly reduced symptom severity by Cucumber mosaic virus (CMV) . In some cases, CMV accumulation was also significantly reduced in systemically infected leaves . The signal transduction pathway(s) associated with induced resistance against CMV by strain 90-166 was determined using mutant strains and transgenic and mutant Arabidopsis lines . NahG plants treated with strains 90-166 and SE34 had reduced symptom severity indicating that the resistance did not require salicylic acid (SA) . Strain 90-166 naturally produces SA under iron-limited conditions . Col-0 and NahG plants treated with the SA-deficient mutant, 90-166-1441, had significantly reduced CMV symptom severity with reduced virus accumulation in Col-0 plants . Another PGPR mutant, 90-166-2882, caused reduced disease severity in Col-0 and NahG plants . In a time course study, strain 90-166 reduced virus accumulation at 7 but not at 14 and 21 days post-inoculation (dpi) on the non-inoculated leaves of Col-0 plants . NahG and npr1-1 plants treated with strain 90-166 had reduced amounts of virus at 7 and 14 dpi but not at 21 dpi . In contrast, no decrease in CMV accumulation occurred in strain 90-166-treated fad3-2 fad7-2 fad8 plants . These data indicate that the protection of Arabidopsis against CMV by strain 90-166 follows a signaling pathway for virus protection that is independent of SA and NPR1, but dependent on jasmonic acid. Indian J Exp Biol, 2003 Apr, 41(4), 341 - 5 Associative diazotrophs of pearl millet (Pennisetum glaucum) from semi arid region--isolation and characterization; Tiwari M et al.; Diversity of the native diazotrophs associated with the rhizosphere of pearl millet (P . glaucumn), grown in nutritionally poor soils of semi-arid regions was studied with a view to isolate effective nitrogen fixing and plant growth stimulating bacteria with root associative characteristics . The native population varied from 10(3)-10(4) g(-1) of rhizosphere soil after 40 d growth and belonged to genera Azospirillum, Azotobacter and Klebsiella . Another non-diazotrophic root associative group was Pseudomonas sp., which also produced IAA and enhanced plant growth . Some of these rhizobacteria showed high in vitro acetylene reduction activity along with production of indole acetic acid . Out of 11 selected diazotrophs used as seed inoculants, M10B (Azospirillum sp.), M11E (Azotobacter sp.) and M12D4 (Klebsiella sp.) resulted in significant increase in total root and shoot nitrogen at 45 and 60 days of plant growth under pot culture conditions. C R Biol, 2004 May, 327(5), 445 - 53 Performance of phaseolus bean rhizobia in soils from the major production sites in the Nile Delta; Moawad H et al.; The symbiotic and competitive performances of two highly effective rhizobia nodulating French bean P . vulgaris were studied in silty loam and clayey soils . The experiments were carried out to address the performance of two rhizobia strains (CE3 and Ph . 163} and the mixture thereof with the two major cultivated bean cultivars in two soil types from major growing French bean areas in Egypt . Clay and silty loam soils from Menoufia and Ismailia respectively were planted with Bronco and Giza 6 phaseolus bean cultivars . The data obtained from this study indicated that rhizobial inoculation of Giza 6 cultivar in clayey soil showed a positive response to inoculation in terms of nodule numbers and dry weight . This response was also positive in dry matter and biomass accumulation by the plants . The inoculant of strain CE3 enhanced plant growth and N-uptake relative to Ph . 163 . However, the mixed inoculant strains were not always as good as single strain inoculants . The competition for nodulation was assessed using two techniques namely fluorescent antibody testing (FA) and REP-PCR fingerprinting . The nodule occupancy by inoculant strain Ph . 163 in both soils occupied 30-40% and 38-50 of nodules of cultivar Bronco . The mixed inocula resulted in higher proportions of nodules containing CE3 in silty loam soil and Ph . 163 in clayey soil . The native rhizobia occupied at least 50% of the nodules on the Bronco cultivar . For cultivar Giza 6, the native rhizobia were more competitive with the inoculant strains . Therefore, we suggest using the studied strains as commercial inocula for phaseolus bean. FEMS Microbiol Lett, 2004 Jul 15, 236(2), 291 - 9 Construction of a recA mutant of Azospirillum lipoferum and involvement of recA in phase variation; Vial L et al.; The plant-growth promoting rhizobacterium Azospirillum lipoferum strain 4B generates in vitro a stable phase variant designated 4VI at frequencies of 10(-4) to 10(-3) per cell per generation . Variant 4VI displays pleitropic modifications, such as the loss of swimming motility and the inability to assimilate certain sugars compared to the wild type . The mechanism underlying phase variation is unknown . To determine whether RecA-mediated processes are involved in phase variation, the recA gene of A . lipoferum 4B was cloned and sequenced and a recA mutant (termed 4BrecA) was constructed by allelic exchange . Strain 4BrecA showed increased sensitivity to UV and MMS compared with 4B and impaired recombinase activity . The ability to generate variants in vitro was not altered; the variants from 4BrecA exhibited all morphological and biochemical features characteristic of the variant generated by strain 4B . However, the frequency of variants generated by 4BrecA was increased by up to 10-fold . So, in contrast with many studies showing the abolition or a large reduction of the frequency of phase variation in recA mutants, this study describes an enhancement of phase variation in the absence of a functional recA. Indian J Exp Biol, 2003 Aug, 41(8), 912 - 4 Curing of symbiotic plasmid of Mesorhizobium huakuii subsp . rengei isolated from Astragalus sinicus; Balachandar D et al.; Astragalus sinicus (Chinese Milk vetch), a green manure leguminous plant, harbors Mesorhizobium huakuii subsp . rengei strain B3 in the root nodules . The visualization of symbiotic plasmid of strain B3 showed the presence of one sym plasmid of about 425 kbp . Curing of sym plasmid by temperature and acrydine orange was studied . Growing rhizobial cells at high temperature (37 degrees C) or treating the cells with acrydine orange at 50 mg/l eliminated sym plasmid of M . huakuii strain B3, which was confirmed by sym plasmid visualization and plant infection test of cured strains. Mol Ecol, 2004 Aug, 13(8), 2435 - 44 Diversity and specificity of Rhizobium leguminosarum biovar viciae on wild and cultivated legumes; Mutch LA et al.; The symbiotic partnerships between legumes and their root-nodule bacteria (rhizobia) vary widely in their degree of specificity, but the underlying reasons are not understood . To assess the potential for host-range evolution, we have investigated microheterogeneity among the shared symbionts of a group of related legume species . Host specificity and genetic diversity were characterized for a soil population of Rhizobium leguminosarum biovar viciae (Rlv) sampled using six wild Vicia and Lathyrus species and the crop plants pea (Pisum sativum) and broad bean (Vicia faba) . Genetic variation among 625 isolates was assessed by restriction fragment length polymorphism (RFLP) of loci on the chromosome (ribosomal gene spacer) and symbiosis plasmid (nodD region) . Broad bean strongly favoured a particular symbiotic genotype that formed a distinct phylogenetic subgroup of Rlv nodulation genotypes but was associated with a range of chromosomal backgrounds . Host range tests of 80 isolates demonstrated that only 34% of isolates were able to nodulate V . faba . By contrast, 89% were able to nodulate all the local wild hosts tested, so high genetic diversity of the rhizobial population cannot be ascribed directly to the diversity of host species at the site . Overall the picture is of a population of symbionts that is diversified by plasmid transfer and shared fairly indiscriminately by local wild legume hosts . The crop species are less promiscuous in their interaction with symbionts than the wild legumes . J Appl Microbiol, 1998 Jan, 84(1), 81 - 9 Metabolic properties, stress tolerance and macromolecular profiles of rhizobia nodulating Hedysarum coronarium; Struffi P et al.; The drought-tolerant legume Hedysarum coronarium is a Mediterranean species valued as a forage crop for its high performance in stressful conditions . The plant shows peculiar capabilities of nodulating above pH 9 and thriving in highly calcareous soils . With the aim of providing an adequate characterization of its bacterial symbiotic partner, a study was undertaken, approaching from several viewpoints the physiology and structural features of bacteria isolated from nodules of H . coronarium . Tests involved trophic capabilities on different carbon and nitrogen sources, vitamin requirements, and resistance to factors including antibiotics, heavy metals, salinity, pH, and temperature . Enzyme activities, including those of cellulase, pectinase, urease, beta-galactosidase, nitrate and nitrite reductase, were evaluated . The DNA G + C percentage content was determined . Species-specific bacteriophages were isolated and a strain-typing grid established . In order to characterize further and fingerprint the different Rhizobium 'hedysari' isolates, electrophoretic pattern of proteins, plasmid DNA, and digested genomic DNA (in pulsed-field gel separation) were compared . Adansonian taxonomy yielded similarity clusters of the different isolates. Indian J Exp Biol, 2003 Oct, 41(10), 1205 - 8 11th International Congress on Molecular Plant-Microbe Interactions held at St . Petersburg--a report; Rolfe BG et al.; The report is a short summary of the most interesting presentations at the 11th International Congress on Molecular Plant-Microbe Interactions held during July 18-27, 2003 at St . Petersburg, Russia . The key elements from several sessions on the legume-Rhizobium interactions have been discussed. Indian J Exp Biol, 2003 Oct, 41(10), 1198 - 204 Isolation and symbiotic characterization of transposon Tn5-induced arginine auxotrophs of Sinorhizobium meliloti; Kumar A et al.; Seventeen arginine auxotrophic mutants of Sinorhizobium meliloti Rmd201 were isolated by random transposon Tn5 mutagenesis using Tn5 delivery vector pGS9 . Based on intermediate feeding studies, these mutants were designated as argA/argB/argC/argD/argE (ornithine auxotrophs), argF/argI, argG and argH mutants . The ornithine auxotrophs induced ineffective nodules whereas all other arginine auxotrophs induced fully effective nodules on alfalfa plants . In comparison to the parental strain induced nodule, only a few nodule cells infected with rhizobia were seen in the nitrogen fixation zone of the nodule induced by the ornithine auxotroph . TEM studies showed that the bacteroids in the nitrogen fixation zone of ornithine auxotroph induced nodule were mostly spherical or oval unlike the elongated bacteroids in the nitrogen fixation zone of the parental strain induced nodule . These results indicate that ornithine or an intermediate of ornithine biosynthesis, or a chemical factor derived from one of these compounds is required for the normal development of nitrogen fixation zone and transformation of rhizobial bacteria into bacteroids during symbiosis of S . meliloti with alfalfa plants. Indian J Exp Biol, 2003 Oct, 41(10), 1184 - 97 Recent advances in Rhizobium-legume symbiosis; Randhawa GS et al.; The research findings in the field of Rhizobium-legume symbiosis reported worldwide during the years 2002 and 2003 (up to September) have been summarized . The information is presented under the various topics, viz., isolation and characterization of rhizobial strains, physiological aspects of nitrogen fixation, rhizosphere interactions and root surface signals, genomics and proteomics, plant genes involved in nodule formation, bioremediation and biocontrol, and review articles and conference reports . The postal and e-mail addresses of the concerned scientists have also been included. Indian J Exp Biol, 2003 Oct, 41(10), 1165 - 83 Symbiosis between Frankia and actinorhizal plants: root nodules of non-legumes; Pawlowski K et al.; In actinorhizal symbioses, filamentous nitrogen-fixing soil bacteria of the genus Frankia induce the formation of nodules on the roots of a diverse group of dicotyledonous plants representing trees or woody shrubs, with one exception, Datisca glomerata . In the nodules, Frankia fixes nitrogen and exports the products to the plant cytoplasm, while being supplied with carbon sources by the host . Possibly due to the diversity of the host plants, actinorhizal nodules show considerable variability with regard to structure, oxygen protection mechanisms and physiology . Actinorhizal and legume-rhizobia symbioses are evolutionary related and share several features. Indian J Exp Biol, 2003 Oct, 41(10), 1160 - 4 Rhizobia as a biological control agent against soil borne plant pathogenic fungi; Deshwal VK et al.; Rhizobia promote the growth of plants either directly through N2 fixation, supply of nutrients, synthesis of phytohormones and solubilization of minerals, or indirectly as a biocontrol agent by inhibiting the growth of pathogens . The biocontrol effect of rhizobia is due to the secretion of secondary metabolites such as antibiotics and HCN . Siderophore production in iron stress conditions provides rhizobia an added advantage, resulting in exclusion of pathogens due to iron starvation. Indian J Exp Biol, 2003 Oct, 41(10), 1142 - 59 Effects of biotic and abiotic constraints on the symbiosis between rhizobia and the tropical leguminous trees Acacia and Prosopis; Rasanen LA et al.; N2-fixing, drought tolerant and multipurpose Acacia and Prosopis species are appropriate trees for reforestation of degraded areas in arid and semiarid regions of the tropics and subtropics . Acacia and Prosopis trees form N2-fixing nodules with a wide range of rhizobia, for example African acacias mainly with Sinorhizobium sp . and Mesorhizobium sp., and Australian acacias with Bradyrhizobium sp . Although dry and hot seasons restrict formation of N2-fixing nodules on Acacia and Prosopis spp., fully grown trees and their symbiotic partners are well adapted to survive in harsh growth conditions . This review on one hand deals with major constraints of arid and semiarid soils, i.e . drought, salinity and high soil temperature, which affect growth of trees and rhizobia, and on the other hand with adaptation mechanisms by which both organisms survive through unfavourable periods . In addition, defects in infection and nodulation processes due to various abiotic and biotic constraints are reviewed . This knowledge is important when Acacia and Prosopis seedlings are used for forestation of degraded areas in arid and semiarid tropics. Indian J Exp Biol, 2003 Oct, 41(10), 1136 - 41 Effects of drought stress on legume symbiotic nitrogen fixation: physiological mechanisms; Serraj R; Drought stress is one of the major factors affecting nitrogen fixation by legume-rhizobium symbiosis . Several mechanisms have been previously reported to be involved in the physiological response of symbiotic nitrogen fixation to drought stress, i.e . carbon shortage and nodule carbon metabolism, oxygen limitation, and feedback regulation by the accumulation of N fixation products . The carbon shortage hypothesis was previously investigated by studying the combined effects of CO2 enrichment and water deficits on nodulation and N2 fixation in soybean . Under drought, in a genotype with drought tolerant N2 fixation, approximately four times the amount of 14C was allocated to nodules compared to a drought sensitive genotype . It was found that an important effect of CO2 enrichment of soybean under drought was an enhancement of photo assimilation, an increased partitioning of carbon to nodules, whose main effect was to sustain nodule growth, which helped sustain N2 rates under soil water deficits . The interaction of nodule permeability to O2 and drought stress with N2 fixation was examined in soybean nodules and led to the overall conclusion that O2 limitation seems to be involved only in the initial stages of water deficit stresses in decreasing nodule activity . The involvement of ureides in the drought response of N2 fixation was initially suspected by an increased ureide concentration in shoots and nodules under drought leading to a negative feedback response between ureides and nodule activity . Direct evidence for inhibition of nitrogenase activity by its products, ureides and amides, supported this hypothesis . The overall conclusion was that all three physiological mechanisms are important in understanding the regulation of N2 fixation and its response of to soil drying. Indian J Exp Biol, 2003 Oct, 41(10), 1133 - 5 Proteomics: a novel approach to explore signal exchanges in Rhizobium-legume symbiosis; Vij N; Recent developments and future strategies on the proteomics approach to explore the signal exchanges in Rhizobium-legume symbiosis have been discussed . It is expected that this approach will provide new possibilities for investigating the complex interactions of rhizobia and legumes. Indian J Exp Biol, 2003 Oct, 41(10), 1101 - 13 Regulation of expression of symbiotic genes in Rhizobium sp . NGR234; Perret X et al.; Research in the field of Rhizobium-legume symbiosis faces a new challenge: integrate the wealth of information generated by genomic projects . The goal: apprehend the complexity of the molecular mechanisms involved in symbiotic associations . At the time of writing, the genomes of three micro-symbionts (Bradyrhizobium japonicum, Mesorhizobium loti and Sinorhizobium meliloti) have been sequenced, and two more (those of Rhizobium leguminosarum and Rhizobium etli) will be completed in the near future . Together, completed rhizobial genomes represent already 23,393,822 bp of DNA sequence and 21,797 predicted open reading frames (ORFs) . To identify candidate-symbiotic genes in such a broad database, predict their function and dissect the regulatory networks that govern their expression are no simple tasks . One way to confront this problem is to combine different datasets, in particular genetic and transcriptional maps as well as predicted promoters from bioinformatics analyses . Here, we would like to illustrate this type of approach with the analysis of the symbiotic plasmid (pNGR234a) of the broad host-range Rhizobium sp . NGR234. Indian J Exp Biol, 2003 Oct, 41(10), 1095 - 100 Milestones in the genetical research on rhizobia; Randhawa GS et al.; The first isolation of the rhizobial bacteria from the legume roots was done in 1888 . Since then a large number of scientists have made efforts to understand the molecular basis of Rhizobium-legume symbiosis . The important developments of 115 years of genetical research on rhizobia have been listed in this article. Mol Plant Microbe Interact, 2004 Jul, 17(7), 816 - 23 Accumulation of lipochitin oligosaccharides and NodD-activating compounds in an efficient plant--Rhizobium nodulation assay; Tak T et al.; During legume plant--Rhizobium spp . interactions, leading to the formation of nitrogen-fixing root nodules, the two major determinants of host plant-specificity are plant-produced nod gene inducers (NodD protein activating compounds) and bacterial lipochitin oligosaccharides (LCOs or Nod factors) . In a time course, we describe the accumulation of LCOs in an efficient nodulation assay with Vicia sativa subsp . nigra and Rhizobium leguminosarum, in connection with the presence of NodD-activating compounds in the exudate of V . sativa roots . Relatively small amounts of both LCOs and NodD-activating compounds were found to be required for initiation of nodulation during the first days after inoculation . A strong increase in the amount of NodRlv-V{18:4,Ac} LCOs preceded root infection and nodule primordium formation . In contrast to the situation with non-nodulating rhizobia and nonmitogenic LCOs, the amount of NodD-activating compounds in the culture medium remained small after addition of nodulating rhizobia or mitogenic LCOs . Furthermore, addition of nodulating rhizobia or mitogenic LCOs resulted in nearly complete inhibition of root hair formation and elongation, whereas nonmitogenic LCOs stimulated root hair growth . Retention of NodD-activating compounds in the root may inhibit root hair growth. Mol Plant Microbe Interact, 2004 Jul, 17(7), 720 - 8 Glutamine utilization by Rhizobium etli; Tate R et al.; We undertook the study of the use of glutamine (Gln) as the source of carbon and energy by Rhizobium etli . Tn5-induced mutagenesis allowed us to identify several genes required for Gln utilization, including those coding for two broad-range amino acid transporters and a glutamate dehydrogenase . The isolated mutants were characterized by the analysis of their capacity i) to grow on different media, ii) to transport Gln (uptake assays), and iii) to utilize Gln as the C energy source (CO2 production from Gln) . We show that Gln is degraded through the citric acid cycle and that its utilization as the sole C source is related to a change in the bacterial cell shape (from bacillary to coccoid form) and a high susceptibility to a thiol oxidative insult . Both these data and the analysis of ntr-dependent promoters suggested that Gln-grown bacteria are under a condition of C starvation and N sufficiency, and as expected, the addition of glucose counteracted the morphological change and increased both the bacterial growth rate and their resistance to oxidative stress . Finally, a nodulation analysis indicates that the genes involved in Gln transport and degradation are dispensable for the bacterial ability to induce and invade developing nodules, whereas those involved in gluconeogenesis and nucleotide biosynthesis are strictly required. J Appl Microbiol, 2004, 97(2), 256 - 61 Degradation of trehalose by rhizobia and characteristics of a trehalose-degrading enzyme isolated from Rhizobium species NGR234; Boboye B; AIMS: This study was designed to examine the breakdown of trehalose by rhizobia and to characterize the trehalose-degrading enzyme isolated from Rhizobium sp . NGR234 . METHODS AND RESULTS: Rhizobium sp . NGR234, Rhizobium fredii USDA257, R . phaseoli RCR3622, R . tropici CIAT899 and R . etli CE3 showed good growth in the presence of carbohydrate . Validamycin A did not prevent the growth of NGR234 on trehalose . The expression of a trehalose-degrading enzyme by NGR234 was intracellular and inducible by trehalose . The isolated enzyme digested other disaccharides, p-nitrophenyl-alpha-d-glucopyranoside and the substrate . The enzyme showed optimum activities at pH 7.0 and 30 degrees C . Its pI was 4.75 and the V(max) of the enzyme occurred at 35.7 micromol s(-1) mg(-1) protein with the K(m) of 23 mmol when trehalose was hydrolysed . CONCLUSIONS: An enzyme capable of breaking down trehalose was produced . Some of the properties of the trehalose-degrading enzyme are similar to those isolated from other organisms but, this enzyme was validamycin resistant . These rhizobia like other trehalose-degrading microbes use trehalose by enzymatic catabolic action . SIGNIFICANCE AND IMPACT OF THE STUDY: Trehalose which accumulates during legume-rhizobia symbiosis is toxic to plants . Detoxification by trehalose-degrading enzymes is important for the progress of symbiosis. Q Rev Biol, 2004 Jun, 79(2), 135 - 60 The evolution of cooperation; Sachs JL et al.; Darwin recognized that natural selection could not favor a trait in one species solely for the benefit of another species . The modern, selfish-gene view of the world suggests that cooperation between individuals, whether of the same species or different species, should be especially vulnerable to the evolution of noncooperators . Yet, cooperation is prevalent in nature both within and between species . What special circumstances or mechanisms thus favor cooperation? Currently, evolutionary biology offers a set of disparate explanations, and a general framework for this breadth of models has not emerged . Here, we offer a tripartite structure that links previously disconnected views of cooperation . We distinguish three general models by which cooperation can evolve and be maintained: (i) directed reciprocation--cooperation with individuals who give in return; (ii) shared genes--cooperation with relatives (e.g., kin selection); and (iii) byproduct benefits--cooperation as an incidental consequence of selfish action . Each general model is further subdivided . Several renowned examples of cooperation that have lacked explanation until recently--plant-rhizobium symbioses and bacteria-squid light organs--fit squarely within this framework . Natural systems of cooperation often involve more than one model, and a fruitful direction for future research is to understand how these models interact to maintain cooperation in the long term. J Bacteriol, 2004 Jul, 186(14), 4774 - 80 Characterization of NopP, a type III secreted effector of Rhizobium sp . strain NGR234; Ausmees N et al.; The type three secretion system (TTSS) encoded by pNGR234a, the symbiotic plasmid of Rhizobium sp . strain NGR234, is responsible for the flavonoid- and NodD1-dependent secretion of nodulation outer proteins (Nops) . Abolition of secretion of all or specific Nops significantly alters the nodulation ability of NGR234 on many of its hosts . In the closely related strain Rhizobium fredii USDA257, inactivation of the TTSS modifies the host range of the mutant so that it includes the improved Glycine max variety McCall . To assess the impact of individual TTSS-secreted proteins on symbioses with legumes, various attempts were made to identify nop genes . Amino-terminal sequencing of peptides purified from gels was used to characterize NopA, NopL, and NopX, but it failed to identify SR3, a TTSS-dependent product of USDA257 . By using phage display and antibodies that recognize SR3, the corresponding protein of NGR234 was identified as NopP . NopP, like NopL, is an effector secreted by the TTSS of NGR234, and depending on the legume host, it may have a deleterious or beneficial effect on nodulation or it may have little effect . Curr Opin Plant Biol, 2004 Aug, 7(4), 408 - 13 Genetic and genomic analysis in model legumes bring Nod-factor signaling to center stage; Riely BK et al.; The control of host-specificity in the Rhizobium-legume symbiosis has been a topic of long-standing interest to plant biologists . By the early 1990s, biologists had deciphered the chemical signals that trigger early symbiotic responses . Flavonoids from the plant root trigger bacterial gene expression and the production of lipo-chitooligosaccharide signals (called Nod factors) that are recognized by the plant host . Genetic differences between bacterial strains modify the oligosaccharide backbone, for example by the addition of sulfate, acetate or fucose, and simultaneously alter the host-specificity of the purified Nod factor and the bacterium . Recent studies have begun to reveal the genetic and molecular basis of Nod-factor perception in legumes, a signaling system that also controls plant interactions with mycorrhizal fungi. J Environ Qual, 2004 May-Jun, 33(3), 976 - 83 Short- and longer-term effects of the willow root system on metal extractability in contaminated dredged sediment; Vervaeke P et al.; Willow (Salix spp.) stands are often proposed as vegetation covers for the restoration and stabilization of contaminated and derelict land . Planting willows on dredged sediment disposal sites for biomass production can be an alternative to traditional capping techniques . However, with the introduction of willow stands on dredged sediment disposal sites, the possibility of increased contaminant availability in the root zone must be acknowledged as it can increase the risk of leaching . Two trials investigated the availability of Cd, Zn, Cu, and Pb in the root zones of willows grown on contaminated sediment . To assess the effects of willow root growth on metal extractability and mobility, bulk and rhizosphere sediment samples were extracted with deionized water, ammonium acetate at pH 7, and ammonium acetate-EDTA at pH 4.65 . A rhizobox experiment was used to investigate the short-term effect of willow roots on metal availability in oxic and anoxic sediment . Longer-term effects were assessed in a field trial . The rhizobox trial showed that Cd, Zn, and Cu extractability in the rhizosphere increased while the opposite was observed for Pb . This was attributed to the increased willow-induced oxidation rate in the root zone as a result of aeration and evapotranspiration, which masked the direct chemical and biological influences of the willow roots . The field trial showed that Cu and Pb, but not Cd, were more available in the root zone after water and ammonium acetate (pH 7) extraction compared with the bulk sediment . Sediment in the root zone was better structured and aggregated and thus more permeable for downward water flows, causing leaching of a fraction of the metals and significantly lower total contents of Cd, Cu, and Pb . These findings indicate that a vegetation cover strategy to stabilize sediments can increase metal availability in the root zone and that potential metal losses to the environment should be considered. Int J Phytoremediation, 2004, 6(1), 49 - 61 Hyperaccumulation of metals by Thlaspi caerulescens as affected by root development and Cd-Zn/Ca-Mg interactions; Saison C et al.; The aim of this work was to study, in a rhizobox experiment, the phytoextraction of metals by the hyperaccumulator plant Thlaspi caerulescens in relation to the heterogeneity of metal pollution . Six treatments were designed with soils containing various levels of metals . Homogeneous soils and inclusions of soils in other soil matrices were prepared in order to vary metal concentration and localization . Growth parameters of the plant (rosette diameter and shoot biomass) and localization of roots and shoot uptake of Zn, Cd, Ca, and Mg were determined after 10 weeks of growth . The plants grown on the polluted industrial soils provided a larger biomass and had lower mortality rates than those grown on the agricultural soil . Moreover, these plants accumulated more Zn and Cd (up to 17,516 and 375 mg kg(-1) DM, respectively) than plants grown on the agricultural soil (up to 7300 mg Zn kg(-1) and 83 mg Cd kg(-1) DM) . The roots preferentially explored metal-contaminated areas . The exploration of polluted soil inclusions by the roots was associated with a higher extraction of metals . Zinc and Cd in the shoots of Thlaspi caerulescens were negatively correlated with Ca and Mg concentrations; however, the soil supply for these two elements was identical . This suggests that there is competition for the uptake of these elements and that Zn is preferentially accumulated. Proc Natl Acad Sci U S A, 2004 Jul 6, 101(27), 10217 - 22 Epub 2004 Jun 25. Six nonnodulating plant mutants defective for Nod factor-induced transcriptional changes associated with the legume-rhizobia symbiosis; Mitra RM et al.; As the legume-rhizobia symbiosis is established, the plant recognizes bacterial-signaling molecules, Nod factors (NFs), and initiates transcriptional and developmental changes within the root to allow bacterial invasion and the construction of a novel organ, the nodule . Plant mutants defective in nodule initiation (Nod(-)) are thought to have defects in NF-signal transduction . However, it is unknown whether WT plants respond to NF-independent bacterial-derived signals or whether Nod(-) plant mutants show defects in global symbiosis-associated gene expression . To characterize plant gene expression in the establishment of the symbiosis, we used an Affymetrix oligonucleotide microarray representing 9,935 Medicago truncatula expressed sequences . We identified 46 sequences that are differentially expressed in plants exposed for 24 h to WT Sinorhizobium meliloti or to the invasion defective S . meliloti mutant, exoA . Eight of these genes encode nucleolar proteins, which are implicated in ribosome biogenesis . We also identified differentially expressed transcription factors, signaling components, defense response proteins, stress response proteins, and several previously uncharacterized genes . NF appears both necessary and sufficient to induce most changes . Six of seven Nod(-) M . truncatula mutants (nfp, dmi1, dmi2, dmi3, nsp1, and nsp2) showed no transcriptional response to S . meliloti, suggesting that the encoded proteins are required for initiating new transcription . The Nod(-) mutant hcl, however, exhibits a reduced transcriptional response to S . meliloti, indicating that the machinery responsible for initiating new transcription is at least partially functional in this mutant. Fungal Genet Biol, 2004 Aug, 41(8), 794 - 804 Recognition events in AM symbiosis: analysis of fungal gene expression at the early appressorium stage; Breuninger M et al.; Arbuscular mycorrhizal symbiosis is induced upon a series of recognition events involving the reorganization of both plant and fungal cellular programs culminating in the formation of appressoria on the epidermal root cells . In this work we monitored for the first time the genetic changes occurring in the fungal partner during early appressorium development . We established an in vitro system of Glomus mosseae and Petroselinum crispum for studying appressorium formation and found that after 120 h first appressoria developed in the root epidermis . We have constructed a fungal subtractive suppressive library enriched in genes up-regulated at this stage . Our aim was to identify early signaling events during plant recognition leading to appressoria formation . The library contains 375 clones with an average size of 500 bp . From these, 200 clones were sequenced and most of them represent gene fragments with no known homologues (63%) and therefore putative new genes specific to the mycorrhiza symbiosis . Reverse-Northern blot and RT-PCR analyses confirmed that ca . 30% of the genes present in the library were up-regulated upon plant induction after 120 h . Among the genes with homologues in other organisms we found several genes common to other plant-microbe interactions including some genes related to Ca2+-dependent signaling . The up-regulation of these genes opens the possibility that Ca2+ plays a role in the early stages of mycorrhiza formation as it has been found in other plant-microbe interactions such as the Rhizobium symbiosis or the Magnaporthe grisea/rice pathogenic interaction. Lett Appl Microbiol, 2004, 38(4), 296 - 300 Cloning and characterization of ce/8A gene from Rhizobium leguminosarum bv . trifolii 1536; An JM et al.; AIMS: To isolate the cellulase gene from Rhizobium leguminosarum bv . trifolii 1536 . METHODS AND RESULTS: By the shot-gun method a clone (cel8A) harbouring 3.1 kb genomic DNA fragment from R . leguminosarum bv . trifolii 1536 was obtained . The cel8A gene coded 348 amino acids and it belongs to the glycosyl hydrolase family 8 . The molecular mass of Cel8A protein induced from Escherichia coli DH5alpha, appeared to be 35 kDa . The optimum pH and optimum temperature was 7.0, and about 30 degrees C for its enzymatic activity respectively . CONCLUSIONS: R . leguminosarum bv . trifolii 1536 had cel8A gene having an open reading frame of 1047 bp coded for the activity of hydrolyzation of carboxymethyl cellulose . SIGNIFICANCE AND IMPACT OF THE STUDY: The production of celluloytic enzyme by R . leguminosarum bv . trifolii was confirmed, which would play specific roles in rhizobia . Future study should focus on its role in the infection and nodulation phenomena. Syst Appl Microbiol, 2004 May, 27(3), 380 - 95 Characterisation of wild legume nodulating bacteria (LNB) in the infra-arid zone of Tunisia; Zakhia F et al.; We report on the isolation and the characterization of nitrogen-fixing root nodule bacteria isolated from natural legumes in a region of South Tunisia corresponding to the infra-arid climatic zone . A collection of 60 new bacterial root nodule isolates were obtained from 19 legume species belonging to the genera Acacia, Anthyllis, Argyrolobium, Astragalus, Calycotome, Coronilla, Ebenus, Genista, Hedysarum, Hippocrepis, Lathyrus, Lotus, Medicago, Ononis . The isolates were characterised by (1) comparative 16S ARDRA using 7 enzymes, (2) total cell protein SDS-PAGE analysis and (3) 16S rDNA sequencing . The results show that these isolates are diverse and belong to the genera Rhizobium, Sinorhizobium, Mesorhizobium and Bradyrhizobium . Bradyrhizobium were further characterised by 16S-23S rDNA IGS sequencing . Surprisingly strains nodulating Astragalus cruciatus, Lotus creticus and Anthyllis henoniana were identified as Rhizobium galegae, a species recorded only as endosymbiont of Galega officinalis and G . orientalis in northern regions so far. Can J Microbiol, 2004 May, 50(5), 313 - 22 Phylogeny based on 16S rDNA and nifH sequences of Ralstonia taiwanensis strains isolated from nitrogen-fixing nodules of Mimosa pudica, in India; Verma SC et al.; Bacterial symbionts present in the indeterminate-type nitrogen (N)-fixing nodules of Mimosa pudica grown in North and South India showed maximum similarity to Ralstonia taiwanensis on the basis of carbon-source utilization patterns and 16S rDNA sequence . Isolates from the nodules of M . pudica from North India and South India showed identical ARDRA (Amplified Ribosomal DNA Restriction Analysis) patterns with Sau3AI and RsaI, but AluI revealed dimorphy between the North Indian and South Indian isolates . Alignment of 16S rDNA sequences revealed similarity of North Indian isolates with an R . taiwanensis strain isolated from M . pudica in Taiwan, whereas South Indian isolates showed closer relatedness with the isolates from Mimosa diplotricha . Alignment of nifH sequences from both North Indian and South Indian isolates with that of the related isolates revealed their closer affinity to alpha-rhizobia, suggesting that nif genes in the beta-rhizobia might have been acquired from alpha-rhizobia via lateral transfer during co-occupancy of nodules by alpha-rhizobia and progenitors of R . taiwanensis, members of the beta-subclass of Proteobacteria . Immunological cross-reaction of the bacteroid preparation of M . pudica nodules showed strong a positive signal with anti-dinitrogenase reductase antibody, whereas a weak positive cross-reaction was observed with free-living R . taiwanensis grown microaerobically in minimal medium with and without NH4Cl . In spite of the expression of dinitrogenase reductase under free-living conditions, acetylene reduction was not observed under N-free conditions even after prolonged incubation. Ann Bot (Lond), 2004 Aug, 94(2), 251 - 8 Epub 2004 Jun 17. The influence of Rhizobium and arbuscular mycorrhizal fungi on nitrogen and phosphorus accumulation by Vicia faba; Jia Y et al.; BACKGROUND AND AIMS: The aim of this study was to investigate the effects of the interactions between the microbial symbionts, Rhizobium and arbuscular mycorrhizal fungi (AMF) on N and P accumulation by broad bean (Vicia faba) and how increased N and P content influence biomass production, leaf area and net photosynthetic rate . METHODS: A multi-factorial experiment consisting of four different legume-microbial symbiotic associations and two nitrogen treatments was used to investigate the influence of the different microbial symbiotic associations on P accumulation, total N accumulation, biomass, leaf area and net photosynthesis in broad bean grown under low P conditions . KEY RESULTS: AMF promoted biomass production and photosynthetic rates by increasing the ratio of P to N accumulation . An increase in P was consistently associated with an increase in N accumulation and N productivity, expressed in terms of biomass and leaf area . Photosynthetic N use efficiency, irrespective of the inorganic source of N (e.g . NO3- or N2), was enhanced by increased P supply due to AMF . The presence of Rhizobium resulted in a significant decline in AMF colonization levels irrespective of N supply . Without Rhizobium, AMF colonization levels were higher in low N treatments . Presence or absence of AMF did not have a significant effect on nodule mass but high N with or without AMF led to a significant decline in nodule biomass . Plants with the Rhizobium and AMF symbiotic associations had higher photosynthetic rates per unit leaf area . CONCLUSIONS: The results indicated that the synergistic or additive interactions among the components of the tripartite symbiotic association (Rhizobium-AMF-broad bean) increased plant productivity. Mikrobiologiia, 2004 Mar-Apr, 73(2), 195 - 8 {The effect of tryptophan of plant root metabolites on the phyto stimulating activity of rhizobacteria }; Kravchenko LV et al.; Aseptic tomato and radish roots were found to exude 2.8-5.3 and 290-390 ng tryptophan per seedling per day . The inoculation of radish plants with rhizosphere pseudomonads increased the root biomass by 1.4 times . The inoculation of tomato plants with the same pseudomonads was ineffective . The beneficial effect of bacterial inoculation on the radish plants can be explained by the fact that the introduced rhizobacteria produce the plant growth-stimulating hormone indole-3-acetic acid . In pot experiments, the addition of this phytohormone to the soil increased the mass of radish roots by 36% . The phytohormonal action of the rhizosphere microflora was found to be efficient provided that the concentration of tryptophan in the rhizosphere is sufficiently high. Biotechnol Lett, 2004 May, 26(9), 723 - 7 Expression in sugar beet of the introduced cercosporin toxin export (CFP) gene from Cercospora kikuchii, the causative organism of purple seed stain in soybean; Kuykendall LD et al.; The Cercospora kikuchii cercosporin export gene, CFP, introduced into Beta vulgaris L . by conjugation with Rhizobium radiobacter, was stably maintained during vegetative propagation as verified by PCR using primers specific for the CFP gene . Transcriptional expression of the CFP gene in leaves was determined by RT-PCR using CFP-specific primers . CFP protein was detected using Western analysis with an affinity-purified polypeptide-specifc antibody . Analysis of the relative susceptibility of CFP-transgenic and non-transgenic sugar beet plants is planned but will probably take several years to complete. Mol Plant Microbe Interact, 2004 Jun, 17(6), 613 - 22 The expression of MaEXP1, a Melilotus alba expansin gene, is upregulated during the sweetclover-Sinorhizobium meliloti interaction; Giordano W et al.; Expansins are a highly conserved group of cell wall-localized proteins that appear to mediate changes in cell wall plasticity during cell expansion or differentiation . The accumulation of expansin protein or the mRNA for specific expansin gene family members has been correlated with the growth of various plant organs . Because expansin proteins are closely associated with plant cell wall expansion, and as part of a larger study to determine the role of different gene products in the legume-Rhizobium spp . symbiosis, we investigated whether a Melilotus alba (white sweetclover) expansin gene is expressed during nodule development . A cDNA fragment encoding an expansin gene (EXP) was isolated from Sinorhizobium meliloti-inoculated sweetclover root RNA by reverse-transcriptase polymerase chain reaction using degenerate primers, and a full-length sweetclover expansin sequence (MaEXP1) was obtained using 5' and 3' rapid amplification of cDNA end cloning . The predicted amino acid of the sweetclover expansin is highly conserved with the various alpha-expansins in the GenBank database . MaEXP1 contains a series of eight cysteines and four tryptophans that are conserved in the alpha-expansin protein family . Northern analysis and whole-mount in situ hybridization analyses indicate that MaEXP1 mRNA expression is enhanced in roots within hours after inoculation with S . meliloti and in nodules . Western and immunolocalization studies using a cucumber expansin antibody demonstrated that a cross-reacting protein accumulated in the expanding cells of the nodule. Microbiol Mol Biol Rev, 2004 Jun, 68(2), 280 - 300 Infection and invasion of roots by symbiotic, nitrogen-fixing rhizobia during nodulation of temperate legumes; Gage DJ; Bacteria belonging to the genera Rhizobium, Mesorhizobium, Sinorhizobium, Bradyrhizobium, and Azorhizobium (collectively referred to as rhizobia) grow in the soil as free-living organisms but can also live as nitrogen-fixing symbionts inside root nodule cells of legume plants . The interactions between several rhizobial species and their host plants have become models for this type of nitrogen-fixing symbiosis . Temperate legumes such as alfalfa, pea, and vetch form indeterminate nodules that arise from root inner and middle cortical cells and grow out from the root via a persistent meristem . During the formation of functional indeterminate nodules, symbiotic bacteria must gain access to the interior of the host root . To get from the outside to the inside, rhizobia grow and divide in tubules called infection threads, which are composite structures derived from the two symbiotic partners . This review focuses on symbiotic infection and invasion during the formation of indeterminate nodules . It summarizes root hair growth, how root hair growth is influenced by rhizobial signaling molecules, infection of root hairs, infection thread extension down root hairs, infection thread growth into root tissue, and the plant and bacterial contributions necessary for infection thread formation and growth . The review also summarizes recent advances concerning the growth dynamics of rhizobial populations in infection threads. Appl Environ Microbiol, 2004 Jun, 70(6), 3272 - 81 Engineering the nifH promoter region and abolishing poly-beta-hydroxybutyrate accumulation in Rhizobium etli enhance nitrogen fixation in symbiosis with Phaseolus vulgaris; Peralta H et al.; Rhizobium etli, as well as some other rhizobia, presents nitrogenase reductase (nifH) gene reiterations . Several R . etli strains studied in this laboratory showed a unique organization and contained two complete nifHDK operons (copies a and b) and a truncated nifHD operon (copy c) . Expression analysis of lacZ fusion demonstrated that copies a and b in strain CFN42 are transcribed at lower levels than copy c, although this copy has no discernible role during nitrogen fixation . To increase nitrogenase production, we constructed a chimeric nifHDK operon regulated by the strong nifHc promoter sequence and expressed it in symbiosis with the common bean plant (Phaseolus vulgaris), either cloned on a stably inherited plasmid or incorporated into the symbiotic plasmid (pSym) . Compared with the wild-type strain, strains with the nitrogenase overexpression construction assayed in greenhouse experiments had, increased nitrogenase activity (58% on average), increased plant weight (32% on average), increased nitrogen content in plants (15% at 32 days postinoculation), and most importantly, higher seed yield (36% on average), higher nitrogen content (25%), and higher nitrogen yield (72% on average) in seeds . Additionally, expression of the chimeric nifHDK operon in a poly-beta-hydroxybutyrate-negative R . etli strain produced an additive effect in enhancing symbiosis . To our knowledge, this is the first report of increased seed yield and nutritional content in the common bean obtained by using only the genetic material already present in Rhizobium. Environ Pollut, 2004 Aug, 130(3), 465 - 76 A multi-process phytoremediation system for removal of polycyclic aromatic hydrocarbons from contaminated soils; Huang XD et al.; To improve phytoremediation processes, multiple techniques that comprise different aspects of contaminant removal from soils have been combined . Using creosote as a test contaminant, a multi-process phytoremediation system composed of physical (volatilization), photochemical (photooxidation) and microbial remediation, and phytoremediation (plant-assisted remediation) processes was developed . The techniques applied to realize these processes were land-farming (aeration and light exposure), introduction of contaminant degrading bacteria, plant growth promoting rhizobacteria (PGPR), and plant growth of contaminant-tolerant tall fescue (Festuca arundinacea) . Over a 4-month period, the average efficiency of removal of 16 priority PAHs by the multi-process remediation system was twice that of land-farming, 50% more than bioremediation alone, and 45% more than phytoremediation by itself . Importantly, the multi-process system was capable of removing most of the highly hydrophobic, soil-bound PAHs from soil . The key elements for successful phytoremediation were the use of plant species that have the ability to proliferate in the presence of high levels of contaminants and strains of PGPR that increase plant tolerance to contaminants and accelerate plant growth in heavily contaminated soils . The synergistic use of these approaches resulted in rapid and massive biomass accumulation of plant tissue in contaminated soil, putatively providing more active metabolic processes, leading to more rapid and more complete removal of PAHs. Environ Pollut, 2004 Aug, 130(3), 453 - 63 Responses of three grass species to creosote during phytoremediation; Huang XD et al.; Phytoremediation of creosote-contaminated soil was monitored in the presence of Tall fescue, Kentucky blue grass, or Wild rye . For all three grass species, plant growth promoting rhizobacteria (PGPR) were evaluated for plant growth promotion and protection of plants from contaminant toxicity . A number of parameters were monitored including plant tissue water content, root growth, plant chlorophyll content and the chlorophyll a/b ratio . The observed physiological data indicate that some plants mitigated the toxic effects of contaminants . In addition, in agreement with our previous experiments reported in the accompanying paper (Huang, X.-D., El-Alawi, Y., Penrose, D.M., Glick, B.R., Greenberg, B.M., 2004 . A multi-process phytoremediation system for removal of polycyclic aromatic hydrocarbons from contaminated soil . Environ . Poll . doi: 10.1016/j.envpol.2003.09.031), PGPR were able to greatly enhance phytoremediation . PGPR accelerated plant growth, especially roots, in heavily contaminated soils, diminishing the toxic effects of contaminants to plants . Thus, the increased root biomass in PGPR-treated plants led to more effective remediation. Eur J Biochem, 2004 Jun, 271(12), 2494 - 503 Temperature and concentration-controlled dynamics of rhizobial small heat shock proteins; Lentze N et al.; A hallmark of alpha-crystallin-type small heat shock proteins (sHsps) is their highly dynamic oligomeric structure which promotes intermolecular interactions involved in subunit exchange and substrate binding (chaperone-like activity) . We studied the oligomeric features of two classes of bacterial sHsps by size exclusion chromatography and nanoelectrospray mass spectrometry . Proteins of both classes formed large complexes that rapidly dissociated upon dilution and at physiologically relevant heat shock temperatures . As the secondary structure was not perturbed, temperature- and concentration-dependent dissociations were fully reversible . Complexes formed between sHsps and the model substrate citrate synthase were stable and exceeded the size of sHsp oligomers . Small Hsps, mutated in a highly conserved glycine residue at the C-terminal end of the alpha-crystallin domain, formed labile complexes that disassembled more readily than the corresponding wild-type proteins . Reduced complex stability coincided with reduced chaperone activity. Genetika, 2004 Apr, 40(4), 454 - 61 {Instability of a cryptic plasmid in Sinorhizobium meliloti P108 during symbiosis of it with alfalfa Medicago sativa}; Rumiantseva ML et al.; Instability of cryptic plasmids in Sinorhizobium meliloti laboratory strains SKhM1-188, DM7-R, and P108 as well as in their clones isolated from nodules of alfalfa grown during a long-term microvegetation experiment (120 days) was studied . The isolated clones of strains SKhM1-188 and DM7-R manifested stable inheritance of plasmids, whereas 12.7-14.0% of clones with changed plasmid profile were detected in a population of clones from strain P108 . These segregants were designated as P108c . Segregants P108c exhibited significantly decreased symbiotic effectiveness, nitrogenase activity, and the competitiveness with respect to alfalfa, compared to the original strain P108 . It was established that a 80-kb deletion occurred in a larger of two cryptic plasmids (240 and 230 kb) of segregants P108c . It was concluded that genetic rearrangements are possible in rhizobial clones that did not undergo structural transformation and retained viability in the nodule during the natural vegetation period of alfalfa. J Biol Chem, 2004 Aug 13, 279(33), 34624 - 30 Epub 2004 May 24. The galactolipid digalactosyldiacylglycerol accumulates in the peribacteroid membrane of nitrogen-fixing nodules of soybean and Lotus; Gaude N et al.; The peribacteroid membrane (PBM) surrounding nitrogen fixing rhizobia in the nodules of legumes is crucial for the exchange of ammonium and nutrients between the bacteria and the host cell . Digalactosyldiacylglycerol (DGDG), a galactolipid abundant in chloroplasts, was detected in the PBM of soybean (Glycine max) and Lotus japonicus . Analyses of membrane marker proteins and of fatty acid composition confirmed that DGDG represents an authentic PBM lipid of plant origin and is not derived from the bacteria or from plastid contamination . In Arabidopsis, DGDG is known to accumulate in extraplastidic membranes during phosphate deprivation . However, the presence of DGDG in soybean PBM was not restricted to phosphate limiting conditions . Complementary DNA sequences corresponding to the two DGDG synthases, DGD1 and DGD2 from Arabidopsis, were isolated from soybean and Lotus . The two genes were expressed during later stages of nodule development in infected cells and in cortical tissue . Because nodule development depends on the presence of high amounts of phosphate in the growth medium, the accumulation of the non-phosphorus galactolipid DGDG in the PBM might be important to save phosphate for other essential processes, i.e . nucleic acid synthesis in bacteroids and host cells. Infect Immun, 2004 Jun, 72(6), 3398 - 409 Characterization of the icmH and icmF genes required for Legionella pneumophila intracellular growth, genes that are present in many bacteria associated with eukaryotic cells; Zusman T et al.; Legionella pneumophila, the causative agent of Legionnaires' disease, replicates intracellularly within a specialized phagosome of mammalian and protozoan host cells, and the Icm/Dot type IV secretion system has been shown to be essential for this process . Unlike all the other known Icm/Dot proteins, the IcmF protein, which was described before, and the IcmH protein, which is characterized here, have homologous proteins in many bacteria (such as Yersinia pestis, Salmonella enterica, Rhizobium leguminosarum, and Vibrio cholerae), all of which associate with eukaryotic cells . Here, we have characterized the L . pneumophila icmH and icmF genes and found that both genes are present in 16 different Legionella species examined . The icmH and icmF genes were found to be absolutely required for intracellular multiplication in Acanthamoeba castellanii and partially required for intracellular growth in HL-60-derived human macrophages, for immediate cytotoxicity, and for salt sensitivity . Mutagenesis of the predicted ATP/GTP binding site of IcmF revealed that the site is partially required for intracellular growth in A . castellanii . Analysis of the regulatory region of the icmH and icmF genes, which were found to be cotranscribed, revealed that it contains at least two regulatory elements . In addition, an icmH::lacZ fusion was shown to be activated during stationary phase in a LetA- and RelA-dependent manner . Our results indicate that although the icmH and icmF genes probably have a different evolutionary origin than the rest of the icm/dot genes, they are part of the icm/dot system and are required for L . pneumophila pathogenesis. Commun Agric Appl Biol Sci, 2003, 68(4 Pt A), 129 - 34 Managing the mycorrhizosphere--an approach to sustainable agriculture after the phaseout of methyl bromide? Reimann S, Sikora RA. Plant Health Promoting Rhizobacteria (PHPR) with known biocontrol activity toward the root knot nematode, Meloidogyne incognito, were tested for their ability to promote root colonization of arbuscular mycorrhizal fungi on tomato under greenhouse conditions . In addition, bacteria isolated from mycorrhizal spores were tested for their direct biological control activity on nematode early root penetration . The nematode antagonistic rhizobacteria Rhizobium etli G12 significantly increased mycorrhizal establishment . In addition, two of nine bacteria isolated from the mycorrhizosphere were shown to significantly reduce M . incognita early root penetration . The experiments produced important data on the interaction between rhizobacteria and the symbiotic fungus that in some combinations work synergistically in controlling the root-knot nematode . The potential of using such multitrophic treatment combinations in integrated management targeted first at reducing nematode early root penetration in young transplants and then later for sustainable biocontrol of root-knot under field conditions are discussed. DNA Res, 2004 Feb 29, 11(1), 57 - 65 Genome-wide comparison of the His-to-Asp phosphorelay signaling components of three symbiotic genera of Rhizobia; Hagiwara D et al.; Histidine-to-aspartate (His-Asp) phosphorelay (or two-component) systems are very common signal transduction mechanisms that are implicated in a wide variety of cellular responses to environmental stimuli . The His-Asp phosphorelay components include "sensor histidine kinase (HK)", "phosphotransfer intermediate (HPt)", and "response regulator (RR)" . With special reference to three bacterial species (Mesorhizobium loti, Bradyrhizobium japonicum, Sinorhizobium meliloti), each of which belongs to a different genera of Rhizobia, here we attempted to compile all of the His-Asp phosphorelay components in order to reveal a comparative genome-wide overview as to the His-Asp phosphorelay . It was revealed that M . loti has 47 HKs, 1 HPts, and 58 RRs; B . japonicum has 80 HKs, 3 HPts, and 91 RRs; whereas S . meliloti has 40 HKs, 1 HPt, and 58 RRs . These His-Asp phosphorelay components were extensively compiled and characterized . The resulting overview as to the His-Asp phosphorelay of Rhizobia will provide us with a basis for understanding of the fundamental mechanisms underlying interactions between plants and microorganisms (including symbiosis), as well as nitrogen fixation. Ying Yong Sheng Tai Xue Bao, 2004 Jan, 15(1), 44 - 8 {Diversity and resistance of rhizobia isolated from Caragana intermedia in Maowusu sandland}; Gao L et al.; Fifteen rhizobia strains were isolated from wild shrubby legume Caragana intermedia in Maowusu sandland . A dendrogram was constructed based on esterase profiles, showing a rich diversity of these rhizobia . Many biochemical characteristics were detected, including acid or alkali production, catalase activity, utilization of sole carbon sources, and resistance to salt, acid-alkali and temperature variation . The results indicated that all the rhizobia strains isolated from Caragana intermedia could excrete H+ on YMA agar and produce catalase . 73.3% strains could tolerate NaCl stress at 3% concentration, and 80% strains could grow at 50 degrees C . Except the difference in lactose and starch utilization, rhizobia strains had no bias on the rest carbon sources . However, the difference in resistance to stress existed among strains, which might be related to the adaptation of rhizobia to diverse landscapes in Maowusu sandland . It was revealed that rhizobia nodulating Caragana intermedia could be used as a new germplasm to fix nitrogen under severe environment. FEMS Microbiol Lett, 2004 May 15, 234(2), 225 - 30 The nitrogen-fixing symbiotic bacterium Mesorhizobium loti has and expresses the gene encoding pyridoxine 4-oxidase involved in the degradation of vitamin B6; Yuan B et al.; The gene product of mll6785 of a nitrogen-fixing symbiotic bacterium Mesorhizobium loti MAFF303099 was identified as pyridoxine 4-oxidase, the first enzyme in the vitamin B6-degradation pathway . The gene was cloned and ligated into pET-21a+ . Escherichia coli BL21(DE3) was co-transformed with the constructed plasmid plus pKY206 containing groESL genes encoding chaperonins . The overexpressed protein was purified to homogeneity by the ammonium sulfate fractionation and three chromatography steps . The enzymatic properties of the purified protein, such as K(m) values for pyridoxine (213+/-19 microM) and oxygen (78+/-10 microM), were compared to those of pyridoxine 4-oxidase from two bacteria with known vitamin B6-degradation pathway . M . loti grown in a Rhizobium medium showed the enzyme activity . The results suggest that M . loti also contains the degradation pathway of vitamin B6 . Microbiology, 2004 May, 150(Pt 5), 1447 - 56 The Fur-like protein Mur of Rhizobium leguminosarum is a Mn(2+)-responsive transcriptional regulator; Diaz-Mireles E et al.; In wild-type Rhizobium leguminosarum, the sitABCD operon specifies a Mn(2+) transporter whose expression is severely reduced in cells grown in the presence of this metal . Mutations in the R . leguminosarum gene, mur (manganese uptake regulator), whose product resembles the Fur transcriptional regulator, cause high-level expression of sitABCD in the presence of Mn(2+) . In gel-shift mobility assays, purified R . leguminosarum Mur protein bound to at least two regions near the sitABCD promoter region, although this DNA has no conventional consensus Fur-binding sequences (fur boxes) . Thus, in contrast to gamma-proteobacteria, where Fur binds Fe(2+), the R . leguminosarum Fur homologue, Mur, act as a Mn(2)-responsive transcriptional regulator. Biotechnol Lett, 2004 Mar, 26(6), 487 - 91 Growth promotion of red pepper plug seedlings and the production of gibberellins by Bacillus cereus, Bacillus macroides and Bacillus pumilus; Joo GJ et al.; The growth of red pepper plug seedlings was promoted by Bacillus cereus MJ-1, B . macroides CJ-29, and B . pumilus CJ-69 isolated from the rhizosphere . Gibberellins (GAs), a well-known plant growth-promoting hormone, were detected in the culture broth of their rhizobacteria . Among the GAs, the contents of GA1, GA3, GA4, and GA7, physiologically active GAs, were comparatively higher than those of others, suggesting that the growth promoting effect was originated from the GAs . This isthe first report on the production of GA5, GA8, GA34, GA44, and GA53 by bacteria. J Bacteriol, 2004 May, 186(10), 2996 - 3005 Identification of rhtX and fptX, novel genes encoding proteins that show homology and function in the utilization of the siderophores rhizobactin 1021 by Sinorhizobium meliloti and pyochelin by Pseudomonas aeruginosa, respectively; Cuiv PO et al.; Rhizobactin 1021 is a hydroxymate siderophore produced by the soil bacterium Sinorhizobium meliloti 2011 . A regulon comprising rhtA, encoding the outer membrane receptor protein for the ferrisiderophore; the biosynthesis operon rhbABCDEF; and rhrA, the Ara-C-like regulator of the receptor and biosynthesis genes has been previously described . We report the discovery of a gene, located upstream of rhbA and named rhtX (for "rhizobactin transport"), which is required, in addition to rhtA, to confer the ability to utilize rhizobactin 1021 on a strain of S . meliloti that does not naturally utilize the siderophore . Rhizobactin 1021 is structurally similar to aerobactin, which is transported in Escherichia coli via the IutA outer membrane receptor and the FhuCDB inner membrane transport system . E . coli expressing iutA and fhuCDB was found to also transport rhizobactin 1021 . We demonstrated that RhtX alone could substitute for FhuCDB to transport rhizobactin 1021 in E . coli . RhtX shows similarity to a number of uncharacterized proteins which are encoded proximal to genes that are either known to be or predicted to be involved in iron acquisition . Among these is PA4218 of Pseudomonas aeruginosa, which is located close to the gene cluster that functions in pyochelin biosynthesis and outer membrane transport . PA4218 was mutated by allelic replacement, and the mutant was found to have a pyochelin utilization-defective phenotype . It is proposed that PA4218 be named fptX (for "ferripyochelin transport") . RhtX and FptX appear to be members of a novel family of permeases that function as single-subunit transporters of siderophores. Environ Health Perspect, 2004 May, 112(6), 648 - 53 Chemical communication threatened by endocrine-disrupting chemicals; Fox JE; Communication on a cellular level--defined as chemical signaling, sensing, and response--is an essential and universal component of all living organisms and the framework that unites all ecosystems . Evolutionarily conserved signaling "webs," existing both within an organism and between organisms, rely on efficient and accurate interpretation of chemical signals by receptors . Therefore, endocrine-disrupting chemicals (EDCs), which have been shown to disrupt hormone signaling in laboratory animals and exposed wildlife, may have broader implications for disrupting signaling webs that have yet to be identified as possible targets . In this article, I explore common evolutionary themes of chemical signaling (e.g., estrogen signaling in vertebrates and phytoestrogen signaling from plants to symbiotic soil bacteria) and show that such signaling systems are targets of disruption by EDCs . Recent evolutionary phylogenetic data have shown that the estrogen receptor (ER) is the ancestral receptor from which all other steroid receptors have evolved . In addition to binding endogenous estrogens, ERs also bind phytoestrogens, an ability shared in common with nodulation D protein (NodD) receptors found in Rhizobium soil bacteria . Recent data have shown that many of the same synthetic and natural environmental chemicals that disrupt endocrine signaling in vertebrates also disrupt phytoestrogen-NodD receptor signaling in soil bacteria, which is necessary for nitrogen-fixing symbiosis . Bacteria-plant symbiosis is an unexpected target of EDCs, and other unexpected nontarget species may also be vulnerable to EDCs found in the environment. Plant Cell Physiol, 2004 Apr, 45(4), 427 - 35 Transgenic Lotus japonicus with an ethylene receptor gene Cm-ERS1/H70A enhances formation of infection threads and nodule primordia; Nukui N et al.; Ethylene inhibits the establishment of symbiosis between rhizobia and legumes . To examine how and when endogenous ethylene inhibits rhizobial infection and nodulation, we produced transgenic Lotus japonicus carrying the mutated melon ethylene receptor gene Cm-ERS1/H70A that confers ethylene insensitivity and fixes the transgene in the T(3) generation . The resultant transgenic plants showed reduced ethylene sensitivity because of 1-aminocyclopropane-1-carboxylate resistance and increased flowering duration, probably due to a dominant negative mechanism . When inoculated with Mesorhizobium loti, transgenic plants showed markedly higher numbers of infection threads and nodule primordia on their roots than did either wild-type or azygous plants during the early stage of cultivation period as well as during later stages, when the number of mature nodules had reached a steady state . In addition, transcripts of NIN, a gene governing infection thread formation, increased in the inoculated transgenic plants as compared with the wild-type plants . The infection responses of transgenic plants were similar to those of wild-type plants treated with ethylene inhibitors . These results imply that the endogenous ethylene in L . japonicus roots inhibits rhizobial infection at the primary nodulation, probably via NIN gene, and suggest that ethylene perception assists negative feedback regulation of secondary nodule initiation. Plasmid, 2004 May, 51(3), 203 - 16 Incompatibility and the partitioning site of the repABC basic replicon of the symbiotic plasmid from Rhizobium etli; Soberon N et al.; The basic replicon of the symbiotic plasmid (p42d) of Rhizobium etli CE3 is constituted by the repABC operon . Whereas RepC is essential for plasmid replication, RepA and RepB are involved in plasmid partitioning . Three incompatibility regions have been previously identified in this plasmid: the first one encodes RepA, a partitioning protein that also down-regulates the repABC transcription . The second region is situated within the repB-repC intergenic sequence (inc(alpha)), and the last one, inc(beta), is located in a 502 bp EcoRI fragment spanning the last 72-bp of the coding region of repC and the following downstream sequence . In this paper we show that: (1) The inc(beta) region is required for plasmid partitioning . (2) A 16-bp palindrome sequence, located 40 bp downstream of the repC gene of plasmid p42d, is necessary and sufficient to induce incompatibility towards the parental plasmid, and accounts for all the incompatibility properties of this region (inc(beta)) . (3) . The palindrome is the DNA target site for RepB binding . With these findings we propose that inc(beta) contains the partitioning site (par site) of the basic replicon of plasmid p42d, and that the 16-bp palindrome is the core sequence to nucleate the RepB binding . Plasmid, 2004 May, 51(3), 185 - 91 A gfp reporter plasmid to visualize Azorhizobium caulinodans during nodulation of Sesbania rostrata; D'Haeze W et al.; Compared with other labeling techniques, the use of the green fluorescent protein (GFP) is advantageous to visualize bacteria because observations can be performed in real time . This feature is particularly interesting to study invasion events of rhizobia during nodule development on their legume host plant . To investigate the symbiotic interaction between Azorhizobium caulinodans ORS571 and Sesbania rostrata, we constructed two plasmids, pMP220-hem-gfp5 and pBBR5-hem-gfp5-S65T, that carry a modified gfp gene, the expression of which is controlled by the constitutive hem promoter . Introduction of either of these plasmids into A . caulinodans allowed the visualization of single bacteria . Determination of the plasmid stability in cultured bacteria and in nodules demonstrated that pBBR5-hem-gfp5-S65T is more stable than pMP220-hem-gfp5 . The plasmid pBBR5-hem-gfp5-S65T can be used to study early invasion events during nodule development on hydroponic roots of S . rostrata . Planta, 2004 Aug, 219(4), 626 - 38 Epub 2004 Apr 24. Sinorhizobium meliloti-induced chitinase gene expression in Medicago truncatula ecotype R108-1: a comparison between symbiosis-specific class V and defence-related class IV chitinases; Salzer P et al.; The Medicago truncatula (Gaertn.) ecotypes Jemalong A17 and R108-1 differ in Sinorhizobium meliloti-induced chitinase gene expression . The pathogen-inducible class IV chitinase gene, Mtchit 4, was strongly induced during nodule formation of the ecotype Jemalong A17 with the S . meliloti wild-type strain 1021 . In the ecotype R108-1, the S . meliloti wild types Sm1021 and Sm41 did not induce Mtchit 4 expression . On the other hand, expression of the putative class V chitinase gene, Mtchit 5, was found in roots of M . truncatula cv . R108-1 nodulated with either of the rhizobial strains . Mtchit 5 expression was specific for interactions with rhizobia . It was not induced in response to fungal pathogen attack, and not induced in roots colonized with arbuscular mycorrhizal (AM) fungi . Elevated Mtchit 5 gene expression was first detectable in roots forming nodule primordia . In contrast to Mtchit 4, expression of Mtchit 5 was stimulated by purified Nod factors . Conversely, Mtchit 4 expression was strongly elevated in nodules formed with the K-antigen-deficient mutant PP699 . Expression levels of Mtchit 5 were similarly increased in nodules formed with PP699 and its parental wild-type strain Sm41 . Phylogenetic analysis of the deduced amino acid sequences of Mtchit 5 (calculated molecular weight = 41,810 Da, isoelectric point pH 7.7) and Mtchit 4 (calculated molecular weight 30,527 Da, isoelectric point pH 4.9) revealed that the putative Mtchit 5 chitinase forms a separate clade within class V chitinases of plants, whereas the Mtchit 4 chitinase clusters with pathogen-induced class IV chitinases from other plants . These findings demonstrate that: (i) Rhizobium-induced chitinase gene expression in M . truncatula occurs in a plant ecotype-specific manner, (ii) Mtchit 5 is a putative chitinase gene that is specifically induced by rhizobia, and (iii) rhizobia-specific and defence-related chitinase genes are differentially influenced by rhizobial Nod factors and K antigens. Can J Microbiol, 2004 Mar, 50(3), 201 - 11 Environmental modulation of the pssTNOP gene expression in Rhizobium leguminosarum bv . trifolii; Wielbo J et al.; Exopolysaccharide production by Rhizobium leguminosarum bv . trifolii is required for successful establishment of nitrogen-fixing symbiosis with clover (Trifolium pratense L.) . Using plasmid-borne transcriptional fusions of promoters of pss genes with promoterless lacZ the effect of root exudate, phosphate, and ammonia on expression of pssT, pssN, pssO, and pssP genes in wild-type strain RtTA1 background was determined . A stimulating effect of these environmental factors on pssO and pssP gene expression was observed . The putative pssO gene promoter was determined to be a strong promoter within which the divergent nod-box element was identified . The pssO promoter was slightly inducible in a flavonoid-dependent manner in wild-type R . leguminosarum bv . trifolii strains RtTA1 and ANU843 and very weakly active in a mutant of strain ANU843 that lacks the regulatory nodD gene . The expression of pssO and pssP genes in planta was investigated using plasmid-borne pssO-gusA and pssP-gusA fusions under different phosphate availability to clover . The level of pssO-gusA fusion expression was shown to be dependent on phosphate concentration in the plant growth medium. Antonie Van Leeuwenhoek, 2004 Jul, 86(1), 1 - 25 Applications of free living plant growth-promoting rhizobacteria; Lucy M et al.; Free-living plant growth-promoting rhizobacteria (PGPR) can be used in a variety of ways when plant growth enhancements are required . The most intensively researched use of PGPR has been in agriculture and horticulture . Several PGPR formulations are currently available as commercial products for agricultural production . Recently developing areas of PGPR usage include forest regeneration and phytoremediation of contaminated soils . As the mechanisms of plant growth promotion by these bacteria are unravelled, the possibility of more efficient plant-bacteria pairings for novel and practical uses will follow . The progress to date in using PGPR in a variety of applications with different plants is summarized and discussed here. J Microsc, 2004 May, 214(Pt 2), 104 - 13 Dissection of Nod factor signalling in legumes: cell biology, mutants and pharmacological approaches; Esseling JJ et al.; Nodulation factors (NFs) are lipochito-oligosaccharide signal molecules excreted by soil-living rhizobia . These molecules elicit a range of responses in the legume roots, with which the bacteria can live in symbiosis . In this review we focus on the genetic, pharmacological and cell biological approaches that have been, and are being, undertaken to decipher the signalling pathways that lead to the symbiotic responses in the plant. Environ Pollut, 1991, 73(1), 11 - 23 Radioactive isotope uptake in a grass-legume association; Douka CE et al.; The radioactive uptake of Medicago sativa and Rye grass in a pasture exposed to the fallout from the Chernobyl reactor accident, was determined in four consecutive harvests covering a period of one year after the accident,In plants of Medicago sativa, inoculated with an effective Rhizobia meliloti strain isolated from Greek soils, a high degree of biological nitrogen fixation was observed at all harvests using N-15 techniques . At the second and third harvests, the percentage nitrogen derived from fixation (%NdfF), the percentage nitrogen derived from soil (%NdfS), as well as the radioactive uptake from the soil remained stable . At the fourth harvest, however, the %NdfF decreased while the %NdfS and the radioactive uptake from soil significantly increased . At the first harvest the radioactivity in both plants, caused mainly by direct fallout contamination, was considerably higher than that observed at the later harvests . Medicago sativa contained significantly less radioactivity than the grass at all harvests, although both plants were grown under the same environmental conditions . Even at the fourth harvest, almost one year after the initial contamination, the radioactivity of grass remained at high levels ( 20 Bq g(-1) of protein) while in Medicago sativa it assumed considerably lower values (3.6 Bq g(-1) of protein) . A possible involvement of biological nitrogen fixation in the reduction of radioactive uptake is discussed . Finally, certain practical conclusions are drawn with respect to a safer management of pastures exposed to radioactivity. Environ Pollut, 1993, 79(2), 105 - 12 The effect of heavy metals on dinitrogen fixation by Rhizobium-white colover in a range of long-term sewage sludge amended and metal-contaminated soils; Obbard JP et al.; An investigation was conducted to determine whether effective strains of Rhizobium leguminosarum biovar . trifolii capable of symbiotic N(2) fixation with white clover (Trifolium repens) were present in a range of metal-contaminated soils . A number of historically sewage-amended sites (including experimental, pasture grassland and arable sites) were selected and compared with highly contaminated samples from abandoned heavy metal mines . Many sites had metal concentrations above the limits established by the UK Government, based on those developed by the European Commission (EC) for sludge-amended soils . Acetylene reduction activity (ARA) was used to screen the samples for effective N(2) fixation . When the host plant was indigenous to the sward, rhizobia were found in the nodules and in the soil rhizosphere at all the sites tested . They were shown to be capable of effective symbiosis and N(2) fixation, even though metal concentrations greatly exceeded the soil metal limits in some cases . However, nodulation failed to occur in some cases where T . repens was not indigenous to metal-contaminated soils . This indicated either that an ineffective rhizobial population was present, or that effective cells were absent from the soil . The influence of individual metals on ARA could not be determined conclusively because of the confounding effects of soil physicochemical variability and the presence of different metals at high concentrations together in the soil . However, Cd concentrations appeared to be particularly important in determining the presence of effective ARA in soils with no indigenous clover . In contrast to previous studies, the results presented here suggest that heavy metals may have had a quantitative effect on the free-living population of rhizobia, rather than a genetic effect. Environ Pollut, 1996, 92(1), 55 - 66 Effects of rhizobium, arbuscular mycorrhizal fungi and anion content of simulated rain on subterranean clover; Shafer SR et al.; An experiment was conducted to determine the extent to which rhizobia, mycorrhizal fungi, and anions in simulated rain affect plant growth response to acid deposition . Germinating subterranean clover seeds were planted in steam-pasteurized soil in pots and inoculated with Rhizobium leguminosarum, Glomus intraradices, Glomus etunicatum, R . leguminosarum + G . intraradices, R . leguminosarum + G . etunicatum, or no microbial symbionts . Beginning 3 weeks later, plants and the soil surface were exposed to simulated rain in a greenhouse on 3 days week(-1) for 12 weeks . Rain solutions were deionized water amended with background ions only (pH 5.0) or also adjusted to pH 3.0 with HNO(3) only, H(2)SO(4) only, or a 50/50 mixture of the two acids . Glomus intraradices colonized plant roots poorly, and G . intraradices-inoculated plants responded like nonmycorrhizal plants to rhizobia and rain treatments . Variation in plant biomass attributable to different rain formulations was strongest for G . etunicatum-inoculated plants, and the effect of rain formulation differed with respect to nodulation by rhizobia . The smallest plants at the end of the experiment were noninoculated plants exposed to rains (0.38 g mean dry weight total for 3 plants pot(-1)) . Among nonnodulated plants infected by G . etunicatum, those exposed to HNO(3) rain were largest, followed by plants exposed to HNO(3) + H(2)SO(4), pH 5.0, and H(2)SO(4) rain, in that order . Among plants inoculated with both R . leguminosarum + G . etunicatum, however, the greatest biomass occurred with pH 5.0 rains, resulting in the largest plants in the study (1.00 g/3 plants) . Treatment-related variation among root and shoot biomass data reflected those for whole-plant biomass . Based on quantification of biomass and N concentrations in shoot and root tissues, total N content of plants inoculated with G . etunicatum alone and exposed to the HNO(3) + H(2)SO(4) rains was approximately the same as plants inoculated with R . leguminosarum + G . entunicatum and exposed to pH 5 rains . Thus, the acid-mixture rains and rhizobia under no acid deposition provided approximately equal amounts of N in biomass . The significant interactions among rain formulation and the symbiotic status of the plants suggest that conclusions concerning the impact of acid deposition on plants in the environment cannot be considered reliable because most experiments on which such assessments are based have not tested confounding influences of microorganisms and precipitation characteristics. BMC Biochem . 2004 Apr 13;5(1):4. Radiolabeling of lipo-chitooligosaccharides using the NodH sulfotransferase: a two-step enzymatic procedure; Gressent F et al.; BACKGROUND: The NodH sulfotransferase from Sinorhizobium meliloti has been used to radiolabel lipochitooligosaccharidic (LCO) Nod factor signals with 35S from inorganic sulfate in a two-step enzymatic procedure . The first step involved the production of 3'-phosphoadenosine 5'-phosphosulfate (PAPS), a sulphate donor, using enzymes contained in a yeast extract, and the second step used the NodH enzyme . However with this established procedure, only a low incorporation of the initial inorganic sulfate into the Nod factors was obtained (about 7% after purification of the labeled compounds) . The aim of this work was to optimize the radiolabelling of Nod factors with 35S . RESULTS: The limiting step has been shown to be the sulfation of ATP and its subsequent conversion into PAPS (first step), the sulfate donor for the NodH sulfotransferase activity (second step) . By the addition of GTP to the reaction mixture and by manipulating the {ATP}/{Mg2+} ratio the yield of PAPS has been increased from 13% to 80% . Using the radiolabeled PAPS we have shown that the efficiency of sulfate transfer to LCOs, by the recombinant S . meliloti NodH sulfotransferase is strongly influenced by the length of the oligosaccharide chain . Variations in the substitutions on the non-reducing sugar, including the structure of the fatty acyl chain, had little effect and Nod factors from the heterologous bacterium Rhizobium tropici could be sulfated by NodH from S . meliloti . CONCLUSIONS: By characterizing the two steps we have optimized the procedure to radiolabel biologically-important, lipo-chitooligosaccharide (LCO) Nod factors to a specific radioactivity of about 800 Ci x mmol(-1) with an incorporation of 60% of the initial inorganic sulfate . The two-step sulfation procedure may be used to radiolabel a variety of related LCO molecules. Proc Natl Acad Sci U S A, 2004 Apr 20, 101(16), 6303 - 8 Epub 2004 Apr 12. Switch from intracellular to intercellular invasion during water stress-tolerant legume nodulation; Goormachtig S et al.; Rhizobia colonize their legume hosts by different modes of entry while initiating symbiotic nitrogen fixation . Most legumes are invaded via growing root hairs by the root hair-curl mechanism, which involves epidermal cell responses . However, invasion of a number of tropical legumes happens through fissures at lateral root bases by cortical, intercellular crack entry . In the semiaquatic Sesbania rostrata, the bacteria entered via root hair curls under nonflooding conditions . Upon flooding, root hair growth was prevented, invasion on accessible root hairs was inhibited, and intercellular invasion was recruited . The plant hormone ethylene was involved in these processes . The occurrence of both invasion pathways on the same host plant enabled a comparison to be made of the structural requirements for the perception of nodulation factors, which were more stringent for the epidermal root hair invasion than for the cortical intercellular invasion at lateral root bases. Plant J, 2004 Apr, 38(2), 203 - 14 Cytokinins play opposite roles in lateral root formation, and nematode and Rhizobial symbioses; Lohar DP et al.; We used the cytokinin-responsive Arabidopsis response regulator (ARR)5 gene promoter fused to a beta-glucuronidase (GUS) reporter gene, and cytokinin oxidase (CKX) genes from Arabidopsis thaliana (AtCKX3) and maize (ZmCKX1) to investigate the roles of cytokinins in lateral root formation and symbiosis in Lotus japonicus . ARR5 expression was undetectable in the dividing initial cells at early stages of lateral root formation, but later we observed high expression in the base of the lateral root primordium . The root tip continues to express ARR5 during subsequent development of the lateral root . These results suggest a dynamic role for cytokinin in lateral root development . We observed ARR5 expression in curled/deformed root hairs, and also in nodule primordia in response to Rhizobial inoculation . This expression declined once the nodule emerged from the parent root . Root penetration and migration of root-knot nematode (RKN) second-stage larvae (L2) did not elevate ARR5 expression, but a high level of expression was induced when L2 reached the differentiating vascular bundle and during early stages of the nematode-plant interaction . ARR5 expression was specifically absent in mature giant cells (GCs), although dividing cells around the GCs continued to express this reporter . The same pattern was observed using a green fluorescent protein (GFP) reporter driven by the ARR5 promoter in tomato . Overexpression of CKX genes rendered the transgenic hairy roots resistant to exogenous application of the cytokinin {N6-(Delta2 isopentenyl) adenine riboside} (iPR) . CKX roots have significantly more lateral roots, but fewer nodules and nematode-induced root galls per plant, than control hairy roots. J Plant Physiol, 2004 Mar, 161(3), 329 - 38 Nitrogenase and antioxidant enzyme activities in Phaseolus vulgaris nodules formed by Rhizobium tropici isogenic strains with varying tolerance to salt stress; Tejera NA et al.; Common bean plants inoculated with salt-tolerant Rhizobium tropici wild-type strain CIAT899 formed a more active symbiosis than did its decreased salt-tolerance (DST) mutant derivatives (HB8, HB10, HB12 and HB13) . The mutants formed partially effective (HB10, HB12) or almost ineffective (HB8, HB13) nodules (Fix(d)) under non-saline conditions . The DST mutant formed nodules that accumulated more proline than did the wild-type nodules, while soluble sugars were accumulated mainly in ineffective nodules . Under salt stress, plant growth, nitrogen fixation, and the activities of the antioxidant defense enzymes of nodules were affected in all symbioses tested . Overall, mutant nodules showed lower antioxidant enzyme activities than wild-type nodules . Levels of nodule catalase appeared to correlate with symbiotic nitrogen-fixing efficiency . Superoxide dismutase and dehydroascorbate reductase seem to function in the molecular mechanisms underlying the tolerance of nodules to salinity. Mikrobiologiia, 2004 Jan-Feb, 73(1), 62 - 7 {The influence of lipopolysaccharides and glucans from two Rhizobium leguminosarum bv . viciae strains on the formation and efficiency of their symbioses with pea plants}; Antipchuk AF et al.; The influence of lipopolysaccharides (LPS), glucans, and their unseparated complexes on nodulation activity of rhizobia and efficiency of their symbioses with pea plants was studied in vegetation experiments . Two Rhizobium leguminosarum bv . viciae strains which differed in their symbiotic properties were used: strain 31 (fix+, efficient, moderately virulent, moderately competitive), and strain 248b (fix-, inefficient, highly virulent, highly competitive) . Preparations of LPS-glucan complex and the respective LPS from the highly virulent strain 248b increased the nodulation activity of both strains by 10-26% . Analogous preparations from a less virulent strain 31 did not have this ability . Unseparated LPS-glucan complexes from these strains increased the productivity of plants infected with the efficient strain by 18-23% but did not change it in plants inoculated with the other, inefficient strain . No significant influence of LPS preparations on the symbiosis productivity was observed . Glucans from both strains enhanced the nodulation ability of the highly virulent strain by 36-56% . In addition, treatment of pea plants with glucan from strain 248b increased nitrogen fixation by root nodules by 27% in plants inoculated with strain 31 . In general, the formation and efficiency of the symbiosis of R . leguminosarum bv . viciae with pea plants was more influenced by preparations from strain 248b, highly virulent but deficient in nitrogen fixation, than by preparations from the nitrogen fixation-proficient but less virulent strain 31. J Hered, 2004 Mar-Apr, 95(2), 154 - 7 Genetics of promiscuous nodulation in soybean: nodule dry weight and leaf color score; Gwata ET et al.; The symbiotic relationship between the soybean plant and rhizobium results in fixation of atmospheric nitrogen (N(2)) in the root nodules, with the result that nitrogenous fertilization of the soybean is unnecessary . The effectiveness of nodule formation and N(2) fixation with rhizobial strains is under genetic control with two general categories identified: (1) promiscuous, which produces functional nodules with cowpea-type rhizobial strains; and (2) nonpromiscuous, which forms no or nonfunctional nodules with these strains . The segregation pattern of this promiscuity trait was studied using nodule dry weight (NDW) and leaf color score (LCS) as indicators of N(2) fixation effectiveness . Individual plants in each of six populations {P(1) = nonpromiscuous, P(2) = promiscuous, F(1) = P(1) x P(2) (and the reciprocal cross), BC(1)(P(1)) = F(1) (female) x P(1), BC(1)(P(2)) = F(1) (female) x P(2), F(2)} were scored for these characters after inoculation with a rhizobial strain that would distinguish between both types . For NDW, nonpromiscuity was found to be partially dominant (h/d = 0.37), controlled by four loci . For LCS, nonpromiscuity was shown to be almost completely dominant (h/d = 0.74), controlled by two loci . LCS was a more meaningful estimate of N(2) fixation because it represented the total effectiveness of nodulation to provide nitrogen for the plant. Proc Natl Acad Sci U S A, 2004 Mar 30, 101(13), 4701 - 5 Epub 2004 Mar 01. A Ca2+/calmodulin-dependent protein kinase required for symbiotic nodule development: Gene identification by transcript-based cloning; Mitra RM et al.; In the establishment of the legume-rhizobial symbiosis, bacterial lipochitooligosaccharide signaling molecules termed Nod factors activate the formation of a novel root organ, the nodule . Nod factors elicit several responses in plant root hair cells, including oscillations in cytoplasmic calcium levels (termed calcium spiking) and alterations in root hair growth . A number of plant mutants with defects in the Nod factor signaling pathway have been identified . One such Medicago truncatula mutant, dmi3, exhibits calcium spiking and root hair swelling in response to Nod factor, but fails to initiate symbiotic gene expression or cell divisions for nodule formation . On the basis of these data, it is thought that the dmi3 mutant perceives Nod factor but fails to transduce the signal downstream of calcium spiking . Additionally, the dmi3 mutant is defective in the symbiosis with mycorrhizal fungi, indicating the importance of the encoded protein in multiple symbioses . We report the identification of the DMI3 gene, using a gene cloning method based on transcript abundance . We show that transcript-based cloning is a valid approach for cloning genes in barley, indicating the value of this technology in crop plants . DMI3 encodes a calcium/calmodulin-dependent protein kinase . Mutants in pea sym9 have phenotypes similar to dmi3 and have alterations in this gene . The DMI3 class of proteins is well conserved among plants that interact with mycorrhizal fungi, but it is less conserved in Arabidopsis thaliana, which does not participate in the mycorrhizal symbiosis. Int Rev Cytol, 2004, 234, 201 - 62 Organogenesis of legume root nodules; Patriarca EJ et al.; The N(2)-fixing nodules elicited by rhizobia on legume roots represent a useful model for studying plant development . Nodule formation implies a complex progression of temporally and spatially regulated events of cell differentiation/dedifferentiation involving several root tissues . In this review we describe the morphogenetic events leading to the development of these histologically well-structured organs . These events include (1) root hair deformation, (2) development and growth of infection threads, (3) induction of the nodule primordium, and (4) induction, activity, and persistence of the nodular meristem and/or of foci of meristematic activities . Particular attention is given to specific aspects of the symbiosis, such as the early stages of intracellular invasion and to differentiation of the intracellular form of rhizobia, called symbiosomes . These developmental aspects were correlated with (1) the regulatory signals exchanged, (2) the plant genes expressed in specific cell types, and (3) the staining procedures that allow the recognition of some cell types . When strictly linked with morphogenesis, the nodulation phenotypes of plant and bacterial mutants such as the developmental consequence of the treatment with metabolic inhibitors, metabolic intermediates, or the variation of physical parameters are described . Finally, some aspects of nodule senescence and of regulation of nodulation are discussed. Carbohydr Res, 2004 Apr 28, 339(6), 1061 - 7 Acacia senegal and Prosopis chilensis-nodulating rhizobia Sinorhizobium arboris HAMBI 2361 and S . kostiense HAMBI 2362 produce tetra- and pentameric LCOs that are N-methylated, O-6-carbamoylated and partially sulfated; Nowak P et al.; Sinorhizobium arboris and S . kostiense are rhizobia that nodulate the tropical leguminous trees Acacia senegal and Prosopis chilensis . The lipochito-oligosaccharidic signalling molecules (LCOs) of S . arboris HAMBI 2361 and S . kostiense HAMBI 2362 were analyzed by mass spectrometry . The major LCOs produced by the strains were shown to be pentameric, acylated with common fatty acids, N-methylated, O-6-carbamoylated and partially sulfated, as are the LCOs characterized to date for other Acacia-nodulating rhizobia . Besides the major LCOs the two strains produced (i) tetrameric LCOs, (ii) LCOs acylated with fatty acids other than those commonly found, (iii) LCOs with only an acyl substituent and (iv) noncarbamoylated LCOs . Production of LCOs (i) to (iii) are novel among Acacia-nodulating rhizobia . The roles of the different structural characteristics of LCOs in the rhizobium-A . senegal symbiosis are discussed . Specific structural features of the LCOs are proposed to be important in the selection of effective nitrogen-fixing rhizobia by A . senegal. J Bacteriol, 2004 Apr, 186(8), 2439 - 48 Expression islands clustered on the symbiosis island of the Mesorhizobium loti genome; Uchiumi T et al.; Rhizobia are symbiotic nitrogen-fixing soil bacteria that are associated with host legumes . The establishment of rhizobial symbiosis requires signal exchanges between partners in microaerobic environments that result in mutualism for the two partners . We developed a macroarray for Mesorhizobium loti MAFF303099, a microsymbiont of the model legume Lotus japonicus, and monitored the transcriptional dynamics of the bacterium during symbiosis, microaerobiosis, and starvation . Global transcriptional profiling demonstrated that the clusters of genes within the symbiosis island (611 kb), a transmissible region distinct from other chromosomal regions, are collectively expressed during symbiosis, whereas genes outside the island are downregulated . This finding implies that the huge symbiosis island functions as clustered expression islands to support symbiotic nitrogen fixation . Interestingly, most transposase genes on the symbiosis island were highly upregulated in bacteroids, as were nif, fix, fdx, and rpoN . The genome region containing the fixNOPQ genes outside the symbiosis island was markedly upregulated as another expression island under both microaerobic and symbiotic conditions . The symbiosis profiling data suggested that there was activation of amino acid metabolism, as well as nif-fix gene expression . In contrast, genes for cell wall synthesis, cell division, DNA replication, and flagella were strongly repressed in differentiated bacteroids . A highly upregulated gene in bacteroids, mlr5932 (encoding 1-aminocyclopropane-1-carboxylate deaminase), was disrupted and was confirmed to be involved in nodulation enhancement, indicating that disruption of highly expressed genes is a useful strategy for exploring novel gene functions in symbiosis. J Gen Appl Microbiol, 2004 Feb, 50(1), 17 - 27 A novel symbiotic nitrogen-fixing member of the Ochrobactrum clade isolated from root nodules of Acacia mangium; Ngom A et al.; Ten strains of root nodule bacteria were isolated from the nodules of Acacia mangium grown in the Philippines and Thailand . Partial sequences (approx . 300 bp) of the 16S rRNA gene of each isolate were analyzed . The nucleotide sequences of strain DASA 35030 indicated high homology (>99%) with members of the genus Ochrobactrum in Brucellaceae, although the sequences of other isolates were homologous to those of two distinct genera Bradyrhizobium and Rhizobium . The strain DASA 35030 was strongly suggested to be a strain of Ochrobactrum by full length sequences of the 16S rRNA gene, fatty acids composition, G+C contents of the DNA, and other physiological characteristics . Strain DASA 35030 induced root nodules on A . mangium, A . albida and Paraserianthes falcataria . The nodules formed by strain DASA 35030 fixed nitrogen and the morphology of the nodules is the same as those of nodules formed by the other isolates . This is the first report that the strain of Ochrobactrum possesses complete symbiotic ability with Acacia. Appl Biochem Biotechnol, 2004 Spring, 113-116, 639 - 52 Effect of process parameters on production of a biopolymer by Rhizobium sp; Duta FP et al.; The production of biopolymers by a Rhizobium strain was studied under batch and bioreactor conditions . The best viscosity levels were obtained under low mannitol concentrations as well as low agitation and aeration conditions . Infrared spectra indicated the presence of chemical groups characteristic of microbially produced biopolymers, including C = O and O-acetyl groups . Thermogravimetric analysis showed the characteristic degradation profiles of the exopolysaccharide produced (T(onset) = 290degreesC) . The experimental design showed that a low substrate concentration (10.0 g/L), and low aeration (0.2 vvm) and agitation (200 rpm) levels should be used . The maximum yield of the process was a Yp/s (g/g) of 0.19 +/- 0.1, obtained under optimized conditions. J Ind Microbiol Biotechnol, 2004 Mar, 31(3), 122 - 6 Epub 2004 Mar 30. Cheese whey: an alternative growth and protective medium for Rhizobium loti cells; Estrella MJ et al.; Cheese whey (CW)-based growth medium efficiently protects Rhizobium loti cells during freezing and desiccation and can maintain their growth in a manner similar to that of traditional mannitol-based medium (YEM) . The cheese-whey-based medium (CW) improved viability when used to re-suspend cell pellets kept at -20 degrees C and -80 degrees C and resulted in the survival of over 90% of the cells . Moreover, bacterial pellets obtained from cells grown in CW withstand desiccation better than cells grown in YEM . Survival was over 60% after 30 days at 4 degrees C . No differences were observed in nodulation effi