Curr Microbiol, 2001 Aug, 43(2), 120 - 3 UV-induced increase in RNA polymerase activity in Xanthomonas oryzae pathovar oryzae; Lin SH et al.; UV radiation is thought to inhibit transcriptional elongation, as a result of the formation of pyrimidine dimers in the DNA template, as well as to activate specific transcription factors . However, the effect of UV radiation on the enzymatic activity of RNA polymerase has remained unknown . With the use of an in vitro assay, UV irradiation of Xanthomonas oryzae pathovar oryzae has now been shown to increase RNA polymerase activity . This effect was maximal at a UV dose of approximately 12 J m(-2) and at approximately 60 min after irradiation . It was also not inhibited by pretreatment of cells with chloramphenicol, an inhibitor of protein synthesis . Immunoprecipitation with antibodies to the RNA polymerase core enzyme revealed that exposure of the bacterial cells to UV radiation induced the association of the core enzyme with a protein of approximately 29 kDa . These results demonstrate that UV radiation increases the activity of RNA polymerase, and they suggest that this effect may be related to the repair of DNA damage. Novartis Found Symp, 2001, 236, 190 - 200; discussion 200-4 Dissection of defence response pathways in rice; Leach JE et al.; The cloning of major resistance genes has led to a better understanding of the molecular biology of the steps for induction of resistance, yet much remains to be discovered about the downstream genes that collectively confer resistance, i.e . the defence response (DR) genes . We are dissecting the pathways contributing to resistance in rice by identifying a collection of mutants with deletions or other structural rearrangements in DR genes . The collection of rice mutants has been screened for many characters, including increased susceptibility or resistance to Magnaporthe grisea and Xanthomonas oryzae pv . oryzae . A collection of enhanced sequence tags (ESTs) and putative DR genes has been established to facilitate detection of mutants with deletions in DR genes . Arrays of DR genes will be used to create gene expression profiles of interesting mutants . Successful application of the mutant screen will have broad utility in identifying candidate genes involved in disease response and other metabolic pathways. Mol Plant Microbe Interact, 2001 Jun, 14(6), 785 - 92 Induction of hydroxycinnamoyl-tyramine conjugates in pepper by Xanthomonas campestris, a plant defense response activated by hrp gene-dependent and hrp gene-independent mechanisms; Newman MA et al.; Inoculation of pepper leaves, Capsicum annuum cv . Early Calwonder ECW 10R, with strains of Xanthomonas campestris led to an accumulation of the phenolic conjugates feruloyltyramine (FT) and p-coumaroyltyramine (CT) 24 h postinoculation in nonhost- and gene-for-gene-determined incompatible interactions with X . campestris pv . campestris and X . campestris pv . vesicatoria, respectively . In contrast, neither compound was detected in compatible interactions with X . campestris pv . vesicatoria . The accumulation of FT and CT was preceded by an increase in the extractable activity of tyrosine decarboxylase as well as increases in the transcription of genes encoding phenylalanine ammonia-lyase and tyramine hydroxycinnamoyl transferase . No such changes were detected in compatible interactions . Very rapid accumulation of FT and CT occurred (4 h postinoculation) in pepper in response to a X . campestris pv . campestris mutant carrying a deletion of the hrp gene cluster . In contrast, hrp mutants of X . campestris pv . vesicatoria failed to elicit the production of FT and CT . These observations suggest the existence of hrp gene-dependent and -independent activation mechanisms of a defense response involving hydroxycinnamoyltyramines. Mol Plant Microbe Interact, 2001 Jun, 14(6), 768 - 74 Expression of the gum operon directing xanthan biosynthesis in Xanthomonas campestris and its regulation in planta; Vojnov AA et al.; The gum gene cluster of Xanthomonas campestris pv . campestris comprises 12 genes whose products are involved in the biosynthesis of the extracellular polysaccharide xanthan . These genes are expressed primarily as an operon from a promoter upstream of the first gene, gumB . Although the regulation of xanthan synthesis in vitro has been well studied, nothing is known of its regulation in planta . A reporter plasmid was constructed in which the promoter region of the gum operon was fused to gusA . In liquid cultures, the expression of the gumgusA reporter was correlated closely with the production of xanthan, although a low basal level of beta-glucuronidase activity was seen in the absence of added carbon sources when xanthan production was very low . The expression of the gumgusA fusion also was subject to positive regulation by rpfF, which is responsible for the synthesis of the diffusible signal factor (DSF) . The expression of the gumgusA fusion in bacteria recovered from inoculated turnip leaves was maximal at the later phases of growth and was subject to regulation by rpfF . These results provide indirect support for the operation of the DSF regulatory system in bacteria in planta. Mikrobiologiia, 2001 Mar-Apr, 70(2), 270 - 4 {Role of the surface and extracellular substances of the phytopathogenic bacterium Xanthomonas campestris in its interactions with cabbage plants}; Stadnik GI et al.; Changes in some physiological and biochemical characteristics of cabbage (cv . Slava) seedling roots in response to inoculation with the phytopathogen Xanthomonas campestris and its surface and extracellular substances were evaluated . Seven days after the inoculation, the growth of the roots was slightly suppressed and they contained increased amounts of peroxidase . The effect of the lipopolysaccharides stripped from the cell surface or isolated from the culture liquid of X . campestris was similar to that of the whole cells of the phytopathogen . The bacterial lectin isolated from the cell surface material did not induce any defense response in cabbage plants but, presumably, could play a role in the contact interactions between bacteria and plants. Mol Genet Genomics, 2001 Mar, 265(1), 118 - 25 Chromosome landing at the bacterial blight resistance gene Xa4 locus using a deep coverage rice BAC library; Wang W et al.; Xa4 is a dominantly inherited rice gene that confers resistance to Philippine race 1 of the bacterial blight pathogen Xanthomonas oryzae pv . oryzae in rice . In order to isolate the gene by positional cloning, a bacterial artificial chromosome (BAC) library was constructed from genomic DNA isolated from an Xa4-harboring accession, IRBB56 . The library contains 55,296 clones with an average insert size of 132 kb, providing 14 rice genome equivalents . Three DNA markers closely linked to Xa4 were used to screen the library . The marker RS13, a resistance gene analogue that co-segregates with Xa4, identified 18 clones, of which four and six, respectively, were simultaneously detected by the other two markers, G181 and L1044 . Fingerprinting and Southern analysis indicated that these clones overlapped and define an interval spanning 420 kb . In an F2 population derived from an indica variety, IR24, and its Xa4-containing near isogenic line (NIL), IRBB4, the susceptible plants were screened in order to map the Xa4 gene genetically and physically . Out of 24 insert ends isolated from the BACs in the contig, three revealed polymorphisms between IR24 and IRBB4 . Two insert ends, 56M22F and 26D24R, flanked Xa4 on each side . Based on the overlap of the BACs, six overlapping clones were considered to include the Xa4 allele, one of which, 106P13, was chosen for further investigation. Mol Genet Genomics, 2001 Apr, 265(2), 316 - 26 Structural and functional characterization of the lexA gene of Xanthomonas campestris pathovar citri; Yang YC et al.; The role of the LexA protein and, specifically, its effect on recA expression were analyzed in Xanthomonas campestris pathovar citri (X.c . pv . citri) . Overexpression of LexA from X.c . pv . citri, in the plant pathogen, as well as in Escherichia coli, results in increased sensitivity to the DNA-damaging agents mitomycin C and ultraviolet radiation, indicating that the recombinant X.c . pv . citri LexA protein is functional in a different bacterial species . Immunoblot analysis revealed that the overexpressed LexA protein functioned as a repressor of recA expression in X.c . pv . citri, and that the mitomycin C-induced increase in the abundance of RecA was accompanied by specific proteolysis of LexA that required RecA . Although the LexA protein from X.c . pv . citri also blocked the expression of recA in E . coli, the E . coli RecA protein was not able to support the autocatalytic cleavage of LexA from the plant pathogen . The transcription start site of the X.c . pv . citri lexA gene was identified, and the region upstream of this gene was shown to confer responsiveness to mitomycin C on a luciferase reporter gene construct . Electrophoretic mobility-shift assays demonstrated that X.c . pv . citri LexA interacts with the promoter region of X.c . pv . citri lexA, as well as with those of the recA genes of X.c . pv . citri and E . coli . These results indicate that LexA functions as a repressor of gene expression in X.c . pv . citri just as it does in E . coli. J Mol Microbiol Biotechnol, 2001 Jul, 3(3), 471 - 81 The early stages of filamentous phage phiLf infection require the host transcription factor, Clp; Lee TC et al.; Xanthomonas campestris pv . campestris produces great amounts of an exopolysaccharide (EPS), xanthan gum . Eight eps loci involved in biosynthesis of the EPS were previously located in the chromosome map of strain Xc17 . In this study, the eps8 region was cloned, sequenced and found to contain a crp homologue whose deduced amino acid sequence possesses similarity to that of the cyclic AMP receptor protein of bacteria, with the highest identity (97%) being shared with the X . campestris pv . campestris B-1459 clp gene previously shown to be involved in pathogenicity and regulation of the production of xanthan, extracellular enzymes, and pigment (de Crecy-Lagard V., Glaser P., Lejeune P., Sismeiro O., Barber C.E., Daniels M.J., and Danchin A., J . Bacteriol . 172:5877-5883, 1990) . Based on sequence identity, pleiotropic effects of the mutation, the ability to complement an Escherichia coli cya crp mutant, and Southern hybridization detecting a single copy in the chromosome, we propose this eps8 gene to be the Xc17 clp . In addition to the previously reported properties, a clp mutant (AU56E) cannot be plaqued with filamentous phage phiLf, although it retains the capability to support phiLf DNA replication and release authentic phage particles upon electroporation of the RF DNA . Infective center assays demonstrated that the frequency of infection is 460- to 7,500-fold lower in AU56E compared to that in the wild-type Xc17 . Electron microscopy, which showed no surface appendages other than the monotrichous flagellum, confirmed that AU56E drastically diminishes in the efficiency of phage adsorption . These results suggest Clp to be regulating the biosynthesis of the primary receptor, most likely a type IV pilus . Upstream to clp is a homologue of the E . coli speD gene required for spermidine synthesis . Mutation of the clp flanking regions and transcriptional analyses suggest clp to be monocistronic and the only gene contained at the eps8 locus. J Appl Microbiol, 2001 May, 90(5), 829 - 35 The effect of olive mill wastewaters variability on xanthan production; Lopez MJ et al.; AIMS: Xanthan production by Xanthomonas campestris from several olive mill wastewaters (OMW) was investigated . METHODS AND RESULTS: Maximum xanthan production of 4 g l(-1) was obtained in media with 50% OMW as sole source of nutrients . OMW storage decreased effluent quality for xanthan production . The range of effluent concentration for X . campestris growth and xanthan production varied depending on OMW extraction METHOD: Wastewaters from press and two-phase extraction methods required higher dilution rates (< 10%) than those from the three-phase extraction method (50%) . Nitrogen supplementation improved xanthan production in press and two-phase OMW . CONCLUSION: Factors affecting wastewaters composition, namely, waste storage, time of olive harvesting, and method for oil extraction, were found to influence xanthan production in shake-flask cultures . SIGNIFICANCE AND IMPACT OF THE STUDY: Conditions for xanthan production from OMW should be optimized in accordance with the nature of the waste material. Water Res, 2001 May, 35(7), 1828 - 30 Xanthomonas campestris strain selection for xanthan production from olive mill wastewaters; Lopez MJ et al.; Four Xanthomonas campestris strains were tested in olive mill wastewaters (OMW) for xanthan production . Differences among strains were found in the range of tolerance to OMW concentration and xanthan amount obtained . X . campestris NRRL B-1459 S4LII was chosen by its capability for xanthan production from 50-60% OMW as the sole nutrient source. Mol Plant Microbe Interact, 2001 Apr, 14(4), 487 - 95 Reduced expression of the tomato ethylene receptor gene LeETR4 enhances the hypersensitive response to Xanthomonas campestris pv . vesicatoria; Ciardi JA et al.; The hypersensitive response (HR) involves rapid death of cells at the site of pathogen infection and is thought to limit pathogen growth through the plant . Ethylene regulates senescence and developmental programmed cell death, but its role in hypersensitive cell death is less clear . Expression of two ethylene receptor genes, NR and LeETR4, is induced in tomato (Lycopersicon esculentum cv . Mill) leaves during an HR to Xanthomonas campestris pv . vesicatoria, with the greatest increase observed in LeETR4 . LeETR4 antisense plants previously were shown to exhibit increased sensitivity to ethylene . These plants also exhibit greatly reduced induction of LeETR4 expression during infection and an accelerated HR at inoculum concentrations ranging from 10(5) to 10(7) CFU/ml . Increases in ethylene synthesis and pathogenesis-related gene expression are greater and more rapid in infected LeETR4 antisense plants, indicating an enhanced defense response . Populations of avirulent X . campestris pv . vesicatoria decrease more quickly and to a lower level in the transgenic plants, indicating a greater resistance to this pathogen . Because the ethylene action inhibitor 1-methylcyclopropene alleviates the enhanced HR phenotype in LeETR4 antisense plants, these changes in pathogen response are a result of increased ethylene sensitivity. Plant J, 2001 Mar, 25(5), 529 - 40 Effects of urate, a natural inhibitor of peroxynitrite-mediated toxicity, in the response of Arabidopsis thaliana to the bacterial pathogen Pseudomonas syringae; Alamillo JM et al.; Urate, a natural peroxynitrite scavenger, has been used to investigate the possible role of peroxynitrite during plant-pathogen interactions . Urate greatly reduced lesion formation in Arabidopsis leaves treated with an abiotic peroxynitrite-generating system or with a peroxynitrite solution, indicating that it can act as an effective scavenger in planta . In the interaction with the avirulent Pseudomonas syringae pv . phaseolicola (avrRPM1+), cell death in the inoculated area was strongly reduced by urate, without compromising disease resistance . In contrast, urate promoted discrete cell death in response to an isogenic Pseudomonas syringae (avrRPM1-), which did not trigger an HR when inoculated alone, and it induced resistance and arrest of pathogen growth . Scavenging of peroxynitrite did not modify the response of Arabidopsis to an avirulent strain of Xanthomonas campestris pv campestris, that showed a high resistance to NO and peroxynitrite . Our data indicate that peroxynitrite plays a significant role in the responses of plants to Pseudomonas syringae. Plant Sci, 2001 Apr, 160(5), 1035 - 1042 Transgenic rice plants expressing the ferredoxin-like protein (AP1) from sweet pepper show enhanced resistance to Xanthomonas oryzae pv . oryzae; Tang K et al.; We used particle bombardment to cotransform mature seed-derived rice callus (Oryza sativa L., ssp . japonica, cv . Eyi 105) with plasmids containing the linked marker genes gusA and hpt, and the ap1 gene encoding an amphipathic protein previously shown to delay the hypersensitive response induced in non-host plants by the pathogen Pseudomonas syringae pv . syringae (Pss) . Thirty-two independent lines of transgenic rice plants were regenerated, and 27 of these lines carried all three transgenes as shown by molecular analysis . A bacterial blight inoculation test was carried out on ten lines . In each case, plants carrying the ap1 gene showed enhanced resistance to Xanthomonas oryzae pv . oryzae (Xoo) race 6 at various levels . This suggests the ap1 gene could be a useful candidate for genetic engineering strategies in rice to provide bacterial blight resistance. FEMS Microbiol Lett, 2001 Apr 1, 197(1), 35 - 40 Xanthomonas oryzae pv . oryzae recA is transcribed and regulated from multiple promoters; Sukchawalit R et al.; Transcription regulation of Xanthomonas oryzae pv . oryzae recA was characterized . Primer extension experiments showed that recA is transcribed from three promoters designated P1, P2 and P3 . The sequences of -10 and -35 regions of these promoters have moderate homology to the proposed consensus sequence for a Xanthomonas promoter . Putative SOS boxes were identified in the vicinity of P1 and P2 promoters . Deletion analysis and in vivo monitoring of promoter activity of these promoters revealed that the three promoters have different characteristics . P1 and P2 show stress-inducible high and low promoter strengths respectively . P3 is a non-inducible moderate promoter strength . These promoters are regulated by two SOS boxes . The multiplicity of promoters and SOS boxes provides back-up systems to ensure proper regulation of recA. Curr Microbiol, 2001 Mar, 42(3), 155 - 9 Xanthomonas albilineans diversity and identification based on rep-PCR fingerprints; Lopes SA et al.; PCR with BOX and ERIC primers was used to analyze DNA of Xanthomonas albilineans and other bacteria associated with sugarcane . Generated fingerprints permitted clear separation of X . albilineans from other bacteria and revealed variation within the species . Good agreement between fingerprint groups and geographic origin and serovars was observed. Mol Cells, 2001 Feb 28, 11(1), 115 - 21 Molecular characterization of the cDNA encoding an acidic isoform of PR-1 protein in rice; Kim S et al.; Rice cDNA encoding an acidic type of pathogenesis-related protein-1 (PR-1a) was cloned and characterized . The deduced PR-1a protein consisted of 168 amino acid residues, including 24 hydrophobic signal sequences at the N-terminus . The predicted molecular mass of the PR-1a was 15,728 Da with a theoretical pI of 4.5, an indication of an acidic protein . The PR-la showed high homology to an acidic PR-1 of Zea mays (74%) and a previously identified basic type PR-1 of rice (64%) . Both rice PR-1 and PR-1a genes were found to exist as small gene families through Southern blot hybridization analyses . The PR-1 mRNA was accumulated only in leaves, while the PR-1a transcript was accumulated throughout the plant at a low level . Expression of both PR-1 genes was induced by infections of the rice blast fungus, Magnaporthe grisea, or the bacterial leaf blight pathogen, Xanthomonas oryzae pv . oryzae, and the treatment of benzo (1, 2, 3) thiadiazole-7-carbothioic acid S-ethyl ester, H2O2, or CuSO4 . The expression of both PR-1 genes was higher and more rapidly induced in an incompatible interaction than in a compatible interaction in the rice M . grisea interactions. Enzyme Microb Technol, 2001 Mar 8, 28(4-5), 439 - 445 Production of inulooligosaccharides from chicory extract by endoinulinase from Xanthomonas oryzae No . 5; Cho YJ et al.; Inulooligosaccharides (IOS) production from chicory extract was carried out using endoinulinase obtained from a new isolate, Xanthomonas oryzae No . 5 . The IOS production from chicory extract was maximum when 50 g/liter of chicory extract was utilized as the substrate . As the substrate concentration increased, the IOS production accordingly decreased probably due to substrate inhibition . For a comparative study, enzyme reactions were carried out from pure inulin as substrate . Though total IOS contents indicated higher IOS yield with pure inulin compared to that of chicory extract, the distribution of inulooligosaccharide components between pure inulin and chicory extract was not significantly different; i.e . DP5 and higher oligosaccharides are major products in case of both chicory extract and pure inulin as substrate . A considerable amount of oligofructose (about 30%, w/w), which were originally present in chicory extract, resulted in the change of the enzyme kinetics . A reaction pH 7 was found to be most suitable for enzyme reaction . The initial reaction rates increased with increasing enzyme dosage, although the relative composition of the IOS produced remain unchanged. Microbiology, 2001 Mar, 147(Pt 3), 631 - 42 A multifunctional polyketide-peptide synthetase essential for albicidin biosynthesis in Xanthomonas albilineans; Huang G et al.; Albicidins, a family of potent antibiotics and phytotoxins produced by the sugarcane leaf scald pathogen Xanthomonas albilineans, inhibit DNA replication in bacteria and plastids . A gene located by Tn5-tagging was confirmed by complementation to participate in albicidin biosynthesis . The gene (xabB) encodes a large protein (predicted M:(r) 525695), with a modular architecture indicative of a multifunctional polyketide synthase (PKS) linked to a non-ribosomal peptide synthetase (NRPS) . At 4801 amino acids in length, XabB is the largest reported PKS-NRPS . Twelve catalytic domains in this multifunctional enzyme are arranged in the order N terminus-acyl-CoA ligase (AL)-acyl carrier protein (ACP)-beta-ketoacyl synthase (KS)-beta-ketoacyl reductase (KR)-ACP-ACP-KS-peptidyl carrier protein (PCP)-condensation (C)-adenylation-PCP-C . The modular architecture of XabB indicates likely steps in albicidin biosynthesis and approaches to enhance antibiotic yield . The novel pattern of domains, in comparison with known PKS-NRPS enzymes for antibiotic production, also contributes to the knowledge base for rational design of enzymes producing novel antibiotics. Carbohydr Res, 2001 Jan 30, 330(2), 215 - 21 Structures of the O4 and O18 antigens of Stenotrophomonas maltophilia: a case of enantiomeric repeating units; Winn AM et al.; The O-specific side-chain polymers of lipopolysaccharides from the reference strains for Stenotrophomonas maltophilia serogroups 04 and O18 are both xylosylated rhamnans . In the 04 polymer, both sugar components are the D isomers, whereas the O18 polymer contains only the L isomers . By means of NMR spectroscopy, methylation analysis and Smith degradation, the repeating unit of the 04 polymer was identified as a doubly-branched pentasaccharide of the structure shown below . The O18 polymer is based on the enantiomeric pentasaccharide, but the xylosyl substituent at the 4-position is apparently absent from some units . The polymers closely resemble the O antigens found in Xanthomonas campestris pathovars . {structure: see text} Mol Plant Microbe Interact, 2001 Feb, 14(2), 204 - 13 Isolation of a Xanthomonas oryzae pv . oryzae flagellar operon region and molecular characterization of flhF; Shen Y et al.; An 8.1-kb DNA fragment from Xanthomonas oryzae pv . oryzae that contains six open reading frames (ORF) was cloned . The ORF encodes proteins similar to flagellar proteins FlhB, FlhA, FlhF, and FliA, plus two proteins of unknown function, ORF234 and ORF319, from Bacillus subtilis and other organisms . These ORF have a similar genomic organization to those of their homologs in other bacteria . TheflhF gene product, FlhF, has a GTP-binding motif conserved in its homologs . Unlike its homologs, however, X . oryzae pv . oryzae FlhF carries two transmembrane-like domains . Insertional mutations of theflhF gene with the omega cassette or the kanamycin resistance gene significantly retard but do not abolish the motility of the bacteria . Complementation of the mutants with the wild-type flhF gene restored the motility . The X . oryzae pv . oryzae FlhF interacts with itself; the disease resistance gene product XA21; and a protein homologous to the Pill protein of Pseudomonas aeruginosa, XooPilL, in the yeast two-hybrid system . The biological relevance of these interactions remains to be determined. Plant J, 2001 Feb, 25(3), 315 - 23 Ethylene-dependent salicylic acid regulates an expanded cell death response to a plant pathogen; O'Donnell PJ et al.; The molecular events associated with susceptible plant responses to disease-causing organisms are not well understood . We have previously shown that ethylene-insensitive tomato plants infected with Xanthomonas campestris pv . vesicatoria have greatly reduced disease symptoms relative to wild-type cultivars . Here we show that salicylic acid (SA) is also an important component of the susceptible disease response . SA accumulates in infected wild-type tissues and is correlated with necrosis but does not accumulate in ethylene-insensitive plants . Exogenous feeding of SA to ethylene-deficient plants restores necrosis, indicating that reduced disease symptoms are associated with failure to accumulate SA . These results indicate a mechanism for co-ordination of phytohormone signals that together constitute a susceptible response to pathogens. Curr Microbiol, 2001 Apr, 42(4), 257 - 63 Molecular characterization and expression of the recX gene of Xanthomonas campestris pv . citri; Yang MK et al.; Two genes important in DNA repair, recA and lexA, were recently identified in Xanthomonas campestris pathovar citri (X.c . pv . citri) . An open reading frame located immediately downstream of lexA and recA has now been isolated from this pathovar and characterized . This 486-bp open reading frame encodes a protein of 162 amino acids and shares substantial sequence similarity with recX of other bacterial species . The X.c . pv . citri RecX protein was overexpressed in Escherichia coli and purified; SDS-polyacrylamide gel electrophoresis revealed a molecular size of 18 kDa for the purified protein . Whereas Northern blot analysis failed to detect recX mRNA in X.c . pv . citri, recX transcripts were detected in this pathovar by reverse transcription and polymerase chain reaction analysis . The increased abundance of recX transcript in X.c . pv . citri revealed that the recX promoter was activated by exposure of cells to DNA-damaging agents . Southern blot and polymerase chain reaction analyses revealed the presence of a recX-related gene in all nine additional X . campestris pathovars tested . The genetic arrangement of lexA-recA-recX was apparent in X . campestris and each of the three genes transcribed from their own promoters. Microbiology, 2001 Feb, 147(Pt 2), 491 - 8 Catalase has a novel protective role against electrophile killing of Xanthomonas; Vattanaviboon P et al.; The ability of XANTHOMONAS: campestris pv . phaseoli to protect itself against lethal concentrations of man-made (N:-ethylmaleimide, NEM) and endogenously produced (methylglyoxal, MG) electrophiles was investigated . Pretreatment of X . c . pv . phaseoli with a low concentration of NEM induced protection against lethal concentrations of NEM and MG . MG pretreatment weakly induced protection against NEM but not against MG itself . NEM-induced protection against electrophile killing required new protein synthesis and was abolished by the addition of a protein synthesis inhibitor . By contrast, MG-induced protection against NEM killing was independent of de novo protein synthesis . X . c . pv . phaseoli harbouring an expression vector carrying a catalase gene was over 100-fold more resistant to MG and NEM killing . High expression levels of genes for other peroxide-protective enzymes, such as those for alkyl hydroperoxide reductase (ahpC and ahpF) and ohr, failed to protect against electrophile killing . Thus, catalase appears to have a novel protective role(s) against electrophile toxicity . This finding suggests that in X . c . pv . phaseoli NEM and MG toxicity might involve accumulation and/or increased production of H(2)O(2) . This idea was supported by the observation that addition of 10 mM sodium pyruvate, a compound that can react chemically with peroxide or hydroxyl radical scavengers (DMSO and glycerol), was found to protect XANTHOMONAS: from electrophile killing . The protective role of catalase and the role of H(2)O(2) in electrophile toxicity are novel observations and could be generally important in other bacteria . In addition, unlike other bacteria, XANTHOMONAS: in stationary phase was more susceptible to electrophile killing compared to cells in exponential phase. Pediatr Nephrol, 2000 Mar, 14(3), 198 - 202 Management of hemodialysis catheter-related bacteremia--a 10-year experience; Chawla PG et al.; Between January 1986 and December 1995, 18 episodes of bacteremia occurred in our pediatric patients undergoing chronic hemodialysis on an outpatient basis . Seven episodes were caused by coagulase-negative Staphylococcus, 6 by Staphylococcus aureus, 2 by Mycobacterium, and 1 each by Pseudomonas, Xanthomonas, and Enterococcus . In 6 cases, the catheter was retained with antimicrobial therapy alone, whereas 12 cases required removal of the catheter after some period of time . The subset of cases in which catheter removal was necessary included 2 cases of Mycobacterium fortuitum complex and 5 cases of Staphylococcus aureus . We found that Staphylococcus aureus bacteremia may be cleared with antibiotic therapy alone in a minority of cases (17%) . In the 6 cases in which catheters were retained and infections cleared, the maximum length of time to sterilization of blood with appropriate antibiotics was 48 h. Can J Microbiol, 2000 Dec, 46(12), 1171 - 5 Evidence for conserved tRNA genes in the 16S-23S rDNA spacer sequence and two rrn operons of Xylella fastidiosa; Chen J et al.; The 16S-23S rDNA spacer of the type strain (ATCC 35879) of Xylella fastidiosa was amplified by PCR, cloned, and sequenced . The spacer sequence (455 bp) contains two tRNA (tRNA(ala) and tRNA(ile)) genes . Identical tRNA genes were also found in the 16S-23S spacer sequences of all the 51 strains of X . fastidiosa retrieved from the GenBank database . At this particular locus, the gene order of tRNA(ala)-tRNA(ile) is conserved among all the studied strains of Xylella and Xanthomonas, and different from those of other bacteria . Sequence analysis showed that Xanthomonas is the most closely related genus . Results from restriction endonuclease analysis suggested the presence of two rrn operons in the genome of a Xylella fastidiosa Pierce's disease strain. Plant J, 2000 Dec, 24(6), 749 - 61 hxc2, an Arabidopsis mutant with an altered hypersensitive response to Xanthomonas campestris pv . campestris; Godard F et al.; A chemical mutagenized population of Arabidopsis Col-0-gl plants was screened for an altered hypersensitive response (HR) after spray inoculation with an HR-inducing isolate of Xanthomonas campestris pv . campestris (strain 147) . Three classes of mutant were identified: those exhibiting an HR- phenotype or partial loss of HR; hyper-responsive mutants showing necrotic lesions rapidly leading to the collapse of leaves; and susceptible mutants . One mutant belonging to the susceptible class, hxc-2, was extensively characterized . The compatible phenotype observed several days after initiation of the interaction was confirmed by measurement of in planta bacterial growth and use of bacterial strains constitutively expressing the GUS reporter gene . In the same way, accumulation of autofluorescent compounds, salicylic acid production and defence gene expression in the mutant were found to be similar to that displayed by the susceptible ecotype . Inoculation of hxc-2 with different avirulent bacteria suggests that the mutation is specific for the interaction with the Xcc 147 strain, although the mutation has been shown to affect a single dominant locus, different from the resistance locus defined by genetic analysis of resistance to Xcc 147 . Genetic mapping of the mutation indicated that it is located on chromosome III, defining a previously unknown resistance function in response to X . c . campestris. J Bacteriol, 2001 Jan, 183(2), 528 - 35 Involvement of the XpsN protein in formation of the XpsL-xpsM complex in Xanthomonas campestris pv . campestris type II secretion apparatus; Lee HM et al.; The xps gene cluster is required for the second step of type II protein secretion in Xanthomonas campestris pv . campestris . Deletion of the entire gene cluster caused accumulation of secreted proteins in the periplasm . By analyzing protein abundance in the chromosomal mutant strains, we observed mutual dependence for normal steady-state levels between the XpsL and the XpsM proteins . The XpsL protein was undetectable in total lysate prepared from the xpsM mutant strain, and vice versa . Introduction of the wild-type xpsM gene carried on a plasmid into the xpsM mutant strain was sufficient for reappearance of the XpsL protein, and vice versa . Moreover, both XpsL and XpsM proteins were undetectable in the xpsN mutant strain . They were recovered either by reintroducing the wild-type xpsN gene or by introducing extra copies of wild-type xpsL or xpsM individually . Overproduction of wild-type XpsL and -M proteins simultaneously, but not separately, in the wild-type strain of X . campestris pv . campestris caused inhibition of secretion . Complementation of an xpsL or xpsM mutant strain with a plasmid-borne wild-type gene was inhibited by coexpression of XpsL and XpsM . The presence of the xpsN gene on the plasmid along with the xpsL and the xpsM genes caused more severe inhibition in both cases . Furthermore, complementation of the xpsN mutant strain was also inhibited . In both the wild-type strain and a strain with the xps gene cluster deleted (XC17433), carrying pCPP-LMN, which encodes all three proteins, each protein coprecipitated with the other two upon immunoprecipitation . Expression of pairwise combinations of the three proteins in XC17433 revealed that the XpsL-XpsM and XpsM-XpsN pairs still coprecipitated, whereas the XpsL-XpsN pair no longer coprecipitated. Appl Environ Microbiol, 2001 Jan, 67(1), 245 - 50 Pigment and virulence deficiencies associated with mutations in the aroE gene of Xanthomonas oryzae pv . oryzae; Goel AK et al.; Xanthomonadins are yellow, membrane-bound pigments produced by members of the genus Xanthomonas . We identified an ethyl methanesulfonate-induced Xanthomonas oryzae pv . oryzae mutant (BXO65) that is deficient for xanthomonadin production and virulence on rice, as well as auxotrophic for aromatic amino acids (Pig(-) Vir(-) Aro(-)) . Reversion analysis indicated that these multiple phenotypes are due to a single mutation . A genomic library of the wild-type strain was used to isolate a 7.0-kb clone that complements BXO65 . By transposon mutagenesis, marker exchange, sequence analysis, and subcloning, the complementing activity was localized to a 849-bp open reading frame (ORF) . This ORF is homologous to the aroE gene, which encodes shikimate dehydrogenase in various bacterial species . Shikimate dehydrogenase activity was present in the wild-type strain and the mutant with the complementing clone, whereas no activity was found in BXO65 . This clone also complemented an Escherichia coli aroE mutant for prototrophy, indicating that aroE is functionally conserved in X . oryzae pv . oryzae and E . coli . The nucleotide sequence of the 2.9-kb region containing aroE revealed that a putative DNA helicase gene is located adjacent to aroE . Our results indicate that aroE is required for normal levels of virulence and xanthomonadin production in X . oryzae pv . oryzae. Carbohydr Res, 2000 Dec 1, 329(4), 831 - 8 Structure of the O-specific polysaccharides of the lipopolysaccharides of Xanthomonas campestris pv . vignicola GSPB 2795 and GSPB 2796; Senchenkova SN et al.; The O-specific polysaccharides of Xanthomonas campestris pv . vignicola GSPB 2795 and GSPB 2796 were studied by sugar and methylation analyses, Smith degradation, ID, 2D 1H and 13C NMR spectroscopy . It was found that the polysaccharides are similar branched D-rhamnans lacking strict regularity, and their structures can be described as follows: {carbohydrate equation: see text} where Rha(v) is present in a non-stoichiometric amount, which varies from strain to strain. Mol Microbiol, 2000 Dec, 38(5), 986 - 1003 A two-component system involving an HD-GYP domain protein links cell-cell signalling to pathogenicity gene expression in Xanthomonas campestris; Slater H et al.; The synthesis of extracellular enzymes and extracellular polysaccharide (EPS) in Xanthomonas campestris pv . campestris (Xcc) is regulated by a cluster of genes called rpf (for regulation of pathogenicity factors) . Two of the genes, rpfF and rpfB, have previously been implicated in the synthesis of a diffusible regulatory molecule, DSF . Here, we describe a screen of transposon insertion mutants of Xcc that identified two DSF-overproducing strains . In each mutant, the gene disrupted is rpfC, which encodes a hybrid two-component regulatory protein in which the sensor and regulator domains are fused and which contains an additional C-terminal phosphorelay (HPt) domain . We show that rpfC is in an operon with rpfH and rpfG . The predicted protein RpfG has a regulatory input domain attached to a specialized version of an HD domain, previously suggested to function in signal transduction . The predicted protein RpfH is structurally related to the sensory input domain of RpfC . We show that RpfC and RpfG act positively to regulate the synthesis of extracellular enzymes and EPS, but that RpfC acts negatively to regulate the synthesis of DSF . We propose that RpfGHC is a signal transduction system that couples the synthesis of pathogenicity factors to sensing of environmental signals that may include DSF itself. Yeast, 2000 Dec, 17(4), 263 - 71 Xylella genomics and bacterial pathogenicity to plants; Dow JM et al.; Xylella fastidiosa, a pathogen of citrus, is the first plant pathogenic bacterium for which the complete genome sequence has been published . Inspection of the sequence reveals high relatedness to many genes of other pathogens, notably Xanthomonas campestris . Based on this, we suggest that Xylella possesses certain easily testable properties that contribute to pathogenicity . We also present some general considerations for deriving information on pathogenicity from bacterial genomics . Int Microbiol, 1999 Jun, 2(2), 111 - 4 Evaluation of Xanthomonas campestris survival in a soil microcosm system; Lopez NI et al.; Xanthomonas campestris pv . campestris is a pathogen of cruciferous plants . We studied the survival of the wild type strain and mutant derivatives which are deficient in exopolysaccharide (EPS) or in extracellular protease synthesis in soil microcosms in order to test the hypothesis that, in this environment, adherence to soil particles and scavenging of nutrients are very important strategies for bacterial survival . In sterile soil microcosms, differences in survival were only observed between the EPS producer and its mutant . In non-sterile soil experiments, survival of Prt- mutant was similar to EPS- mutant, suggesting that both characteristics have a strong influence in survival in the presence of the natural bacterial community . Bacterial decrease represented by the slope of regression lines was higher in non-sterile soil microcosms due to the influence of biotic interactions. Syst Appl Microbiol, 2000 Oct, 23(3), 349 - 54 16S rDNA sequence analysis of Xylella fastidiosa strains; Chen J et al.; The 16S rDNA encoding the small subunit ribosomal RNA were amplified by PCR, cloned, and sequenced from 16 strains of Xylella fastidiosa originating from nine different hosts . In pair-wise comparisons, X . fastidiosa strains showed a maximum variation of 1.0% or 14 nucleotide positions . When all 16 sequences were considered as a set, 54 variable positions were found . Analysis of the sequence data indicated that the X . fastdiosa strains formed three rDNA groups . Group one includes Pierce's disease and mulberry leaf scorch strains; Group two, periwinkle wilt, plum leaf scald, phony peach, oak leaf scorch, and elm leaf scorch strains; and Group three, citrus variegated chlorosis and coffee leaf scorch strains . All X . fastidiosa strains exhibited significantly higher levels of sequence heterogeneity (63 to 83 nucleotide positions) when compared to species from Xanthomonas and Stenotrophomonas . Our data demonstrate that 16S rDNA sequence data could provide valuable information for future classification of X . fastidiosa at the sub-species level. Mol Plant Microbe Interact, 2000 Dec, 13(12), 1346 - 55 Xv4-vrxv4: a new gene-for-gene interaction identified between Xanthomonas campestris pv . vesicatoria race T3 and wild tomato relative Lycopersicon pennellii; Astua-Monge G et al.; Strains of tomato race 3 (T3) of Xanthomonas campestris pv . vesicatoria elicit a hypersensitive response (HR) in leaves of Lycopersicon pennellii LA716 . Genetic segregation of the resistance exhibited ratios near 3:1 in F2 populations, which confirmed that a single dominant gene controlled the inheritance of this trait . With the aid of a collection of introgression lines, restriction fragment length polymorphism, and cleaved amplified polymorphic sequence markers, the resistance locus was located on chromosome 3 between TG599 and TG134 . An avirulence gene named avrXv4 was also isolated by mobilizing a total of 600 clones from a genomic DNA library of the T3 strain 91-118 into the X . campestris pv . vesicatoria strain ME90, virulent on L . pennellii . One cosmid clone, pXcvT3-60 (29-kb insert), induced HR in resistant plants . The avirulent phenotype of pXcvT3-60 was confirmed by comparing growth rates in planta and electrolyte leakages among transconjugants carrying a mutated or intact clone with the wild-type T3 strain 91-118 . A 1.9-kb DNA fragment contained within a 6.8-kb active subclone was sequenced and was determined to carry an open reading frame of 1,077 bp . The predicted AvrXv4 protein exhibits high similarity to members of an emerging new family of bacterial proteins from plant and mammalian pathogens comprising AvrRxv, AvrBsT, YopJ, YopP, AvrA, and YL40. Mol Plant Microbe Interact, 2000 Dec, 13(12), 1322 - 9 Xanthomonas oryzae pv . oryzae avirulence genes contribute differently and specifically to pathogen aggressiveness; Bai J et al.; Genomic copies of three Xanthomonas oryzae pv . oryzae avirulence (avr) genes, avrXa7, avrXal0, and avrxa5, and four homologous genes, aB3.5, aB3.6, aB4.3, and aB4.5, were mutagenized individually or in combination to study the roles of avr genes in one component of pathogen fitness, i.e., aggressiveness or the amount of disease X . oryzae pv . oryzae causes in susceptible rice lines . These X . oryzae pv . oryzae genes are members of the highly related Xanthomonas avrBs3 gene family . Compared to the wild-type strain, X . oryzae pv . oryzae strains with mutations in avrXa7, avrxa5, and the four homologous genes caused shorter lesions on rice line IR24, which contains no resistance genes relevant to the wild-type strain . The contribution of each gene to lesion length varied, with avrXa7 contributing the most and avrXal0 showing no measurable effect on aggressiveness . The functional, plasmidborne copies of avrXa7, aB4.5, and avrxa5 restored aggressiveness only to strains with mutations in avrXa7, aB4.5, and avrxa5, respectively . Mutations in avrXa7 were not complemented by plasmids carrying any other avr gene family members . These data indicate that some, but not all, avr family members contribute to pathogen aggressiveness and that the contributions are quantitatively different . Furthermore, despite their sequence similarity, the aggressiveness functions of these gene family members are not interchangeable . The results suggest that selection and pyramiding resistance genes can be guided by the degree of fitness penalty that is empirically determined in avr gene mutations. Appl Environ Microbiol, 2000 Dec, 66(12), 5123 - 7 Biological role of xanthomonadin pigments in Xanthomonas campestris pv . campestris; Poplawsky AR et al.; Previous studies have indicated that the yellow pigments (xanthomonadins) produced by phytopathogenic Xanthomonas bacteria are unimportant during pathogenesis but may be important for protection against photobiological damage . We used a Xanthomonas campestris pv . campestris parent strain, single-site transposon insertion mutant strains, and chromosomally restored mutant strains to define the biological role of xanthomonadins . Although xanthomonadin mutant strains were comparable to the parent strain for survival when exposed to UV light; after their exposure to the photosensitizer toluidine blue and visible light, survival was greatly reduced . Chromosomally restored mutant strains were completely restored for survival in these conditions . Likewise, epiphytic survival of a xanthomonadin mutant strain was greatly reduced in conditions of high light intensity, whereas a chromosomally restored mutant strain was comparable to the parent strain for epiphytic survival . These results are discussed with respect to previous results, and a model for epiphytic survival of X . campestris pv . campestris is presented. Proc Natl Acad Sci U S A, 2000 Dec 5, 97(25), 13500 - 5 Predicting durability of a disease resistance gene based on an assessment of the fitness loss and epidemiological consequences of avirulence gene mutation; Vera Cruz CM et al.; Durability of plant disease resistance (R) genes may be predicted if the cost of pathogen adaptation to overcome resistance is understood . Adaptation of the bacterial blight pathogen, Xanthomonas oryzae pv . oryzae (Xoo), to virulence in rice is the result of the loss of pathogen avirulence gene function, but little is known about its effect on aggressiveness under field conditions . We evaluated the cost in pathogenic fitness (aggressiveness and persistence) associated with adaptation of Xoo to virulence on near-isogenic rice lines with single R genes (Xa7, Xa10, and Xa4) at two field sites endemic for bacterial blight . Disease severity was high in all 3 years on all lines except the line with Xa7 . Of two Xoo lineages (groups of strains inferred to be clonally related based on DNA fingerprinting) detected, one, lineage C, dominated the pathogen population at both sites . All Xoo strains were virulent to Xa4, whereas only lineage C strains were virulent to Xa10 . Only a few strains of lineage C were virulent to Xa7 . Adaptation to virulence on Xa7 occurred through at least four different pathways and was associated with a reduction in aggressiveness . Loss of avirulence and reduced aggressiveness were associated with mutations at the 3' terminus of the avrXa7 allele . Strains most aggressive to Xa7 were not detected after the second year, suggesting they were less persistent than less aggressive strains . These experiments support the prediction that Xa7 would be a durable R gene because of a fitness penalty in Xoo associated with adaptation to Xa7. FEMS Microbiol Lett, 2000 Dec 1, 193(1), 129 - 36 Characterization of the acyl carrier protein gene and the fab gene locus in Xanthomonas albilineans; Huang G et al.; A genomic region containing the fatty acid biosynthetic (fab) genes was isolated from the sugarcane leaf-scald pathogen Xanthomonas albilineans . The order and predicted products of fabG (beta-ketoacyl reductase), acpP (acyl carrier protein), fabF (ketoacyl synthase II) and downstream genes in X . albilineans are very similar to those in Escherichia coli, with one exception . Sequence analysis, confirmed by insertional knockout and specific substrate feeding experiments, shows that the position occupied by pabC (encoding aminodeoxychorismate lyase) in other bacteria is occupied instead by pabB (encoding aminodeoxychorismate synthase component I) in X . albilineans . Downstream of pabB, X . albilineans resumes the arrangement common to characterized Gram-negative bacteria, with three transcriptionally coupled genes, encoding an ORF340 protein of undefined function, thymidylate kinase and delta' subunit of DNA polymerase III holoenzyme (HolB) . Different species may obtain a common advantage from coordinated regulation of the same biosynthetic pathways using different genes in this region. J Bacteriol, 2000 Dec, 182(24), 7053 - 9 Molecular evolution of virulence in natural field strains of Xanthomonas campestris pv . vesicatoria; Gassmann W et al.; The avrBs2 avirulence gene of the bacterial plant pathogen Xanthomonas campestris pv . vesicatoria triggers disease resistance in pepper plants containing the Bs2 resistance gene and contributes to bacterial virulence on susceptible host plants . We studied the effects of the pepper Bs2 gene on the evolution of avrBs2 by characterizing the molecular basis for virulence of 20 X . campestris pv . vesicatoria field strains that were isolated from disease spots on previously resistant Bs2 pepper plants . All field strains tested were complemented by a wild-type copy of avrBs2 in their ability to trigger disease resistance on Bs2 plants . DNA sequencing revealed four mutant alleles of avrBs2, two of which consisted of insertions or deletions of 5 nucleotides in a repetitive region of avrBs2 . The other two avrBs2 alleles were characterized by point mutations with resulting single amino acid changes (R403P or A410D) . We generated isogenic X . campestris pv . vesicatoria strains by chromosomal avrBs2 gene exchange to study the effects of these mutations on the dual functions of avrBs2 in enhancing bacterial virulence and inducing plant resistance by in planta bacterial growth experiments . The deletion of 5 nucleotides led to loss of avrBs2-induced resistance on Bs2 pepper plants and abolition of avrBs2-mediated enhancement of fitness on susceptible plants . Significantly, the point mutations led to minimal reduction in virulence function of avrBs2 on susceptible pepper plants, with either minimal (R403P allele) or an intermediate level of (A410D allele) triggering of resistance on Bs2 plants . Consistent with the divergent selection pressures on avrBs2 exerted by the Bs2 resistance gene, our results show that avrBs2 is evolving to decrease detection by the Bs2 gene while at the same time maintaining its virulence function. Biotechnol Bioeng, 2001 Jan 5, 72(1), 62 - 8 Improvement in bioreactor productivities using free radicals: HOCl-induced overproduction of xanthan gum from Xanthomonas campestris and its mechanism; Rao YM et al.; Free-radical induction has been employed as a novel strategy to improve bioreactor productivity and, more specifically, the quality and productivity of xanthan gum from Xanthomonas campestris cultures . A 210% increase in xanthan yield and a 20% increase in viscosity (quality) resulted from HOCl (oxidant) treatment . The acetate mass fraction in xanthan gum decreased by 42% and its pyruvate mass fraction increased by 63% as a result of HOCl treatment . The growth rate was almost unaffected by HOCl treatment . A hypothesis to explain the mechanism of xanthan gum overproduction by free-radical induction has been formulated . The significant aspects of the hypothesis, such as SoxS protein binding to the promoter region of the gum gene and the consequent increase in mRNA concentrations, have been experimentally verified . J Bacteriol, 2000 Dec, 182(23), 6845 - 9 A Xanthomonas alkyl hydroperoxide reductase subunit C (ahpC) mutant showed an altered peroxide stress response and complex regulation of the compensatory response of peroxide detoxification enzymes; Mongkolsuk S et al.; Alkyl hydroperoxide reductase subunit C (AhpC) is the catalytic subunit responsible for alkyl peroxide metabolism . A Xanthomonas ahpC mutant was constructed . The mutant had increased sensitivity to organic peroxide killing, but was unexpectedly hyperresistant to H(2)O(2) killing . Analysis of peroxide detoxification enzymes in this mutant revealed differential alteration in catalase activities in that its bifunctional catalase-peroxidase enzyme and major monofunctional catalase (Kat1) increased severalfold, while levels of its third growth-phase-regulated catalase (KatE) did not change . The increase in catalase activities was a compensatory response to lack of AhpC, and the phenotype was complemented by expression of a functional ahpC gene . Regulation of the catalase compensatory response was complex . The Kat1 compensatory response increase in activity was mediated by OxyR, since it was abolished in an oxyR mutant . In contrast, the compensatory response increase in activity for the bifunctional catalase-peroxidase enzyme was mediated by an unknown regulator, independent of OxyR . Moreover, the mutation in ahpC appeared to convert OxyR from a reduced form to an oxidized form that activated genes in the OxyR regulon in uninduced cells . This complex regulation of the peroxide stress response in Xanthomonas differed from that in other bacteria. Carbohydr Res, 2000 Sep 22, 328(3), 435 - 9 O-specific polysaccharide structure of the aqueous lipopolysaccharide fraction from Xanthomonas campestris pv . vitians strain 1839; Molinaro A et al.; The structure of Xanthomonas campestris pv . vitians O-specific polysaccharide of the lipopolysaccharide fraction, extracted from the aqueous phase, was defined, on the basis of chemical and spectroscopical methods, as constituted by the following repeating unit: {--> 3)-alpha-L-Rhap-(1 -->}n 3)-beta-L-Rhap-(1 --> where n is more frequently equal to 2, but it also assumes values equal to 1 and to 3. FEBS Lett, 2000 Oct 27, 484(1), 7 - 11 Transgenic expression of cecropin B, an antibacterial peptide from Bombyx mori, confers enhanced resistance to bacterial leaf blight in rice; Sharma A et al.; The short persistence of cecropin B peptide in plants, due to post-translational degradation, is a serious impediment in its effective utilization for developing bacterial resistance transgenic plants . Two DNA constructs encoding the full-length precursor of cecropin B peptide and the mature sequence of cecropin B peptide preceded by a signal peptide derived from rice chitinase gene were transformed in rice . The differences in the transcriptional levels in independent transgenic lines showed moderate to high expression of cecropin B gene that correlated well with the differences in cecropin B accumulation observed by Western blot analysis . The development of lesions resulting from infection by Xanthomonas oryzae pv . oryzae was significantly confined in the infected leaflet of transgenic lines, when compared with the control plants. Biochemistry (Mosc), 2000 Sep, 65(9), 1036 - 40 Intracellular glucosaminidase of the bacterium Xanthomonas campestris IBPM B-124: purification and properties; Tsfasman IM et al.; A system of intracellular autolytic enzymes of the bacterium Xanthomonas campestris IBPM B-124 was found to include enzymes with muramidase and glucosaminidase activities, while a system of extracellular bacteriolytic enzymes of the same bacterium includes muramidase, muramoylalanine amidase, and endopeptidase . Using a purification technique including fractional precipitation with ammonium sulfate, gel-filtration on Toyopearl HW-55F, and FPLC ion-exchange chromatography on Mono Q, a preparation of intracellular glucosaminidase was purified 435-fold with 16% yield (SDS-PAGE data indicated the presence of minor protein contaminants) . Some physicochemical properties of the purified enzyme were determined: molecular mass 26 kD, Km = 5.6 x 10(-4) M with p-nitrophenyl-2-acetamido-2-deoxy-beta-D-glucopyranoside as the substrate, and pH optimum 8.0-8.5 . The enzyme is active over a wide range of Tris-HCl buffer concentrations (0.01-0.5 M) and has temperature optimum at 37-40 degrees C . The glucosaminidase activity is sensitive to p-chloromercuribenzoate (PCMB), phenylmethylsulfonyl fluoride (PMSF), and the disodium salt of ethylenediamine tetraacetic acid (EDTA) . The properties of this glucosaminidase markedly differ from those of all extracellular bacteriolytic enzymes of Xanthomonas campestris . These findings indicate that the system of autolytic enzymes of this bacterium functions independently and is not connected with the system of extracellular bacteriolytic enzymes. Gene, 2000 Sep 19, 255(2), 327 - 33 Analysis of the genes flanking xabB: a methyltransferase gene is involved in albicidin biosynthesis in Xanthomonas albilineans; Huang G et al.; Transposon mutagenesis and complementation studies previously identified a gene (xabB) for a large (526kDa) polyketide-peptide synthase required for biosynthesis of albicidin antibiotics and phytotoxins in the sugarcane leaf scald pathogen Xanthomonas albilineans . A cistron immediately downstream from xabB encodes a polypeptide of 343aa containing three conserved motifs characteristic of a family of S-adenosyl-L-methionine (SAM)-dependent O-methyltransferases . Insertional mutagenesis and complementation indicate that the product of this cistron (designated xabC) is essential for albicidin production, and that there is no other required downstream cistron . The xabB promoter region is bidirectional, and insertional mutagenesis of the first open reading frame (ORF) in the divergent gene also blocks albicidin biosynthesis . This divergent ORF (designated thp) encodes a protein of 239aa displaying high similarity to several IS21-like transposition helper proteins . The thp cistron is not located in a recognizable transposon, and is probably a remnant from a past transposition event that may have contributed to the development of the albicidin biosynthetic gene cluster . Failure of 'in trans' complementation of thp indicates that a downstream cistron transcribed with thp is required for albicidin biosynthesis. Gene, 2000 Sep 19, 255(2), 245 - 55 Isolation and characterization of disease resistance gene homologues from rice cultivar IR64; Ilag LL et al.; We initiated a search for disease resistance (R) gene homologues in rice cultivar IR64, one of the most agronomically important rice varieties in the world, with the assumption that some of these homologues would correspond to previously identified disease resistance loci . A family of rice R gene homologues was identified using the Arabidopsis NBS-LRR disease resistance gene RPS2 as a hybridization probe . Because member genes of this rice R gene family exhibit features characteristic of the NBS-LRR class of resistance genes, the family was given the name NRH (for NBS-LRR resistance gene homologues) . Three members of the NRH family, NRH1, NRH2, and NRH3, were cloned and studied in detail . In IR64, NRH1 and NRH2 appear to encode full-length polypeptides, whereas NRH3 is prematurely truncated with a stop codon generated by a frameshift . NRH1 maps on chromosome 5, and NRH2 and NRH3 are less than 48kb apart on chromosome 11 . Although NRH1, NRH2, and NRH3 map to regions of the rice genome where disease resistance loci to Xanthomonas oryzae pv . oryzae (Xoo) have been identified, susceptible rice varieties transformed with either NRH1 or NRH2 failed to exhibit increased resistance to a set of well-characterized Xoo strains. J Med Chem, 2000 Oct 5, 43(20), 3632 - 40 Design, synthesis, and SAR of novel carbapenem antibiotics with high stability to Xanthomonas maltophilia oxyiminocephalosporinase type II; Hakimelahi GH et al.; Racemic cis-6-(phenylacetamido)carbapenem (21), 2-hydroxycarbonyl-cis-6-(phenylacetamido)carbapenem (22), 2-methoxycarbonyl-cis-6-(phenylacetamido)carbapenem (30), 2-methoxycarbomethyl-cis-6-(phenylacetamido)carbapenem (33), 2-hydroxyethyl-cis-6-(phenylacetamido)carbapenem (34), and 2-acetoxyethyl-cis-6-(phenylacetamido)carbapenem (35) were synthesized . Formation of the carbapenem nuclei in 21, 22, and 30 involved dehydrophosphonation of the corresponding 2-diphenylphosphono-6-(phenylacetamido)carbapenam precursors 14, 15, and 28 using trimethylsilyl triflate and 1,8-diazabicyclo{5.4.0}undec-7-ene in THF . Syntheses of carbapenems 33-35 involved a Wittig reaction of carbapenam 14 with methyl glyoxylate in the presence of lithium 2,2,6,6-tetramethylpiperidine in THF . For the antibacterial activities against Staphylococcus aureus FDA 209P, S . aureus 95, Escherichia coli ATCC 39188, Klebsiellapneumoniae NCTC 418, Pseudomonas aeruginosa 1101-75, and P . aeruginosa 18S-H, carbapenems (+/-)-21, (+/-)-22, (+/-)-30, and (+/-)-33-35 were found comparable with imipenem ((+)-3), yet they were notably more potent than (+)-3 against Xanthomonas maltophilia GN 12873 . On the other hand, unlike (+)-3, carbapenems (+/-)-21, (+/-)-22, (+/-)-30, and (+/-)-33-35 were stable to X . maltophilia oxyiminocephalosporinase type II . Their beta-lactamase inhibitory properties, however, were found to be more comparable with those of penicillin G ((+)-4) than to those of imipenem ((+)-3) . A combination of imipenem ((+)-3) with (+/-)-21, (+/-)-22, (+/-)-30, and (+/-)-33-35 resulted in synergistic antibacterial activity against X . maltophilia GN 12873 . Results from the biological tests were correlated with the distribution of the electron density at C(2)=C(3) of carbapenems upon reaction with transpeptidases or beta-lactamases. Plant Sci, 2000 Oct 16, 159(1), 97 - 106 Pepper gene encoding a basic beta-1,3-glucanase is differentially expressed in pepper tissues upon pathogen infection and ethephon or methyl jasmonate treatment; Jung HW et al.; A basic beta-1,3-glucanase cDNA clone (CABGLU) was isolated from the cDNA library constructed from hypersensitive response lesions of pepper leaves infected with avirulent strain of Xanthomonas campestris pv . vesicatoria . The deduced polypeptide of CABGLU which contains a C-terminal extension N-glycosylated at a single site characterized as typical structure of class I beta-1,3-glucanase has a high level of identity with tobacco basic beta-1,3-glucanase (77.4%), but only a moderate level of identity with tomato acidic beta-1,3-glucanase (42.6%) . Genomic DNA gel blot analysis indicates that the pepper genome contains one or two beta-1,3-glucanase copy genes . Transcripts of the CABGLU gene were more induced in incompatible interactions than in compatible interactions, when inoculated with X . campestris pv . vesicatoria or Phytophthora capsici . Accumulation of CABGLU mRNA was strongly induced in pepper leaves by both ethephon and methyl jasmonate . The CABGLU mRNA was constitutively expressed only in the roots of all the plant organs . These data indicate that the basic beta-1,3-glucanase gene may be induced by pathogen attack and abiotic stresses. Plant Sci, 2000 Oct 16, 159(1), 39 - 49 Pepper gene encoding a basic class II chitinase is inducible by pathogen and ethephon; Hong JK et al.; A chitinase cDNA clone (designated CAChi2) was isolated from the cDNA library of pepper leaves infected with Xanthomonas campestris pv . vesicatoria . The 1004-bp full-length CAChi2 cDNA encodes a basic chitinase with an N-terminal 24 amino acid signal peptide followed by a catalytic region . An analysis of its sequence indicates that CAChi2 is a class II chitinase, because it does not have chitin-binding domain and C-terminal extension sequences . The deduced amino acid sequence of CAChi2 has a high level of identity with class II chitinases from potato, tomato, tobacco and petunia . Southern analysis demonstrated that the CAChi2 chitinase is encoded by a single or two copy genes in the pepper genome . Following X . campestris pv . vesicatoria or Phytophthora capsici infection, the CAChi2 chitinase mRNA was more highly expressed in the incompatible interaction, compared to expression in the compatible interaction . Treatment with ethylene-releasing ethephon resulted in a strong accumulation of the transcripts in the leaves . In contrast, DL-beta-amino-n-butyric acid, salicylic acid and methyl jasmonate were not effective in inducing CAChi2 transcripts in pepper leaves. J Biol Chem, 2000 Dec 22, 275(51), 40568 - 75 Identification of essential amino acids in the bacterial alpha -mannosyltransferase aceA; Abdian PL et al.; The alpha-mannosyltransferase AceA from Acetobacter xylinum belongs to the CaZY family 4 of retaining glycosyltransferases . We have identified a series of either highly conserved or invariant residues that are found in all family 4 enzymes as well as other retaining glycosyltransferases . These residues included Glu-287 and Glu-295, which comprise an EX(7)E motif and have been proposed to be involved in catalysis . Alanine replacements of each conserved residue were constructed by site-directed mutagenesis . The mannosyltransferase activity of each mutant was examined by both an in vitro transferase assay using recombinant mutant AceA expressed in Escherichia coli and by an in vivo rescue assay by expressing the mutant AceA in a Xanthomonas campestris gumH(-) strain . We found that only mutants K211A and E287A lost all detectable activity both in vitro and in vivo, whereas E295A retained residual activity in the more sensitive in vivo assay . H127A and S162A each retained reduced but significant activities both in vitro and in vivo . Secondary structure predictions of AceA and subsequent comparison with the crystal structures of the T4 beta-glucosyltransferase and MurG suggest that AceA Lys-211 and Glu-295 are involved in nucleotide sugar donor binding, leaving Glu-287 of the EX(7)E as a potential catalytic residue. Mol Microbiol, 2000 Sep, 37(6), 1504 - 14 Molecular and physiological analysis of an OxyR-regulated ahpC promoter in Xanthomonas campestris pv . phaseoli; Loprasert S et al.; In Xanthomonas campestris pv . phaseoli, a gene for the alkyl hydroperoxide reductase subunit C (ahpC) had unique patterns of regulation by various forms of OxyR . Reduced OxyR repressed expression of the gene, whereas oxidized OxyR activated its expression . This dual regulation of ahpC is unique and unlike all other OxyR-regulated genes . The ahpC transcription start site was determined . Analysis of the region upstream of the site revealed promoter sequences that had high homology to the Xanthomonas consensus promoter sequence . Data from gel shift experiments indicated that both reduced and oxidized OxyR could bind to the ahpC regulatory region . Moreover, the reduced and the oxidized forms of OxyR gave different DNase I footprint patterns, indicating that they bound to different sites . The oxidized OxyR binding site overlapped the -35 region of the ahpC promoter by a few bases . This position is consistent with the role of the protein in activating transcription of the gene . Binding of reduced OxyR to the ahpC promoter showed an extended DNase I footprint and DNase I hypersensitive sites, suggesting that binding of the protein caused a shift in the binding site and bending of the target DNA . In addition, binding of reduced OxyR completely blocked the -35 region of the ahpC promoter and prevented binding of RNA polymerase, leading to repression of the gene . Monitoring of the ahpC promoter activity in vivo confirmed the location of the oxidized OxyR binding site required for activation of the promoter . A mutant that separated OxyR regulation from basal ahpC promoter activity was constructed . The mutant was unable to respond to oxidants by increasing ahpC expression . Physiologically, it had a slower aerobic growth rate and was more sensitive to organic peroxide killing . This indicated that oxidant induction of ahpC has important physiological roles in normal growth and during oxidative stress. Heart Lung, 2000 Sep-Oct, 29(5), 351 - 5 Stenotrophomonas maltophilia endocarditis of prosthetic aortic valve: report of a case and review of literature; Mehta NJ et al.; Stenotrophomonas Maltophilia (previously known as Xanthomonas maltophilia and Pseudomonas maltophilia ) is an aerobic, nonfermenting, gram-negative bacillus, which has emerged as a serious nosocomial pathogen in patients with compromised immunity . It is a rare cause of endocarditis with only 20 cases previously reported in medical literature . The risk factors associated with S maltophilia endocarditis include intravenous drug abuse, dental treatment, previous cardiac surgery, and infected intravascular devices . S maltophilia is resistant to multiple antibiotics, which leads to frequent therapeutic failures . Although the optimal antibiotic treatment for S maltophilia endocarditis remains unknown, most of the patients received 2 or more antibiotics . We report a case of S maltophilia endocarditis of prosthetic aortic valve, associated with a painless aortic dissection, that responded well to a combination of ciprofloxacin and chloramphenicol . The literature is reviewed to elaborate the disease characteristics, the treatments used, and the prognosis of the S maltophilia endocarditis. Acta Cient Venez, 1999, 50(4), 201 - 9 {Xanthan production by Xanthomonas campestris in a non-conventional culture medium}; Azuaje RA et al.; Among 3 varieties of Xanthomonas campestris, the variety ocumo (X . campestris pv . ocumo), showed the greatest capacity for producing xanthan . This bacteria grows appropriately and produces this polysaccharide in a wide diversity of carbohydrate sources . However, this strain does not produce xanthan when the carbohydrate comes from lignocellulosic materials . The glucose syrup FAVEPRO was the carbon source that showed the best yield (23 g/l) with the greatest viscosity (7000 cps) of xanthan . The optimum production conditions in 1 L erlenmeyer flasks, with a working volume of 0.2 L and in a 14 L (stirred tank type bioreactor) with a working volume of 10 L, were the following: total sugar 5%, urea 0.05%, di-potassium hydrogen phosphate 0.5%, pH 7.5, inoculum 10%, temperature 30 degrees C, agitation 250-1000 rpm and aereation 0.3-1.0 vvm . This strain of X . campestris pv . ocumo was able to produce xanthan (10 g/l) in a culture medium based on a previously treated agricultural waste, called soluble acid extract of cassava bark . The viscosity of this medium increased up to 1500 cps. Lett Appl Microbiol, 2000 Aug, 31(2), 149 - 53 Rapid amplification and cloning of Tn5 flanking fragments by inverse PCR; Huang G et al.; A simple approach is described to efficiently amplify DNA sequences flanking transposon Tn5 insertions . The method involves: (i) digestion with a restriction enzyme that cuts within Tn5; (ii) self-ligation under conditions favouring the production of monomeric circles; (iii) four parallel PCR reactions using primers designed to amplify left or right flanking sequences, and to distinguish target amplicons from non-specific products . This reveals the number of Tn5 insertions and the size of flanking genomic restriction fragments, without Southern blot analysis . The amplified product contains restriction sites that facilitate cohesive-end cloning . This rapid method is demonstrated using Tn5 and Tn5-Mob tagged DNA sequences involved in albicidin biosynthesis in Xanthomonas albilineans . It is generally applicable for efficient recovery of DNA sequences flanking transposon Tn5 derivatives in insertional mutagenesis studies. Appl Environ Microbiol, 2000 Sep, 66(9), 4017 - 21 Exposure of phytopathogenic Xanthomonas spp . to lethal concentrations of multiple oxidants affects bacterial survival in a complex manner; Sriprang R et al.; During plant-microbe interactions and in the environment, Xanthomonas campestris pv . phaseoli is likely to be exposed to high concentrations of multiple oxidants . Here, we show that simultaneous exposures of the bacteria to multiple oxidants affects cell survival in a complex manner . A superoxide generator (menadione) enhanced the lethal effect of an organic peroxide (tert-butyl hydroperoxide) by 1, 000-fold; conversely, treatment of cells with menadione plus H(2)O(2) resulted in 100-fold protection compared to that for cells treated with the individual oxidants . Treatment of X . campestris with a combination of H(2)O(2) and tert-butyl hydroperoxide elicited no additive or protective effect . High levels of catalase alone are sufficient to protect cells against the lethal effect of menadione plus H(2)O(2) and tert-butyl hydroperoxide plus H(2)O(2) . These data suggest that H(2)O(2) is the lethal agent responsible for killing the bacteria as a result of these treatments . However, increased expression of individual genes for peroxide (alkyl hydroperoxide reductase, catalase)- and superoxide (superoxide dismutase)-scavenging enzymes or concerted induction of oxidative stress-protective genes by menadione gave no protection against killing by a combination of menadione plus tert-butyl hydroperoxide . However, X . campestris cells in the stationary phase and a spontaneous H(2)O(2)-resistant mutant (X . campestris pv . phaseoli HR) were more resistant to killing by menadione plus tert-butyl hydroperoxide . These findings give new insight into oxidant killing of Xanthomonas spp . that could be generally applied to other bacteria. J Biochem (Tokyo), 2000 Sep, 128(3), 499 - 507 Subsite preferences of pepstatin-insensitive carboxyl proteinases from prokaryotes: kumamolysin, a thermostable pepstatin-insensitive carboxyl proteinase; Oda K et al.; Kumamolysin, a carboxyl proteinase from Bacillus novosp . MN-32, is characterized by its thermostability and insensitivity to aspartic proteinase inhibitors such as pepstatin, diazoacetyl-DL-norleucine methylester, and 1,2-epoxy-3-(p-nitro-phenoxy)propane . Here, its substrate specificity was elucidated using two series of synthetic chromogenic substrates: P(5)-P(4)-P(3)-P(2)-Phe*Nph (p-nitrophenylalanine: *cleavage site)-P(2)'-P(3)', in which the amino acid residues at the P(5)-P(2), P(2)' and P(3)' positions were systematically substituted . Among 74 substrates, kumamolysin was shown to hydrolyze Lys-Pro-Ile-Pro-Phe-Nph-Arg-Leu most effectively . The kinetic parameters of this peptide were K(m) = 41+/-5 microM, k(cat) = 176+/- 10 s(-1), and k(cat)/K(m) = 4.3+/-0.6 mM(-1) x s(-1) . These systematic analyses revealed the following features: (i) Kumamolysin had a unique preference for the P(2) position . Kumamolysin preferentially hydrolyzed peptides having an Ala or Pro residue at the P(2) position; this was also observed for the pepstatin-insensitive carboxyl proteinase from Bacillus coagulans J-4 {J-4; Shibata et al . (1998) J . Biochem . 124, 642-647} . Other carboxyl proteinases, including Pseudomonas sp . 101 pepstatin-insensitive carboxyl proteinase (PCP) and Xanthomonas sp . T-22 pepstatin-insensitive carboxyl proteinase (XCP), preferred peptides having hydrophobic and bulky amino acid residue such as Leu at the P(2) position . (ii) Kumamolysin preferred such charged amino acid residues as Glu or Arg at the P(2)' position, suggesting that the S(2)' subsite of kumamolysin is occupied by hydrophilic residues, similar to that of PCP, XCP, and J-4 . In general, the S(2)' subsite of pepstatin-sensitive carboxyl proteinases (aspartic proteinases) is hydrophobic in nature . Thus, the hydrophilic nature of the S(2)' subsite was confirmed to be a distinguishing feature of pepstatin-insensitive carboxyl proteinases from prokaryotes. Plasmid, 2000 Sep, 44(2), 163 - 72 Characterization of the IncW cryptic plasmid pXV2 from Xanthomonas campestris pv . vesicatoria; Wu LT et al.; The gram-negative plant pathogen Xanthomonas campestris pv . vesicatoria strain Xv2 harbors an indigenous, cryptic plasmid pXV2 of 14.6 kb . This plasmid can only be maintained in Xanthomonas and is incapable of self-transmission . However, incompatibility testing classified it in IncW, a group containing the smallest number of naturally occurring, broad-host-range, conjugative plasmids . A pXV2 derivative containing only a 5.5-kb PstI fragment is stably maintained . Deletion of a 3.0-kb region from the PstI fragment causes a loss of plasmid stability . Nucleotide sequencing of the 2 . 1-kb region essential for autonomous replication revealed a repA gene and a downstream noncoding region containing four iterons, two 17- and two 19-nt direct repeats, and an AT-rich region lying between the two sets of iterons . The sequence of the deduced RepA and the iterons shows homology to the RepA (39% identity) and the iterons, respectively, of the IncW plasmid pSa . Maxicell expression of the repA gene produced a protein of 35 kDa, a size similar to that deduced from the nucleotide sequence . Trans-complementation test confirmed that the repA gene and the iterons are indeed the essential elements for pXV2 replication . J Microbiol Methods, 2000 Aug, 41(3), 211 - 7 Modified pyrogallol-initiated immunogold-silver enhancement technique applicable to prokaryotes; Kangatharalingam N et al.; A modified immunogold-silver enhancement technique that was designed to reduce the nonspecific granular background staining, particularly for application on prokaryotic organisms, is reported . Aerial oxidation of pyrogallol contained in the commercial silver enhancer solution was effectively controlled during storage and in the reaction mixture . A combination of strategies such as storing the reagent under argon, modifying it using 0.5% (w/v) anhydrous sodium sulfite, reducing the concentration of silver ions in the reaction mixture and limiting the length of the silver enhancement reaction considerably reduced the granular background staining . The modified technique was demonstrated on the bacterium Xanthomonas campestris pv . malvacearum (Smith) Dye . A 7-min silver enhancement step produced little background staining, while optimal silver intensification of the bacterium pre-treated with the immunogold label was achieved. Nephron, 2000 Aug, 85(4), 348 - 50 Use of 'locked-in' antibiotic to treat an unusual gram-negative hemodialysis catheter infection; Shah J et al.; A 37-year-old woman on maintenance hemodialysis for 3 years had multiple vascular access failures due to antiphospholipid syndrome . She was dialyzed via a tunneled left subclavian catheter, but after 1 year developed chills and fever during each dialysis session . Blood cultures grew out Xanthomonas maltophilia sensitive to ceftazidime and ciprofloxacin . Intravenous administration of both antibiotics failed to eradicate infection . We added 'locked-in' ceftazidime, instilling it daily into the catheter along with heparinized saline for 3 weeks . Within 24 h the patient was dialyzed uneventfully, and all subsequent blood cultures have been negative . This case shows the successful use of a 'locked-in' antibiotic to treat an unusual gram-negative catheter infection . Two prior series have reported similar good results in infections with more common organisms . Such treatment may permit continued use of tunneled hemodialysis catheters for longer periods . J Bacteriol, 2000 Sep, 182(17), 4797 - 802 Stationary-phase variation due to transposition of novel insertion elements in Xanthomonas oryzae pv . oryzae; Rajeshwari R et al.; Xanthomonas oryzae pv . oryzae causes bacterial leaf blight, a serious disease of rice . Spontaneous mutants which are deficient for virulence and extracellular polysaccharide (Eps) production accumulate in large numbers in stationary-phase cultures of this bacterium, a phenomenon which we have called stationary-phase variation . A clone (pSD1) carrying the Eps biosynthetic gene (gum) cluster of X . oryzae pv . oryzae restored Eps production and virulence to several spv (for stationary-phase variation) mutants . Data from localized recombination analysis, Southern hybridization, PCR amplification, and sequence analysis showed that the mutations are due to insertion of either one of two novel endogenous insertion sequence (IS) elements, namely, ISXo1 and ISXo2, into gumM, the last gene of the gum gene cluster . The results of Southern analysis indicate the presence of multiple copies of both IS elements in the genome of X . oryzae pv . oryzae . These results demonstrate the role of IS elements in stationary-phase variation in X . oryzae pv . oryzae. Int J Syst Evol Microbiol, 2000 Jul, 50 Pt 4, 1471 - 8 Genomic and phenotypic characterization of Xanthomonas cynarae sp . nov., a new species that causes bacterial bract spot of artichoke (Cynara scolymus L.); Trebaol G et al.; A bacterial disease of artichoke (Cynara scolymus L.) was first observed in 1954 in Brittany and the Loire Valley, France . This disease causes water-soaked spots on bracts and depreciates marketability of the harvest . Ten strains of the pathogen causing bacterial spot of artichoke, previously identified as a member of the genus Xanthomonas, were characterized and compared with type and pathotype strains of the 20 Xanthomonas species using a polyphasic study including both phenotypic and genomic methods . The ten strains presented general morphological, biochemical and physiological traits and G+C content characteristic of the genus Xanthomonas . Sequencing of the 165 rRNA gene confirmed that this bacterium belongs to the genus Xanthomonas, and more precisely to the Xanthomonas campestris core . DNA-DNA hybridization results showed that the strains that cause bacterial spot of artichoke were 92-100% related to the proposed type strain CFBP 4188T and constituted a discrete DNA homology group that was distinct from the 20 previously described Xanthomonas species . The results of numerical analysis were in accordance with DNA-DNA hybridization data . Strains causing the bacterial bract spot of artichoke exhibited consistent determinative biochemical characteristics, which distinguished them from the 20 other Xanthomonas species previously described . Furthermore, pathogenicity tests allowed specific identification of this new phytopathogenic bacterium . Thus, it is concluded that this bacterium is a new species belonging to the genus Xanthomonas, for which the name Xanthomonas cynarae is proposed . The type strain, CFBP 4188T, has been deposited in the Collection Francaise des Bacteries Phytopathogenes (CFBP). Metab Eng, 2000 Apr, 2(2), 79 - 91 Parameters affecting gene expression from the Pm promoter in gram-negative bacteria; Winther-Larsen HC et al.; The Pm promoter inserted chromosomally or in broad-host-range replicons based on plasmid RSF1010 or RK2 are useful systems for both high- and low-level expression of cloned genes in several gram-negative bacterial species . The positive Pm regulator XylS is activated by certain substituted benzoic acid derivatives, and here we show that these effectors induce expression of Pm at similar relative ranking levels in both Escherichia coli and Pseudomonas aeruginosa However, the kinetics of expression was not the same in the two organisms . Different carbon sources and dissolved oxygen levels displayed limited effects on expression, but surprisingly the pH of the growth medium was found to be of major importance . By combining the effects of genetic and environmental parameters, expression from Pm could be varied over a ten-thousand- to a hundred-thousand-fold continuous range, and as an example of its applications we showed that Pm can be used to control the xanthan biosynthesis in Xanthomonas campestris. Proc Natl Acad Sci U S A, 2000 Aug 15, 97(17), 9807 - 12 The virulence factor AvrXa7 of Xanthomonas oryzae pv . oryzae is a type III secretion pathway-dependent nuclear-localized double-stranded DNA-binding protein; Yang B et al.; AvrXa7 is a member of the avrBs3 avirulence gene family, which encodes proteins targeted to plant cells by a type III secretion apparatus . AvrXa7, the product of avrXa7, is also a virulence factor in strain PXO86 of Xanthomonas oryzae pv . oryzae . Avirulence and virulence specificities are associated with the central repeat domain, which, in avrXa7, consists of 25.5 direct repeat units . Mutations in three C-terminal nuclear localization signal motifs eliminated avirulence and virulence activities in rice and severely reduced nuclear localization in a yeast assay system . Both pathogenicity functions and nuclear localization were restored on the addition of the sequence for the nuclear localization signal motif from SV40 T-antigen . The loss of avirulence activity because of mutations in the acidic transcriptional activation domain was restored by addition of the activation domain from the herpes simplex viral protein VP16 . The activation domain was also required for virulence activity . However, the VP16 domain could not substitute for the endogenous domain in virulence assays . In gel shift assays, AvrXa7 bound double-stranded DNA with a preference for dA/dT rich sequences . The results indicate that products of the avrBs3-related genes are virulence factors targeted to host cell nuclei and have the potential to interact with the host DNA and transcriptional machinery as part of their mode of action . The results also suggest that the host defensive recognition mechanisms are targeted to the virulence factor site of action. DNA Seq, 2000, 11(1-2), 167 - 73 Cloning and molecular characterization of hrpX from Xanthomonas axonopodis pv . citri; Iwamoto M et al.; The hrpX gene of plant pathogenic Xanthomonas species is essential for pathogenicity on host plants and to cause hypersensitive reaction on non-host plants . We cloned and analyzed a hrpX homologue, designated hrpXct, of X . axonopodis pv . citri, a pathogen of citrus canker . The open reading frame of hrpXct has 1431 bp in nucleotides which has a coding capacity of 476 amino acid residues with a molecular mass of 52.4 kDa . The predicted amino acid sequence of HrpXct has 90% identity to the AraC family type transcriptional activator protein HrpXc of X . campestris pv . campestris, 95% to HrpXo of X . oryzae pv . oryzae and 97% to X . vesicatoria . These findings clearly indicate and confirm that the structure of the hrpX genes in plant pathogenic Xanthomonas species is highly conserved. Biochim Biophys Acta, 2000 Jul 24, 1492(2-3), 553 - 9 Sequence and molecular analysis of the rpoA cluster genes from Xanthomonas campestris pv . campestris; Lai JY et al.; The Xanthomonas campestris rpsM (S13)-rpsK (S11)-rpsD (S4)-rpoA (alpha)-rplQ (L17) cluster, encoding RNA polymerase alpha-subunit and four ribosomal proteins, reside in a 3164-bp DNA region . The N-terminal sequence of the authentic alpha-protein determined chemically matches that predicted from the nucleotide sequence . rplQ is monocistronic, instead of being co-transcribed with the other genes as in Escherichia coli . Antiserum against the His-tagged alpha-protein cross-reacted with the E . coli alpha-protein. Yi Chuan Xue Bao, 2000, 27(1), 34 - 8 {Major-polygene effect analysis of resistance to bacterial blight (Xanthomonas campestris pv . oryzae) in rice}; Wang JS et al.; Five crosses between resistance and susceptible were analyzed to study major-polygene effect using major-polygene mixed mode . The result showed that 3 of 5 crosses were controlled by both major gene and polygene . In addition, there were large variation of additive effect, variance as well as heredity of major gene polygene in 3 crosses . Major gene was predominant in resistant variation, but durability should be considered . We suggested that construct major-polygene system be constructed in the long run in breeding program to ensure a durable and high level of resistance to constrain fluctuation of races of Xanthomonas campestris pv . oryzae population. Syst Appl Microbiol, 2000 Apr, 23(1), 148 - 55 Variation among strains of Xanthomonas campestris pv . vasculorum from Mauritius and other countries based on fatty acid analysis; Dookun A et al.; Fatty acid profiling was used to study variation amongst strains of Xanthomonas campestris pv . vasculorum (Xcv) . They could be divided into five groups using cellular fatty acid profiles . Group A strains represent a new and little known taxon and all came from plants of broom bamboo (Thysanolaena maxima) from Mauritius . Group B strains included the Xcv pathotype reference strain and were from palms, broom bamboo and sugarcane from Mauritius, Reunion and Australia . Group C contained southern African and Malagasy strains from sugarcane and maize, together with X . campestris pv . holcicola strain . No Mascarene strains fell into this group . Group D strains isolated from sugarcane, maize and royal palm (Roystonea regia) were from Mauritius and Reunion, the earliest known strains coming from Reunion . These groups represented in the Mascarene Islands possibly belong to three different Xanthomonas species . A further Group E comprised one Xcv strain (NCPPB 182) from Puerto Rico, one X . vasicola pv . holcicola strain plus 6 other unclassified Xanthomonas strains causing red stripe disease symptoms in sugarcane . Three of these groups occur on Mauritius and two occur on Reunion . Group B strains originally caused serious problems in noble canes . As resistant interspecific hybrids were introduced, group D strains appeared in Mauritius possibly being introduced from Reunion but having similar host ranges within the Gramineae and Palmae . The findings that 3 of these groups (A, B, D) can cause gumming disease in a grass species (T . maxima) and that 2 of them (B, D) also cause gumming disease in sugar cane (Gramineae) and palms (Palmae) is unusual. Res Microbiol, 2000 May, 151(4), 291 - 302 Tn5044, a novel Tn3 family transposon coding for temperature-sensitive mercury resistance; Kholodii G et al.; We report the discovery and characterization of the mercury resistance transposon, Tn5044, from a Xanthomonas strain from the Kamchatka peninsula . In addition to the standard set of merRTPCAD genes, the mer operon of Tn5044 contains a gene named sigY that encodes the RNA polymerase sigma factor-like protein . Mercury resistance determined by Tn5044 is expressed at low (30 degrees C) but not at elevated temperatures (37 degrees C) . None of the mer operon genes downstream of merA is responsible for the temperature-sensitive mercury resistance . The transposition module of Tn5044 is closely related to those of Tn1412 isolated from medical sources and to Tn5563 and ISXc5 from environmental sources . However, Tn5044 differs from these transposons in that it has unusually long terminal inverted repeats . Sequence analysis of the transposase (tnpA) genes places Tn5044 and its close relatives into the Tn3 subgroup of the Tn3 family . However, the orientation of their resolvase and transposase genes is unusual for the Tn3 family: tnpR is proximal to the end of the transposon, while divergently transcribed tnpA is oriented inwardly . The region between tnpA and tnpR genes is unusually large and contains two short conserved open reading frames . In addition to the complete set of sequence motifs common to true resolvases, the resolvase of Tn5044 and its close relatives possesses a C-terminal extension showing no homology to known proteins . Despite this peculiarity, Tn5044 resolvase can resolve cointegrates formed during Tn5044 transposition controlled by tnpA . Genetic data suggest that the extension is essential for TnpR functioning. Prikl Biokhim Mikrobiol, 2000 May-Jun, 36(3), 303 - 6 {Hydrolase from Xanthomonas rubrilineans for synthesis of cefalexin}; Ivankin AN et al.; The use of peptide hydrolase (EC 3.4.13.1) from Xanthomonas rubrilineans for synthesis of the antibiotic cephalexin from 7-aminodesacetoxycephalosporanic acid was studied . The optimum conditions for production of cephalexin were determined, and the yield exceeded 80% . A method for monitoring the synthesis of this antibiotic synthesis by means of a conventional amino acid analyzer is proposed. J Bacteriol, 2000 Jul, 182(13), 3846 - 9 Mutations in oxyR resulting in peroxide resistance in Xanthomonas campestris; Mongkolsuk S et al.; A spontaneous Xanthomonas campestris pv . phaseoli H(2)O(2)-resistant mutant emerged upon selection with 1 mM H(2)O(2) . In this report, we show that growth of this mutant under noninducing conditions gave high levels of catalase, alkyl hydroperoxide reductase (AhpC and AhpF), and OxyR . The H(2)O(2) resistance phenotype was abolished in oxyR-minus derivatives of the mutant, suggesting that elevated levels and mutations in oxyR were responsible for the phenotype . Nucleotide sequence analysis of the oxyR mutant showed three nucleotide changes . These changes resulted in one silent mutation and two amino acid changes, one at a highly conserved location (G197 to D197) and the other at a nonconserved location (L301 to R301) in OxyR . Furthermore, these mutations in oxyR affected expression of genes in the oxyR regulon . Expression of an oxyR-regulated gene, ahpC, was used to monitor the redox state of OxyR . In the parental strain, a high level of wild-type OxyR repressed ahpC expression . By contrast, expression of oxyR5 from the X . campestris pv . phaseoli H(2)O(2)-resistant mutant and its derivative oxyR5G197D with a single-amino-acid change on expression vectors activated ahpC expression in the absence of inducer . The other single-amino-acid mutant derivative of oxyR5L301R had effects on ahpC expression similar to those of the wild-type oxyR . However, when the two single mutations were combined, as in oxyR5, these mutations had an additive effect on activation of ahpC expression. Int J Syst Evol Microbiol, 2000 May, 50 Pt 3, 1211 - 9 Systematic analysis of xanthomonads (Xanthomonas spp.) associated with pepper and tomato lesions; Jones JB et al.; The taxonomy and evolutionary relationships among members of the genus Xanthomonas associated with tomato and pepper have been a matter of considerable controversy since their original description in 1921 . These bacteria, which are a major affliction of tomato and pepper crops in warm and humid regions, were originally described as a single species, but subsequent research has shown the existence of at least two genetic groups differentiated by physiological, biochemical and pathological characteristics . This work synthesizes the findings from several approaches, including pathogenicity tests, enzymic activity, restriction fragment analysis of the entire genome, DNA-DNA hybridization and RNA sequence comparisons based on a 2097 base sequence comprising the 16S rRNA gene, the intergenic spacer located between the 16S and 23S rRNA genes and a small region of the 23S rRNA gene . Within the group of xanthomonads pathogenic on pepper and tomato four distinct phenotypic groups exist, of which three form distinct genomic species . These include Xanthomonas axonopodis pv . vesicatoria (A and C group), Xanthomonas vesicatoria (B group) and Xanthomonas gardneri (D group) . On the basis of phenotypic and genotypic differences between A- and C-group strains, the C strains should be considered as a subspecies within Xanthomonas axonopodis pv . vesicatoria. Microbiology, 2000 May, 146 ( Pt 5), 1053 - 60 The exbD2 gene as well as the iron-uptake genes tonB, exbB and exbD1 of Xanthomonas campestris pv . campestris are essential for the induction of a hypersensitive response on pepper (Capsicum annuum); Wiggerich HG et al.; The tonB, exbB and exbD1 genes of Xanthomonas campestris pv . campestris are essential for ferric iron uptake . In contrast, the exbD2 gene located in the same gene cluster is not essential . Mutational analysis revealed that the ferric-iron-uptake genes tonB, exbB and exbD1 are necessary for the induction of a hypersensitive response (HR) on the nonhost plant pepper (Capsicum annuum) and the induction of typical black rot symptoms on the host plant cauliflower (Brassica oleracea) . Again, the exbD2 gene behaved differently . It was found to play a role only in the induction of the HR in pepper but not in the induction of black rot symptoms in cauliflower . Due to the low iron concentration in the plant tissue, the titre of viable bacteria of the ferric-iron-uptake mutants tonB, exbB and exbD1 decreased after leaf infiltration of pepper . The exbD2 mutant, however, which is not impaired in ferric iron uptake, multiplied in the pepper leaf tissue and grew even better than the wild-type strain, probably due to its failure to induce the HR . Nevertheless, the tonB, exbB and exbD1 mutant strains were able to spread systemically in cauliflower. Plant Physiol, 2000 May, 123(1), 81 - 92 Response to Xanthomonas campestris pv . vesicatoria in tomato involves regulation of ethylene receptor gene expression; Ciardi JA et al.; Although ethylene regulates a wide range of defense-related genes, its role in plant defense varies greatly among different plant-microbe interactions . We compared ethylene's role in plant response to virulent and avirulent strains of Xanthomonas campestris pv . vesicatoria in tomato (Lycopersicon esculentum Mill.) . The ethylene-insensitive Never ripe (Nr) mutant displays increased tolerance to the virulent strain, while maintaining resistance to the avirulent strain . Expression of the ethylene receptor genes NR and LeETR4 was induced by infection with both virulent and avirulent strains; however, the induction of LeETR4 expression by the avirulent strain was blocked in the Nr mutant . To determine whether ethylene receptor levels affect symptom development, transgenic plants overexpressing a wild-type NR cDNA were infected with virulent X . campestris pv . vesicatoria . Like the Nr mutant, the NR overexpressors displayed greatly reduced necrosis in response to this pathogen . NR overexpression also reduced ethylene sensitivity in seedlings and mature plants, indicating that, like LeETR4, this receptor is a negative regulator of ethylene response . Therefore, pathogen-induced increases in ethylene receptors may limit the spread of necrosis by reducing ethylene sensitivity. Carbohydr Res, 2000 Apr 20, 325(3), 222 - 9 Structure elucidation of the O-chain from the major lipopolysaccharide of the Xanthomonas campestris strain 642; Molinaro A et al.; A novel O-polysaccharide consisting of D-Xylp and L-Rhap in the molar ratio of 1:2.5 was identified as the major component in the lipopolysaccharide fraction of Xanthomonas campestris strain 642, which is responsible for a new bacterial disease of the strawberry plant . Its structure was mainly determined using chemical analysis, Smith degradation and 1D and 2D NMR spectroscopy experiments as: carbohydrate sequence {see text}. Lett Appl Microbiol, 2000 Apr, 30(4), 287 - 93 Genetic polymorphism in Xanthomonas albilineans strains originating from 11 geographical locations, revealed by two DNA probes; Jaufeerally-Fakim Y et al.; Two DNA fragments from Xanthomonas albilineans were used as probes to study the molecular diversity among strains of this pathogen . Two serologically distinct groups, serovars I and II, could be differentiated by hybridization to the probes . These probes, designated 830 and 838, were cloned after subtractive DNA hybridization of common sequences of Xanthomonas campestris pv . vasculorum from a serovar I strain of X . albilineans . They did not hybridize to the DNA of several other xanthomonads or to sugarcane DNA under the conditions of hybridization used . Faint bands were observed upon hybridization of probe 830 with one strain of X . campestris pv . phaseoli . The same banding patterns were obtained with a strain of X . albilineans from Burkina Faso and the serovar II strains of Mauritius . The serovar I strains from Mauritius and two other strains each from Reunion and South Africa had similar pattern. Microbiology, 2000 Apr, 146 ( Pt 4), 885 - 91 Novel genes involved in the regulation of pathogenicity factor production within the rpf gene cluster of Xanthomonas campestris; Dow JM et al.; The synthesis of extracellular enzymes and extracellular polysaccharide (EPS) in Xanthomonas campestris pathovar campestris (Xcc) is subject to co-ordinate regulation by a cluster of genes called rpf (for regulation of pathogenicity factors) . These genes are located within a 21.9 kb region of the chromosome isolated as the cosmid clone pIJ3020 . The genes in the left-hand section of this region of the chromosome have previously been characterized . This paper reports on the genes in the right-hand section and on the phenotypes of mutants with transposon insertions in these genes . Sequence analysis identified eight genes or ORFs with the gene order rpfD-orf1-orf2-orf3-orf4-recJ-rpf E-greA . RecJ and GreA have established functions in recombination and transcriptional elongation, respectively . rpfD encoded a protein with some amino acid sequence relatedness to a hypothetical protein from Caulobacter crescentus and an autolysin response regulator in Bacillus subtilis . The predicted protein products of orf1, 2 and 3 were related to each other and had substantial amino acid sequence relatedness to hypothetical proteins from C . crescentus . Transposon insertions in orf1, 2 and 3 had no effect on the synthesis of extracellular enzymes or EPS . The predicted proteins RpfE and Orf4 showed the highest amino acid sequence relatedness to hypothetical proteins from Bordetella pertussis and Klebsiella pneumoniae, respectively . Transposon insertions in rpfE led to reduced levels of some extracellular enzymes (endoglucanase and protease) and increased levels of others (polygalacturonate lyase) . Transposon insertions in orf4 had no effect on polygalacturonate lyase but led to reduced levels of protease and endoglucanase . Levels of EPS were reduced in both rpfE and orf4 mutants . These alterations in the levels of extracellular enzymes, which were relatively modest (between two- and threefold), did not affect the pathogenicity of Xcc on turnip . It is proposed that the gene designation should be rpfI for orf4. Carbohydr Res, 2000 Jan 12, 323(1-4), 235 - 9 Structure of the O-chain polysaccharide of the lipopolysaccharide of Xanthomonas campestris pv . manihotis GSPB 2755 and GSPB 2364; Shashkov AS et al.; The O-chain polysaccharide of the lipopolysaccharide of Xanthomonas campestris pv . manihotis strains GSPB 2755 and GSPB 2364 was studied by sugar and methylation analyses and 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, NOESY, and H-detected 1H, 13C heteronuclear multiple-quantum coherence (HMQC) experiments . The polysaccharide was found to contain L-rhamnose and L-xylose in the ratio 3:1, and the following structure of the tetrasaccharide repeating unit was established: {formula: see text} Genetika, 2000 Mar, 36(3), 357 - 60 {RAPD-markers linked to the locus for resistance to the race 4 pathogen for black rot, Xanthomonas campestris pv . campestris (Pamm.) Dow., in Brassica rapa L.}; Ignatov AN et al.; Association between the RAPD markers and the resistance to race 4 of the black rot causative agent was studied in Brassica rapa L . Experiments were carried out using doubled haploid lines, obtained via crosses between the race 4-susceptible fodder turnip and resistant pak-choi, and the F2 progeny of the crosses between the doubled haploid lines with contrasting resistance . The WE(22)980 RAPD marker inherited from the pak-choi and associated with the clubroot susceptibility was also linked to the locus responsible for the resistance to race 4 of Xanthomonas campestris pv . campestris . The two other RAPD markers were linked to susceptibility to black rot . Simultaneous association of the same DNA markers with the resistance/susceptibility to two different obligate pathogens favored the hypothesis on cluster organization of the resistance genes in plants . The markers described can be used in plant breeding and in further investigation of the genetic bases of resistance in plants. Appl Microbiol Biotechnol, 2000 Mar, 53(3), 323 - 7 Characterization of an extracellular poly(3-hydroxy-5-phenylvalerate) depolymerase from Xanthomonas sp . JS02; Kim H et al.; A bacterium, JS02, capable of degrading an aromatic medium-chain-length polyhydroxyalkanoate (PHA(MCL)), poly(3-hydroxy-5-phenylvalerate) (PHPV), was isolated from wastewater-treatment sludge (Ju et al . 1998), and was identified as a Xanthomonas species . An extracellular PHPV depolymerase was purified from the concentrated culture broth of Xanthomonas sp . JS02 by using a chromatography series on Sephadex G-75, QAE-Sephadex A-50 and hydroxyapatite . The molecular mass of the purified enzyme was estimated to be 41.7 kDa . The purified enzyme could hydrolyse PHPV and p-nitrophenyl (PNP)-esters of fatty acids, but did not hydrolyse short-chain-length PHAs, though the culture supernatant could hydrolyse them . The optimum pH range was 8.0-9.0 and the optimum temperature was 60 degrees C for PNP-octanoate hydrolysis . The Km values for PNP-hexanoate and PNP-octanoate were 10.9 and 0.88 microM, respectively. Turk J Pediatr, 1999 Apr-Jun, 41(2), 283 - 6 Stenotrophomonas maltophilia pneumonia in a premature infant; Ozkan H et al.; Stenotrophomonas (Xanthomonas) maltophilia is an aerobic, non-fermentative, gram-negative bacillus that is generally considered an opportunistic pathogen . Infections due to S . maltophilia have become increasingly important in the hospital environment . Patients compromised by debilitating illnesses, surgical procedures or indwelling vascular catheters are most prone to S . maltophilia infections . To our knowledge, we report the first case of S . maltophilia pneumonia in a premature infant of 31 weeks gestational age . Although the therapy of choice for severe infections caused by S . maltophilia remains to be decided, this patient was successfully treated by amikacin. Int J Syst Evol Microbiol, 2000 Mar, 50 Pt 2, 811 - 21 Genotypic characterization of xanthomonad strains isolated from passion fruit plants (Passiflora spp.) and their relatedness to different Xanthomonas species; Goncalves ER et al.; The genetic diversity of 55 xanthomonad strains isolated from passion fruit plants (Passiflora spp.) and identified as Xanthomonas campestris pv . passiflorae was initially assessed by randomly amplified polymorphic DNA (RAPD) analysis . The strains showed a high level of polymorphism with almost unique fingerprints . Fifteen clusters with a similarity of approximately 70% were identified, three of which were prevalent . There was a correlation between the clusters and the geographic origin of the strains . A representative strain of each cluster, together with the pathovar reference strain, were used to verify the relationships of these strains to 18 Xanthomonas species and Pseudomonas syringae pv . passiflorae . All Xanthomonas species yielded a unique RAPD profile and no consistent relatedness to the X . campestris pv . passiflorae strains was observed . Amplification products were also analysed by repetitive (rep) primers (BOX, ERIC and REP), RFLP of the 16S-23S rDNA intergenic spacer and SDS-PAGE of whole-cell proteins . All of these approaches generated profiles characteristic for each Xanthomonas species but the taxonomic position of the X . campestris pv . passiflorae strains could not be unequivocally assigned . Finally, DNA-DNA hybridization allowed a sound taxonomic allocation of the strains to Xanthomonas axonopodis pv . passiflorae. Int J Syst Evol Microbiol, 2000 Mar, 50 Pt 2, 665 - 77 Comparison of AFLP and rep-PCR genomic fingerprinting with DNA-DNA homology studies: Xanthomonas as a model system; Rademaker JL et al.; The genus Xanthomonas contains a large number of strains, which have been characterized by a variety of phenotypic and genotypic classification methods . The Xanthomonas collection constitutes one of the largest groups of bacteria that have been characterized phylogenetically by DNA-DNA homology studies and genomic fingerprinting . Presently, a total genomic DNA-DNA homology value of 70% represents an internationally accepted criterion to define bacterial species levels . However, the complexity of DNA-DNA reassociation kinetics methods precludes the rapid analysis of large numbers of bacterial isolates, which is imperative for molecular microbial diversity studies . Therefore, the aim of this study was to compare more facile PCR-based genomic fingerprinting techniques, such as repetitive-sequence-based (rep)-PCR and AFLP genomic fingerprinting, to DNA-DNA hybridization studies . Using three different primer sets, rep-PCR genomic fingerprint patterns were generated for 178 Xanthomonas strains, belonging to all 20 previously defined DNA-DNA homology groups, and one Stenotrophomonas maltophilia strain . In addition, AFLP genomic fingerprints were produced for a subset of 80 Xanthomonas strains belonging to the 20 DNA-DNA homology groups and for the S . maltophilia strain . Similarity values derived from rep-PCR- and AFLP-generated fingerprinting analyses were calculated and used to determine the correlation between rep-PCR- or AFLP-derived relationships and DNA-DNA homology values . A high correlation was observed, suggesting that genomic fingerprinting techniques truly reveal genotypic and phylogenetic relationships of organisms . On the basis of these studies, we propose that genomic fingerprinting techniques such as rep-PCR and AFLP can be used as rapid, highly discriminatory screening techniques to determine the taxonomic diversity and phylogenetic structure of bacterial populations. Scand J Urol Nephrol, 2000 Feb, 34(1), 67 - 9 Xanthomonas maltophilia infection in chronic peritoneal dialysis patients; Al-Hilali N et al.; Xanthomonas maltophilia infection has only been occasionally reported in patients receiving chronic peritoneal dialysis . We describe four cases of Xanthomonas maltophilia infection associated with chronic peritoneal dialysis . Two patients presented with peritonitis and two with exit site infection . All patients were diabetics, who immediately prior to the study had not received antibiotic therapy . Failure to respond to multiple antibiotic therapy resulted in catheter removal in both patients with peritonitis . In those patients with only exit site infections, dialysis could be continued following antibiotic the