Carbohydr Res, 1997 Oct 28, 304(1), 69 - 76 Novel alginate lyases from marine bacterium Alteromonas sp . strain H-4; Sawabe T et al.; A bacterium Alteromonas sp . strain H-4 isolated from Laminaria fronds produced extra- and intra-cellular alginate lyases and utilized alginate as its sole carbon source . An extracellular alginate lyase was purified from the culture supernatant of the strain and its substrate specificity was characterized . The estimated molecular mass of the enzyme was 32 kDa and the isoelectric point was 4.7 . Both polyM and polyG block degrading activities were observed using the substrate-containing gel overlay technique after isoelectric focusing of the enzyme . By analyzing the reaction products from the polyM block, polyG block, MG random block and intact alginate, three major peaks containing unsaturated tri-uronide through octa-uronide were detected for each substrate . The results indicate that the enzyme of Alteromonas sp . H-4 can degrade both polyM and polyG blocks with a K(m) in mg/mL 20-times higher for the polyM block. J Bacteriol, 1997 Dec, 179(24), 7617 - 24 Characterization of genes encoding dimethyl sulfoxide reductase of Rhodobacter sphaeroides 2.4.1T: an essential metabolic gene function encoded on chromosome II; Mouncey NJ et al.; Rhodobacter sphaeroides 2.4.1T is a purple nonsulfur facultative phototrophic bacterium which exhibits remarkable metabolic diversity as well as genomic complexity . Under anoxic conditions, in the absence of light and the presence of dimethyl sulfoxide (DMSO) or trimethylamine N-oxide (TMAO), R . sphaeroides 2.4.1T utilizes DMSO or TMAO as the terminal electron acceptor for anaerobic respiration, which is mediated by the molybdoenzyme DMSO reductase . Sequencing of a 13-kb region of chromosome II revealed the presence of 10 putative open reading frames, of which 5 possess homology to genes encoding the TMAO reductase (the tor system) of Escherichia coli . The dorS and dorR genes encode a sensor-regulator pair of the two-component sensory transduction protein family, homologous to the torS and torR gene products . The dorC gene was shown to encode a 44-kDa DMSO-inducible c-type cytochrome . The dorB gene encodes a membrane protein of unknown function homologous to the torD gene product . The dorA gene encodes DMSO reductase, containing the molybdopterin active site . Mutations were constructed in each of these dor genes, and the resulting mutants were shown to be impaired for DMSO-dependent anaerobic growth in the dark . The mutant strains exhibited negligible levels of DMSO reductase activity compared to the wild-type strain under similar growth conditions . Further, no DorA protein was detected in DorS and DorR mutant strains with anti-DorA antisera, suggesting that the products of these genes are required for the positive regulation of dor expression in response to DMSO . This characterization of the dor gene cluster is the first evidence that genes of chromosome CII encode metabolic functions which are essential under particular growth conditions. Helicobacter, 1996 Mar, 1(1), 62 - 4 Culture of Helicobacter pylori: effect of preimmersion of biopsy forceps in formalin; Yousfi MM et al.; BACKGROUND: Treatment of antibiotic-resistant Helicobacter pylori should be based on bacterial sensitivity testing that requires the ability to isolate the bacterium from gastric mucosal biopsies . The aim of this study was to determine whether the yield for detecting H . pylori infection by culture is reduced by immersion of biopsy forceps in formalin prior to obtaining the specimen . MATERIALS AND METHODS: Gastric antral mucosal biopsies (100 specimens) from 50 patients were obtained for culture of H . pylori . An antral biopsy was taken for culture, and with the same forceps a biopsy was taken for histological examination . The biopsy specimen was removed by shaking, whereas the forceps was immersed in 10% buffered formalin for the histological investigation . The forceps was then used without rinsing to obtain a second specimen for culture from an area adjacent to the first site . H . pylori status was determined by histological assessment with the Genta stain and a rapid urease test . RESULTS: Fifty patients with H . pylori infection documented by histological inquiry and positive rapid urease testing entered the study; 29 had duodenal ulcers, 5 had gastric ulcers, 1 had mucosal associated lymphoid tissue (MALT) lymphoma, and 15 were without ulcer disease . The results of culture both before and after immersion in formalin were identical . One patient had both cultures negative; the sensitivity of culture for detection of H . pylori infection was 98% (95% confidence interval = 93%-100%) . CONCLUSION: Preimmersion of biopsy forceps in formalin does not adversely affect the ability to culture H . pylori. Helicobacter, 1996 Sep, 1(3), 159 - 64 Gastric juice polymerase chain reaction: an alternative to histology in the diagnosis of Helicobacter pylori infection; Basso D et al.; BACKGROUND: Infection from Helicobacter pylori plays a role in several gastroduodenal diseases . The recent availability of molecular techniques, particularly the polymerase chain reaction (PCR), allows us to detect small amounts of this bacterium . The aims of this study were to compare PCR and histological findings and to ascertain the clinical usefulness of H . pylori PCR identification in different biological samples . MATERIALS AND METHODS: We studied 94 consecutive patients . Saliva, gastric juice, and four antral and four body biopsies were obtained from each patient . H . pylori was evaluated histologically in two antral and two body biopsies (Giemsa or Warthin-Starry stain) . After extraction, DNA was submitted for PCR amplification using the two primers HPU1 and HPU2, which amplified a 411-bp product from the urease gene A . RESULTS: Forty-nine patients were H . pylori-positive at histological workup . The sensitivity of PCR was 92% for gastric juice, 73% for antral biopsies, 61% for body biopsies, and 13% for saliva . Of the 45 H . pylori-negative patients at histological assessment, 7 (16%) had positive findings on PCR, mainly when gastric juice was examined . CONCLUSIONS: These results indicate that PCR is as sensitive as histological assessment . We suggest that PCR H . pylori detection in gastric juice is a sensitive method for diagnosing this infection. Biochem Biophys Res Commun, 1997 Nov 26, 240(3), 787 - 92 A pluripotent polyphenol oxidase from the melanogenic marine Alteromonas sp shares catalytic capabilities of tyrosinases and laccases; Sanchez-Amat A et al.; The recently characterized marine melanogenic bacterium MMB-1 contains a pluripotent polyphenol oxidase (PPO) which catalyzes the oxidation of a very wide range of substrates considered specific for tyrosinase or laccase . This range includes monophenols such as L-tyrosine, o-diphenols such as L-dopa, p-diphenols such as hydroquinone, o-aminophenols such as 3-hydroxyanthranilic acid, activated monophenols such as 2,6-dimethoxyphenol and syringaldazine, and chromophores such as ABTS . This is the first report of an enzyme that is able to catalyze the oxidation of compounds so far considered specific for tyrosinases (L-tyrosine) or laccase (syringaldazine), showing cresolase, catechol oxidase and laccase activities . Such PPO could be a very useful model to study the structural requirements, catalytic mechanisms and involvement of the copper sites existing in non-blue and blue copper-oxidases. Eur J Biochem, 1997 Nov 1, 249(3), 820 - 5 Characterization, gene cloning and expression of isocitrate lyase involved in the assimilation of one-carbon compounds in Hyphomicrobium methylovorum GM2; Tanaka Y et al.; Isocitrate lyase of an obligate methylotrophic bacterium, Hyphomicrobium methylovorum GM2, was purified to homogeneity and characterized . The enzyme is a homotetramer of identical 62-kDa subunits . After the enzyme had been incubated at temperatures up to 25 degrees C for 30 min, no loss of activity was observed . The enzyme was stable in the pH range of 7.5-9.0 . Maximum activity was observed at pH 7.5 and around 45 degrees C . The Km value for Ds-isocitrate was 0.51 mM . The activity required Mg2+ and was inhibited by oxalate, succinate and glycolate . The gene encoding the isocitrate lyase and its flanking regions were isolated from H . methylovorum GM2 . Nucleotide sequencing of recombinant plasmids revealed that the isocitrate lyase gene codes for a 540-amino-acid protein . The amino acid sequence of the enzyme is similar to those of the enzymes from Escherichia coli (40% identity) and cucumber (37% identity) . The recombinant plasmid, which was constructed by ligation of the cloned gene and an expression vector, pKK223-3, was introduced into E . coli HB101 . The transformed E . coli cells expressed isocitrate lyase, which was indistinguishable from the purified H . methylovorum GM2 isocitrate lyase on analysis by SDS/PAGE. Gastroenterology, 1997 Dec, 113(6 Suppl), S31 - 4; discussion S50 How does Helicobacter pylori cause mucosal damage? Direct mechanisms; Smoot DT; Helicobacter pylori-associated gastritis is characterized by an abundant inflammatory response and gastric epithelial cell injury . Adherence of H . pylori to gastric epithelial cells seems to be required for bacterial colonization of the gastric mucosa . Attachment of the bacterium to polarized gastric epithelial cells causes damage to microvilli and stimulates actin polymerization, which is associated with adherence pedestal formation . Studies suggest that H . pylori directly contributes to the injury of gastric epithelial cells by the elaboration of cytotoxic factors . The first toxin identified from H . pylori strains, known as vacuolating cytotoxin, induces vacuole formation in eukaryotic cells . Elaborated enzymes by H . pylori may also contribute directly to epithelial cell injury . Ammonia produced through urease activity may be toxic to gastric epithelial cells . H . pylori protease and lipase degrade gastric mucus and disrupt the phospholipid-rich layer at the apical epithelial cell surface, allowing for cell injury from back diffusion of gastric acid . This cell injury may lead to cell death, believed to result from induction of apoptosis . There are sufficient data to suggest that H . pylori, through direct pathogenic mechanisms, contributes significantly to the gastric mucosal injury associated with this infection, and may enhance the susceptibility of gastric epithelial cells to carcinogenic conversion. Gastroenterology, 1997 Dec, 113(6 Suppl), S21 - 8 Helicobacter pylori factors associated with disease development; Mobley HL; Although certain factors appear to predispose the host to infection by Helicobacter pylori, clearly the bacterium possesses a well-defined battery of virulence factors that allow the organism to: (1) colonize the gastric mucosa (urease, flagella, adhesins, acid-inhibitory protein, iron acquisition proteins, and heat shock proteins); (2) evade host defense (shedding of surface proteins, catalase, superoxide dismutase, and poorly reactive lipopolysaccharide); and (3) damage host tissue (vacuolating cytotoxin, protease, CagA-related factors, inducers of cytokines, and chemotaxins) . Together these factors allow H . pylori to persist in the host, establishing a chronic infection . Although many of these virulence factors are produced by all strains of H . pylori, there are also well-defined pathogenicity islands (contiguous stretches of chromosomal DNA) present in some strains that encode additional proteins including CagA that potentiate virulence . Strains possessing these "virulence cassettes" are isolated more frequently from patients with the more serious clinical manifestations associated with duodenal ulcer than from patients with gastritis alone or nonulcer dyspepsia. Infect Immun, 1997 Dec, 65(12), 5222 - 30 Identification and characterization of a K88- and CS31A-like operon of a rabbit enteropathogenic Escherichia coli strain which encodes fimbriae involved in the colonization of rabbit intestine; Adams LM et al.; Initiation of attaching-effacing lesions, which characterize infections with rabbit enteropathogenic Escherichia coli (REPEC), requires bacteria to adhere to the intestinal epithelium . This adherence is reflected in vitro by the affinity of these E . coli strains for various types of eukaryotic cells . TnphoA mutants of REPEC 83/39 (O15:H-) which had lost the ability to adhere to HEp-2 epithelial cells, guinea pig ileal brush borders, and mouse erythrocytes were generated . DNA sequencing of the region surrounding the inactivating transposon insertions within a 95-kb plasmid, designated pRAP for REPEC adherence plasmid, revealed extensive homology between that region and the structural genes of enterotoxigenic E . coli operons encoding the K88 and CS31A fimbrial adhesins and the genes for the afr2 adhesin from REPEC B10 (O103:H2) . Seven genes of the ral operon (for REPEC adherence locus), including three putative minor fimbrial subunit genes (ralC, ralF, and ralH), a major fimbrial subunit gene (ralG), a gene of unknown function (ralI), and genes for two fimbrial subunit chaperones (ralD and ralE), were sequenced . When inoculated perorally into weanling rabbits, a mutant with a TnphoA insertion in the ralE gene showed a 10-fold reduction in colonizing ability, with only 1 of 10 rabbits excreting bacteria compared to all 5 of those infected with the wild-type parent strain (P = 0.002) . The severity of the diarrheal illness caused by the mutant strain was also reduced . Western blotting of surface protein extracts of strain 83/39 with hyperimmune anti-83/39 antiserum, adsorbed with the ralE mutant, revealed a 32-kDa protein which was absent from protein extracts of two nonadherent mutants . The adsorbed antiserum also bound to the surface of strain 83/39 but not to nonadherent mutants, as detected by immunogold labeling . These results indicate that the ral operon of REPEC 83/39 contains genes necessary for the biosynthesis of fine fimbriae which are responsible for in vitro adherence of the bacteria and play a role in their colonization of, and hence virulence for, rabbits . The putative major fimbrial subunit is a protein with an observed molecular size of approximately 32 kDa which, when assembled, appears to form a capsule of fimbriae surrounding the bacterium similar to that described for CS31A. J Bacteriol, 1997 Dec, 179(23), 7435 - 45 Genetic requirements and mutational specificity of the Escherichia coli SOS mutator activity; Fijalkowska IJ et al.; To better understand the mechanisms of SOS mutagenesis in the bacterium Escherichia coli, we have undertaken a genetic analysis of the SOS mutator activity . The SOS mutator activity results from constitutive expression of the SOS system in strains carrying a constitutively activated RecA protein (RecA730) . We show that the SOS mutator activity is not enhanced in strains containing deficiencies in the uvrABC nucleotide excision-repair system or the xth and nfo base excision-repair systems . Further, recA730-induced errors are shown to be corrected by the MutHLS-dependent mismatch-repair system as efficiently as the corresponding errors in the rec+ background . These results suggest that the SOS mutator activity does not reflect mutagenesis at so-called cryptic lesions but instead represents an amplification of normally occurring DNA polymerase errors . Analysis of the base-pair-substitution mutations induced by recA730 in a mismatch repair-deficient background shows that both transition and transversion errors are amplified, although the effect is much larger for transversions than for transitions . Analysis of the mutator effect in various dnaE strains, including dnaE antimutators, as well as in proofreading-deficient dnaQ (mutD) strains suggests that in recA730 strains, two types of replication errors occur in parallel: (i) normal replication errors that are subject to both exonucleolytic proofreading and dnaE antimutator effects and (ii) recA730-specific errors that are not susceptible to either proofreading or dnaE antimutator effects . The combined data are consistent with a model suggesting that in recA730 cells error-prone replication complexes are assembled at sites where DNA polymerization is temporarily stalled, most likely when a normal polymerase insertion error has created a poorly extendable terminal mismatch . The modified complex forces extension of the mismatch largely at the exclusion of proofreading and polymerase dissociation pathways . SOS mutagenesis targeted at replication-blocking DNA lesions likely proceeds in the same manner. J Bacteriol, 1997 Dec, 179(23), 7264 - 73 Analysis of the fnrL gene and its function in Rhodobacter capsulatus; Zeilstra-Ryalls JH et al.; The fnr gene encodes a regulatory protein involved in the response to oxygen in a variety of bacterial genera . For example, it was previously shown that the anoxygenic, photosynthetic bacterium Rhodobacter sphaeroides requires the fnrL gene for growth under anaerobic, photosynthetic conditions . Additionally, the FnrL protein in R . sphaeroides is required for anaerobic growth in the dark with an alternative electron acceptor, but it is not essential for aerobic growth . In this study, the fnrL locus from Rhodobacter capsulatus was cloned and sequenced . Surprisingly, an R . capsulatus strain with the fnrL gene deleted grows like the wild type under either photosynthetic or aerobic conditions but does not grow anaerobically with alternative electron acceptors such as dimethyl sulfoxide (DMSO) or trimethylamine oxide . It is demonstrated that the c-type cytochrome induced upon anaerobic growth on DMSO is not synthesized in the R . capsulatus fnrL mutant . In contrast to wild-type strains, R . sphaeroides and R . capsulatus fnrL mutants do not synthesize the anaerobically, DMSO-induced reductase . Mechanisms that explain the basis for FnrL function in both organisms are discussed. Scand J Immunol, 1997 Nov, 46(5), 500 - 5 Down-regulatory effect of Mycobacterium leprae cell wall lipids on phagocytosis, oxidative respiratory burst and tumour cell killing by mouse bone marrow derived macrophages; Moura AC et al.; The authors have previously demonstrated that lipids from Mycobacterium leprae cell walls inhibit macrophage functions and are endowed with anti-inflammatory properties in vivo . To investigate these observations further, the authors describe here the influence of dead M . leprae or of the lipids extracted from the cell wall of the mycobacterium, enclosed in liposomes, on the phagocytic, oxidative respiratory burst and tumouricidal ability of bone marrow derived macrophages in vitro . Dead M . leprae or its cell wall lipids abrogated the oxidative respiratory burst and phagocytic ability of mouse bone marrow derived macrophages . A dose-dependent inhibitory effect of the bacterial lipid extract on tumour cell killing by lipopolysaccharide (LPS)-activated bone marrow derived macrophages was demonstrated . However, when delipidated M . leprae was added to cultures of bone marrow derived macrophages, immune phagocytosis and superoxide production was up-regulated . Mycobacterium leprae or its lipids did not appear to be toxic to those cells assayed by the MTT (methyl thiazol tetrazolium) test . These data, added to our preceding observations, support the hypothesis that the down-regulatory activity of M . leprae wall lipids on macrophage function might be one of the evasive mechanisms of the bacterium to enable it to perpetuate itself in the host tissues. Mol Gen Genet, 1997 Oct, 256(3), 211 - 22 Differential activation of two ACC oxidase gene promoters from melon during plant development and in response to pathogen attack; Lasserre E et al.; ACC (1-aminocyclopropane-1-carboxylate) oxidase genes are differentially expressed in melon during development and in response to various stresses . We investigated the molecular basis of their transcription by analyzing the 5' untranslated regions of the ACC oxidase genes CM-ACO1 and CM-ACO3 . In order to determine how their temporal and spatial expression patterns were established, we fused the promoter regions of CM-ACO1 (726 bp) and CM-ACO3 (2260 bp) to the beta-glucuronidase (GUS) reporter gene and examined their regulation in transgenic tobacco plants . The CM-ACO1 promoter was able to drive GUS expression in response to wounding, and to treatment with ethylene or copper sulfate . It was also rapidly induced (8-12 h postinoculation) in tobacco leaves inoculated with the hypersensitive response (HR)-inducing bacterium Ralstonia solanacearum . Expression was also observed during compatible interactions but was delayed . In contrast, the CM-ACO3 promoter was not expressed in response to infection, but was up-regulated during flower development . Both promoters were regulated during leaf senescence but in different patterns . The CM-ACO1-driven GUS activity increased sharply concomitantly with the onset of chlorophyll breakdown, while the CM-ACO3 promoter drove strong GUS expression in green, fully expanded leaves and this declined at the onset of senescence . This result is consistent with the expression patterns of these two genes in senescent melon leaves . These data suggest that the regulation of expression of CM-ACO1 is related preferentially to stress responses, whereas CM-ACO3 seems to be associated with developmental processes . The possible role of ethylene is discussed, particularly in the regulation of the CM-ACO1 gene in response to stress and during senescence. J Wildl Dis, 1997 Oct, 33(4), 733 - 7 Humoral immune response of cottontail rabbits naturally infected with Francisella tularensis in southern Illinois; Shoemaker D et al.; Cottontail rabbits (Sylvilagus floridanus) usually are thought to succumb to infection with Francisella tularensis . Reports of a rabbit population from southern Illinois (USA) with a high prevalence of F . tularensis antibodies suggested that some cottontails survived infection with this typically fatal bacterium . Our goal was to examine the humoral response of cottontails from a study area in southern Illinois for which multiple serum samples existed . Multiple sera were collected from 79 cottontails from 1986 to 1990 and 63% gained, lost, or maintained ELISA titers of IgM and IgG isotype antibodies . The typical pattern of antibody response appeared to be IgM isotype antibodies first, followed by IgG isotype antibodies, with both generally increasing to high titers . Negative culture attempts of liver tissue from 51 cottontails with varying antibody responses suggested that chronic infection did not occur in rabbits that developed antibody . The significance of the cottontail antibody response in resolution or prevention of tularemia infection remains unclear. Eur J Gastroenterol Hepatol, 1997 Oct, 9(10), 935 - 7 Helicobacter pylori and non-steroidal anti-inflammatory drugs: lone agents or partners in crime? Roseveare CD, Colin-Jones DG. A variety of mechanisms are responsible for the gastric and duodenal mucosal injury known to result from the consumption of non-steroidal anti-inflammatory drugs (NSAIDs) . Many of these mechanisms may be influenced by coexistent infection with Helicobacter pylori . However, evidence of increased risk from NSAIDs in patients with this bacterium is contradictory . While some authors have reported that symptoms, severity and prevalence of mucosal damage are higher in H . pylori-positive individuals taking NSAIDs than in those who are H . pylori negative, others have noted no significant difference . Reasons for this conflict may include the age of the subjects studied, duration of treatment, toxicity of the NSAID employed and pathogenicity factors related to different strains of H . pylori. J Bacteriol, 1997 Nov, 179(22), 7161 - 4 Plasmid pRQ7 from the hyperthermophilic bacterium Thermotoga species strain RQ7 replicates by the rolling-circle mechanism; Yu JS et al.; The hyperthermophilic bacterium Thermotoga species strain RQ7 harbors an 846-bp plasmid, pRQ7, with a single open reading frame . Previously published analyses of the DNA sequence of pRQ7 suggested that it may replicate by a rolling-circle (RC) replication mechanism, and this report provides experimental evidence supporting this hypothesis . Single-stranded pRQ7 DNA accumulates in strain RQ7, as evidenced by the facts that this DNA bound to nitrocellulose membranes under nondenaturing conditions, was sensitive to S1 nuclease digestion, and hybridized to only one of two homologous DNA probes specific for each strand of the plasmid . The DNA encoding the open reading frame was cloned and expressed in Escherichia coli and gave a protein with a molecular mass of 26 kDa, similar to that deduced by sequence analysis . This protein bound to a fragment of pRQ7 that contains a putative double-stranded replication region in a magnesium-dependent reaction and made this fragment sensitive to S1 nuclease activity . It did not cause this same S1 nuclease sensitivity in the remainder of pRQ7 . This activity on pRQ7 DNA suggests that this protein plays a role in plasmid replication. Eur J Biochem, 1997 Oct 15, 249(2), 630 - 6 Electron transfer towards the RCI-type photosystem in the green sulphur bacterium Chlorobium limicola forma thiosulphatophilum studied by time-resolved optical spectroscopy in vivo; Albouy D et al.; Flash-induced spectral changes in the wavelength region of the alpha-peaks of heme proteins and in the time domain from microseconds to seconds have been recorded on whole cells of the green sulphur bacterium Chlorobium limicola forma thiosulfatophilum . Extensive flash-excitation by trains of flashes resulted in oxidation of 7-8 c-type heme molecules/photosynthetic reaction centre . The complement of heme species was found to be spectrally heterogeneous allowing the study of electron transfer events induced by an isolated single-turnover flash . Under single-flash conditions, a c553 heme was seen to become oxidised with tau = 30 micros, concommitant with the reduction of the primary donor of the reaction centre . Subsequently, the alpha-peak of the photooxidised heme broadened and shifted towards longer wavelengths (tau = 70 micros) indicating equilibration of the positive charge over two differing heme species . In the time domain t > 1 ms, rereduction of c-type hemes was seen to be paralleled by a blue shift and further broadening of the alpha-peak . Concommitantly, b-type hemes were observed to first become reduced (within a few milliseconds), then over-oxidised (t > 200 ms) and eventually rereduced to their redox state prior to the flash . The results obtained are discussed with respect to the question of the identity of the immediate electron donor to the photosynthetic reaction centre and with respect to the involvement of a cytochrome bc complex in photo-induced electron transport of green sulphur bacteria. Eur J Biochem, 1997 Oct 15, 249(2), 564 - 75 Molecular characterisation of the pifC gene encoding translation initiation factor 3, which is required for normal photosynthetic complex formation in Rhodobacter sphaeroides NCIB 8253; Babic S et al.; In order to determine whether translation initiation events play a selective role in regulating the expression of photosynthetic complexes in the photosynthetic bacterium Rhodobacter sphaeroides, we have undertaken an initial study to investigate the potential role of translation initiation factor IF3, which also behaves as a pleiotropic regulatory factor in some bacteria . Following the isolation and purification of a 24-kDa IF3-like protein (PifC) from R . sphaeroides, we used nested PCR to clone and characterise the encoding gene, pifC (photosynthesis-affecting initiation factor) . The 545-bp pifC encodes a protein exhibiting 60% identity (78.6% similarity) with the Escherichia coli IF3 (InfC) protein and, in common with all other IF3 genes identified to date, pifC possesses a rare initiation codon (AUA) . Furthermore, in common with IF3, PifC was shown here to perform a discriminatory function towards CUG start codons, confirming its role and function as an IF3 in R . sphaeroides . Insertion of a kanamycin resistance cassette into the 5' end of pifC resulted in a viable phenotype which exhibits growth rates similar to wild type but which possesses reduced bacteriochlorophyll and photosynthetic complexes in semi-aerobic cultures . It is shown here that the mutant is still able to produce a PifC protein but that it possesses reduced IF3 activity . This may account for the viable nature of the mutant strain, and may indicate that the effect of the mutation on photosynthesis can be more severe than shown in the present study . The mechanisms by which PifC may exert its selective regulatory effect on photosynthesis expression are discussed. Gene, 1997 Oct 1, 198(1-2), 171 - 80 Codon usage and nucleotide composition in Coxiella burnetii; Lin Z et al.; Coxiella burnetii, the causative agent of Q fever, is an obligate intracellular bacterium . With the development of molecular biology techniques, there have been increasing efforts on gene cloning and other genetic analyses of this organism . In this report, we tabulate the codon usage (CU) and nucleotide (nt) co-occurrence in C . burnetii, based on available nt sequence data . The average G+C content of the C . burnetii genome is 42.4%, where the G+C content is 42.7% for the chromosome and 38.7% for the plasmid . In comparison to Escherichia coli, there is biased CU . Some codons are frequently used in C . burnetii, but rarely used in E . coli and vice versa . Plasmid genes prefer A or T at the first or third position of a codon . However, TAA remains the most used stop codon . In the AT-rich DNA of C . burnetii, A or T tend to occur together, forming A or T tracks. Mol Microbiol, 1997 Sep, 25(5), 847 - 58 Assembly of the cell division protein FtsZ into ladder-like structures in the aerial hyphae of Streptomyces coelicolor; Schwedock J et al.; In the filamentous bacterium Streptomyces coelicolor, the cell division protein FtsZ is required for the conversion of multinucleoidal aerial hyphae into chains of uninucleoidal spores, although it is not essential for viability . Using immunofluorescence microscopy, we have shown that FtsZ assembles into long, regularly spaced, ladder-like arrays in developing aerial hyphae, with an average spacing of about 1.3 microm . Within individual hyphae, ladder formation was relatively synchronous and extended for distances over 100 microm . These ladders were present only transiently, decreasing in intensity as chromosomes separated into distinct nucleoids and disappearing upon the completion of septum formation . Evidence from the overall intensity of immunofluorescence staining suggested that ladder formation was regulated in part at the level of the accumulation and degradation of FtsZ within individual aerial hyphae . Finally, FtsZ ladder formation was under developmental control in that long arrays of FtsZ rings could not be detected in certain so-called white mutants (whiG, whiH and whiB), which are blocked in spore formation . The assembly of FtsZ into ladders represents the earliest known molecular manifestation of the process of spore formation, and its discovery provides insight into the role of whi genes in the conversion of aerial hyphae into chains of spores . We have also described a novel use of a cell wall-staining technique to visualize apical tip growth in vegetatively growing hyphae. Vaccine, 1997 Nov, 15(16), 1779 - 83 Comparative efficacy of a Coxiella burnetii chloroform:methanol residue (CMR) vaccine and a licensed cellular vaccine (Q-Vax) in rodents challenged by aerosol; Waag DM et al.; Q fever is an acute and self-limited febrile illness caused by the obligate intracellular bacterium Coxiella burnetii . While phase I cellular Q fever vaccines are efficacious in humans, vaccination of immune individuals may result in sterile abscesses and granulomas . The chloroform:methanol residue vaccine (CMR) was developed as a safer alternative . The efficacy of a licensed phase I cellular vaccine (Q-Vax) was compared with that of CMR vaccine in A/J mice and Hartley guinea pigs challenged with virulent phase I C . burnetii by aerosol . Both vaccines were efficacious . The CMR vaccine dose required to protect 50% of mice (PD50) against lethal aerosol challenge (11 LD50) was one-third of the Q-Vax dose . However, the PD50 for CMR was four times the Q-Vax dose in guinea pigs challenged by aerosol (60 LD50) . It was concluded that CMR is an efficacious alternative to cellular Q fever vaccines for the prevention of Q fever. Appl Environ Microbiol, 1997 Nov, 63(11), 4355 - 9 Glycogen biosynthesis via UDP-glucose in the ruminal bacterium Prevotella bryantii B1(4); Lou J et al.; Prevotella bryantii is an important amylolytic bacterium in the rumen that produces considerable amounts of glycogen when it is grown on maltose . Radiolabel studies indicated that glucose-1-phosphate was converted to UDP-glucose, and this latter intermediate served as the immediate precursor for glycogen synthesis . High levels of UDP-glucose pyrophosphorylase activities (> 1,492 nmol/min/mg of protein) were detected in cells grown on maltose, cellobiose, glucose, or sucrose, and activity was greatly stimulated (by approximately 60-fold) by the addition of fructose-1,6-bis phosphate (half-maximal activation concentration was 240 microM) . However, ADP-glucose pyrophosphorylase activity was not detected in any of the cultures . Glycogen synthase activity in maltose-grown cultures (48 nmol/min/mg of protein) was higher than that in cellobiose-, sucrose-, and glucose-grown cultures (< 26 nmol/min/mg of protein) . This is the first report of a bacterium that exclusively uses UDP-glucose to synthesize glycogen . The elucidation of this unique glycogen biosynthesis pathway provides information necessary to further investigate the role of bacterial glycogen accumulation in rumen metabolism. J Wildl Dis, 1996 Oct, 32(4), 691 - 4 Isolation of Mycoplasma felis from a serval (Felis serval) with severe respiratory disease; Johnsrude JD et al.; We report cytologic observations and isolation of Mycoplasma felis in September 1992 from the lower respiratory tract of a 3-week-old captive serval (Felis serval) cub with pneumonia, in Florida (USA) . Septic, neutrophilic inflammation with a large, monomorphic population of unique, pleomorphic, intracellular and extracellular rods was diagnosed from a transtracheal wash . Mycoplasma felis was the only bacterium isolated in significant numbers from the transtracheal wash. Microbiology, 1997 Oct, 143 ( Pt 10), 3085 - 99 Low-resolution sequencing of Rhodobacter sphaeroides 2.4.1T: chromosome II is a true chromosome; Choudhary M et al.; The photosynthetic bacterium Rhodobacter sphaeroides 2.4.1T has two chromosomes, CI (approximately 3.0 Mb) and CII (approximately 0.9 Mb) . In this study a low-redundancy sequencing strategy was adopted to analyse 23 out of 47 cosmids from an ordered CII library . The sum of the lengths of these 23 cosmid inserts was approximately 495 kb, which comprised approximately 417 kb of unique DNA . A total of 1145 sequencing runs was carried out, with each run generating 559 +/- 268 bases of sequence to give approximately 640 kb of total sequence . After editing, approximately 2.8% bases per run were estimated to be ambiguous . After the removal of vector and Escherichia coli sequences, the remaining approximately 565 kb of R . sphaeroides sequences were assembled, generating approximately 291 kb of unique sequences . BLASTX analysis of these unique sequences suggested that approximately 131 kb (45% of the unique sequence) had matches to either known genes, or database ORFs of hypothetical or unknown function (dORFs) . A total of 144 strong matches to the database was found; 101 of these matches represented genes encoding a wide variety of functions, e.g . amino acid biosynthesis, photosynthesis, nutrient transport, and various regulatory functions . Two rRNA operons (rrnB and rrnC) and five tRNAs were also identified . The remaining 160 kb of DNA sequence which did not yield database matches was then analysed using CODONPREFERENCE from the GCG package . This analysis suggested that 122 kb (42% of the total unique DNA sequence) could encode putative ORFs (pORFs), with the remaining 38 kb (13%) possibly representing non-coding intergenic DNA . From the data so far obtained, CII does not appear to be specialized for encoding any particular metabolic function, physiological state or growth condition . These data suggest that CII contains genes which are functionally as diverse as those found on any other bacterial chromosome and also contains sequences (pORFs), which may prove to be unique to this organism. IARC Sci Publ, 1997, (138), 325 - 9 Infection with Helicobacter pylori and parasites, social class and cancer; Boffetta P; Three genera of parasites are known or suspected risk factors for cancer in humans: Schistosoma, Opisthorchis and Clonorchis . No adequate information is available on the determinants of infections related to social class . Infection with the bacterium Helicobacter pylori is an important cause of stomach cancer . Studies, in particular from the United Kingdom and the United States of America, strongly suggest that social class factors, especially those acting during childhood, are determinants of the infection, with odds ratios of seroprevalence of the order of 1.5-5 for lower social class as compared with higher social class . A conservative estimate of the contribution of social class, acting through an increased prevalence of H . pylori infection, to the burden of stomach cancer gives a figure of over 50,000 stomach cancers per year worldwide, or 8% of all stomach cancers . In countries with both high and low prevalence of infection with H . pylori, it is likely that a sizeable proportion of this difference is due to social-class-related risk factors of infection. Infect Immun, 1997 Nov, 65(11), 4738 - 46 Utilization of similar mechanisms by Legionella pneumophila to parasitize two evolutionarily distant host cells, mammalian macrophages and protozoa; Gao LY et al.; The Legionnaires' disease bacterium, Legionella pneumophila, is an intracellular pathogen of humans that is amplified in the environment by intracellular multiplication within protozoa . Within both evolutionarily distant hosts, the bacterium multiplies in a rough endoplasmic reticulum-surrounded phagosome that is retarded from maturation through the endosomal-lysosomal degradation pathway . To gain an understanding of the mechanisms utilized by L . pneumophila to invade and replicate within two evolutionarily distant hosts, we isolated a collection of 89 mini-Tn10::kan insertion mutants that exhibited defects in cytotoxicity, intracellular survival, and replication within both U937 macrophage-like cells and Acanthamoeba polyphaga . Interestingly, the patterns of defects in intracellular survival and replication of the mutants within both host cells were highly similar, and thus we designated the defective loci in these mutants pmi (for protozoan and macrophage infectivity loci) . On the basis of their ability to attach to host cells and their growth kinetics during the intracellular infection, the mutants were grouped into five groups . Groups 1 and 2 included 41 mutants that were severely defective in intracellular survival and were completely or substantially killed during the first 4 h of infection in both host cells . Three members of group 1 were severely defective in attachment to both U937 cells and A . polyphaga, and another four mutants of group 1 exhibited severe defects in attachment to A . polyphaga but only a mild reduction in their attachment to U937 cells . Four members of groups 1 and 2 were serum sensitive . Intracellular replication of mutants of the other three groups was less defective than that of mutants of groups 1 and 2, and their growth kinetics within both host cells were similar . The mutants were tested for several other phenotypes in vitro, revealing that 14 of the pmi mutants were resistant to NaCl, 3 had insertions in dot or icm, 3 were aflagellar, 12 were highly intolerant to a hyperosmotic medium, and one failed to grow in a minimal medium . Our data indicated that similar mechanisms are utilized by L . pneumophila to replicate within two evolutionarily distant hosts . Although some mechanisms of attachment to both host cells were similar, other distinct mechanisms were utilized by L . pneumophila to attach to A . polyphaga . Our data supported the hypothesis that preadaptation of L . pneumophila to infection of protozoa may play a major role in its ability to replicate within mammalian cells and cause Legionnaires' disease. Infect Immun, 1997 Nov, 65(11), 4531 - 8 A novel component different from endotoxin extracted from Prevotella intermedia ATCC 25611 activates lymphoid cells from C3H/HeJ mice and gingival fibroblasts from humans; Iki K et al.; A novel immunobiologically active fraction was prepared from a phenol-water extract of Prevotella intermedia ATCC 25611 by Sephadex G-100 column chromatography . The fraction consisted mainly of carbohydrate and protein and was devoid of fatty acid . The fraction showed high-molecular-weight bands (10,000 to 12,000) on deoxycholate polyacrylamide gel electrophoresis (DOC-PAGE) and was scarcely active in a Limulus test . We designated the fraction Prevotella glycoprotein (PGP) . The PGP fraction showed strong mitogenicity on splenocytes and cytokine-inducing activities on peritoneal macrophages from both C3H/HeJ and C3H/HeN mice, and it stimulated human gingival fibroblasts to produce cytokines . The activities of the PGP fraction were resistant to heat inactivation (100 degrees C for 1 h) and protease treatments and were scarcely inhibited by polymyxin B . In contrast, the purified lipopolysaccharide fraction (LPS-PCP) extracted from the same bacterium with a phenol-chloroform-petroleum ether mixture, which showed strong Limulus activity and a single low-molecular-weight band (approximately 3,000) on DOC-PAGE, lacked the activities on splenocytes and macrophages from C3H/HeJ mice and human gingival fibroblasts . The activities of the LPS-PCP fraction on cells from C3H/HeN mice were completely inhibited by polymyxin B . The LPS extracted from the same bacterium with hot phenol-water (LPS-PW) exhibited the properties of both the PGP fraction and the LPS-PCP fraction . These findings suggest that the unique bioactivities of the LPS-PW fraction of oral black-pigmented bacteria reported to date, which differed from those of the classical endotoxin, were derived from the PGP fraction and not from the LPS itself. Appl Microbiol Biotechnol, 1997 Sep, 48(3), 367 - 72 Extracellular reduction of selenite by a novel marine photosynthetic bacterium; Yamada A et al.; A novel purple nonsulfur bacterium strain NKPB030619, which has resistance to over 5 mM selenite, was isolated from a marine environment . An initial concentration of 1.1 mM selenite, added to the medium, was decreased to under 0.05 mM within 5 days . The color of the cell suspension turned red within 2 days . The red coloration gradually decreased and black precipitates appeared during 2 weeks of cultivation . Under these conditions, two main types of deposit were formed extracellularly . These deposits were thought to contain red amorphous selenium and black vitreous selenium . The selenite reduction to elemental selenium in this bacterium was induced by the introduction of light and L-malic acid under anaerobic conditions . These results suggest that selenite reduction is coupled with photosynthesis and L-malic acid can serve as the indirect electron donor for its reduction . Phylogenetic analysis based on the 16S rDNA sequence showed that NKPB0360619 belongs to the alpha subdivision of Proteobacteria and is classified into the Rhodobacter species . The highest similarity of 86.2% was observed with R . sphaeroides. Lett Appl Microbiol, 1997 Sep, 25(3), 162 - 8 Isolation and characterization of a transposon mutant of Shewanella putrefaciens MR-1 deficient in fumarate reductase; Myers CR et al.; A transposon mutant, designated CMTn-3, of Shewanella putrefaciens MR-1 that was deficient in fumarate reduction was isolated and characterized . In contrast to the wild-type, CMTn-3 could not grow anaerobically with fumarate as the electron acceptor, and it lacked benzyl viologen-linked fumarate reductase activity . Consistent with this, CMTn-3 lacked a 65 kDa c-type cytochrome, which is the same size as the fumarate reductase enzyme . CMTn-3 retained the wild-type ability to use nitrate, iron(III), manganese(IV) and trimethylamine N-oxide (TMAO) as terminal electron acceptors . The results indicate that the loss of the fumarate reductase enzyme does not affect other anaerobic electron transport systems in this bacterium. Eur J Biochem, 1997 Sep 1, 248(2), 323 - 8 Multiheme cytochromes from the sulfur-reducing bacterium Desulfuromonas acetoxidans; Pereira IA et al.; Two new multiheme cytochromes were isolated from the anaerobic sulfur reducing bacterium Desulfuromonas acetoxidans . They have monomeric molecular masses of 50 and 65 kDa and contain six and eight hemes, respectively . Visible and EPR spectroscopies, in the as-isolated (oxidised) cytochromes, show the presence of only low-spin hemes in the 50-kDa cytochrome, and of high-spin and low-spin hemes in the 65-kDa cytochrome . The EPR spectra of the native 65-kDa cytochrome indicate multiple heme-heme interactions, including integer-spin systems as judged by parallel-mode EPR . The 50-kDa cytochrome has a complex redox pattern, as shown by EPR redox titrations, and contains one heme with unusual characteristics . Both cytochromes cover an extremely wide range of reduction potentials, which go from +100 mV to -375 mV for the 50-kDa cytochrome, and +185 mV to -235 mV for the 65-kDa cytochrome . The two cytochromes were tested for hydroxylamine oxidoreductase activity and polysulfide reductase activity, but neither displayed any activity . In contrast, it was found for the first time that the previously characterised cytochrome c551.5, from the same bacterium is very active in the reduction of polysulfide, which suggests that it acts as a terminal reductase in D . acetoxidans. Biochem Biophys Res Commun, 1997 Oct 20, 239(2), 626 - 32 Apoptosis in gastric epithelial cells is induced by Helicobacter pylori and accompanied by increased expression of BAK; Chen G et al.; Carriage of the bacterium H . pylori in the human stomach is associated with evidence of increased epithelial cell apoptosis . This may be of significance in the etiology of gastritis, peptic ulcers, and neoplasia . The ability of H . pylori to directly induce epithelial apoptosis was examined in vitro by fluorescence and electron microscopy, flow cytometry, and DNA fragmentation ELISA . The induction of apoptosis by H . pylori was time and concentration-dependent and inhibited by preventing direct bacterial-epithelial cell contact . Apoptosis was accompanied by increased expression of Bak, with little change in expression of other Bcl-2 family proteins . The expression of Bak was also increased in gastric biopsies from patients colonized by H . pylori . Thus, H . pylori induces gastric epithelial cell apoptosis, by a Bak-dependent pathway . Am J Pathol, 1997 Oct, 151(4), 933 - 41 Increased oxidative DNA damage and hepatocyte overexpression of specific cytochrome P450 isoforms in hepatitis of mice infected with Helicobacter hepaticus; Sipowicz MA et al.; A recently discovered bacterium, Helicobacter hepaticus, infects the intrahepatic bile canaliculi of mice, causing a severe chronic hepatitis culminating in liver cancer . Thus, it affords an animal model for study of bacteria-associated tumorigenesis including H . pylori-related gastric cancer . Reactive oxygen species are often postulated to contribute to this process . We now report that hepatitis of male mice infected with H . hepaticus show significant increases in the oxidatively damaged DNA deoxynucleoside 8-hydroxydeoxyguanosine, with the degree of damage increasing with progression of the disease . Perfusion of infected livers with nitro blue tetrazolium revealed that superoxide was produced in the cytoplasm of hepatocytes, especially in association with plasmacytic infiltrates near portal triads . Contrary to expectations, Kupffer cells, macrophages, and neutrophils were rarely involved . However, levels of cytochrome P450 (CYP) isoforms 1A2 and 2A5 in hepatocytes appeared to be greatly increased, as indicated by the number of cells positive in immunohistochemistry and the intensity of staining in many cells, concomitant with severe hepatitis . The CYP2A5 immunohistochemical staining co-localized with formazan deposits resulting from nitro blue tetrazolium reduction and occurred in nuclei as well as cytoplasm . These findings suggest that CYP2A5 contributes to the superoxide production and 8-hydroxydeoxyguanosine formation, although reactive oxygen species from an unknown source in the hepatocytes leading to CYP2A5 induction or coincidental occurrence of these events are also possibilities . Three glutathione S-transferase isoforms, mGSTP1-1 (pi), mGSTA1-1 (YaYa), and mGSTA4-4, also showed striking increases evidencing major oxidative stress in these livers. Appl Environ Microbiol, 1997 Oct, 63(10), 4135 - 8 Detection of Mycobacterium ulcerans in environmental samples during an outbreak of ulcerative disease; Ross BC et al.; Mycobacterium ulcerans is an environmental bacterium which causes chronic skin ulcers . Despite significant epidemiological evidence to suggest that water is the source of infection, the organism has never been identified in the environment . Environmental water samples were collected from a small town in which an outbreak of 29 cases had occurred in a 3-year period . These were examined by mycobacterial culture and PCR amplification . Similar to previous studies, M . ulcerans was not cultured from the water samples . However, five samples were positive for M . ulcerans by PCR . These samples were collected from a swamp and a golf course irrigation system within the outbreak area . This is the first time that M . ulcerans has been demonstrated to be present in the environment and supports the postulated epidemiology of disease due to this organism. Berl Munch Tierarztl Wochenschr, 1997 Jul-Aug, 110(7-8), 267 - 71 {Pilot study on the prevalence of Ornithobacterium rhinotracheale infections in food chickens in northwest Germany}; Ryll M et al.; Samples of sera from broiler chicken and broiler chicken breeder flocks of North Western Germany were examined for presence of antibodies against Ornithobacterium (O.) rhinotracheale with a self-developed ELISA system . A total of 3600 samples of sera from 190 broiler flocks in 70 different farms were tested . In 332 samples of sera (9.4%) from 25 flocks (13.2%) in 22 farms specific antibodies were detected . Additionally, serum samples from the breeder hens, taken between the 9, and 61, weeks of age were tested . In 28 from 29 flocks (96.6%) specific antibodies were detected using this ELISA-system . First detectable antibodies were found between the 14, and 36, week of age in the parent breeder flocks . These results show that infections with O . rhinotracheale are widely distributed in the parent-breeder chicken broiler flocks . The significance of this bacterium as the cause of respiratory diseases in chickens are discussed. Eur J Epidemiol, 1997 Sep, 13(6), 729 - 31 Copy number of the 16S rRNA gene in Coxiella burnetii; Afseth G et al.; Coxiella burnetii is an obligate intracellular bacterium with a doubling time of 5-7 hours . Chromosomal DNA from C . burnetii was digested with various restriction enzymes previously determined to not cut within the genomic 16S rRNA gene, or with a combination of these noncutting enzymes in conjunction with AflIII, a restriction enzyme that cuts twice within the 16S rRNA gene . Restriction fragments were resolved electrophoretically and probed with a radiolabeled DNA fragment containing the 3' AflIII portion of the C . burnetii 16S rRNA gene . Only a single DNA fragment in these digests hybridized to the probe, indicating that there is a single genomic copy of the 16S rRNA gene in C . burnetii and thus only a single copy of the rRNA operon. Mol Gen Genet, 1997 Aug, 255(6), 637 - 42 Genes required for assembly and function of the protein synthetic system in Chlamydia trachomatis are expressed early in elementary to reticulate body transformation; Gerard HC et al.; Following binding and internalization into the host cell cytoplasm, elementary bodies (EB) of the obligate intracellular bacterium Chlamydia trachomatis undergo a developmental process resulting in production of reticulate bodies (RB), the vegetative growth form of the organism . EB are metabolically inactive, but EB to RB transformation requires bacterial protein synthesis . Using HeLa cells infected with EB of C . trachomatis serovar C, we examined the time of first appearance of transcripts from several genes whose products are required for assembly and function of the chlamydial protein synthetic system . We monitored appearance of chlamydial RNAs using reverse transcription-polymerase chain reaction assays targeting primary transcripts from the bacterial rRNA operons, and mRNAs encoding the glycyl tRNA synthetase and the ribosomal proteins S5 and L5 . Transcripts from the proximal rRNA promoters, and those from the r-protein and tRNA synthetase genes, are detectable as early as 4 h after EB-host binding; transcripts from distal rRNA promoters do not appear until 6 h post-infection . Thus, expression of bacterial genes whose products are required for protein synthesis begins earlier in chlamydial EB to RB development than previously thought. EXS, 1997, 83, 135 - 54 Phenotypic and evolutionary adaptation of a model bacterial system to stressful thermal environments; Bennett AF et al.; We studied both phenotypic and evolutionary adaptation to various thermal environments using the bacterium Escherichia coli as an experimental model system . We determined that 42 degrees C was stressful to a bacterial clone adapted to 37 degrees C, based on reductions in both absolute and competitive fitness, as well as induction of a heat stress response . This clone was also used to found replicated populations that were propagated for thousands of generations under several different thermal regimes, including 42 degrees C . Evolutionary adaptation of the populations to 42 degrees C resulted in an increase in both absolute and relative fitness at that temperature, measured respectively as an increase in the number of descendants (and their biovolume) and in competitive ability relative to the ancestral clone . The replicated experimental lineages achieved their evolutionary improvement by several distinct pathways, which produced differential preadaptation to a non-stressful nutrient environment . Adaptation to this stressful temperature entailed neither a change in the ancestral thermal niche nor any pronounced trade-offs in fitness within the thermal niche, contrary to a priori predictions . This study system was several important advantages for evaluating hypotheses concerning the effects of stress on phenotypic and evolutionary adaptation, including the ability to obtain lineages that have evolved in controlled and defined environments, to make direct measurements of fitness and to quantify the degree of stress imposed by different environments. Biosci Biotechnol Biochem, 1997 Sep, 61(9), 1577 - 9 Orientation of photosynthetic reaction center reconstituted in neutral and charged liposomes; Hara M et al.; The photosynthetic reaction center from the photosynthetic bacterium Rhodobacter sphaeroides was reconstituted into neutral, positively charged, or negatively charged liposomes . About 70% of photosynthetic reaction centers were reconstituted in the proteoliposomes exposing their H-subunit outside with positively charged lipids while only 30-40% of them were in the same topological orientation with neutral or negatively charged lipids. J Bacteriol, 1997 Oct, 179(19), 6053 - 60 Purification and molecular characterization of the H2 uptake membrane-bound NiFe-hydrogenase from the carboxidotrophic bacterium Oligotropha carboxidovorans; Santiago B et al.; The membrane-bound hydrogenase of Oligotropha carboxidovorans was solubilized with n-dodecyl-beta-D-maltoside and purified 28-fold with a yield of 29% and a specific activity of 173 to 178 micromol of H2 x min(-1) x mg(-1) . It is the first hydrogenase studied in a carboxidotrophic bacterium . The enzyme acts on artificial electron-accepting dyes, such as methylene blue, but is ineffective with pyridine nucleotides or other soluble physiological electron acceptors . Hydrogenase of O . carboxidovorans belongs to class I of hydrogenases and is a heterodimeric 101,692-Da NiFe-protein composed of the polypeptides HoxL and HoxS . Molecular cloning data revealed, that HoxL comprises 604 amino acid residues and has a molecular mass of 67,163 Da . Pre-HoxS comprises 360 amino acid residues and is synthesized as a precursor protein which is cleaved after alanine at position 45, thus producing a mature HoxS of 33,767 Da . The leader sequence corresponds to the signal peptide of small subunits of hydrogenases . The hydropathy plots of HoxL and HoxS were indicative for the absence of transmembranous helices . HoxZ has four transmembranous helices and is considered the potential membrane anchor of hydrogenase in O . carboxidovorans . Hydrogenase genes show the transcriptional order 5' hoxV --> hoxS --> hoxL --> hoxZ 3' . The hox gene cluster as well as the clustered CO dehydrogenase (cox) and Calvin cycle (cbb) genes are arranged within a 30-kb DNA segment of the 128-kb megaplasmid pHCG3 of O . carboxidovorans. J Physiol Pharmacol, 1997 Sep, 48(3), 345 - 51 Suppression of Helicobacter pylori protease activity towards growth factors by sulglycotide; Piotrowski J et al.; Infection with H . pylori is now recognized as a major factor in the pathogenesis of gastric disease . Here, we examined the susceptibility of epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), transforming growth factor-beta (TGF beta) and platelet derived growth factor (PDGF) to degradation by H . pylori protease, and assessed the effect of a cytoprotective agent, sulglycotide, on this process . The 125I-labeled EGF, bFGF, TGF beta and PDGF were incubatet with H . pylori protease, obtained from the filtrates of saline washes of the bacterium culture, in the presence of 0-100 micrograms sulglycotide . The results showed that, under the assay conditions, H . pylori protease caused only 5% degradation of EGF and 7% degradation of bFGF . However, the protease evoked a 61.7% degradation of PDGF and a 62.3% degradation of TGF beta . Introduction of sulglycotide to the reaction assay system caused a dose-dependent inhibition in PDGF and TGF beta proteolysis by the H . pylori enzyme . The maximal inhibitory effect was obtained with sulglycotide at 100 micrograms/ml, at which dose an 84.4% decrease in PDGF and 88.3% decrease in TGF beta degradation was achieved . The results provide a strong evidence for the effectiveness of sulglycotide in the protection of gastric mucosal growth factors against degradation by H . pylori. Int J Syst Bacteriol, 1997 Oct, 47(4), 1140 - 4 In vitro culture and phylogenetic analysis of "Candidatus Arsenophonus triatominarum," an intracellular bacterium from the triatomine bug, Triatoma infestans; Hypsa V et al.; An intracellular symbiotic bacterium was isolated from the hemolymph of Triatoma infestans and cultured in an Aedes albopictus cell line . 16S ribosomal DNA sequence analysis revealed that the bacterium was a member of the gamma-3 subgroup of the class Proteobacteria, having 96.2% sequence identity with the most closely related bacterium, Arsenophonus nasoniae, the causative agent of the son-killer trait in the parasitoid wasp Nasonia vitripennis . These bacteria share morphological features and a common tissue distribution and transmission mode . The A . nasoniae-T . infestans symbiont branch represents a lineage of insect symbionts which may be capable of horizontal transmission between phylogenetically distant host insects . We propose that the intracellular symbiont from T . infestans be classified as "Candidatus Arsenophonus triatominarum." The bacterium found in the hemocytes of T . infestans is designated the type strain of this species. Int J Syst Bacteriol, 1997 Oct, 47(4), 933 - 8 Nocardioides pyridinolyticus sp . nov., a pyridine-degrading bacterium isolated from the oxic zone of an oil shale column; Yoon JH et al.; A bacterial strain which is able to degrade pyridine was previously isolated from the oxic zone of an oil shale column and described as Pimelobacter sp . strain OS4T . However, Pimelobacter species have been transferred to the genera Nocardioides and Terrabacter . Strain OS4T was identified as a member of the genus Nocardioides on the basis of chemotaxonomic analysis and phylogenetic inference based on 16S ribosomal DNA (rDNA) sequence analysis . The G+C content of strain OS4T is 72.5 mol% . The cell wall peptidoglycan contains LL-diaminopimelic acid as the diamino acid . The predominant menaquinone is MK-8(H4) . The cellular fatty acid profile of strain OS4T is similar to that of the genus Nocardioides . The 16S rDNA similarity of strain OS4T with previously described Nocardioides species is 94.5% +/- 0.7%, and a phylogenetic tree based on 16S rDNA sequences revealed a distinct lineage for strain OS4T within the evolutionary radiation enclosed by the genus Nocardioides . Therefore, on the basis of our data, we propose that strain OS4T should be placed in the genus Nocardioides as a member of a new species, Nocardioides pyridinolyticus . The type strain of the new species is strain OS4 (= KCTC 0074BP). Protein Sci, 1997 Oct, 6(10), 2159 - 65 Dissection of the gene of the bifunctional PGK-TIM fusion protein from the hyperthermophilic bacterium Thermotoga maritima: design and characterization of the separate triosephosphate isomerase; Beaucamp N et al.; Triosephosphate isomerase (TIM), from the hyperthermophilic bacterium Thermotoga maritima, has been shown to be covalently linked to phosphoglycerate kinase (PGK) forming a bifunctional fusion protein with TIM as the C-terminal portion of the subunits of the tetrameric protein (Schurig et al., EMBO J 14:442-451, 1995) . To study the effect of the anomalous state of association on the structure, stability, and function of Thermotoga TIM, the isolated enzyme was cloned and expressed in Escherichia coli, and compared with its wild-type structure in the PGK-TIM fusion protein . After introducing a start codon at the beginning of the tpi open reading frame, the gene was expressed in E.c.BL21(DE3)/ pNBTIM . The nucleotide sequence was confirmed and the protein purified as a functional dimer of 56.5 kDa molecular mass . Spectral analysis, using absorption, fluorescence emission, near- and far-UV circular dichroism spectroscopy were used to compare the separated Thermotoga enzyme with its homologs from mesophiles . The catalytic properties of the enzyme at approximately 80 degrees C are similar to those of its mesophilic counterparts at their respective physiological temperatures, in accordance with the idea that under in vivo conditions enzymes occupy corresponding states . As taken from chaotropic and thermal denaturation transitions, the separated enzyme exhibits high intrinsic stability, with a half-concentration of guanidinium-chloride at 3.8 M, and a denaturation half-time at 80 degrees C of 2 h . Comparing the properties of the TIM portion of the PGK-TIM fusion protein with those of the isolated recombinant TIM, it is found that the fusion of the two enzymes not only enhances the intrinsic stability of TIM but also its catalytic efficiency. Biophys J, 1997 Oct, 73(4), 2090 - 6 Pump-probe anisotropies of Fenna-Matthews-Olson protein trimers from Chlorobium tepidum: a diagnostic for exciton localization? Savikhin S, Buck DR, Struve WS. Exciton calculations on symmetric and asymmetric Fenna-Matthews-Olson (FMO) trimers, combined with absorption difference anisotropy measurements on FMO trimers from the green bacterium Chlorobium tepidum, suggest that real samples exhibit sufficient diagonal energy disorder so that their laser-excited exciton states are noticeably localized . Our observed anisotropies are clearly inconsistent with 21-pigment exciton simulations based on a threefold-symmetric FMO protein . They are more consistent with a 7-pigment model that assumes that the laser-prepared states are localized within a subunit of the trimer . Differential diagonal energy shifts of 50 cm(-1) between symmetry-related pigments in different subunits are large enough to cause sharp localization in the stationary states; these shifts are commensurate with the approximately 95 cm(-1) inhomogeneous linewidth of the lowest exciton levels . Experimental anisotropies (and by implication steady-state linear and circular dichroism) likely arise from statistical averaging over states with widely contrasting values of these observables, in consequence of their sensitivity to diagonal energy disorder. J Bacteriol, 1997 Oct, 179(20), 6448 - 52 Transcriptional characterization of the Rickettsia prowazekii major macromolecular synthesis operon; Shaw EI et al.; Recent studies have demonstrated that Rickettsia prowazekii can regulate transcription of selected genes at the level of initiation . However, little information concerning the existence of operons and coordinate gene regulation in this obligate intracellular parasitic bacterium is available . To address these issues, we have focused on the rpoD gene linkage group (greA-open reading frame 23 {ORF23}-dnaG-rpoD), which includes the rickettsial analog (ORF23-dnaG-rpoD) of the major macromolecular synthesis operon (MMSO) . The rickettsial MMSO consists of an ORF coding for a protein of unknown function the structural genes for DNA primase (dnaG) and the major sigma factor of RNA polymerase (rpoD) . RNase protection assays (RPA) were used to determine if these genes are organized into an operon controlled by multiple promoters and the quantities of transcripts produced by these genes relative to each other . RPA with a probe spanning the 270-base greA-ORF23 intervening region identified a putative transcriptional promoter within the intervening sequence . Multiple RPA probes spanning the next 4,041 bases of the linkage group demonstrated the presence of a continuous transcript and thus the existence of an operon . A probe spanning the dnaG-rpoD region revealed that two additional mRNA fragments were also protected, which enabled us to identify additional putative promoters for rpoD within dnaG . Primer extension determined that the 5' ends of the three transcripts consist separately of adenine (located 227 bases upstream of ORF23) and uracil and adenine (located 336 and 250 bases upstream of rpoD, respectively) . Quantitation of transcripts produced by the three ORFs determined the relative amounts of transcripts (ORF23 to dnaG to rpoD) to be 1:2.7:5.1. J Biotechnol, 1997 Oct 2, 58(1), 59 - 66 Overproduction and purification of an agarase of bacterial origin; Parro V et al.; The agarase gene from Streptomyces coelicolor has been cloned in the non-producer bacterium Streptomyces lividans under the control of its own set of promoters and under the control of a heterologous promoter that is functional only during exponential growth . The best level of overproduction was obtained when the strain containing the natural gene was cultivated in fed batch with mannitol as carbon source . The protein, with a relative molecular mass of 32 kDa, has been purified following an affinity purification method . Contaminating activities seem to be absent from the purified enzyme preparation that can be used to purify DNA from agarose gels. J Exp Med, 1997 Oct 20, 186(8), 1241 - 6 Mycobacterium tuberculosis chaperonin 10 stimulates bone resorption: a potential contributory factor in Pott's disease; Meghji S et al.; Pott's disease (spinal tuberculosis), a condition characterized by massive resorption of the spinal vertebrae, is one of the most striking pathologies resulting from local infection with Mycobacterium tuberculosis (Mt; Boachie-Adjei, O., and R.G . Squillante . 1996 . Orthop . Clin . North Am . 27:95-103) . The pathogenesis of Pott's disease is not established . Here we report for the first time that a protein, identified by a monoclonal antibody to be the Mt heat shock protein (Baird, P.N., L.M . Hall, and A.R.M . Coates . 1989 . J . Gen . Microbiol . 135:931-939) chaperonin (cpn) 10, is responsible for the osteolytic activity of this bacterium . Recombinant Mt cpn10 is a potent stimulator of bone resorption in bone explant cultures and induces osteoclast recruitment, while inhibiting the proliferation of an osteoblast bone-forming cell line . Furthermore, we have found that synthetic peptides corresponding to sequences within the flexible loop and sequence 65-70 of Mt cpn10 may comprise a single conformational unit which encompasses its potent bone-resorbing activity . Our findings suggest that Mt cpn10 may be a valuable pharmacological target for the clinical therapy of vertebral tuberculosis and possibly other bone diseases. Proc Natl Acad Sci U S A, 1997 Oct 14, 94(21), 11439 - 44 The role of Wolbachia bacteria in reproductive incompatibilities and hybrid zones of Diabrotica beetles and Gryllus crickets; Giordano R et al.; A rickettsial bacterium in the genus Wolbachia is the cause of a unidirectional reproductive incompatibility observed between two major beetle pests of maize, the western corn rootworm, Diabrotica virgifera virgifera, and the Mexican corn rootworm, D . v . zeae . These subspecies are allopatric except for two known regions of sympatry in Texas and Mexico . We demonstrate that populations of D . v . virgifera, with the exception of two populations in southern Arizona, are infected with a strain of Wolbachia . Populations of D . v . zeae are not infected . Treatment of D . v . virgifera with tetracycline eliminated the Wolbachia and removed the reproductive incompatibility . Similar patterns of reproductive incompatibility exist among taxa of the cricket genus Gryllus . Gryllus assimilis, G . integer, G . ovisopis, G . pennsylvanicus, and G . rubens are infected with Wolbachia whereas G . firmus is usually not . Populations of G . rubens and G . ovisopis carry the same Wolbachia strain, which is distinct from that of G . integer . G . pennsylvanicus is infected with two Wolbachia strains, that found in G . rubens and one unique to G . pennsylvanicus . Moreover, a proportion of G . pennsylvanicus individuals harbors both strains . Wolbachia may have influenced speciation in some members of the genus Gryllus by affecting the degree of hybridization between species . Given that Wolbachia infections are relatively common in insects, it is likely that other insect hybrid zones may be influenced by infections with Wolbachia. Proc Natl Acad Sci U S A, 1997 Oct 14, 94(21), 11216 - 20 CooA, a CO-sensing transcription factor from Rhodospirillum rubrum, is a CO-binding heme protein; Shelver D et al.; Biological sensing of small molecules such as NO, O2, and CO is an important area of research; however, little is know about how CO is sensed biologically . The photosynthetic bacterium Rhodospirillum rubrum responds to CO by activating transcription of two operons that encode a CO-oxidizing system . A protein, CooA, has been identified as necessary for this response . CooA is a member of a family of transcriptional regulators similar to the cAMP receptor protein and fumavate nitrate reduction from Escherichia coli . In this study we report the purification of wild-type CooA from its native organism, R . rubrum, to greater than 95% purity . The purified protein is active in sequence-specific DNA binding in the presence of CO, but not in the absence of CO . Gel filtration experiments reveal the protein to be a dimer in the absence of CO . Purified CooA contains 1.6 mol heme per mol of dimer . Upon interacting with CO, the electronic spectrum of CooA is perturbed, indicating the direct binding of CO to the heme of CooA . A hypothesis for the mechanism of the protein's response to CO is proposed. J Clin Microbiol, 1997 Oct, 35(10), 2606 - 11 Comparison of major antigenic proteins of six strains of the human granulocytic ehrlichiosis agent by Western immunoblot analysis; Zhi N et al.; The etiologic agent of human granulocytic ehrlichiosis (HGE) is an obligate intracellular bacterium . In 1996, blood specimens from 53 patients suspected of having HGE were examined by indirect fluorescent antibody (IFA) testing with the HGE agent no . 13 isolate as the antigen, by nested PCR, and by culture . All patients resided in Westchester County, N.Y . Twelve patient specimens were positive for IFA (titer > or = 1:40) . Seven of these were also positive by PCR . Of the seven specimens positive by both IFA testing and PCR, the HGE agent was isolated from four (no . 2, 3, 6, and 11) and continuously cultured in HL-60 cells . These were confirmed as the HGE agent by sequencing of 16S rDNA . Both purified whole-cell organisms and the outer membrane fractions of the new isolates were compared with no . 13 isolate and a tick (USG) isolate by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western immunoblot analysis . No . 11 and 13 isolates had identical SDS-PAGE patterns with respect to 49- and 47-kDa proteins . No . 3 and USG isolates lacked the 47-kDa protein, and no . 6 isolate lacked the 49-kDa protein . Both 49- and 47-kDa bands were absent in no . 2 isolate . Western blot results with seven different sera, including five convalescent-phase sera from these patients, one dog anti-USG isolate, and one horse anti-BDS isolate, showed that all major antigens in six isolates were recognized by all sera . However, the molecular sizes and the numbers of major antigens recognized varied among the six isolates . Overall, HGE agent no . 3, 6, 11, and 13, and USG isolates had similar patterns, with 1 or 2 major antigens with molecular masses of around 49 and 47 kDa . No . 2 isolate was quite distinct in having a major antigen of 43 kDa . This indicates that although these antigenic epitopes are all cross-reactive among strains, the HGE agent has a strain pleomorphism in its major antigenic proteins . The major antigen profiles of the outer membrane protein fractions and of whole organisms of six HGE agent isolates were similar, suggesting that 49- and 47-kDa major antigens are the outer membrane proteins of the HGE agent. Proc Natl Acad Sci U S A, 1997 Sep 30, 94(20), 10606 - 11 Both DNA gyrase and reverse gyrase are present in the hyperthermophilic bacterium Thermotoga maritima; Guipaud O et al.; Like all hyperthermophiles yet tested, the bacterium Thermotoga maritima contains a reverse gyrase . Here we show that it contains also a DNA gyrase . The genes top2A and top2B encoding the two subunits of a DNA gyrase-like enzyme have been cloned and sequenced . The Top2A (type II DNA topoisomerase A protein) is more similar to GyrA (DNA gyrase A protein) than to ParC {topoisomerase IV (Topo IV) C protein} . The difference is especially striking at the C-terminal domain, which differentiates DNA gyrases from Topo IV . DNA gyrase activity was detected in T . maritima and purified to homogeneity using a novobiocin-Sepharose column . This hyperhermophilic DNA gyrase has an optimal activity around 82-86 degrees C . In contrast to plasmids from hyperthermophilic archaea, which are from relaxed to positively supercoiled, we found that the plasmid pRQ7 from Thermotoga sp . RQ7 is negatively supercoiled . pRQ7 became positively supercoiled after addition of novobiocin to cell cultures, indicating that its negative supercoiling is due to the DNA gyrase of the host strain . The findings concerning DNA gyrase and negative supercoiling in Thermotogales put into question the role of reverse gyrase in hyperthermophiles. Mol Microbiol, 1997 Aug, 25(4), 671 - 81 Localization of the Escherichia coli cell division protein Ftsl (PBP3) to the division site and cell pole; Weiss DS et al.; FtsI, also known as penicillin-binding protein 3, is a transpeptidase required for the synthesis of peptidoglycan in the division septum of the bacterium, Escherichia coli . FtsI has been estimated to be present at about 100 molecules per cell, well below the detection limit of immunoelectron microscopy . Here, we confirm the low abundance of FtsI and use immunofluorescence microscopy, a highly sensitive technique, to show that FtsI is localized to the division site during the later stages of cell growth . FtsI was also sometimes observed at the cell pole; polar localization was not anticipated and its significance is not known . We conclude (i) that immunofluorescence microscopy can be used to localize proteins whose abundance is as low as approximately 100 molecules per cell; and (ii) that spatial and temporal regulation of FtsI activity in septum formation is achieved, at least in part, by timed localization of the protein to the division site. J Biochem (Tokyo), 1997 Aug, 122(2), 467 - 73 Fatty acid synthesis of an eicosapentaenoic acid-producing bacterium: de novo synthesis, chain elongation, and desaturation systems; Watanabe K et al.; The fatty acid synthesis systems of a Shewanella sp., strain SCRC-2738, that produces a large amount of eicosapentaenoic acid were investigated . Two kinds of fatty acid synthesis system, de novo synthesis and chain elongation ones, were detected in the cytosol . The de novo synthesis system required an acyl carrier protein, and produced palmitoyl- and palmitoleoyl-acyl carrier proteins as final products . The chain elongation system also required an acyl carrier protein, and produced an acyl-acyl carrier protein as a product, using palmitoyl-, palmitoleoyl-, stearoyl-, and oleoyl-CoAs as primers but not eicosanoyl- or eicosenoyl-CoA . There were an anaerobic pathway and an aerobic desaturation one for the production of unsaturated fatty acids . Eicosapentaenoic acid seemed to be produced through the aerobic desaturation pathway and not through the anaerobic one, since the latter pathway produced n-7 type monoenoic fatty acids, which are different from eicosapentaenoic acid in the position of the double bond . The desaturase utilized an acyl-acyl carrier protein as a substrate, and this activity increased in the presence of ferredoxin and ferredoxin NADP+ reductase . Thus, Shewanella sp., strain SCRC-2738, has novel characteristics as to both fatty acid chain elongation and desaturation systems. Br J Surg, 1997 Sep, 84(9), 1190 - 9 Helicobacter pylori and gastric cancer; McFarlane GA et al.; BACKGROUND: Considerable progress has been made over the past two decades in understanding gastric carcinogenesis . Genetic and environmental factors have been shown to play a part . Infection with Helicobacter pylori leads to chronic gastritis and evidence is accumulating to link this disease with the subsequent development of gastric cancer . METHOD: A literature review was undertaken using Medline (National Library of Medicine, Washington DC, USA) searches of the headings gastrointestinal neoplasms and H . pylori for the years 1993-1997; further relevant references were examined . RESULTS: H . pylori is implicated in gastric carcinogenesis . Proposed mechanisms centre on the inflammatory response of the gastric mucosa to the bacterium . CONCLUSION: Investigation is still required to elucidate the exact role of H . pylori in the development of gastric carcinoma . Eradication of the organism in high-risk groups might lead to a reduction in the incidence of gastric cancer. Schweiz Rundsch Med Prax, 1997 May 14, 86(20), 856 - 60 {JOMOL--immunostimulation and rejection of tumor cells?}; Allewelt MC et al.; Jomol contains cell wall fragments of the bacterium Nocardia opaca composed of 40% oligopeptides, 40% lipids, 10-15% polysaccharides, and 5-10% peptidoglycans . Technetium labeled--Jomo tech--and Indium-labeled--Jomo in--preparations are used for diagnosing cancer . Jomol is promoted to cure any cancer, except Non-Hodgkin lymphoma and ovarian cancer . It is claimed that Jomol has no side effects, however chills and high fever have been observed . Following initial intensive therapy with daily injections of Jomol, a maintenance therapy is recommended to prevent relapses . One vial of Jomol or Jomo-tech costs 450.--DM . Dr . U . Ehrenfeld, an oral surgeon, developed the aqueous extract of Nocardia opaca and patented it in 1983 under the name of Jomol . Ehrenfeld is promoting Jomo-tech and Jomo-in for qualitative and semi-quantitative cancer diagnosis with whole body scintigraphy . The following action of mechanisms of Jomol are claimed: 1 . Unspecific stimulation of cellular immune mechanisms, 2 . xenogenization of tumor cells towards a bacterial surface by adhesion of Jomol and then attraction and activation of macrophages . Despite the positive claims of the promoters the preclinical and clinical investigations are insufficient or missing, therefore a routine treatment of malignancies with Jomol is not justified except in study protocols . Jomol is not registered at the Intercantonal Office for Drug Control in Switzerland and is not approved by the Public Health Department in Germany and is not reimbursed by most of the state health insurances. Pediatr Med Chir, 1997 Mar-Apr, 19(2), 143 - 4 {Atypical cat-scratch disease: a case report of splenic granulomatosis}; Dodi I et al.; Generally cat-scratch disease is a benign inflammatory adenopathy . The Authors describe an atypical form of this disease, characterized by persistent fever and splenic granulomatosis requiring a diagnostic and therapeutic prolonged effort . They point out the important role of new immuno-fluorescent techniques to exactly identify the bacterium--Bartonella henselae--causing cat-scratch disease and suggest to include cat-scratch disease among the causes of unknown origin fever. Bull Math Biol, 1997 Sep, 59(5), 833 - 56 Mathematical modeling of adhesion of bacteria to host cell lines; Galvez J et al.; A mathematical model which describes adhesion of bacteria to host cell lines is presented . The model is flexible enough to account for the following situations: extracellular bacteria are either in exponential or in stationary phase . Adhesion is described as a reversible binding process in which the bacteria attach to or detach from specific receptors uniformly distributed on the cell surface . In turn, attached bacteria can either replicate or, conversely, they are restrained to remain in stationary phase . In the first case, however, we must consider the problem of whether the decrease of unoccupied receptors as adhesion progresses imposes a limit to the replicating capacity of the attached bacteria . The effect exerted by the multiplicity of infection (MOI), i.e . the ratio of the number of bacteria to the number of host cells, on the process of adhesion is also contemplated by the model . This has revealed that experiments performed at the same values of MOI can show completely different levels of adhered bacteria, depending on the number of host cells in the assays . This finding demonstrates that the report of the MOI values is insufficient to characterize comparative studies of bacterial adhesion since it could lead to a misunderstanding of the corresponding data . Simplified models based on the steady-state approximation and in equilibrium analysis by means of a Lagmuir absorption isotherm for the attached bacteria are also discussed . This allows us to define the adhesion coefficient ( beta) in a given bacterium-cell system so that, with the exception of those systems where these coefficients cannot be defined, larger values of beta are related to a greater adhesion capacity . An overview of the procedures to perform quantitative adhesion data analysis is outlined . Finally, theoretical predictions are compared with experimental results from the literature. EMBO J, 1997 Oct 1, 16(19), 5827 - 36 Nucleator function of CsgB for the assembly of adhesive surface organelles in Escherichia coli; Bian Z et al.; Curli are surface organelles in Escherichia coli that assemble outside the bacterium through the precipitation of secreted soluble CsgA monomers, requiring the CsgB nucleator protein . Using immunoelectron microscopy and immunoblotting assays, CsgB is shown to be located on the bacterial surface and also as a minor component of wild-type curli . CsgB lacking its 20 N-terminal residues when fused to maltose-binding protein (MBP) can still trigger polymerization of CsgA monomers in vivo . However, the resulting surface organelles are only formed at one of the two bacterial poles and are morphologically distinct from wild-type curli . These Bfco organelles (CsgB-Free Curli-related Organelles) are highly regular structures reacting with anti-CsgA, but not anti-CsgB antibodies . The CsgB of the active MBP-CsgBII fusion is surface exposed but, unlike the native CsgB in wild-type curli, is not detectable in the Bfco organelles . Overexpression of csgB within a csgA mutant results in the formation of short CsgB polymers on the cell surface . It is suggested that in wild-type bacteria, both CsgA and CsgB are secreted proteins . Interaction between CsgA and CsgB triggers wild-type curli formation, resulting in CsgA-CsgB heteropolymers, while surface-anchored CsgB in MBP-CsgBII triggers morphologically distinct, CsgB-free/CsgA Bfco organelles . In the absence of CsgA, CsgB can self-assemble into polymers. FEMS Microbiol Lett, 1997 Sep 15, 154(2), 201 - 5 Relationship between pathogenicity of Coxiella burnetii isolates and gene sequences of the macrophage infectivity potentiator (Cbmip) and sensor-like protein (qrsA); Masuzawa T et al.; Coxiella burnetii, the Q fever agent, is an obligate intracellular bacterium and survival in phagolysosomes is an important virulence factor . The present study was performed to determine the relationship between its pathogenicity and genes related to its survival in macrophages, i.e . macrophage infectivity potentiator and Q fever agent regulatory sensor-like protein . The sequence similarity was more than 99% among Japanese, European and American strains, and no relationship was found between pathogenicity in guinea pigs and these genes. Biochimie, 1997 Jun, 79(6), 315 - 22 Artefactual cleavage of E coli H-NS by OmpT; Goldberg MD et al.; In the bacterium Escherichia coli, H-NS-(H1, H1a) is a heat-stable protein with a molecular mass of 15.5 kDa involved in nucleoid organisation and gene regulation linked to certain signal transduction pathways . We have shown that, following addition of preparations of everted inner membrane vesicles, heat-stable cleavage products of approximately 10 kDa of H-NS are formed in vitro from newly synthesised, radio-labelled H-NS and from purified H-NS . The 15.5 kDa protein and its cleavage products were also recovered from a minicell system . These results raised the possibility that cleavage of H-NS is physiologically significant . However, the cleavage of H-NS observed appears to occur during cell breakage and to depend on the method of protein extraction and the presence of the outer membrane protease, OmpT . Nevertheless, the results indicate that H-NS may contain at least two separate domains with cleavage occurring between these domains at a preferred OmpT site . Failure to take account of H-NS cleavage in sample preparation and analysis can lead to serious underestimation of H-NS levels. Lipids, 1997 Sep, 32(9), 975 - 8 Lipid and fatty acid compositions of a novel docosahexaenoic acid-producing marine bacterium; Watanabe K et al.; An unidentified bacterial strain, SCRC-21406, isolated from the intestine of a marine fish, Glossanodon semifasciatus, produced docosahexaenoic acid at 23% (mol/mol) {= 28% (w/w)} of total fatty acids in a medium containing 0.5% (wt/vol) peptone and 0.1% (wt/vol) yeast extract at 12 degrees C under atmospheric pressure . The cell yield was 0.43 g/L . The major lipids of the strain were phosphatidylethanolamine and phophatidylglycerol . Docosahexaenoic acid was localized at the sn-2 positions of both phospholipids . The amounts of polyunsaturated fatty acids other than docosahexaenoic acid were extremely small {< 3% (mol/mol)} . Monounsaturated fatty acids of the cis-7, cis-9 and cis-11 types were detected. Curr Microbiol, 1997 Oct, 35(4), 221 - 7 Cellobiose and cellodextrin metabolism by the ruminal bacterium Ruminococcus albus; Lou J et al.; Ruminococcus albus is an important fibrolytic bacterium in the rumen . Cellobiose is metabolized by this organism via hydrolytic and well as phosphorylytic enzymes, but the relative contributions of each pathway were not clear . The cellobiose consumption rate by exponentially growing cells was less than that of crude extracts (75 versus 243 nmol/min/mg protein) . Cellobiose phosphorolytic cleavage was much greater than hydrolytic activity (179 versus 19 nmol/min/mg protein) indicating that phosphorylases were key enzymes in the initial metabolism of the soluble products of cellulose degradation . Cellodextrin phosphorylase appeared to be active against substrates as large as cellohexaose . Phosphorylase activities were cytoplasmic, but hydrolytic activities were associated with both the membrane and cytoplasmic fractions . Free glucose was phosphorylated with a GTP-dependent glucokinase, and this enzyme showed 20-fold higher activity with GTP or ITP (>324 nmol/min/mg protein) than with ATP, UTP, CTP, GDP, or PEP . The activity was decreased at least 57% when mannose, 2-deoxyglucose, or fructose was used as substrate compared with glucose . The Kms for glucose and GTP were 321 and 247 microM, respectively . Since phosphorolytic cleavage conserves more metabolic energy than simple hydrolysis, it is likely that such pathways provide for more efficient growth of R . albus in substrate-limiting conditions like those found in the rumen. FEBS Lett, 1997 Sep 1, 414(1), 45 - 9 The assimilatory nitrate reductase from the phototrophic bacterium, Rhodobacter capsulatus E1F1, is a flavoprotein; Blasco R et al.; The assimilatory nitrate reductase from the phototrophic bacterium Rhodobacter capsulatus has been purified to electrophoretic homogeneity and its molecular and kinetic parameters determined . The native nitrate reductase is a dimer of 144 kDa composed of two subunits of 46 and 95 kDa . The purified enzyme catalyzes the electron transfer from NADH, reduced bromophenol blue or reduced viologens to nitrate . The nitrate reductase contains 1 mol FAD per mole of enzyme and also reduces cytochrome c or dichlorophenol indophenol with NADH as the electron donor . The diaphorase activity is located in the small subunit. Aliment Pharmacol Ther, 1997 Aug, 11(4), 699 - 703 A new 1-week therapy for Helicobacter pylori eradication: ranitidine bismuth citrate plus two antibiotics; Savarino V et al.; BACKGROUND: One-week triple regimens are currently the most recommended therapy for the eradication of Helicobacter pylori . No previous study has evaluated the efficacy of a short-term regimen combining ranitidine bismuth citrate with two antibiotics . METHODS: Seventy-two consecutive H . pylori-positive dyspeptic patients were recruited for this randomized, three-centre, open, parallel-group study . They were subdivided into two groups receiving either ranitidine bismuth citrate 400 mg b.d . + clarithromycin 250 mg b.d . and metronidazole 500 mg b.d . (group A) or ranitidine bismuth citrate 400 mg b.d . + clarithromycin 250 mg b.d . and metronidazole 250 mg q.d.s (group B) for 1 week . H . pylori infection was assessed by CLO-test and histology on both antral and corpus biopsies before and at least 4 weeks after the end of therapy . The bacterium was considered eradicated when both tests were negative . Eradication rates and the number of side-effects were evaluated in each group . The Chi-squared test was used for statistical analysis . RESULTS: One patient with only CLO-test positivity was erroneously randomized to group B and four patients dropped out of the study (two in group A and two in group B), mainly because they refused the second endoscopy . In group A, H . pylori was eradicated in 31 of 36 patients (intention-to-treat = 86%; 95% CI = 71-95% and per protocol 31/34 = 91%; 95% CI = 76-98%) . Side-effects occurred in 10 patients (27%) and they were generally mild . In group B, H . pylori was eradicated in 29 of 35 patients (intention-to-treat = 83%; 95% CI = 66-93%; and per protocol 29/33 = 88%; 95% CI = 72-97%) . Seven patients (20%) complained of modest side-effects . There was no significant difference between the two treatment arms (P = N.S.): no severe adverse events occurred and none of the patients was withdrawn from the study because of them . CONCLUSIONS: The co-administration of ranitidine bismuth citrate plus clarithromycin at low dosage and metronidazole in twice daily doses for 1 week is a short, effective and well-tolerated regimen for the eradication of H . pylori . These findings should provide the impetus for large-scale investigations. Zhonghua Hu Li Za Zhi, 1996 Dec, 31(12), 690 - 1 {Study of surgical instruments contamination by bacteria from air during the operation}; Yin SH et al.; Routinely sterilized surgical instruments were divided into two groups and put on the same instrument table, one group was covered with dressing and the other was exposed to the air . The samples were collected at 30 min, 60 min, and 90 min respectively after operation began and bacterium culture was done . The results showed that the general air contamination rate of the exposed group was 1.18 times higher than that of the covered one . The exposure time had a positive correlation with bacterium contamination rate . This study gave the laboratory evidence for controlling the infection in the operation room. EMBO J, 1997 Aug 1, 16(15), 4777 - 87 Photooxidative stress stimulates illegitimate recombination and mutability in carotenoid-less mutants of Rubrivivax gelatinosus; Ouchane S et al.; Carotenoids are essential to protection against photooxidative damage in photosynthetic and non-photosynthetic organisms . In a previous study, we reported the disruption of crtD and crtC carotenoid genes in the purple bacterium Rubrivivax gelatinosus, resulting in mutants that synthesized carotenoid intermediates . Here, carotenoid-less mutants have been constructed by disruption of the crtB gene . To study the biological role of carotenoids in photoprotection, the wild-type and the three carotenoid mutants were grown under different conditions . When exposed to photooxidative stress, only the carotenoid-less strains (crtB-) gave rise with a high frequency to four classes of mutants . In the first class, carotenoid biosynthesis was partially restored . The second class corresponded to photosynthetic-deficient mutants . The third class corresponded to mutants in which the LHI antenna level was decreased . In the fourth class, synthesis of the photosynthetic apparatus was inhibited only in aerobiosis . Molecular analyses indicated that the oxidative stress induced mutations and illegitimate recombination . Illegitimate recombination events produced either functional or non-functional chimeric genes . The R . gelatinosus crtB- strain could be very useful for studies of the SOS response and of illegitimate recombination induced by oxidants in bacteria. Immunology, 1997 Jul, 91(3), 414 - 20 Mycobacterium avium infection in mice is associated with time-related expression of Th1 and Th2 CD4+ T-lymphocyte response; Azouaou N et al.; Disseminated infection caused by organisms of Mycobacterium avium complex is common in acquired immune deficiency syndrome (AIDS) patients . M . avium is an intracellular bacterium that multiplies within macrophages . We examined the effect of M . avium infection on the T-helper cell response in C57/BL/6 black mice . At weekly intervals, CD4+ T-cells were isolated from spleens and lines were created . T-cell lines were exposed to sonicated M . avium in the presence of feeder cells and macrophages and the supernatant were collected to measure the concentrations of interferon-gamma (IFN-gamma and interleukin-10 (IL-10) . Production of IFN-gamma in CD4+ T-cells obtained from uninfected mice did not vary significantly during the 5 weeks . Levels of IFN-gamma produced by T-cell lines of infected mice were similar to the control mice during the first 2 weeks but significantly reduced (approximately 30 ng/ml) thereafter . In contrast, production of IL-10 by T-cell lines of infected mice was in a range of 190 to 342 pg/ml in weeks 1, 2 and 3, but increased to an average of 1300 pg/ml at weeks 4 and 5 . Pre-immunized mice, when infected with M . avium strain 101, showed a different profile of T-cell cytokines, with high IFN-gamma and low IL-10 production . Proteins purified from a number of disease-associated (D-A) and non-D-A strains of M . avium were tested for the ability to induce IL-10 . 65,000 MW and 60,000 MW proteins of M . avium induced significantly more IL-10 than 45,000 MW, 33,000 MW and 27,000 MW proteins . These results showed that M . avium predominantly stimulates either Th1 or Th2 T-helper cells according to the phase of the infection. Appl Microbiol Biotechnol, 1997 Aug, 48(2), 162 - 7 Production of zeaxanthin in Escherichia coli transformed with different carotenogenic plasmids; Ruther A et al.; Carotenoids are of great commercial interest and attempts are made to produce different carotenoids in transgenic bacteria and yeasts . Development of appropriate systems and optimization of carotenoid yield involves transformation with several new genes on suitable plasmids . Therefore, the non-carotenogenic bacterium Escherichia coli JM101 was transformed in our study with several genes that mediated the biosynthetic production of the carotenoid zeaxanthin in this host . Selection of plasmids for the introduction of five essential genes for zeaxanthin formation showed that a pACYC-derived plasmid was the best . Multiplasmid transformation generally decreased production of zeaxanthin . By cotransformation with different plasmids, limitations in the biosynthetic pathway were found at the level of geranylgeranyl-pyrophosphate synthase and beta-carotene hydroxylase . In our study a maximum zeaxanthin content of 289 micrograms/g dry weight was obtained . This involved the construction of a plasmid that mediate high-level expression of beta-carotene hydroxylase . The level of expression was demonstrated on protein gels and solubilization by the mild detergent Brij 78 revealed that a significant portion of the expressed enzyme is located in the E . coli membranes where it can exert its catalytic function . Based on the results obtained, new strategies for vector construction and strain selection were proposed which could increase the present concentrations drastically . Optimal growth conditions of the transformed E . coli strains for carotenoid formation were found at a temperature of 28 degrees C and a cultivation period of 2 days. Electrophoresis, 1997 Aug, 18(8), 1335 - 46 Proteome analysis of Spiroplasma melliferum (A56) and protein characterisation across species boundaries; Cordwell SJ et al.; Spiroplasma melliferum (Class: Mollicutes) is a wall-less, helical bacterium with a genome of approximately 1460 kbp encoding 800-1000 gene-products . A two-dimensional electrophoresis gel reference map of S . melliferum was produced by Phoretix 2-D gel software analysis of eight high quality gels . The reference map showed 456 silver-stained and replicated protein spots . 156 proteins (34% of visible protein spots) from S . melliferum were further characterised by one, or a combination, of the following: amino acid analysis, peptide-mass fingerprinting via matrix assisted laser desorption ionisation-time of flight (MALDI-TOF) mass spectrometry, and N-terminal protein microsequencing . Proteins with close relationship to those previously determined from other species were identified across species barriers . Thus, this study represents the first larger-scale analysis of a proteome based upon the attribution of predominantly 'unique numerical parameters' for protein characterisation across species boundaries, as opposed to a sequence-based approach . This approach allowed all database entries to be screened for homology, as is currently the case for studies based on nucleic acid or protein sequence information . Several proteins studied from this organism were identified as hypothetical, or having no close homolog already present in the databases . Gene-products from major families such as glycolysis, translation, transcription, cellular processes, energy metabolism and protein synthesis were identified . Several gene-products characterised in S . melliferum were not previously found in studies of the entire Mycoplasma genitalium and Mycoplasma pneumoniae (both closely related Mollicutes) genomes . The presence of such gene-products in S . melliferum is discussed in terms of genome size as compared with the smallest known free-living organisms . Finally, the levels of expression of S . melliferum gene-products were determined with respect to total optical intensity associated with all visible proteins expressed in exponentially grown cells. Eur J Oral Sci, 1997 Aug, 105(4), 310 - 7 Relationship of serotype, leukotoxin gene type and lysogeny in Actinobacillus actinomycetemcomitans to periodontal disease status; Barretto Tinoco EM et al.; Actinobacillus actinomycetemcomitans has been associated with different forms of periodontitis, particularly with localized juvenile periodontitis (LJP) . The bacterium possesses several virulence factors which have been shown to interact with the host immune system . Among these factors, leukotoxin, surface antigens (serotype) and bacteriophages have been suggested directly or indirectly to influence the course of infection . However, few studies have been able to show associations between these factors and periodontal disease, alone or in combination . Thus, the purpose of the present study was to investigate possible correlations between periodontal disease status and selected virulence factors (serotype, presence of bacteriophages, and the presence of a 530 bp deletion in the promoter region of the leukotoxin gene) . 36 subjects took part in the study . Serotype c was the most frequently found serotype among periodontally affected subjects, although serotypes a and b were also present . 27 out of 36 strains harbored bacteriophages, and there was strong evidence that some of the bacteriophages were different from the previously characterized phi Aa phage . A . actinomycetemcomitans containing the F-fragment phage were more frequently associated with periodontal disease . Five strains, all serotype b, 3 from LJP patients and 2 from healthy subjects, showed a 530-bp deletion in the promoter region of the leukotoxin gene. FEMS Microbiol Lett, 1997 Sep 1, 154(1), 73 - 9 Detection of genomic polymorphisms among isolates of the intracellular bacterium Cowdria ruminantium by random amplified polymorphic DNA and Southern blotting; Perez JM et al.; Sixteen primers were successfully used in a RAPD assay to generate reproducible fingerprints for six isolates of Cowdria ruminantium, a tick-transmitted rickettsia of ruminants . Distinction between stocks was possible by using one or at most two primers . Two stocks were very similar although originating from widely distant geographical regions . A genetic distance tree was constructed by analysing 108 fragments in pairwise comparison between stocks . Three amplification fragments probed with C . ruminantium genomic DNA determined a restriction fragment length polymorphism which allowed the distinction between stocks except for the two stocks that had similar RAPD patterns . The potential of RAPD to determine the extent of genetic diversity of C . ruminantium and to develop probes or PCR primers for diagnostic purposes is discussed. Nature, 1997 Sep 11, 389(6647), 206 - 11 Surface of bacteriorhodopsin revealed by high-resolution electron crystallography; Kimura Y et al.; Bacteriorhodopsin is a transmembrane protein that uses light energy, absorbed by its chromophore retinal, to pump protons from the cytoplasm of bacteria such as Halobacterium salinarium into the extracellular space . It is made up of seven alpha-helices, and in the bacterium forms natural, two-dimensional crystals called purple membranes . We have analysed these crystals by electron cryo-microscopy to obtain images of bacteriorhodopsin at 3.0 A resolution . The structure covers nearly all 248 amino acids, including loops outside the membrane, and reveals the distribution of charged residues on both sides of the membrane surface . In addition, analysis of the electron-potential map produced by this method allows the determination of the charge status of these residues . On the extracellular side, four glutamate residues surround the entrance to the proton channel, whereas on the cytoplasmic side, four aspartic acids occur in a plane at the boundary of the hydrophobic-hydrophilic interface . The negative charges produced by these aspartate residues is encircled by areas of positive charge that may facilitate accumulation and lateral movement of protons on this surface. Ann Otolaryngol Chir Cervicofac, 1997, 114(3), 80 - 3 {Cervicofacial manifestations of tularemia . Apropos of a familial case}; Benlyazid A et al.; Tularemia is a rare infectious disease, due to Francisella tularensis, a virulent bacterium transmitted by a carrier insect (essentially ticks) or by the meat of an infected animal (generally hares) . We report 3 cases that occurred in the same family, showing the various symptoms of this disease . Revealing head and neck manifestations may mislead diagnosis. Biochim Biophys Acta, 1997 Aug 16, 1347(2-3), 164 - 76 Polyunsaturated fatty acids in the psychrophilic bacterium Shewanella gelidimarina ACAM 456T: molecular species analysis of major phospholipids and biosynthesis of eicosapentaenoic acid; Nichols DS et al.; The production of eicosapentaenoic acid {20:5omega3; EPA} from Shewanella gelidimarina (ACAM 456T) was investigated with respect to growth temperature and growth on sole carbon sources . The percentage and quantitative yield of EPA remained relatively constant at all growth temperatures within or below the optimal growth temperature region . At higher growth temperatures, these values decreased greatly . Growth on differing sole carbon sources also influenced the percentage and amount of EPA produced, with the fatty acid composition influenced by provision of potential acyl chain primers as sole carbon sources . The highest amounts of EPA occurred from growth on propionic acid and L-leucine respectively, while the highest percentage of EPA occurred from growth on L-proline . Monounsaturated fatty acid components and EPA were concentrated in phosphatidylglycerol (PG), while the proportion of branched-chain fatty acids was elevated in phosphatidylethanolamine (PE); the two major phospholipid classes . Specific associations of EPA with other acyl chains were identified within cellular phospholipid classes . The association of EPA with 17:1 and 18:0 acyl chains in phospholipid species was specific to PG, whereas the association of EPA with i13:0/13:0 and 14:0/i14:0 was specific to PE . Such acyl chain 'tailoring' is indicative of the important role of EPA in bacterial membrane adaptive responses . EPA was also a large component (22%) of a non-esterified fatty acid (NEFA) fraction within the total lipid extract of the bacterium . This may point toward a particular role of NEFA in polyunsaturated fatty acid (PUFA) metabolism . The formation of EPA was investigated by labelling with L-{U-14C}serine and sodium {1-14C}acetate . The accumulation of radiolabel within unsaturated intermediates (di-, tri- and tetraunsaturated fractions) was low, indicating a rapid formation and derivatisation of these components . Similar results were found for the unsaturated fatty acid fractions of both PE and PG using sodium {1-14C}acetate radiolabel . The regulation of triunsaturated fatty acid components may be a potential control site in PUFA biosynthesis. Biochim Biophys Acta, 1997 Aug 16, 1347(2-3), 151 - 63 Membrane lipids of Rhodopseudomonas viridis; Linscheid M et al.; In search of the precyanobacterial origin of the typical thylakoid lipids found in cyanobacteria and chloroplasts, we analyzed the polar lipids of the anaerobic phototrophic bacterium Rhodopseudomonas viridis . Glycolipids (monogalactosyl-, digalactosyl- and glucuronosyl diacylglycerol), phospholipids (phosphatidyl choline, -ethanolamine, -glycerol and cardiolipin) and an ornithine lipid were isolated and identified by NMR (1H, 13C, 31P) and mass spectrometry . Positional distribution and pairing of fatty acids in molecular species show small, but significant differences between glyco- and phospholipids . In this context, a new enzymatic method is described for assigning the enantiomeric structure of the diacylglycerol moiety in glyco- and phospholipids . 14C-Labelling studies suggest that monogalactosyl diacylglycerol is formed by galactosylation of diacylglycerol as in chloroplasts and not by glucosylation followed by epimerization as in cyanobacteria . The two 1,6-linked galactopyranose residues of digalactosyl diacylglycerol are both in beta-linkage and thus differ from the corresponding chloroplast lipid with its alpha-beta-sequence . R . viridis does not contain the sulfolipid, and even phosphate starvation does not induce the synthesis of this most characteristic thylakoid lipid, which on the other hand is present in other anaerobic phototrophic bacteria. Diagn Microbiol Infect Dis, 1997 Jul, 28(3), 149 - 52 Modification of Christensen urease test as an inexpensive tool for detection of Helicobacter pylori; Dominguez-Bello MG et al.; About half the world population is infected with Helicobacter pylori . Most live in developing countries where clinical studies face the constraints of high costs of imported rapid diagnostic tests . In this work, we describe and validate a simple local urease test (LUT) to determine the presence of the bacterium in gastric biopsies, and report the incidence of infection among symptomatic patients in Caracas, Venezuela . Statistical comparison of LUT and CLOtest (Delta West, Bentley, Australia) (N = 216 patients) showed that the probability of 95% agreement between the two test was 0.936 . Overall incidence of infection determined by the LUT was 65% (N = 229), and it was higher in patients from public (72%; N = 153) than from private (50%; N = 76) hospitals (p = .001) . Therefore, the incidence of infection differs in two socioeconomic groups that coexist in the same city . LUT may represent an affordable tool in clinical studies needed to identify social factors that increase the risk of infection by H . pylori. J Bacteriol, 1997 Sep, 179(18), 5892 - 902 Helicobacter pylori ABC transporter: effect of allelic exchange mutagenesis on urease activity; Hendricks JK et al.; Helicobacter pylori urease requires nickel ions in the enzyme active site for catalytic activity . Nickel ions must, therefore, be actively acquired by the bacterium . NixA (high-affi