Search

Helicobacter pylori encounters a wide range of pH within the human stomach. In a comparison of H. pylori cultured in vitro under neutral or acidic conditions, about 15% of genes are differentially expressed, and corresponding changes are detectable for many of the encoded proteins. The ArsRS two-component system (TCS), comprised of the sensor kinase ArsS and its cognate response regulator ArsR, has an important role in mediating pH-responsive changes in H. pylori gene expression. In this study, we sought to delineate the pH-responsive ArsRS regulon and further define the role of ArsR in pH-responsive gene expression. We compared H. pylori strains containing an intact ArsRS system with an arsS null mutant or strains containing site-specific mutations of a conserved aspartate residue (D52) in ArsR, which is phosphorylated in response to signals relayed by the cognate sensor kinase ArsS. We identified 178 genes that were pH-responsive in strains containing an intact ArsRS system but not in ΔarsS or arsR mutants. These constituents of the pH-responsive ArsRS regulon include genes involved in acid acclimatization (ureAB, amidases), oxidative stress responses (katA, sodB), transcriptional regulation related to iron or nickel homeostasis (fur, nikR), and genes encoding outer membrane proteins [including sabA, alpA, alpB, hopD (labA), and horA]. When comparing H. pylori strains containing an intact ArsRS TCS with arsRS mutants, each cultured at neutral pH, relatively few genes are differentially expressed. Collectively, these data suggest that ArsRS-mediated gene regulation has an important role in H. pylori adaptation to changing pH conditions.

Purpose. We investigated the transcription of adhesin-encoding genes sabA, hopZ and labA in Helicobacter pylori strain J99. Each possesses a repeating homopolymeric nucleotide tract within their promoter regions, and sabA and hopZ possess repeats within their 5′ coding regions. Methodology. We altered the repeat lengths associated with the adhesin genes and quantified mRNA levels by real-time quantitative PCR. Using adherence to AGS cells and IL-8 assays, we examined the effects of altered transcript levels. We assessed the role of ArsRS in transcription using an arsS null mutant and by examining ArsR binding to promoter regions via electrophoretic mobility shift assays. Results. Extensions or truncations of promoter region repeats in hopZ and labA increased transcript levels, mirroring results shown by our lab and others for mutations in the sabA promoter. Altered lengths of the poly-cytosine thymine tract within the 5′ coding region of sabA demonstrated that switching from phase-off to phase-on significantly increased mRNA levels. However, mutations in the poly-thymine tract of sabA, which increased mRNA levels, do not behave synergistically with phase-on mutations. Phase-on mutations of sabA resulted in increased H. pylori adherence to AGS cells, but only a modest effect on IL-8. hopZ and labA, and sabA paralogue sabB, transcript levels were increased in an arsS mutant and ArsR bound the promoter regions for each of these genes in vitro. Conclusion. This work highlights the complex nature of adhesin regulation, its impact on H. pylori attachment and the pervasive role of ArsRS in adhesin expression. Such regulation may help facilitate the decades-long persistence of infection.

Helicobacter pylori is the strongest risk factor for gastric adenocarcinoma, which develops within a hypochlorhydric environment. We sequentially isolated H. pylori (strain J99) from a patient who developed corpus-predominant gastritis and hypochlorhydia over a 6-year interval. Archival J99 survived significantly better under acidic conditions than recent J99 strains. H. pylori arsRS encodes a 2-component system critical for stress responses; recent J99 isolates harbored 2 nonsynonymous arsS mutations, and arsS inactivation abolished acid survival. In vivo, acid-resistant archival, but not recent J99, successfully colonized high-acid-secreting rodents. Thus, genetic evolution of arsS may influence progression to hypochlorhydia and gastric cancer.

We report the complete genome sequences of 19 cluster CA bacteriophages isolated from environmental samples using Rhodococcus erythropolis as a host. All of the phages are Siphoviridae, have similar genome lengths (46,314 to 46,985 bp) and G+C contents (58.5 to 58.8%), and share nucleotide sequence similarity.

We report the genome sequences of 14 cluster K mycobacteriophages isolated using Mycobacterium smegmatis mc²155 as host. Four are closely related to subcluster K1 phages, and 10 are members of subcluster K6. The phage genomes span considerable sequence diversity, including multiple types of integrases and integration sites.

OipA is a phase-variable virulence factor of Helicobacter pylori. Mutations in oipA to turn the gene phase on in a cag pathogenicity island (PAI)-negative strain of H. pylori (J68) or phase off in a cag PAI-positive strain (26695) demonstrated that phase on oipA alleles in both strains had both increased oipA mRNA and human gastric adenocarcinoma (AGS) cell adherence compared to isogenic oipA phase off mutants. An oipA phase off mutant of H. pylori 26695 demonstrated decreased IL-8 secretion by AGS cells and failure to translocate the cag PAI effector CagA. Increased attachment by OipA expressing cag PAI-negative H. pylori J68 failed to alter secreted IL-8 levels. Thus, OipA is necessary but not sufficient for the induction of IL-8; however, it is necessary for translocation of the oncoprotein CagA. Perhaps the nearly invariant phase on status of oipA alleles among cag PAI-positive H. pylori isolates relates to the role of this outer membrane protein in effective translocation of CagA. oipA mRNA comparisons between AGS cell-adherent and non-adherent H. pylori 26695 revealed significantly greater levels in the adherent cells. This may allow H. pylori to adapt to conditions of host cell contact by altering expression of this virulence factor.

The pathogenesis of diseases elicited by the gastric pathogen Helicobacter pylori is partially determined by the effectiveness of adaptation to the variably acidic environment of the host stomach. Adaptation includes appropriate adherence to the gastric epithelium via outer membrane protein adhesins such as SabA. The expression of sabA is subject to regulation via phase variation in the promoter and coding regions as well as repression by the two-component system ArsRS. In this study, we investigated the role of a homopolymeric thymine [poly(T)] tract −50 to −33 relative to the sabA transcriptional start site in H. pylori strain J99. We quantified sabA expression in H. pylori J99 by quantitative reverse transcription-PCR (RT-PCR), demonstrating significant changes in sabA expression associated with experimental manipulations of poly(T) tract length. Mimicking the length increase of this tract by adding adenines instead of thymines had similar effects, while the addition of other nucleotides failed to affect sabA expression in the same manner. We hypothesize that modification of the poly(T) tract changes DNA topology, affecting regulatory protein interaction(s) or RNA polymerase binding efficiency. Additionally, we characterized the interaction between the sabA promoter region and ArsR, a response regulator affecting sabA expression. Using recombinant ArsR in electrophoretic mobility shift assays (EMSA), we localized binding to a sequence with partial dyad symmetry −20 and +38 relative to the sabA +1 site. The control of sabA expression by both ArsRS and phase variation at two distinct repeat regions suggests the control of sabA expression is both complex and vital to H. pylori infection.

Phase variation is frequently utilized by bacterial species to affect gene expression such that phenotypic variants are maintained within populations, ensuring survival as environmental or host conditions change. Unusual among Helicobacter pylori phase variable or contingency genes is arsS, encoding a sensory histidine kinase involved in the acid acclimation of the organism. The presence of a 3′ homopolymeric cytosine tract of variable length in arsS among Helicobacter pylori strains allows for the expression of various functional ArsS isoforms, differing in carboxy-terminal protein domains. In this study, we analyzed this 3′ arsS region via amplified fragment length polymorphism (AFLP) and sequencing analyses for H. pylori populations from 3 different gastric sites of 12 patients. Our data indicate the presence of multiple arsS alleles within each population of H. pylori derived from the gastric antrum, cardia, or corpus of these patients. We also show that H. pylori, derived from the same anatomical site and patient, are predicted to express multiple ArsS isoforms in each population investigated. Furthermore, we identify a polymorphic deletion within arsS that generates another alternate ArsS C-terminal end. These findings suggest that four C-terminal variations of ArsS adds to the complexity of the ArsRS acid adaptation mechanism as a whole and may influence the ability of H. pylori to persist in the gastric niche for decades.

Parasites influence the expression of secondary sexual traits and the health of infected individuals. We set out to test the influence of reputed exogenous parasites, plumage bacteria, including feather-degrading bacteria (FDB), on secondary sexual characteristics and body condition of wild adult eastern bluebirds Sialia sialis. Previous work has shown that FDB alter the coloration of structurally-colored bluebird feathers in vitro (Shawkey et al. 2007). In a correlational study of how bacteria affect birds in the wild, we found that female plumage got duller with increasing FDB intensity. Males tended to get brighter with increasing FDB intensity, but the relationship was not significant. We also found significant associations between plumage bacteria intensity and body condition, but, again, with gender-based differences. Female body condition was negatively associated with plumage bacteria intensity, while male body condition was positively associated with plumage bacteria intensity. Interestingly, plumage bacteria intensity of males and females in nesting pairs was significantly positively correlated. We also report the highest prevalence of FDB measured in a wild bird population, with FDB detected on 67/68 (99%) of individuals. Further work is needed to fully understand the relationships between plumage bacteria and birds, but our data indicate that plumage bacteria may have sex-dependent effects on multiple phenotypic traits.

Melanins are common feather pigments that contribute to signaling and crypsis. Melanins may also help feathers resist feather-degrading bacteria (FDB). Two recent studies (Goldstein et al. 2004, Grande et al. 2004) tested the resistance of melanized versus unmelanized feathers to FDB using in vitro experiments, but draw opposite conclusions. Goldstein et al. (2004) concluded that melanized feathers resist FDB more than unmelanized feathers, while Grande et al. (2004) concluded that unmelanized feathers resist FDB more than melanized feathers. To resolve this conflict in the literature, we replicated previous studies but included additional tests not previously used. We inoculated melanized and unmelanized feathers of domestic geese Anser anser domesticus, with the FDB Bacillus licheniformis and measured bacterial activity every two days over two weeks. Three metrics of bacterial activity on feathers were measured: soluble protein content around feathers in solution, bacterial growth on feathers, and loss of feather mass. The latter two metrics were not considered in the aforementioned studies, which indirectly measured bacterial activity. We conducted two trials, one in which feathers were sterilized by autoclaving before inoculation (Goldstein et al. 2004, Grande et al. 2004), and a second in which feathers were sterilized by ethylene oxide gas. This allowed us to test whether autoclaving, done in previous studies, influences bacterial activity on feathers and could confound results. In both trials, unmelanized feathers degraded earlier, supported greater bacterial growth, and lost more mass than melanized feathers. These results support the findings of Goldstein et al. (2004); melanized feathers are more resistant to FDB than unmelanized feathers. Thus, using direct metrics of bacterial activity, we resolve a current conflict in the literature. We also found that autoclaving feathers influences FDB activity on them, and thus autoclaving should be avoided in future studies.

Adaptation to the acidic microenvironment, and adherence to mucosal epithelium, are essential for persistent colonization of the human stomach by Helicobacter pylori. The expression of SabA, an adhesin implicated in the ability of H. pylori to adhere to the host gastric epithelium, can be modulated by phase variation via slipped-strand mispairing in repetitive nucleotide tracts located in both the promoter region and the coding region. This study demonstrates the occurrence of phase variation at the sabA locus within individual strains of H. pylori, and among multiple isolates from a single patient. In addition, transcription of sabA is repressed by the acid-responsive ArsRS two-component signal transduction system in vitro. Our results demonstrate that isogenic inactivation of the arsS (jhp0151/HP0165) histidine kinase locus results in a 10-fold SabA-dependent increase in adherence to gastric epithelial cells in strain J99 (contains an in-frame sabA allele), but not in strain 26695 (out-of-frame sabA allele). The combination of transcriptional regulation of the sabA locus by the ArsRS two-component signal-transduction system and the generation of subpopulations harbouring alternate sabA alleles by slipped-strand mispairing during chromosomal replication could permit H. pylori to rapidly adapt to varying microenvironments or host immune responses. As a pathogen with a paucity of regulatory proteins, this dual regulation indicates that SabA expression is a tightly regulated process in H. pylori infection.

Bacillus licheniformis, a soil bacterium capable of degrading the b-keratin in feathers, is present in the plumage of some wild-caught birds, but the published carriage rate is quite low. Microbial degradation could be a selective agent leading to the evolution of molt and plumage pigmentation, but we hypothesized that for B. licheniformis to have played an important role in avian evolution, it is likely to occur more widely in bird populations than previously reported. We sampled the plumage of 461 wild-caught birds of eight species. We designed a selective and differential culture method to isolate bacteria with the potential to degrade feathers. Putative feather-degrading bacteria were isolated from 21-59% of the individuals of each of the species tested, for an average carriage rate of 39%. 16S rRNA (rrnA) sequencing of 98 of these bacterial isolates indicated that 69% were Bacillus lichenformis, suggesting that the prevalence of this feather-degrading bacterium is 4 3 higher than previously reported. We also hypothesized that interspecific variation in avian plumage, behavior, and habitat may have led to the evolution of host-specific B. licheniformis strains. Fingerprinting of B. licheniformis isolated from Northern Saw-whet Owls (Aegolius acadicus) and Gray Catbirds (Dumetella carolinensis) using REP-PCR demonstrated that for nine owls, one individual carried four different strains and eight individuals carried only one strain. Of 20 catbirds, there was a single strain found on nine birds, but four carried two different strains each. SINOPSIS. Prevalencia y diversidad genetica de Bacillus licheniformis en el plumaje de aves

Attention has recently been focused on microbes that occur in the plumage of wild birds and can degrade feathers under laboratory conditions and in poultry-waste composters. In particular, Bacillus licheniformis, a soil bacterium, was found in the plumage of many birds netted in eastern North America, and poultry feathers were rapidly broken down when incubated in a suspension of this bacterium (Burtt and Ichida 1999). If feather-degrading microbes affect wild birds under normal conditions, they may have played an important role in the evolution of molt, plumage color, and sanitation behavior, such as sunning and preening. We performed the first test on whether a feather-degrading bacterium can degrade feathers of live birds housed outdoors under seminatural conditions. We found no evidence that B. licheniformis degraded wing feathers of Northern Cardinals (Cardinalis cardinalis) when applied twice (with a two-week interval) during the winter, despite the fact that it degraded Northern Cardinal feathers when incubated in our laboratory. In a second experiment, we found no evidence that B. licheniformis degraded feathers of European Starlings (Sturnus vulgaris) when applied twice (with a one-week interval) during the summer, despite the fact that birds were housed in humid conditions that should have favored the growth of B. licheniformis.Las Bacterias que Degradan Plumas no Afectan las Plumas de Aves en Cautiverio

Helicobacter pylori is a genetically diverse bacterial species that chronically infects human stomachs and sometimes causes severe gastroduodenal disease. Studies of polymorphic DNA sequences can suggest geographic origins of individual strains. Here, we describe a 180-bp insertion (ins180), which is just after the translation stop of a gene of unknown function, near the promoter of jhp0152- jhp0151 two-component signal transduction genes in strain J99, and absent from this site in strain 26695. This ins180 insertion was found in 9 of 9 Gambian (West African), 9 of 20 (45%) South African, and 9 of 40 (23%) Spanish strains but in only 2 of 20 (10%) North American strains and none of 20 Lithuanian, 20 Indian, and 20 Japanese strains. Four South African isolates that lacked ins180 and that belonged to an unusual outlier group contained a 480-bp insertion at this site (ins480), whereas none of 181 other strains screened contained ins480. In further tests 56% (10 of 18) of strains from African Americans but only 17% (3 of 18) of strains from Caucasian Americans carried ins180 ( P < 0.05). Thus, the H. pylori strains of modern African Americans seem to retain traces of African roots, despite the multiple generations since their ancestors were taken from West Africa. Fragmentary ins180-like sequences were found at numerous sites in H. pylori genomes, always between genes. Such sequences might affect regulation of transcription and could facilitate genome rearrangement by homologous recombination. Apparent differences between African-American and Caucasian-American H. pylori gene pools may bear on our understanding of H. pylori transmission and disease outcome.

Summary To identify Helicobacter pylori genes with expression that is enhanced under low pH conditions, we used subtractive hybridization methodology. We identified 28 acid-induced genes, of which 18 have known or putative functions. Six pairs of genes were co-transcribed. Primer extension analysis identified single or multiple transcriptional start points (tsp) for 14 of the 22 loci. Sequence analysis of the −10 regions upstream of the tsps revealed consensus motifs for multiple RNA polymerase sigma factors present in H. pylori (σ80, σ54 and σ28). No sequences resembling the −35 Escherichia coli consensus sequence (TTGACA) were present upstream of any of the genes. Both increased gene transcription and decreased mRNA decay contribute to the observed increase in H. pylori transcript abundance at acid pH. These studies document the complex response of H. pylori to environmental pH changes, and provide insight into mechanisms used for intragastric survival.

Broth culture supernatants from Tox + Helicobacter pylori strains induce vacuolation of HeLa cells in vitro and contain VacA in concentrations that are higher than those found in supernatants from Tox − H. pylori strains. To investigate the basis for this phenomenon, we analyzed the transcription of the vacuolating cytotoxin gene ( vacA ) in eight Tox + strains (each with a type s1/m1 vacA genotype) and nine Tox − strains (each with a type s2/m2 vacA genotype). Most of the Tox + and Tox − strains tested used the same vacA transcriptional start point, but Tox + strains yielded significantly stronger primer extension signal intensities than did Tox − strains (mean densitometry values of 15.8 ± 1.9 versus 8.9 ± 1.7, P = 0.0016). Correspondingly, when we introduced vacA :: xylE transcriptional fusions into the chromosomes of a Tox + strain (60190) and a Tox − strain (86-313), the level of XylE activity in 60190 vacA :: xylE was about 30-fold higher than that in 86-313 vacA :: xylE . Sequence analysis and promoter exchange experiments indicated that the different levels of vacA transcription in these two strains cannot be explained solely by a difference in promoter strength. These data indicate that Tox + and Tox − H. pylori strains typically differ not only in the VacA amino acid sequence but also in the level of vacA transcription.

Bilateral conjunctivitis and episcleritis were identified in an adult European starling (Sturnus vulgaris). A novel mycoplasma species, Mycoplasma sturni, was isolated in pure culture from the conjunctiva of both eyes. The clinical presentation was similar to that of conjunctivitis in house finches (Carpodacus mexicanus) caused by Mycoplasma gallisepticum. However, the histologic lesions were distinct, by the presence of ulceration and by the absence of epithelial hyperplasia and lymphoplasmacytic infiltration [corrected]. Mycoplasma sturni ferments glucose, does not hemadsorb or hemagglutinate chicken erythrocytes, and grows rapidly at 37 C in comparison to other Mycoplasma spp. The role of M. sturni in conjunctivitis in other passerine species is presently unknown.

Strain UCMF(T) (T = type strain) was isolated from the conjunctiva of a European starling (Sturnus vulgaris) with conjunctivitis. Colonies grown on conventional mycoplasma agar possessed the typical fried-egg appearance observed with many mycoplasmal species. Electron micrographs of ultrathin sections of UCMF(T) revealed a pleomorphic cellular morphology; the cells ranged from spherical to elliptical or flask shaped. The cell size ranged from 0.3 to 0.5 microns. Strain UCMF(T) grows well in a variety of mycoplasma broth formulations at 25 degrees C, with rapid and heavy growth at 37 degrees C. No growth occurs at 42 degrees C. This organism ferments glucose but does not hydrolyze urea or arginine and has an absolute requirement for sterol from growth. Strain UCMF(T) does not hemagglutinate or hemadsorb chicken erythrocytes. The genome size is 870 kbp, and the guanine-plus-cytosine content is 31 mol%. Sequence analysis of the 16S rRNA gene demonstrated that this organism is unique and has not been described previously. Serological analysis confirmed that strain UCMF(T) is distinct from all previously identified Mycoplasma, Acholeplasma, Spiroplasma, Entomoplasma, and Mesoplasma species. This organism represents a new species, for which we propose the name Mycoplasma sturni. Strain UCMF (= ATCC 51945) is the type strain of M. sturni sp. nov.

We demonstrate here that the arbitrary primer polymerase-chain-reaction-based DNA fingerprinting method (also termed random amplified polymorphic DNA or RAPD) can be used to distinguish among strains of the avian pathogen Mycoplasma gallisepticum. Ten base oligonucleotide primers were used individually to prime DNA synthesis from genomic DNAs. Strain-specific arrays of DNA fragments were generated, which allowed us to identify and group isolates. Isolates of M. synoviae, M. gallinarum and M. iners yielded arrays of DNA fragments that differed markedly from those generated from the M. gallisepticum isolates using the same arbitrary primers. These results show that the RAPD fingerprinting method distinguishes genetically different strains of M. gallisepticum and indicates that it should be valuable for monitoring transmission of this pathogen.

Mycoplasma pneumoniae-specific monoclonal antibodies were constructed for the purpose of developing reagents for clinical diagnostics. The monoclonal antibodies, designated Mp2B12 and Mp3A11, recognize surface exposed antigens of 28 kDa and 170 kDa, respectively. Mp3A11 recognizes an epitope on a cytadhesin molecule, P1, which is not shared on the analogous cytadhesin of M. genitalium. Both monoclonal antibodies are capable of detecting 1 x 10(5) M. pneumoniae in a standard ELISA test.

Summary A64kDa lipoprotein (LP 64) haemagglutinin (pI 4.9–5.0) was isolated from the membrane of Mycoplasma gallisepticum. Triton X-114 phase partitioning has demonstrated that the hydrophobic nature of this haemagglutinin is due to a lipid portion of the molecule. Autoradiography of [3H]-palmitate-labelled M. gallisepticum revealed the presence of several additional lipoproteins. Immunoelectron microscopy demonstrated the localization of LP 64 to the base of the terminal structure. Densitometric scans of stained polyacrylamide gels of M. gallisepticum showed that LP 64 constitutes 1.7% of the total protein. Scans of immunoblots of M. gallisepticum indicate that LP 64 is highly immunogenic in chickens, accounting for 7.4% of the total serum IgG response at four weeks post-infection. A quantitative value for the IgG response to LP 64, relative to the percentage of total protein (the Relative Immunogenicity Index) was 4.4. LP 64 is conserved among several strains of M. gallisepticum, but its presence could not be detected in Mycoplasma synoviae. Antiserum raised to electroeluted LP 64 reacted specifically with this lipoprotein when assessed on either one-or two-dimensional immunoblots of M. gallisepticum. This antiserum, as well as Fab fragments, inhibited haemagglutination of chicken erythrocytes and inhibited the attachment of 14Clabelled M. gallisepticum to chicken tracheal epithelium in vitro by 62%.

The H. pylori cag type 4 secretion system (T4SS) translocates CagA into host cells which can lead to NF-κβ activation. The T4SS component CagY is essential for CagA translocation. cagY harbors two repeat motifs which engender considerable genetic diversity to this locus. We used Mongolian gerbils to select for Hp derivative strains that differed in intensity of host interactions to define the biology of long-term colonization and genetic alteration of virulence factors within the gastric niche. Gerbils were initially challenged with the carcinogenic Hp strain 7.13 for 12 weeks; two derivative isolates, 7.13-1 and 7.13-2, were then obtained from 2 independent gerbils. In vitro, strain 7.13-1 induced significantly higher levels of NF-κβ activation and CagA translocation in AGS gastric epithelial cells compared to strain 7.13-2 (fold/uninfected: 100±7 vs. 26±7, respectively; p

Screening a Helicobacter pylori genomic library with antisera raised against H. pylori broth culture supernatant resulted in the identification of six antigens: urease, HspB, Lpp20, DnaK, MsrA, and a cysteine-rich 28-kDa protein (designated HcpA). H. pylori antigens may be released into the extracellular space by multiple mechanisms, including specific secretion pathways, autolysis, and membrane vesicle formation.

LuxS plays a role in the synthesis of an extracellular signaling molecule, autoinducer 2 (AI-2). To analyze a possible role of AI-2 in regulating Helicobacter pylori gene expression, we constructed a panel of transcriptional reporter strains. We show that the expression of H. pylori flaA is growth phase dependent and that flaA transcription increases in association with increased culture density. Mutating the luxS gene eliminates growth-phase-dependent control of flaA , and this growth phase dependence is restored when the luxS mutant strain is complemented with the wild-type luxS gene.

To identify putative members of a regulon controlled by the H. pylori sensory histidine kinase HP0164 (HK0164), we constructed HK0164 null mutant H. pylori strains and analyzed bacterial gene transcription using DNA arrays. Seven genes were differentially expressed in multiple HK0164 mutant strains compared to their expression in control strains. Strain-dependent variations in differential expression were also detected. These results indicate that the signal transduction circuit utilizing HK0164 controls the transcription of at least seven genes in H. pylori .

Individual bacteria of numerous species can communicate and coordinate their actions via the production, release, and detection of extracellular signaling molecules. In this study, we used the Vibrio harveyi luminescence bioassay to determine whether Helicobacter pylori produces such a factor. Cell-free conditioned media from H. pylori strains 60190 and 26695 each induced >100-fold-greater luminescence in V. harveyi than did sterile culture medium. The H. pylori signaling molecule had a molecular mass of H. pylori 26695 does not contain any gene predicted to encode an acyl homoserine lactone synthase but does contain an orthologue of luxS , which is required for production of autoinducer-2 (AI-2) in V. harveyi . To evaluate the role of luxS in H. pylori , we constructed luxS null mutants derived from H. pylori 60190 and 26695. Conditioned media from the wild-type H. pylori strains induced >100-fold-greater luminescence in the V. harveyi bioassay than did conditioned medium from either mutant strain. Production of the signaling molecule was restored in an H. pylori luxS null mutant strain by complementation with a single intact copy of luxS placed in a heterologous site on the chromosome. In addition, Escherichia coli DH5α produced autoinducer activity following the introduction of an intact copy of luxS from H. pylori . Production of the signaling molecule by H. pylori was growth phase dependent, with maximal production occurring in the mid-exponential phase of growth. Transcription of H. pylori vacA also was growth phase dependent, but this phenomenon was not dependent on luxS activity. These data indicate that H. pylori produces an extracellular signaling molecule related to AI-2 from V. harveyi . We speculate that this signaling molecule may play a role in regulating H. pylori gene expression.

This chapter discusses random amplified polymorphic DNA (RAPD) fingerprinting. One of the most promising analytical methods for the detection of DNA sequence diversity among mycoplasmas involves polymerase chain reaction (PCR) amplification using a single primer under conditions of low stringency. The primer stimulates the synthesis of DNA fragments from paired sites in the target genome sufficiently homologous to itself to allow for annealing and extension. RAPD is rapid and sensitive, requires only nanogram quantities of template DNA, and is useful for strain identification within numerous genera. The requirement for small quantities of pure DNA makes this method particularly suitable for slow-growing organisms such as the mycoplasmas. The quantity of primer used is a critical parameter. It has been found that 400 ng is optimal for precise, informative pattern amplification. Less primer results in fewer bands and more primer results in a pattern that is too complex to accurately evaluate. The chapter indicates the utility of RAPD fingerprinting for distinguishing strains of Mycoplasma gallisepticum.

The gyrAB genes encoding the entire B and a portion of the A subunit of DNA gyrase (E.C. 5.99.1.3) from Mycoplasma gallisepticum (Mg), strain S6, were cloned and sequenced. These gyrAB genes are co-transcribed as a single, polycistronic mRNA transcript. The Mg gyrB appears unique among prokaryotic gyrB in its use of GUG as a start codon.