|
| ||
|
|
||
Cholerae
Kinds of Cholerae Terms modified by Cholerae Selected AbstractsNatural transformation of Vibrio fischeri requires tfoX and tfoYENVIRONMENTAL MICROBIOLOGY, Issue 8 2010Amber Pollack-Berti Summary Recent evidence has indicated that natural genetic transformation occurs in Vibrio cholerae, and that it requires both induction by chitin oligosaccharides, like chitohexaose, and expression of a putative regulatory gene designated tfoX. Using sequence and phylogenetic analyses we have found two tfoX paralogues in all sequenced genomes of the genus Vibrio. Like V. cholerae, when grown in chitohexaose, cells of V. fischeri are able to take up and incorporate exogenous DNA. Chitohexaose-independent transformation by V. fischeri was observed when tfoX was present in multicopy. The second tfoX paralogue, designated tfoY, is also required for efficient transformation in V. fischeri, but is not functionally identical to tfoX. Natural transformation of V. fischeri facilitates rapid transfer of mutations across strains, and provides a highly useful tool for experimental genetic manipulation in this species. The presence of chitin-induced competence in several vibrios highlights the potential for a conserved mechanism of genetic exchange across this family of environmentally important marine bacteria. [source] The association between non-biting midges and Vibrio choleraeENVIRONMENTAL MICROBIOLOGY, Issue 12 2008Meir Broza Summary Vibrio cholerae is a natural inhabitant of aquatic ecosystems, yet its interactions within this habitat are poorly understood. Here we describe the current knowledge on the interaction of V. cholerae with one group of co-inhabitants, the chironomids. Chironomids, non-biting midges (Chironomidae, Diptera), are an abundant macroinvertebrate group encountered in freshwater aquatic habitats. As holometabolous insects, chironomids start life when their larvae hatch from eggs laid at the water/air interface; through various feeding strategies, the larvae grow and pupate to become short-lived, non-feeding, adult flying insects. The discovery of the connection between V. cholerae and chironomids was accidental. While working with Chironomus transavaalensis, we observed the disintegration of its egg masses and searched for a possible microbial agent. We identified V. cholerae as the primary cause of this phenomenon. Haemagglutinin/protease, a secreted extracellular enzyme, degraded the gelatinous matrix surrounding the eggs, enabling bacterial growth. Observation of chironomids in relation to V. cholerae continuously for 7 years in various types of water bodies in Israel, India, and Africa revealed that environmental V. cholerae adhere to egg-mass surfaces of various Chironomini (,bloodworms'). The flying adults' potential to serve as mechanical vectors of V. cholerae from one water body to another was established. This, in turn, suggested that these insects play a role in the ecology of V. cholerae and possibly take part in the dissemination of the pathogenic serogroups during, and especially between, epidemics. [source] Persistence of vibrios in marine bivalves: the role of interactions with haemolymph componentsENVIRONMENTAL MICROBIOLOGY, Issue 6 2005Carla Pruzzo Summary Marine bivalves are widespread in coastal environments and, due to their filter-feeding habit, they can accumulate large numbers of bacteria thus acting as passive carriers of human pathogens. Bivalves possess both humoral and cellular defence mechanisms that operate in a co-ordinated way to kill and eliminate infecting bacteria. Vibrio species are very abundant in coastal waters and are commonly isolated from edible bivalves tissues where they can persist after depuration processes in controlled waters. Such observations indicate that vibrios are regular components of bivalve microflora and that the molluscs can represent an important ecological niche for these bacteria. Here we tried to summarize data on the interactions between vibrios and bivalve haemolymph; the available evidence supports the hypothesis that persistence of bacteria in bivalve tissues depends, at least in part, on their sensitivity to the bactericidal activity of the haemolymph. Results obtained with an in vitro model of Vibrio cholerae challenged against Mytilus galloprovincialis haemocytes indicate that bacterial surface components, soluble haemolymph factors and the signalling pathways of the haemocyte host are involved in determining the result of vibrio,haemolymph interactions. [source] Characterization of a Vibrio cholerae phage isolated from the coastal water of PeruENVIRONMENTAL MICROBIOLOGY, Issue 5 2003Miguel Talledo Summary A Vibrio cholerae bacteriophage, family Myoviridae, was isolated from seawater collected from the coastal water of Lima, Peru. Genome size was estimated to be 29 kbp. The temperate phage was specific to V. cholerae and infected 12/13 V. cholerae O1 strains and half of the four non-O1/non-O139 strains tested in this study. Vibrio cholerae O139 strains were resistant to infection and highest infection rates were obtained in low nutrient media amended with NaCl or prepared using seawater as diluent. [source] Vaccine-induced protection against gastrointestinal bacterial infections in the absence of secretory antibodiesEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 1 2005Tania Abstract Secretory IgA (SIgA) is widely held to be responsible for the defense of the mucosae against pathogenics and other potentially harmful agents. In this study, polymeric Ig receptor (pIgR) knockout mice, which lack secretory antibodies (SAb), were used to investigate the role of vaccine-elicited SAb in protection against gastrointestinal bacterial infections. An essential role for specific SAb in protection against Vibrio cholerae was evident from experiments showing that vaccinated pIgR,/, mice, but not vaccinated C57BL/6 mice, were susceptible to cholera toxin challenge. Vaccination of C57BL/6 mice with Salmonella typhimurium elicited strong antigen-specific, mucosal responses, which blocked in vitro invasion of epithelia. However, vaccinated C57BL/6 and pIgR,/, mice were equally resistant to challenge infection with virulent S. typhimurium. Finally, we investigated the importance of SIgA in protection against recurrent infections with Citrobacter rodentium. Although higher numbers of bacteria were detected early after challenge infection in feces of vaccinated pIgR,/, mice compared with vaccinated C57BL/6 mice, both mouse strains showed complete clearance after 9,days. These results suggested that, in immune animals, SIgA is crucial for the protection of gastrointestinal surfaces against secreted bacterial toxins, may inhibit early colonization by C. rodentium, but is not essential for protection against re-infection with S. typhimurium or C. rodentium. [source] Transcriptional upregulation of inflammatory cytokines in human intestinal epithelial cells following Vibrio cholerae infectionFEBS JOURNAL, Issue 17 2007Arunava Bandyopadhaya Coordinated expression and upregulation of interleukin-1,, interleukin-1,, tumor necrosis factor-,, interleukin-6, granulocyte,macrophage colony-stimulating factor, interleukin-8, monocyte chemotactic protein-1 (MCP-1) and epithelial cell derived neutrophil activator-78, with chemoattractant and proinflammatory properties of various cytokine families, were obtained in the intestinal epithelial cell line Int407 upon Vibrio cholerae infection. These proinflammatory cytokines also showed increased expression in T84 cells, except for interleukin-6, whereas a striking dissimilarity in cytokine expression was observed in Caco-2 cells. Gene expression studies of MCP-1, granulocyte,macrophage colony-stimulating factor, interleukin-1,, interleukin-6 and the anti-inflammatory cytokine transforming growth factor-, in Int407 cells with V. cholerae culture supernatant, cholera toxin, lipopolysaccharide and ctxA mutant demonstrated that, apart from cholera toxin and lipopolysaccharide, V. cholerae culture supernatant harbors strong inducer(s) of interleukin-6 and MCP-1 and moderate inducer(s) of interleukin-1, and granulocyte,macrophage colony-stimulating factor. Cholera toxin- or lipopolysaccharide-induced cytokine expression is facilitated by activation of nuclear factor-,B (p65 and p50) and cAMP response element-binding protein in Int407 cells. Studies with ctxA mutants of V. cholerae revealed that the mutant activates the p65 subunit of nuclear factor-,B and cAMP response element-binding protein, and as such the activation is mediated by cholera toxin-independent factors as well. We conclude that V. cholerae elicits a proinflammatory response in Int407 cells that is mediated by activation of nuclear factor-,B and cAMP response element-binding protein by cholera toxin, lipopolysaccharide and/or other secreted products of V. cholerae. [source] Identification of protein-coding genes in the genome of Vibrio cholerae with more than 98% accuracy using occurrence frequencies of single nucleotidesFEBS JOURNAL, Issue 15 2001Ju Wang The published sequence of the Vibrio cholerae genome indicates that, in addition to the genes that encode proteins of known and unknown function, there are 1577 ORFs identified as conserved hypothetical or hypothetical gene candidates. Because the annotation is not 100% accurate, it is not known which of the 1577 ORFs are true protein-coding genes. In this paper, an algorithm based on the Z curve method, with sensitivity, specificity and accuracy greater than 98%, is used to solve this problem. Twenty-fold cross-validation tests show that the accuracy of the algorithm is 98.8%. A detailed discussion of the mechanism of the algorithm is also presented. It was found that 172 of the 1577 ORFs are unlikely to be protein-coding genes. The number of protein-coding genes in the V. cholerae genome was re-estimated and found to be ,,3716. This result should be of use in microarray analysis of gene expression in the genome, because the cost of preparing chips may be somewhat decreased. A computer program was written to calculate a coding score called VCZ for gene identification in the genome. Coding/noncoding is simply determined by VCZ > 0/VCZ < 0. The program is freely available on request for academic use. [source] Dependent population dynamics between chironomids (nonbiting midges) and Vibrio choleraeFEMS MICROBIOLOGY ECOLOGY, Issue 1 2006Malka Halpern Abstract Vibrio cholerae, the causative agent of cholera, is a natural inhabitant of the aquatic ecosystem. Chironomid (nonbiting midges) egg masses were recently found to harbour V. cholerae non-O1 and non-O139, providing a natural reservoir for the cholera bacterium. Chironomid populations and the presence of V. cholerae in chironomid egg masses were monitored. All V. cholerae isolates were able to degrade chironomid egg masses. The following virulence associated genes were detected in the bacterial isolates: hapA (100%), toxR (100%), hlyA (72%) and ompU (28%). The chironomid populations and the V. cholerae in their egg masses followed the phenological succession and interaction of host,pathogen population dynamics. A peak in the chironomid population was followed by a peak in the V. cholerae population. If such a connection is further substantiated for the pathogenic serogroups of V. cholerae in endemic areas of the disease, it may lead to a better understanding of the role of chironomids as a host for the cholera bacterium. [source] The ToxT-dependent methyl-accepting chemoreceptors AcfB and TcpI contribute to Vibrio cholerae intestinal colonizationFEMS MICROBIOLOGY LETTERS, Issue 2 2010Adriana Paola Chaparro Abstract Vibrio cholerae colonizes the human intestine and causes the acute diarrheal disease cholera. Flagellar-mediated chemotaxis contributes to intestinal colonization as well as infectivity. The virulence-regulatory protein ToxT activates transcription of the genes encoding the major virulence factors cholera toxin and toxin coregulated pilus. ToxT additionally activates transcription of two genes, tcpI and acfB, located within the Vibrio Pathogenicity Island predicted to encode methyl-accepting chemoreceptors. We show that disruption of either tcpI or acfB individually does not noticeably affect V. cholerae intestinal colonization within the infant mouse, but disruption of both tcpI and acfB leads to a decrease in intestinal colonization. These results suggest that TcpI and AcfB may have overlapping or redundant chemotactic functions that contribute to V. cholerae intestinal colonization. [source] Chemotaxis in Vibrio choleraeFEMS MICROBIOLOGY LETTERS, Issue 1 2004Markus A. Boin Abstract The ability of motile bacteria to swim toward or away from specific environmental stimuli, such as nutrients, oxygen, or light provides cells with a survival advantage, especially under nutrient-limiting conditions. This behavior, called chemotaxis, is mediated by the bacteria changing direction by briefly reversing the direction of rotation of the flagellar motors. A sophisticated signal transduction system, consisting of signal transducer proteins, a histidine kinase, a response regulator, a coupling protein, and enzymes that mediate sensory adaptation, relates the input signal to the flagellar motor. Chemotaxis has been extensively studied in bacteria such as Escherichia coli and Salmonella enterica serovar Typhimurium, and depends on the activity of single copies of proteins in a linear pathway. However, growing evidence suggests that chemotaxis in other bacteria is more complex with many bacterial species having multiple paralogues of the various chemotaxis genes found in E. coli and, in most cases, the detailed functions of these potentially redundant genes have not been elucidated. Although the completed genome of Vibrio cholerae, the causative agent of cholera, predicted a multitude of genes with homology to known chemotaxis-related genes, little is known about their relative contribution to chemotaxis or other cellular functions. Furthermore, the role of chemotaxis during the environmental or infectious phases of this organism is not yet fully understood. This review will focus on the complex relationship between chemotaxis and virulence in V. cholerae. [source] Presence of High Numbers of Transcriptionally Active Helicobacter pylori in Vomitus from Bangladeshi Patients Suffering from Acute GastroenteritisHELICOBACTER, Issue 4 2009Anders Janzon Abstract Background:,Helicobacter pylori is one of the most prevalent human bacterial pathogens; however, its transmission pathways remain unknown. New infections of H. pylori during outbreaks of gastroenteritis have been suggested previously, and to explore this transmission route further H. pylori was quantified in vomitus and diarrheal stool of patients suffering from acute gastroenteritis in Dhaka, Bangladesh. Materials and Methods:, Vomitus and stool samples from 28 patients seeking care at the International Centre for Diarrhoeal Disease Research hospital were analyzed for presence of H. pylori and other pathogens using quantitative culturing, real-time polymerase chain reaction (PCR), and H. pylori stool antigen test. Bacterial gene expression was analyzed using reverse transcriptase real-time PCR. Results:, The results of real-time PCR show that 23 (88%) of the 26 vomitus samples and 17 (74%) of the 23 stool samples were H. pylori positive, while stool antigen test show that 14 (67%) of the 21 stool samples were H. pylori positive. H. pylori could not be isolated by culture. Analysis using quantitative culture and real-time PCR to detect Vibrio cholerae showed strong correlation between these methods, and validating real-time PCR. Analysis of H. pylori virulence gene transcription in vomitus, diarrheal stool, antral and duodenal biopsy specimens, and in vitro cultures showed that cagA, flaA, and ureA were highly transcribed in vomitus, biopsy specimens, and cultures, whereas hpaA and vacA were expressed at lower levels. No H. pylori gene expression was detected in diarrheal stool. Conclusions:, We conclude that high numbers of transcriptionally active H. pylori are shed in vomitus, which indicates that new infections may be disseminated through vomiting. [source] Effect of environmental factors on expression and activity of chitinase genes of vibrios with special reference to Vibrio choleraeJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2007R. Bhowmick Abstract Aims:, The aim of this study was to investigate the distribution and inducibility of chitinase genes in vibrios and the effect of environmental factors on the expression level and activity of chitinase genes in Vibrio cholerae strains. Methods and Results:, Chitin agar plate assays showed that V. cholerae strains were more chitinolytic than non- cholerae vibrios. All of the identified or putative chitinase genes were expressed in V. cholerae (four strains) but not in non- cholerae vibrios (seven species/strains) under standard laboratory growth conditions. In non- cholerae vibrios, these genes were induced by chitin, its monomer N -acetyl- d -glucosamine and on exposure to rabbit intestine, while in V. cholerae strains, these genes showed significant variation in expression levels. To study the effects of environmental factors on the expression and activity of chitinase genes in V. cholerae, bacteria were cultured in different pH, temperature, sodium chloride and nutrients. RT-PCR analysis showed that lower temperatures and higher pH, salinity and nutrition favoured expression of these genes, while their activity increased under higher nutrition content and salinity. Conclusions:, Chitinase genes are distributed in all the relatively small number of strains studied here, and biotic and abiotic factors have significant role in the induction, expression level and activity of this gene family in vibrios. Significance and Impact of the Study:, Chitinases have important applications especially in recycling of chitin. Vibrios can be used as chitinolytic agents, using suitable culture conditions that maximize the expression and activity of these genes. [source] The ability of two different Vibrio spp. bacteriophages to infect Vibrio harveyi, Vibrio cholerae and Vibrio mimicusJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2004M. Payne Abstract Aims:, To determine the host range of the Vibrio harveyi myovirus-like bacteriophage (VHML) and the cholera toxin conversion bacteriophage (CTX ,) within a range of Vibrio cholerae and V. mimicus and V. harveyi, V. cholerae and V. mimicus isolates respectively. Methods and Results:, Three V. harveyi, eight V. cholerae and five V. mimicus isolates were incubated with VHML and CTX ,. Polymerase chain reaction (PCR) was used to determine the presence of VHML and CTX , in infected isolates. We demonstrated that it was possible to infect one isolate of V. cholerae (isolate ACM #2773/ATCC #14035) with VHML. This isolate successfully incorporated VHML into its genome as evident by positive PCR amplification of the sequence coding part of the tail sheath of VHML. Attempts to infect all other V. cholerae and V. mimicus isolates with VHML were unsuccessful. Attempts to infect V. cholerae non-01, V. harveyi andV. mimicus isolates with CTX , were unsuccessful. Conclusions:, Bacteriophage infection is limited by bacteriophage-exclusion systems operating within bacterial strains and these systems appear to be highly selective. One system may allow the co-existence of one bacteriophage while excluding another. VHML appears to have a narrow host range which may be related to a common receptor protein in such strains. The lack of the vibrio pathogenicity island bacteriophage (VPI ,) in the isolates used in this study may explain why infections with CTX , were unsuccessful. Significance and Impact of the Study:, The current study has demonstrated that Vibrio spp. bacteriophages may infect other Vibrio spp. [source] Detection of toxigenic Vibrio cholerae from environmental water samples by an enrichment broth cultivation,pit-stop semi-nested PCR procedureJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2000J. Theron A pit-stop semi-nested PCR assay for the detection of toxigenic Vibrio cholerae in environmental water samples was developed and its performance evaluated. The PCR technique amplifies sequences within the cholera toxin operon specific for toxigenic V. cholerae. The PCR procedure coupled with an enrichment culture detected as few as four V. cholerae organisms in pure culture. Treated sewage, surface, ground and drinking water samples were seeded with V. cholerae and following enrichment, a detection limit of as few as 1 V. cholerae cfu ml,1 was obtained with amplification reactions from crude bacterial lysates. The proposed method, which includes a combination of enrichment, rapid sample preparation and a pit-stop semi-nested PCR, could be applicable in the rapid detection of toxigenic V. cholerae in environmental water samples. [source] Prevalence and virulence properties of Vibrio cholerae non-O1, Aeromonas spp. and Plesiomonas shigelloides isolated from Cambé Stream (State of Paraná, Brazil)JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2000A. Gibotti The incidence of Vibrio cholerae, Aeromonas spp. and Plesiomonas shigelloides was determined in water samples from Cambé Stream. The samples were collected from seven different sites. The serogroups, virulence markers and drug resistance profiles were also evaluated. Twelve Aer. hydrophila, 12 Aer. caviae, eight Aer. sobria, seven Ple shigelloides and two V. cholerae non-O1 were isolated. They belonged to different serogroups and all produced haemolysis in different assays. Five of the Aeromonas strains and one of V. cholerae non-O1 were positive for enterotoxin activity. Haemagglutination and its inhibition, using erythrocytes of different origins, was variable for Aeromonas spp. and V. cholerae, while none of the Ple. shigelloides haemagglutinated in association with any type of erythrocyte. All isolates exhibited multiple drug resistance. These results indicate that the occurrence of V. cholerae non-O1, Aeromonas spp. and Ple. shigelloides, in water used for vegetable irrigation, human recreation and animal consumption, among others, represents a potential risk for humans. [source] EFFECT OF PROCESSING ON BACTERIAL POPULATION OF CUTTLE FISH AND CRAB AND DETERMINATION OF BACTERIAL SPOILAGE AND RANCIDITY DEVELOPING ON FROZEN STORAGEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2007THAILAMBAL ANANTHA SUBRAMANIAN ABSTRACT Processing techniques like cooking and freezing exhibited significant (P < 0.001) reduction in the bacterial load of cuttlefish, Sepia pharaonis, and marine crab, Portunus pelagicus. Raw cuttle fish had 2.4 × 107 cfu/g which on cooking reduced to 9.7 × 106 cfu/g. Freezing reduced the bacterial load further as cooked frozen product had only 9.9 × 104 cfu/g. Similarly, raw crab had 2.6 × 107 cfu/g which on cooking reduced to 6.5 × 106 cfu/g. A further reduction in bacterial load was seen after freezing as cooked frozen crab exhibited only 7.3 × 104 cfu/g. Escherichia coli and Staphylococcus aureus were present in the limit of acceptability for fish and fish products. Salmonella typhimurium and Vibrio cholerae were absent even in raw stage. Biochemical analysis performed on stored frozen products of cuttle fish and crab exhibited a significant (P , 0.05) increase in bacterial spoilage and rancidity with increasing days of storage. Total volatile base nitrogen, trimethylamine, thiobarbituric acid and free fatty acid contents in frozen products of cuttle fish and crab increased significantly with 120 days of frozen storage. [source] CALCOFLUOR AS A FLUORESCENT PROBE TO DETECT BIOFILMS OF FOODBORNE PATHOGENSJOURNAL OF FOOD SAFETY, Issue 1 2003C.L. ERIKSSON DE REZENDE ABSTRACT Biofilms enable foodborne pathogens to resist removal from surfaces, survive disinfection and elude detection. This study evaluated the use of Calcofluor, which binds to polysaccharides containing ,-D-glucans, to detect biofilms produced by Salmonella enterica serovar Berta and Salmonella enterica serovar Typhimurium DT104 (St DT104), Escherichia coli, Aeromonas hydrophila, Vibrio cholerae O139 and Hyphomonas adhaerens. Biofilms produced by St DT104, S. berta and V. cholerae on five types of surfaces (glass, polypropylene, TeflonÔ, stainless steel and aluminum) were detected by Calcofluor. Results suggest the potential use of Calcofluor as probes of foodborne pathogens in biofilms. [source] INFECTIVE DOSE OF FOODBORNE PATHOGENS IN VOLUNTEERS: A REVIEWJOURNAL OF FOOD SAFETY, Issue 1 2001MAHENDRA H. KOTHARY ABSTRACT Risk assessment and impact of foodborne pathogens on the health of different populations was one of the goals identified in the Presidential Food Safety Initiative three-year plan. This entailed estimation of dose-response relationship for foodborne pathogens to humans, either by feeding studies or from outbreaks. For certain pathogens, such as Listeria monocytogenes and Escherichia coli O157:H7, there are no feeding studies due to ethical reasons, and the results from outbreaks are normally used to estimate the infectious dose. The focus of this review is to compile dose-response information in volunteers for several foodborne pathogens including Salmonella, Shigella spp., Campylobacter jejuni, Vibrio spp., Escherichia coli, Cryptosporidium parvum and Entamoeba coli. The infectious dose for different serovars of Salmonella and strains of E. coli was quite large (> 105 organisms), while the infectious dose for some Shigella spp. seemed to be as low as less than 10 organisms. Toxigenic V. cholerae (O1 and O139 serotypes) were infective at a dose of 104 organisms; a non-O1 strain was infective at a much higher dose (106 organisms). C. jejuni, C. parvum and Entamoeba coli appeared to have infectious doses as low as 500 organisms, 10 oocysts, and 1 cyst, respectively. The infectious dose and the dose response are dependent upon the strains used, and the age and physical condition of the individuals, and can therefore show wide variations. In addition, since many of the volunteer studies are carried out by feeding the organisms in a nonfood matrix after neutralizing the stomach acidity, results obtained may not reflect the true dose response. [source] Spectroscopic Differentiation and Quantification of Microorganisms in Apple JuiceJOURNAL OF FOOD SCIENCE, Issue 7 2004Chenxu Yu ABSTRACT: A fast and easy-to-operate Fourier Transform Infrared (FTIR) spectrometry-based approach was developed for microbial differentiation and quantification in apple juice. Eight different microorganisms were evaluated: Enterobacter cloacae, Salmonella typhimurium, Enterobacteraerogenes, Salmonella choleraesuis, Serratia marcescens, Pseudomonas vulgaris, Vibrio cholerae, and Hafnia alvei. FTIR spectroscopy combined with chemometrics could differentiate the microorganisms studied at low concentration level of 103 colony-forming units (CFU) /mL in apple juice. The chemometric models developed to count microorganisms in apple juice were validated by an independent test set consisting of 18 samples and correlated against plate counts satisfactorily up to a detection limit of 103 CFU/mL. [source] Genetic heterogeneity of non-O1 and non-O139 Vibrio cholerae isolates from shrimp aquaculture system: a comparison of RS-, REP- and ERIC-PCR fingerprinting approachesLETTERS IN APPLIED MICROBIOLOGY, Issue 1 2010B. Madhusudana Rao Abstract Aims:, The genetic diversity of Vibrio cholerae isolated from black tiger shrimp (Penaeus monodon) aquaculture farms was determined using three PCR typing methods based on enterobacterial repetitive intergenic consensus (ERIC) sequences, ribosomal gene spacer (RS) sequence and repetitive extragenic palindromic (REP) sequences. Methods and Results:, Non-O1 and non-O139 V. cholerae isolates were obtained from shrimp pond water, pond sediment, shrimp head and shrimp muscle. RS-PCR yielded fewer bands than REP-PCR and ERIC-PCR. Higher similarity was observed in RS-PCR (75,100%) than in REP-PCR (60,95%) and ERIC-PCR (40,95%). Conclusions:, A 100% similarity between V. cholerae isolates was only noticed in RS-PCR. The choleratoxigenic V. cholerae (non-O1 and non-O139) showed greater genetic similarity with ctx -negative V. cholerae than among ctx- positive V. cholerae. Significance and Impact of the Study:, The greater similarity of ctx -positive V. cholerae with ctx -negative V. cholerae isolates indicates that the ctx -positive strains (non-O1 and non-O139) might have originated from autochthonous V. cholerae in the aquatic niche. [source] Comparison of automated ribotyping and pulsed-field gel electrophoresis for subtyping of Vibrio choleraeLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2009H.-J. Zhou Abstract Aims:, To compare the discriminatory power of an automated ribotyping method for Vibrio cholerae subtyping with the pulsed-field gel electrophoresis (PFGE), to evaluate the possibility of automated ribotyping in use of outbreak investigations and surveillance of cholera. Methods and Results:, Eight-one epidemiologically unrelated isolates of V. cholerae, and 19 isolates from seven cholera outbreaks were used as the panels. When comparing the two methods using the epidemiologically unrelated isolates, automated ribotyping using PvuII distinguished 38 different ribotypes with a D -value of 0·8956. When combined with serotyping, the D -value is 0·9466. However, PFGE with NotI and SfiI digestions had higher D -values of 0·9951 and 0·9948, respectively. PFGE could cluster the isolates from each outbreak into the same pattern, and distinguish different patterns from different outbreaks, whereas automated ribotyping had lower discriminatory ability. Conclusions:, The automated ribotyping has lower discriminatory ability compared to PFGE, and is limited to application in V. cholerae subtyping and outbreak investigation. Significance and Impact of the Study:, The study evaluated the limitation in subtyping of automated ribotyping for V. cholerae, and raise the question of improvement for the automated ribotyping in subtyping. [source] Investigation of seven Vibrio virulence genes among Vibrio alginolyticus and Vibrio parahaemolyticus strains from the coastal mariculture systems in Guangdong, ChinaLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2005Z.-Y. Xie Abstract Aims:, To investigate the distribution of the virulence of two Vibrio species among different strains obtained from the mariculture systems on the coast of Guangdong in China and the correlation between the virulence strains and the virulence genes among Vibrio alginolyticus. Methods:, Besides three strains, 72 V. alginolyticus strains and seven Vibrio parahaemolyticus strains were examined by PCR or semi-nested PCR for the virulence genes (tlh, trh, tdh, toxR, toxRS, ctxA, VPI). Additionally, the virulence of 18 V. alginolyticus strains was tested. Significance and Impact of the Study:, Virulence genes homologous to those in the V. parahaemolyticus and Vibrio cholerae are widely distributed among V. alginolyticus and V. parahaemolyticus in the coastal mariculture systems in Guangdong, China. Some of the V. alginolyticus strains are pathogenic to aquatic animals, and might have derived their virulence genes from V. parahaemolyticus or V. cholerae, representing a possible reservoir of these genes. However, there is no correlation between presence and absence of the virulence genes used to investigate V. alginolyticus and its virulent strains. In this report, we also show that tlh is distributed among V. alginolyticus. [source] ORIGINAL ARTICLE: Conversion of viable but nonculturable Vibrio cholerae to the culturable state by co-culture with eukaryotic cellsMICROBIOLOGY AND IMMUNOLOGY, Issue 9 2010Mitsutoshi Senoh ABSTRACT VBNC Vibrio cholerae O139 VC-280 obtained by incubation in 1% solution of artificial sea water IO at 4°C for 74 days converted to the culturable state when co-cultured with CHO cells. Other eukaryotic cell lines, including HT-29, Caco-2, T84, HeLa, and Intestine 407, also supported conversion of VBNC cells to the culturable state. Conversion of VBNC V. cholerae O1 N16961 and V. cholerae O139 VC-280/pG13 to the culturable state, under the same conditions, was also confirmed. When VBNC V. cholerae O139 VC-280 was incubated in 1% IO at 4°C for up to 91 days, the number of cells converted by co-culture with CHO cells declined with each additional day of incubation and after 91 days conversion was not observed. [source] The quorum sensing regulator HapR downregulates the expression of the virulence gene transcription factor AphA in Vibrio cholerae by antagonizing Lrp- and VpsR-mediated activationMOLECULAR MICROBIOLOGY, Issue 4 2007Wei Lin Summary HapR is a quorum sensing-regulated transcription factor that represses the virulence cascade in Vibrio cholerae by binding to a specific site centred at ,71 in the aphA promoter, ultimately preventing activation of the tcpPH promoter on the Vibrio pathogenicity island. In an effort to elucidate the mechanism by which HapR represses aphA expression, we identified two transcriptional regulators, Lrp and VpsR, both of which activate the aphA promoter. Lrp, the leucine-responsive regulatory protein, binds to a region between ,136 and ,123 in the promoter to initiate aphA expression. VpsR, the response regulator that controls biofilm formation, binds to a region between ,123 and ,73 to activate aphA expression. HapR represses aphA expression by antagonizing the functions of both of these activators. The HapR binding site at ,71 lies downstream of the Lrp binding site and overlaps the VpsR binding site. HapR binding thus directly blocks access of VpsR to the promoter. A naturally occurring point mutation in the aphA promoter (G-77T), which has previously been shown to prevent HapR binding, also prevents VpsR binding. In the absence of HapR, either Lrp or VpsR is capable of achieving nearly full expression of the aphA promoter, but when present together their effects are to some degree additive. The aphA promoter is also negatively autoregulated and an AphA binding site is centred at ,20. The results here provide a model for the dual activation of the aphA promoter by Lrp and VpsR as well as its dual repression by HapR and AphA. [source] The RprY response regulator of Porphyromonas gingivalisMOLECULAR MICROBIOLOGY, Issue 4 2007Ana E. Duran-Pinedo Summary Porphyromonas gingivalis is a Gram-negative oral anaerobe associated with chronic adult periodontitis. Its ecological niche is the gingival crevice, where the organism adapts to the challenges of the infectious process such as host defence and bacterial products. Bacterial responses to environmental changes are partly regulated by two-component signal transduction systems. Several intact systems were annotated in the genome of P. gingivalis, as well as an orphan regulator encoding a homologue of RprY, a response regulator from Bacteroides fragilis. With the goal of defining the environmental cues that activate RprY in P. gingivalis, we used several strategies to identify its regulon. Results from gene expression and DNA,protein binding assays identified target genes that were either involved in transport functions or associated with oxidative stress, and indicated that RprY can act as an activator and a repressor. RprY positively activated the primary sodium pump, NADH : ubiquinone oxidoreductase (NQR), and RprY protein also interacted with the promoter regions of nqrA genes from B. fragilis and Vibrio cholerae. Given that gingival bleeding and infiltration of host defence cells are symptoms of periodontal infection, iron products released from blood and reactive oxygen species from polymorphonuclear leucocytes may be potential inducers of the RprY regulon. [source] MicroReview: Divided genomes: negotiating the cell cycle in prokaryotes with multiple chromosomesMOLECULAR MICROBIOLOGY, Issue 5 2005Elizabeth S. Egan Summary Historically, the prokaryotic genome was assumed to consist of a single circular replicon. However, as more microbial genome sequencing projects are completed, it is becoming clear that multipartite genomes comprised of more than one chromosome are not unusual among prokaryotes. Chromosomes are distinguished from plasmids by the presence of essential genes as well as characteristic cell cycle-linked replication kinetics; unlike plasmids, chromosomes initiate replication once per cell cycle. The existence of multipartite prokaryotic genomes raises several questions regarding how multiple chromosomes are replicated and segregated during the cell cycle. These divided genomes also introduce questions regarding chromosome evolution and genome stability. In this review, we discuss these and other issues, with particular emphasis on the cholera pathogen Vibrio cholerae. [source] Quorum sensing controls biofilm formation in Vibrio choleraeMOLECULAR MICROBIOLOGY, Issue 1 2003Brian K. Hammer Summary Multiple quorum-sensing circuits function in parallel to control virulence and biofilm formation in Vibrio cholerae. In contrast to other bacterial pathogens that induce virulence factor production and/or biofilm formation at high cell density in the presence of quorum-sensing autoinducers, V. cholerae represses these behaviours at high cell density. Consistent with this, we show here that V. cholerae strains ,locked' in the regulatory state mimicking low cell density are enhanced for biofilm production whereas mutants ,locked' in the regulatory state mimicking high cell density are incapable of producing biofilms. The quorum-sensing cascade we have identified in V. cholerae regulates the transcription of genes involved in exopolysaccharide production (EPS), and variants that produce EPS and form biofilms arise at high frequency from non-EPS, non-biofilm producing strains. Our data show that spontaneous mutation of the transcriptional regulator hapR is responsible for this effect. Several toxigenic strains of V. cholerae possess a naturally occurring frameshift mutation in hapR. Thus, the distinct environments occupied by this aquatic pathogen presumably include niches where cell-cell communication is crucial, as well as ones where loss of quorum sensing via hapR mutation confers a selective advantage. Bacterial biofilms could represent a complex habitat where such differentiation occurs. [source] Regulation of virulence gene expression in Vibrio cholerae by quorum sensing: HapR functions at the aphA promoterMOLECULAR MICROBIOLOGY, Issue 4 2002Gabriela Kovacikova Summary Quorum sensing negatively influences virulence gene expression in certain toxigenic Vibrio cholerae strains. At high cell densities, the response regulator LuxO fails to reduce the expression of HapR, which, in turn, represses the expression of the virulence cascade. A critical regulatory step in the cascade is activation of tcpPH expression by AphA and AphB. We show here that HapR influences the virulence cascade by directly repressing aphA expression. In strain C6706, aphA expression was increased in a ,hapR mutant and decreased in a ,luxO mutant, indicating a negative and positive influence, respectively, of these gene products on the promoter. Overexpression of HapR also reduced aphA expression in both C6706 and Escherichia coli. DNase I footprinting showed that purified HapR binds to the aphA promoter between ,85 and ,58. Although it appears that quorum sensing does not influence virulence gene expression in strain O395 solely because of a frameshift in hapR, overproduced HapR did not repress expression from the O395 aphA promoter in either Vibrio or E. coli, nor did the protein bind to the promoter. Two basepair differences from C6706 are present in the O395 HapR binding site at ,85 and ,77. Introducing the ,77 change into C6706 prevented HapR binding and repression of aphA expression. This mutation also eliminated the repression of toxin-co-regulated pilus (TCP) and cholera toxin (CT) that occurs in a ,luxO mutant, indicating that HapR function at aphA is critical for density-dependent regulation of virulence genes. [source] Haem utilization in Vibrio cholerae involves multiple TonB-dependent haem receptorsMOLECULAR MICROBIOLOGY, Issue 3 2001Alexandra R. Mey Vibrio cholerae has multiple iron transport systems, one of which involves haem uptake through the outer membrane receptor HutA. A hutA mutant had only a slight defect in growth using haemin as the iron source, and we show here that V. cholerae encodes two additional TonB-dependent haem receptors, HutR and HasR. HutR has significant homology to HutA as well as to other outer membrane haem receptors. Membrane fractionation confirmed that HutR is present in the outer membrane. The hutR gene was co-transcribed with the upstream gene ptrB, and expression from the ptrB promoter was negatively regulated by iron. A hutA, hutR mutant was significantly impaired, but not completely defective, in the ability to use haemin as the sole iron source. HasR is most similar to the haemophore-utilizing haem receptors from Pseudomonas aeruginosa and Serratia marcescens. A mutant defective in all three haem receptors was unable to use haemin as an iron source. HutA and HutR functioned with either V. cholerae TonB1 or TonB2, but haemin transport through either receptor was more efficient in strains carrying the tonB1 system genes. In contrast, haemin uptake through HasR was TonB2 dependent. Efficient utilization of haemoglobin as an iron source required HutA and TonB1. The triple haem receptor mutant exhibited no defect in its ability to compete with its Vib, parental strain in an infant mouse model of infection, indicating that additional iron sources are present in vivo. V. cholerae used haem derived from marine invertebrate haemoglobins, suggesting that haem may be available to V. cholerae growing in the marine environment. [source] Transcriptional regulation of transport and utilization systems for hexuronides, hexuronates and hexonates in gamma purple bacteriaMOLECULAR MICROBIOLOGY, Issue 4 2000Dmitry A. Rodionov The comparative approach is a powerful tool for the analysis of gene regulation in bacterial genomes. It can be applied to the analysis of regulons that have been studied experimentally as well as that of regulons for which no known regulatory sites are available. It is assumed that the set of co-regulated genes and the regulatory signal itself are conserved in related genomes. Here, we use genomic comparisons to study the regulation of transport and utilization systems for sugar acids in gamma purple bacteria Escherichia coli, Salmonella typhi, Klebsiella pneumoniae, Yersinia pestis, Erwinia chrysanthemi, Haemophilus influenzae and Vibrio cholerae. The variability of the operon structure and the location of the operator sites for the main transcription factors are demonstrated. The common metabolic map is combined with known and predicted regulatory interactions. It includes all known and predicted members of the GntR, UxuR/ExuR, KdgR, UidR and IdnR regulons. Moreover, most members of these regulons seem to be under catabolite repression mediated by CRP. The candidate UxuR/ExuR signal is proposed, the KdgR consensus is extended, and new operators for all transcription factors are identified in all studied genomes. Two new members of the KdgR regulon, a hypothetical ATP-dependent transport system OgtABCD and YjgK protein with unknown function, are detected. The former is likely to be the transport system for the products of pectin degradation, oligogalacturonides. [source] | |||||||||||||||||||||||||||||||