A Filamentous Phage of Vibrio parahaemolyticus O3:K6 Isolated in Laos

A filamentous phage, ‘lvpf5’, of Vibrio parahaemolyticus O3:K6 strain LVP5 was isolated and characterized. The host range was not restricted to serotype O3:K6, but 7 of 99 V. parahaemolyticus strains with a variety of serotypes were susceptible to the phage. The phage was inactivated by heating at 80 C for 10 min and by treating with chloroform. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the phage exhibited a 3.8 kDa protein. The amino-terminal amino acid sequence of the coat protein was determined as AEGGAADPFEAIDLLGVATL. The phage genome consisted of a single-stranded DNA molecule. The activity of the phages was inhibited by anti-Na2 pili antibody.     

Genetic analyses of the putative O and K antigen gene clusters of pandemic Vibrio parahaemolyticus

Pandemic V. parahaemolyticus strains have rapidly changed their serotypes, but its determinants, especially K antigen, and the genes involved in serotype have been an open question. The purpose of this study was to gain insights into these points. Although V. parahaemolyticus is known to be lacking O-side chain on its lipopolysaccharide, and O antigens are thought to be represented by core OS, the genome sequence of V. parahaemolyticus O3:K6 strain RIMD2210633 suggests that this bacterium potentially synthesizes O-side chain. To explore possible relatedness between this O-side chain biosynthesis gene cluster, which is similar in the serotypes of Vibrio cholerae, and of V. parahaemolyticus, we amplified both core OS and O-side chain gene clusters of the strains belonging to various serotypes of V. parahaemolyticus by long PCR and performed PCR RFLP analyses. The results of our RFLP analyses suggest that the core OS biosynthesis gene cluster is related to the O antigens of pandemic V. parahaemolyticus and that the putative O-side chain gene cluster is related to K antigens of pandemic V. parahaemolyticus. We then determined the sequence of these regions of a pandemic O4:K68 strain, and compared it with the corresponding sequence of RIMD2210633. In addition, PCR analysis showed the putative O4 and K68 antigen gene clusters are unique to the strains belonging to the O4 and K68 serotype respectively. The data implies that the pandemic O4:K68 V. parahaemolyticus strain emerged from the pandemic O3:K6 strain by replacement of the putative O and K antigen gene clusters.     

Isolation and partial characterization of a compound with siderophore activity from Vibrio parahaemolyticus

A compound with siderophore activity was purified by successive column and thin layer chromatographic procedures from Dowex 1 x 8 extracts of culture supernatants of Vibrio parahaemolyticus AQ 3354. The strain synthesized the compound in culture media containing less than 2 microM added FeCl3. Hydrolysis of the compound yielded alanine, ethanolamine, citric acid and 2-ketoglutaric acid. The 1H-NMR spectrum exhibited the presence of a residue from each of these components in the intact molecule. The fast-atom bombardment mass spectrum of the methyl ester derivative indicated a prominent ion at m/z 477, probably corresponding to [M + 1] ion. Other strains of V. parahaemolyticus were also found to produce this compound when grown in an iron-limited medium.     

Isolation of a pandemic O3:K6 clone of a Vibrio parahaemolyticus strain from environmental and clinical sources in Thailand

Application of an immunomagnetic enrichment method selective for Vibrio parahaemolyticus serovar K6 allowed isolation of a strain belonging to the pandemic O3:K6 clone of V. parahaemolyticus from fresh shellfish not implicated in a clinical case in southern Thailand. Arbitrarily primed PCR profiles of this strain, clinical O3:K6 strains isolated from sporadic diarrhea cases in the same area, and a standard pandemic O3:K6 strain were indistinguishable.     

Outbreak of gastroenteritis caused by the pandemic Vibrio parahaemolyticus O3:K6 in Mexico

During 2003 and during late September of 2004, more than 1230 cases of gastroenteritis were reported in the south of Sinaloa State, north-western Mexico. All cases were attributed to the consumption of raw or undercooked shrimp collected at the Huizache-Caimanero lagunary system. Vibrio parahaemolyticus was identified by standard biochemical methods, and many strains were positive for PCR amplifications of the tlh and tdh genes and negative for the trh gene. A representative strain belonged to the O3:K6 serogroup. This is the first outbreak of gastroenteritis caused by the pandemic strains of O3:K6 V. parahaemolyticus in México.     

Proteome profile of a pandemic Vibrio parahaemolyticus SC192 strain in the planktonic and biofilm condition

Vibrio parahaemolyticus is one of the leading causative agents of foodborne diseases in humans. In this study, the proteome profiles of the pandemic strain V. parahaemolyticus SC192 belonging to the O3:K6 serovar during the planktonic and biofilm stages were analyzed by two-dimensional liquid chromatography coupled to tandem mass spectrometry. This non-gel-based multidimensional protein identification technology approach identified 45.5% of the proteome in the reference genome V. parahaemolyticus RIMD 2210633. This is the largest proteome coverage obtained so far in V. parahaemolyticus and provides evidence for expression of 27% of the hypothetical proteins. Comparison of the planktonic and biofilm proteomes based on their cluster of orthologous groups, gene ontologies and KEGG pathways provides basic information on biofilm specific functions and pathways. To the authors’ knowledge, this is the first study to generate a global proteome profile of the pandemic strain of V. parahaemolyticus and the method reported here could be used to rapidly obtain a snapshot of the proteome of any microorganism at a given condition.     

Cloning and characterization of a gene encoding a new thermostable hemolysin from Vibrio parahaemolyticus

A new thermostable hemolysin (delta-VPH) gene was cloned from a Kanagawa-negative Vibrio parahaemolyticus strain into vector pBR322 in Escherichia coli K12. The nucleotide and amino acid sequences had no homology with those of the thermostable direct hemolysin (TDH) which causes the Kanagawa phenomenon, and of the thermolabile hemolysin (TLH) of V. parahaemolyticus. The gene was present in all V. parahaemolyticus strains tested and also in one strain of V. damsela.     

Isolation and characterization of a novel Enterococcus faecalis bacteriophage φEF24C as a therapeutic candidate

Vancomycin-resistant Enterococcus faecalis (VRE) has become a significant threat in nosocomial settings. Bacteriophage (phage) therapy is frequently proposed as a potential alternative therapy for infections caused by this bacterium. To search for candidate therapeutic phages against Enterococcus faecalis infections, 30 Enterococcus faecalis phages were isolated from the environment. One of these, virulent phage φEF24C, which has a broad host range, was selected for analysis. The plaque-forming ability of φEF24C was virtually unaffected by differences in the clinical host strains. Furthermore, the phage had a shorter latent period and a larger burst size than ordinary tailed phages, indicating that φEF24C has effective lytic activity against many Enterococcus faecalis strains, including VRE. Morphological and genomic analyses revealed that φEF24C is a large myovirus (classified as family Myoviridae morphotype A1) with a linear double-stranded DNA genome of c . 143 kbp. Analyses of the N-terminal amino acid sequences of the virion proteins, together with the morphology and the genome size, speculated that φEF24C is closely related to other myoviruses of Gram-positive bacteria that have been used experimentally or practically for therapy or prophylaxis. Considering these results, φEF24C may be a potential candidate therapeutic phage against Enterococcus faecalis infections.     

Frequent,independent transfers of a catabolic gene from bacteria to contrasted filamentous eukaryotes

Even genetically distant prokaryotes can exchange genes between them, and these horizontal gene transfer events play a central role in adaptation and evolution. While this was long thought to be restricted to prokaryotes, certain eukaryotes have acquired genes of bacterial origin. However, gene acquisitions in eukaryotes are thought to be much less important in magnitude than in prokaryotes. Here, we describe the complex evolutionary history of a bacterial catabolic gene that has been transferred repeatedly from different bacterial phyla to stramenopiles and fungi. Indeed, phylogenomic analysis pointed to multiple acquisitions of the gene in these filamentous eukaryotes—as many as 15 different events for 65 microeukaryotes. Furthermore, once transferred, this gene acquired introns and was found expressed in mRNA databases for most recipients. Our results show that effective inter-domain transfers and subsequent adaptation of a prokaryotic gene in eukaryotic cells can happen at an unprecedented magnitude.     

Isolation and characterization of a toxic intracellular protein from Vibrio parahaemolyticus

A toxic factor released from disrupted cells of Vibrio parahaemolyticus was partially purified by gel filtration after precipitation with (NH₄)₂SO₄ at 40% saturation. The factor, which was a thermostable protein of 63 kDa, lysed human erythrocytes at a concentration of 0.15 g ml^-1. Its LD₅₀ by intravenous injection into mice was 6.4 g. Fluid accumulated in suckling mice force-fed with the toxic material (1 to 25 g). Haemolytic activity, which occurred maximall at 37°C and pH 7.0 was enhanced by Ca²⁺, Cu²⁺ and Zn²⁺, each at 1 mm. Anti-toxic-factor serum agglutinated V. parahaemolyticus cells. The factor may play a role in the pathogenesis of V. parahaemolyticus infections and in the host's defence mechanisms against infection by the microorganism.     

Rapid detection of Vibrio parahaemolyticus by PCR targeted to the histone-like nucleoid structure (H-NS) gene and its genetic characterization

Aims: The aim of this study was to explore a new PCR target gene for Vibrio parahaemolyticus, based on the histone‐like nucleoid structure (H‐NS) gene. Methods and Results: Primers for the H‐NS gene were designed for specificity to V. parahaemolyticus and incorporated into a PCR assay. The PCR assay was able to specifically detect all of the 82 V. parahaemolyticus strains tested, but did not result in amplification in the 47 other Vibrio spp. and nonVibrio spp. strains. The detection limit of the PCR assay was 0·14 pg purified genomic DNA and 1·8 × 10⁵ CFU g^?1 spiked oyster samples from V. parahaemolyticus RIMD2210633. Furthermore, a multiplex PCR assay targeting the hns, tdh and trh genes was successfully developed to detect virulent V. parahaemolyticus strains. Conclusions: The H‐NS‐based PCR assay developed in this study was sensitive and specific, with great potential for field detection of V. parahaemolyticus in seawater or seafood samples. Significance and Impact of the Study: The H‐NS gene was validated as a new specific marker gene in PCR assays for accurate detection and identification of V. parahaemolyticus, which has the potential to be applied in diagnostics and taxonomic studies.     

Transduction of a freshwater microbial community by a new Pseudomonas aeruginosa generalized transducing phage,UT1

A pseudolysogenic, generalized transducing bacteriophage, UT1, isolated from a natural freshwater habitat, is capable of mediating the transfer of both chromosomal andplasmid DNA between strains of Pseudomonas aeruginosa. Several chromosomal alleles from three different P. aeruginosa strains were found to transduce at frequencies from 10^-8 to 10^-10 transductants per PFU at multiplicities of infection (MOD between 0.1 and 1. Transduction frequencies of certain alleles increased up to 1000-fold as MOIs were decreased to 0.01. UT1 is also capable of transducing plasmid DNA to indigenous populations of microorganisms in natural lake-water environments. Data obtained in this study suggest that environmentally endemic bacteriophages such as UT1 are formidable transducers of naturally occurring microbial communities. It should be possible to develop model systems to test transduction in freshwater environments using components derived exclusively from these environments.     

Isolation and characterization of a Lactobacillus fermentum temperate bacteriophage from Chinese yogurt

AIMS: The aim of this study was to investigate the properties of temperate bacteriophage of Lactobacillus fermentum, based on its morphology, restriction patterns, protein profile and the impact on the growth of host strain. METHODS AND RESULTS: With Mitomycin C, seven temperate phages were induced from Lactobacilli derived from Chinese yogurt. The temperate phages induced belong to the most common Bradley's group B, having hexagonal head and long, noncontractile tail. They were furthermore confirmed to be the same bacteriophage by identical restriction patterns. SDS-PAGE profile showed that the phage studied had one major structure protein about 31.9 kDa. The presence of the prophage influenced the cell shape and colony size of its lysogenic strain. CONCLUSIONS: The phage obtained had similar, but not complete identical properties with other L. fermentum phages reported. It influenced the growth behaviour of its lysogenic strain. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides some information about bacteriophages occurring in the Chinese yoghurt manufacture and contributes to our knowledge on the bacteriophage diversity in the dairy industry.     

Isolation of a Pandemic O3:K6 Clone of a Vibrio parahaemolyticus Strain from Environmental and Clinical Sources in Thailand

Application of an immunomagnetic enrichment method selective for Vibrio parahaemolyticus serovar K6 allowed isolation of a strain belonging to the pandemic O3:K6 clone of V. parahaemolyticus from fresh shellfish not implicated in a clinical case in southern Thailand. Arbitrarily primed PCR profiles of this strain, clinical O3:K6 strains isolated from sporadic diarrhea cases in the same area, and a standard pandemic O3:K6 strain were indistinguishable.     

The Thermostable Direct Hemolysin Gene (tdh) of Vibrio hollisae Is Dissimilar in Prevalence to and Phylogenetically Distant from the tdh Genes of Other Vibrios: Implications in the Horizontal Transfer of the tdh Gene

Vibrio hollisae strains isolated recently from patients in various locations were examined for the presence of the thermostable direct hemolysin gene (tdh) using nucleic acid hybridization and polymerase chain reaction assays. The results were consistent with the previous finding that all strains of V. hollisae carry the tdh gene. In contrast, the tdh gene has been detected in a minority of strains for other Vibrio species (V. parahaemolyticus, V. cholerae non-O1, and V. mimicus). Detailed phylogenetic analysis showed that the tdh genes of the non-V. hollisae species were very closely related to each other and that the tdh gene of V. hollisae was distantly related to the tdh genes of the non-V. hollisae species. These results and the proposed insertion sequence-mediated tdh transfer mechanism suggest that the tdh gene may have been maintained stably in V. hollisae and that the tdh genes of the non-V. hollisae species may have been involved in recent horizontal transfer.     

PCR detection of a newly emerged pandemic Vibrio parahaemolyticus O3:K6 pathogen in pure cultures and seeded waters from the Gulf of Mexico

This study describes the optimization of PCR parameters and testing of a wide number of microbial species to establish a highly specific and sensitive PCR-based method of detection of a newly emerged pandemic Vibrio parahaemolyticus O3:K6 strain in pure cultures and seeded waters from the Gulf of Mexico (gulf water). The selected open reading frame 8 (ORF8) DNA-specific oligonucleotide primers tested were found to specifically amplify all 35 pathogenic V. parahaemolyticus O3:K6 pandemic isolates, whereas these primers were not found to detectably amplify two strains of V. parahaemolyticus O3:K6 that were isolated prior to the 1996 outbreaks, 122 non-O3:K6 strains of V. parahaemolyticus, 198 non-V. parahaemolyticus spp., or 16 non-Vibrio bacterial spp. The minimum level of detection by the PCR method was 1 pg of purified genomic DNA or 10(2) ORF8-positive V. parahaemolyticus O3:K6 cells in 100 ml of water. The effectiveness of this method for the detection of ORF8-positive isolates in environmental samples was tested in gulf water seeded with 10-fold serial dilutions of this pathogen. A detection level of 10(3) cells per 100 ml of gulf water was achieved. Also, the applicability of this methodology was tested by the detection of this pathogen in gulf water incubated at various temperatures for 28 days. This PCR approach can potentially be used to monitor with high specificity and well within the required range of sensitivity the occurrence and distribution of this newly emerged pathogenic V. parahaemolyticus O3:K6 strain in coastal, marine, and ship ballast waters. Early detection of V. parahaemolyticus O3:K6 will help increase seafood safety and decrease the risk of infectious outbreaks caused by this pathogen.     

Characterization of new O3:K6 strains and phylogenetically related strains of Vibrio parahaemolyticus isolated in Taiwan and other countries

AIMS: We analysed the genetic divergence in the pandemic new O3:K6 and phylogenetically related (new O3:K6-like) strains and compare these two groups in terms of virulence and other biological traits. METHODS AND RESULTS: A total of 160 new O3:K6, new O3:K6-like and other strains of Vibrio parahaemolyticus isolated in Taiwan and other countries were collected and their clonal relationships analysed using SfiI-pulsed-field gel electrophoresis. All of the new O3:K6 and new O3:K6-like strains were grouped in cluster I with five new patterns identified. A O6:K18 strain was identified as a new member of the new O3:K6-like strains in addition to O4:K68, O1:KUT and O1:K25 strains. All of the lipopolysaccharide preparations of the selected strains exhibited closely spaced quadruplet banding patterns with similar mobility. The two groups of strains exhibited 100% sequence identity in the internal sequences of the toxR and laf genes, and also displayed similar virulence properties as determined with a suckling mouse model. CONCLUSIONS: The new O3:K6 and new O3:K6-like strains were highly similar in virulence and in several other phenotypical and genotypical traits. SIGNIFICANCE AND IMPACT OF THE STUDY: This work demonstrated the spread and divergence of the pandemic and related clone of V. parahaemolyticus with similar virulence.     

Isolation and characterization of a bacteriophage with an unusually large genome from the Great Salt Plains National Wildlife Refuge, Oklahoma, USA

In this study we present a bacteriophage isolated from the Great Salt Plains National Wildlife Refuge (GSP) that is shown to have a genome size of 340 kb, unusually large for a bacterial virus. Transmission electron microscopy analysis of the virion showed this to be a Myoviridae, the first reported to infect the genus Halomonas. This temperate phage, PhigspC, exhibits a broad host range, displaying the ability to infect two different Halomonas spp. also isolated from the GSP. The phage infection process demonstrates a high level of tolerance towards temperature, pH and salinity; however, free virions are rapidly inactivated in water unless supplemented with salt. We show that susceptibility to osmotic shock is correlated with the density of the packaged DNA (rho(pack)). Lysogens of Halomonas salina GSP21 were detrimental to host fitness at 10% salinity, but the lysogen was able to grow faster than the wild type at 20% salinity. From these results we propose that the extensive genome of PhigspC may encode environmentally relevant genes (ERGs); genes that are perhaps not essential for the phage life cycle but increase host and phage fitness in some environmental conditions.     

Molecular structure of fd (f1, M13) filamentous bacteriophage refined with respect to X-ray fibre diffraction and solid-state NMR data supports specific models of phage assembly at the bacterial membrane

Filamentous bacteriophage (Inovirus) is a simple and well-characterized model system. The phage particle, or virion, is about 60 angstroms in diameter and several thousand angstrom units long. The virions are assembled at the bacterial membrane as they extrude out of the host without killing it, an example of specific transport of nucleoprotein assemblages across membranes. The Ff group (fd, f1 and M13) has been especially widely studied. Models of virion assembly have been proposed based on a molecular model of the fd virion derived by X-ray fibre diffraction. A somewhat different model of the fd virion using solid-state NMR data has been proposed, not consistent with these models of assembly nor with the X-ray diffraction data. Here we show that reinterpreted NMR data are also consistent with the model derived from X-ray fibre diffraction studies, and discuss models of virion assembly.