Lysogenic Conversion by a Filamentous Phage Encoding Cholera Toxin

Waldor, Matthew K.; Mekalanos, John J.

doi:10.1126/science.272.5270.1910

Cited by 1,646 publications

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“…The structural genes for the ctx element reside on a filamentous phage ctxФ (Waldor and Mekalanos 1996). CTXФ is found in all epidemic V. cholerae isolates but is rarely recovered from the non-O1/non-O139 V. cholerae environmental isolates.…”

Section: Resultsmentioning

confidence: 99%

Detection of ctx gene positive non-O1/non-O139 V. cholerae in shrimp aquaculture environments

Madhusudana

Surendran

2011

J Food Sci Technol

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Water and post-larvae samples from black tiger (Penaeus monodon) shrimp hatcheries; pond water, pond sediment and shrimp from aquaculture farms were screened for the presence of V. cholerae. A V. cholerae-duplex PCR method was developed by utilizing V. cholerae species specific sodB primers and ctxAB genes specific primers. Incidence of V. cholerae was not observed in shrimp hatchery samples but was noticed in aquaculture samples. The incidence of V. cholerae was higher in pond water (7.6%) than in pond sediment (5.2%). Shrimp head (3.6%) portion had relatively higher incidence than shrimp muscle (1.6%). All the V. cholerae isolates (n=42) belonged to non-O1/non-O139 serogroup, of which 7% of the V. cholerae isolates were potentially cholera-toxigenic (ctx positive). All the ctx positive V. cholerae (n=3) were isolated from the pond water. Since, cholera toxin (CT) is the major contributing factor for cholera gravis, it is proposed that the mere presence of non-O1/non-O139 V. cholerae need not be the biohazard criterion in cultured black tiger shrimp but only the presence of ctx carrying non-O1/non-O139 V. cholerae may be considered as potential public health risk.

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Section: Resultsmentioning

confidence: 99%

Detection of ctx gene positive non-O1/non-O139 V. cholerae in shrimp aquaculture environments

Madhusudana

Surendran

2011

J Food Sci Technol

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“…These strains carry a pathogenicity island of 45 kb, which comprises the tcpacf gene cluster, the toxT gene involved in the regulation of the cholera toxin (ctx), and also an integrase gene (Kovach eta/., 1996). Interestingly, the CTX phage uses the Pai-encoded Tcp adhesin as its receptor, providing evidence for co-evolution of the V. cholerae-specific Pai and the phage-associated ctxA5 genes (Waldor and Mekalanos, 1996).…”

Section: Pathogenicity Islands Of Other Gram-negative Bacteriamentioning

confidence: 99%

“…While the ST-enterotoxin genes of Escherichia coli are part of a transposon, genes encoding other toxins, such as Shiga-like toxins of E. coli, cholera toxin of Vibrio cholerae, diphtheria toxin of Corynebacterium diphtheriae, neurotoxins of Clostridium botulinum and cytotoxin of Pseudomonas aeruginosa, are phage encoded (Salyers and Whitt, 1994;Waldor and Mekalanos, 1996). Important virulence factors of Gramnegative pathogens (e.9.…”

Section: Introductionmentioning

confidence: 99%

Pathogenicity islands of virulent bacteria: structure, function and impact on microbial evolution

Hacker¹,

Blum-Oehler²,

Mühldorfer³

et al. 1997

Molecular Microbiology

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738

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Summary Virulence genes of pathogenic bacteria, which code for toxins, adhesins, invasins or other virulence factors, may be located on transmissible genetic elements such as transposons, plasmids or bacteriophages. In addition, such genes may be part of particular regions on the bacterial chromosome, termed‘pathogenicity islands’(Pais). Pathogenicity islands are found in Gram‐negative as well as in Gram‐positive bacteria. They are present in the genome of pathogenic strains of a given species but absent or only rarely present in those of non‐pathogenic variants of the same or related species. They comprise large DNA regions (up to 200 kb of DNA) and often carry more than one virulence gene, the G+C contents of which often differ from those of the remaining bacterial genome. In most cases, Pais are flanked by specific DNA sequences, such as direct repeats or insertion sequence (IS) elements. In addition, Pais of certain bacteria (e.g. uropathogenic Escherichia coli, Yersinia spp., Helicobacter pylori) have the tendency to delete with high frequencies or may undergo duplications and amplifications. Pais are often associated with tRNA loci, which may represent target sites for the chromosomal integration of these elements. Bacteriophage attachment sites and cryptic genes on Pais, which are homologous to phage integrase genes, plasmid origins of replication or IS elements, indicate that these particular genetic elements were previously able to spread among bacterial populations by horizontal gene transfer, a process known to contribute to microbial evolution.

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“…For example, in Vibrio cholerae the cholera toxin, a key virulence determinant, is encoded in the genome of the temperate phage ΦCTX 103 . As another example, Staphylococcus aureus pathogenicity islands (SaPIs) excise from the chromosome and replicate following induction by an infecting phage, and the SaPI DNA is packaged in modified phage particles and transferred to other S. aureus cells 104,105 and even to species from other genera 106 .…”

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Gene transfer agents: phage-like elements of genetic exchange

2012

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Horizontal gene transfer is important in the evolution of bacterial and archaeal genomes. An interesting genetic exchange process is carried out by diverse phage-like gene transfer agents (GTAs) that are found in a wide range of prokaryotes. Although GTAs resemble phages, they lack the hallmark capabilities that define typical phages, and they package random pieces of the producing cell's genome. In this Review, we discuss the defining characteristics of the GTAs that have been identified to date, along with potential functions for these agents and the possible evolutionary forces that act on the genes involved in their production.The prevalence of horizontal gene transfer (HGT), in which DNA is exchanged between closely or distantly related lineages, has altered the way we think about evolution 1,2 , having profound effects on our views of the evolutionary relationships among living organisms. It has caused a shift from a bifurcating 'tree of life' view to a 'net of life' or 'web of life' view [3][4][5] , in which "highways of gene sharing" (REF. 6) represent major connections, with genes (or DNA segments) viewed as "public goods, available for all organisms to integrate into their genomes" (REF. 7). HGT occurs within and between all three domains of life, and it has been estimated that 0.05-80% of genes in bacterial and archaeal genomes have been affected by HGT, depending on the analytical method used and the genome analysed [8][9][10] . Although HGT is widespread, it is not random: patterns of preferential gene exchange among specific groups of organisms that share ancestry or habitat have been * Present address. aslang@mun.ca; olgazh@dartmouth.edu; j.beatty@mail.ubc.ca Competing interests statementThe authors declare no competing financial interests. 6,9,11,12 . Such patterns are probably a consequence of existing barriers to HGT, which have been reviewed in detail elsewhere 13,14 . FURTHER INFORMATIONAlthough we have known about some HGT mechanisms for decades, novel processes that expand the existing repertoire of gene exchange methods are continually being identified. Transformation was the first mechanism of gene exchange to be discovered 15 , wherein DNA is taken up directly from the environment (reviewed elsewhere 16,17 ). In transduction, DNA transfer is mediated by viral particles (BOX 1). In conjugation, which was discovered in the 1940s 18 , DNA is transferred from a donor to a recipient cell during cell-to-cell contact; conjugation is used in the transfer of plasmids, transposons, integrons, and integrative and conjugative elements (ICEs) [19][20][21] . There are other modes of gene exchange that do not fit well into any of these three canonical mechanisms, including temporary cell fusion followed by chromosomal recombination and plasmid exchange 22 , intercellular connection through nanotubes 23 , and the release of membrane vesicles containing chromosomal, plasmid and phage DNA that can then merge with nearby cells 24 . In addition, a novel mechanism of gene transfer that has feature...

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Lysogenic Conversion by a Filamentous Phage Encoding Cholera Toxin

Cited by 1,646 publications

References 32 publications

Detection of ctx gene positive non-O1/non-O139 V. cholerae in shrimp aquaculture environments

Detection of ctx gene positive non-O1/non-O139 V. cholerae in shrimp aquaculture environments

Pathogenicity islands of virulent bacteria: structure, function and impact on microbial evolution

Gene transfer agents: phage-like elements of genetic exchange

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