24 research outputs found
Molecular cloning and transcriptional regulation of ompT , a ToxR-repressed gene in Vibrio cholerae
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72189/1/j.1365-2958.2000.01699.x.pd
Vibrio cholerae non-O1, non-O139 strains isolated before 1992 from Varanasi, India are multiple drug resistant, contain intSXT, dfr18 and aadA5 genes
Molecular analysis of the rstR and orfU genes of the CTX prophages integrated in the small chromosomes of environmental Vibrio cholerae non-O1, non-O139 strains genes of the CTX prophages integrated in the small chromosomes of environmental Vibrio cholerae non-O1, non-O139 strains
The
ctxAB
genes encoding cholera toxin, reside in the
genome of a filamentous bacteriophage CTX φ .The
presence of CTX prophage in non-epidemic environmental
Vibrio cholerae strains is rare. The CTX prophage,
the lysogenic form of CTX φ in V. cholerae , is
comprised of the ‘RS2’ and the ‘Core’. Analysis of the
rstR gene present in the RS2 region of the CTX prophage
revealed the presence of new alleles of the prophages
in four environmental non-O1, non-O139 strains
VCE22 (O36), VCE228 (O27), VCE232 (O4) and VCE233
(O27), and the CTX prophages are located in the small
chromosomes. Phylogenetic analysis based on the
nucleotide sequences of the rstR and orfU (present in
the core) genes of these prophages placed them in a
single unique cluster, which is distally located compared
with that of epidemic V. cholerae O1 strains.
Further analysis indicated that the genome of the
prophage present in the strain VCE22 is devoid of the
ctxAB genes, called pre-CTX prophage and the strain
also possess the toxin-coregulated pilus protein
coding gene tcpA of classical type, another important
pathogenicity determining locus of the epidemic
V. cholerae strains. Comparative analysis of the
nucleotide sequences of the rstR and orfU genes indicated
that the pre-CTX prophage of VCE22 might b
Critical role for a promoter discriminator in RpoS control of virulence in Edwardsiella piscicida
Edwardsiella piscicida is a leading fish pathogen that causes significant economic loses in the aquaculture industry. The pathogen depends on type III and type VI secretion systems (T3/T6SS) for growth and virulence in fish and the expression of both systems is controlled by the EsrB transcription activator. Here, we performed a Tn-seq-based screen to uncover factors that govern esrB expression. Unexpectedly, we discovered that RpoS antagonizes esrB expression and thereby inhibits production of E. piscicida's T3/T6SS. Using in vitro transcription assays, we showed that RpoS can block RpoD-mediated transcription of esrB. ChIP-seq- and RNA-seq-based profiling, as well as mutational and biochemical analyses revealed that RpoS-repressed promoters contain a -6G in their respective discriminator sequences; moreover, this -6G proved critical for RpoS to inhibit esrB expression. Mutation of the RpoS R99 residue, an amino acid that molecular modeling predicts interacts with -6G in the esrB discriminator, abolished RpoS' capacity for repression. In a turbot model, an rpoS deletion mutant was attenuated early but not late in infection, whereas a mutant expressing RpoSR99A exhibited elevated fitness throughout the infection period. Collectively, these findings deepen our understanding of how RpoS can inhibit gene expression and demonstrate the temporal variation in the requirement for this sigma factor during infection
Critical role for a promoter discriminator in RpoS control of virulence in Edwardsiella piscicida.
Edwardsiella piscicida is a leading fish pathogen that causes significant economic loses in the aquaculture industry. The pathogen depends on type III and type VI secretion systems (T3/T6SS) for growth and virulence in fish and the expression of both systems is controlled by the EsrB transcription activator. Here, we performed a Tn-seq-based screen to uncover factors that govern esrB expression. Unexpectedly, we discovered that RpoS antagonizes esrB expression and thereby inhibits production of E. piscicida's T3/T6SS. Using in vitro transcription assays, we showed that RpoS can block RpoD-mediated transcription of esrB. ChIP-seq- and RNA-seq-based profiling, as well as mutational and biochemical analyses revealed that RpoS-repressed promoters contain a -6G in their respective discriminator sequences; moreover, this -6G proved critical for RpoS to inhibit esrB expression. Mutation of the RpoS R99 residue, an amino acid that molecular modeling predicts interacts with -6G in the esrB discriminator, abolished RpoS' capacity for repression. In a turbot model, an rpoS deletion mutant was attenuated early but not late in infection, whereas a mutant expressing RpoSR99A exhibited elevated fitness throughout the infection period. Collectively, these findings deepen our understanding of how RpoS can inhibit gene expression and demonstrate the temporal variation in the requirement for this sigma factor during infection
Investigation of seven Vibrio virulence genes among Vibrio alginolyticus and Vibrio parahaemolyticus strains from the coastal mariculture systems in Guangdong, China
The ability of two different Vibrio spp. bacteriophages to infect Vibrio harveyi, Vibrio cholerae and Vibrio mimicus
Aims: To determine the host range of the Vibrio harveyi myovirus-like bacteriophage (VHML) and the cholera toxin conversion bacteriophage (CTX Φ) within a range of Vibrio cholerae and V. mimicus and V. harveyi, V. cholerae and V. mimicus isolates respectively.\ud
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Methods and Results: Three V. harveyi, eight V. cholerae and five V. mimicus isolates were incubated with VHML and CTX Φ. Polymerase chain reaction (PCR) was used to determine the presence of VHML and CTX Φ 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 Φ were unsuccessful.\ud
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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 Φ) in the isolates used in this study may explain why infections with CTX Φ were unsuccessful.\ud
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Significance and Impact of the Study: The current study has demonstrated that Vibrio spp. bacteriophages may infect other Vibrio spp.\u