Journal
INFECTION AND IMMUNITY
Volume 78, Issue 6, Pages 2554-2570Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/IAI.01073-09
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Funding
- NIH/NIAID [AI073785]
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Strain AM-19226 is a pathogenic non-O1/non-O139 serogroup Vibrio cholerae strain that does not encode the toxin-coregulated pilus or cholera toxin but instead causes disease using a type three secretion system (T3SS). Two genes within the T3SS pathogenicity island, herein named vttR(A) (locus tag A33_1664) and vttR(B) (locus tag A33_1675), are predicted to encode proteins that show similarity to the transcriptional regulator ToxR, which is found in all strains of V. cholerae. Strains with a deletion of vttR(A) or vttR(B) showed attenuated colonization in vivo, indicating that the T3SS-encoded regulatory proteins play a role in virulence. lacZ transcriptional reporter fusions to intergenic regions upstream of genes encoding the T3SS structural components identified growth in the presence of bile as a condition that modulates gene expression. Under this condition, VttR(A) and VttR(B) were necessary for maximal gene expression. In contrast, growth in bile did not substantially alter the expression of a reporter fusion to the vopF gene, which encodes an effector protein. Increased vttR(B) reporter fusion activity was observed in a Delta vttR(B) strain background, suggesting that VttR(B) may regulate its own expression. The collective results are consistent with the hypothesis that T3SS-encoded regulatory proteins are essential for pathogenesis and control the expression of selected T3SS genes.
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