NUCLEOTIDE-SEQUENCE AND SPATIOTEMPORAL EXPRESSION OF THE VIBRIO-CHOLERAE VIESAB GENES DURING INFECTION

The iviVII gene of Vibrio cholerae was previously identified by a scre en for genes induced during intestinal infection. In the present study , nucleotide sequence analysis revealed that iviVII is a 1,659-bp open reading frame, herein designated vies, that is predicted to be last i n a tricistronic operon (vieSAB). The deduced amino acid sequence of V ieS exhibited similarity to the sensor kinase component, and those of VieA and VieB were similar to the response regulator components, respe ctively, of the two-component signal transduction family. Analysis of transcriptional fusions to a site-specific DNA recombinase reporter, t npR, revealed that vieS and vieA are transcribed during in vitro growt h in a vieAB-independent and vieA-dependent manner, respectively. In c ontrast, transcription of vieB occurred exclusively during infection a nd was not dependent upon VieB. We conclude that the vieSAB genes are differentially regulated, at least during laboratory growth. Use of a V. cholerae strain harboring a vieB::tnpR transcriptional fusion allow ed the kinetics and location of vieB expression within the intestine t o be determined, We found that vies transcription is induced shortly a fter infection of the proximal and mid-small intestine.