Author for correspondence: J. M. Ketley. Tel: +44 116 252 3434. Fax: +44 116 252 3378. e-mail: ket@leicester.ac.uk
aPresent ddress: Lbortorio de Fisiologi Celulr, Instituto de Biofisic Crlos Chgs Filho, Universidde Federl do Rio de Jneiro, 21949-900, Rio de Jneiro, Brzil.
b Present address: Deparment of Veterinary Pathology, Glasgow University, Bearsden, Glasgow G61 1QH, UK.
To survive and multiply in different environments, Vibrio cholerae has to co-ordinately regulate the expression of genes involved in adaptive responses. In many pathogens, adaptive responses, including pathogenic responses, are regulated by two-component regulator (TCR) systems. It is likely that members of a TCR family play a role in the regulation of processes involved in intestinal colonization, and therefore pathogenesis, in V. cholerae. We have identified and characterized a TCR system of V. cholerae: this system is a homologue of Escherichia coli PhoBR. The presence of a putative Pho box suggests that the V. cholerae phoBR operon is regulated by inorganic phosphate levels. The phoR and phoB genes are organized the same way as in E. coli. Mutation of the V. cholerae phoB gene affected the expression of the putative Pho regulon, including PhoA, but did not affect the production of cholera toxin. V. cholerae phoB mutants are less able to colonize rabbit intestine than wild-type V. cholerae. The addition of inorganic phosphate at a high concentration to the inoculum only partially restored the ability of the mutants to colonize the intestine, suggesting that the V. cholerae Pho regulon in vivo may not be regulated by inorganic phosphate levels alone.
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A role for the PhoBR regulatory system homologue in the Vibrio cholerae phosphate-limitation response and intestinal colonizationThe GenBank accession number for the sequence reported in this paper is AF043352.