A functional homolog of Escherichia coli NhaR in Vibrio cholerae

Escherichia coli NhaR controls expression of a sodium/proton (Na+/H+) antiporter, NhaA. The Vibrio cholerac NhaR protein shows over 60% identity to those of Escherichia coli and Salmonella enteritidis. V. cholerae NhaR complements an E. coli nhaR mutant for growth in 100 nM LiCl-33 mM NaCl pH 7.6, and enhances the Na+-dependent induction of an E. coli chromosomal nhaA::lacZ fusion, These findings indicate functional homology to E, coli NhaR. Two V. cholerae nhaR mutants were constructed by using kanamycin resistance cartridge insertion at different sites to disrupt the gene, Both mutants showed sensitivity to growth in 120 mM LiCl, pH 9.2, compared with the wild-type strain and could be complemented bg the introduction of V, cholerae nhaR on a low-copy-number plasmid, An nhaR mutation had no detectable effect on the virulence of the ir, cholerae strain in the infant mouse model, suggesting that the antiporter system involved Is not required in vivo, at least in this animal model.