Characterization of the yehUT two-component regulatory system of Salmonella enterica Serovar Typhi and Typhimurium.

Proteins exhibiting hyper-variable sequences within a bacterial pathogen may be associated with host adaptation. Several lineages of the monophyletic pathogen Salmonella enterica serovar Typhi (S. Typhi) have accumulated non-synonymous mutations in the putative two-component regulatory system yehUT. Consequently we evaluated the function of yehUT in S. Typhi BRD948 and S. Typhimurium ST4/74. Transcriptome analysis identified the cstA gene, encoding a carbon starvation protein as the predominantly yehUT regulated gene in both these serovars. Deletion of yehUT had no detectable effect on the ability of these mutant Salmonella to invade cultured epithelial cells (S. Typhi and S. Typhimurium) or induce colitis in a murine model (S. Typhimurium only). Growth, metabolic and antimicrobial susceptibility tests identified no obvious influences of yehUT on these phenotypes.