Expression of the htrB gene is essential for responsiveness of Salmonella typhimurium and Campylobacter jejuni to harsh environments

In Campylobacter jejuni, an htrB homologous gene is located in the lipo-oligosaccharide synthesis gene cluster. This study examined the effects of htrB expression on the responsiveness of Salmonella typhimurium and C. jejuni to harsh environments. Complementation experiments showed that the C. jejuni htrB gene could restore the normal morphology of the Salmonella htrB mutant, and its ability to grow without inhibition under heat, acid and osmotic stresses, but not bile stress. This indicated that the htrB genes in C. jejuni and S. typhimurium exhibit similar pleiotropic effects. Moreover, quantitative real-time RT-PCR showed that expression of the C. jejuni htrB gene was upregulated under acid, heat, oxidative and osmotic stresses, but did not change under bile stress. This indicated that the C. jejuni htrB gene plays a role in regulating cell responses to various environmental changes. Furthermore, deletion mutation of the htrB gene in C. jejuni was lethal, indicating that the htrB gene is essential for C. jejuni survival. Therefore, these results showed that expression of the htrB gene is essential for the response of S. typhimurium and C. jejuni to environmental stresses.