Acid-responsive activity of the Helicobacter pylori metalloregulator NikR

Significance The acid adaptation systems of the pathogen Helicobacter pylori are complex and critical to the survival of this bacterium in the harsh environment of the human stomach. One of the relatively few transcription factors in H. pylori is HpNikR, a metal-responsive protein that controls homeostasis of nickel, an essential nutrient for this organism. In this study, we show that HpNikR also regulates gene expression in direct response to acidic pH. Exposure of H. pylori to acid shock conditions depresses its cytosolic pH, which activates the regulation of multiple promoters by HpNikR. These results demonstrate that HpNikR has a multifaceted response that links nickel homeostasis and acid acclimation, two critical functions in this infectious organism.