The Mechanism of Bidirectional pH Taxis in Bacillus subtilis

Abstract

Many bacteria can sense the pH in their environment and then use this information to direct their movement toward more favorable locations. In this study, we investigated the pH sensing mechanism in Bacillus subtilis . This bacterium preferentially migrates to neutral environments. It employs four chemoreceptors to sense pH. Two are involved in sensing acidic environments, and two are involved in sensing alkaline ones. To identify the mechanism for pH sensing, we constructed receptor chimeras of acid- and base-sensing chemoreceptors. By analyzing the responses of these chimeric receptors, we were able to identify four critical amino acid residues involved in pH sensing and propose a model for the pH sensing mechanism in B. subtilis .