Characterization of an aspartate-dependent acid survival system in Yersinia pseudotuberculosis

Enteric bacteria have developed various survival systems that protect against acid stress. In this study, an aspartate-dependent acid survival system is characterized in Yersinia pseudotuberculosis. The expression of aspartase (AspA) was confirmed to be increased at acidic pH by proteomic and lacZ fusion analyses. Addition of aspartate increased acid survival of the wild type but not the aspA knockout mutant. AspA increases acid survival by producing ammonia as demonstrated by mutation and in vitro enzyme activity analyses. This is the first demonstration that an enzyme involved in aspartate metabolism plays a role in acid survival in an enteric bacterium.