Role of proP and proU in betaine uptake by Yersinia enterocolitica under cold and osmotic stress conditions.

Yersinia enterocolitica is a food-borne pathogen with the ability to grow at cold temperatures and tolerate high osmolarity. The bacterium tolerates osmotic stress by intracellular accumulation of osmolytes, such as betaine. The proP gene and proU operon of Y. enterocolitica were sequenced, and single (ProP(-) ProU(+) and ProP(+) ProU(-)) and double (ProP(-) ProU(-)) mutants were generated. Upon exposure to osmotic or chill stress, the single and double mutants demonstrated a reduction in betaine uptake compared to that in the wild type, suggesting that proP and proU play a role in betaine uptake during osmotic and chill stress responses of Y. enterocolitica.