Influence of temperature on acid-stress adaptation in Listeria monocytogenes

Our findings show that temperature plays a significant role in the induction of acid-stress adaptation in Listeria monocytogenes, and two distinct patterns were observed: (1) Presence of sublethal acid at 37°C or 22°C significantly induced acid-stress adaptation; and (2) Presence of sublethal acid at 4°C did not induce any acid-stress adaptation. Both patterns were confirmed by two experimental models: (1) L. monocytogenes cells were first grown at 37°C and then exposed to sublethal acid at 37°C, 22°C, and 4°C prior to lethal acid challenge; (2) Alternatively, L. monocytogenes cells were first grown at 4°C for 20 days before pre-exposure to sublethal acid and then challenged with lethal acid. Regardless of whether L. monocytogenes cells were simultaneously exposed with both cold stress and sublethal acid stress, or subjected to cold growth first before exposure to sublethal acid, no acid-stress adaptation was induced at 4°C. We also found that acid-stress adaptation in L. monocytogenes did not occur in acidic whey at 4°C. Bead beating treatment prior to mild acid pre-exposure at 4°C partially induced acid adaptation in L. monocytogenes. Our findings suggest that cold temperature can prevent the risk of acid-stress adaptation in L. monocytogenes.