Acid tolerance responses and their mechanisms in LM1001.

Unlabelled: This study investigated the acid tolerance responses of LM1001 at physiological and molecular levels. Upon exposure to low pH, LM1001 demonstrated increased ATPase activity and ammonia consumption, which contributed to a higher intracellular pH. Comparative analysis of cell membrane fatty acids revealed that acid-stressed cells had a significantly higher proportion of unsaturated fatty acids than those of unstressed cells. There was differential upregulation of several genes, notably those involved in alkali production ( and ) and in class I and class III stress responses ( and ). Following 2-h exposure to pH 2.5, LM1001 not only exhibited enhanced survival but also showed increased auto-aggregation and improved mucin adhesion capability, albeit with a reduction in hydrophobicity. These findings indicate that acid stress induces adaptive physiological and metabolic changes in LM1001, enhancing its acid resistance and adherence properties.

Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-024-01582-4.