Influence of differential phosphatidylcholine levels on growth and stress response in <i>Acetobacter pasteurianus</i>

Acetic acid bacteria (AAB) produce phosphatidylcholine (PC) as a major membrane component. PC has long been considered important for acetic acid tolerance in AAB, yet direct experimental support remains limited, and its physiological roles under diverse environmental stresses are not well defined. In this study, we constructed PC-deficient mutants of Acetobacter pasteurianus by deleting the phosphatidylethanolamine N-methyltransferase gene. PC deficiency resulted in phosphatidylglycerol accumulation and a tendency toward acyl-chain shortening. Phenotypic analysis showed that PC deficiency impaired growth under ionic, heat, and acidic stresses, indicating that PC supports membrane integrity under these stress conditions. Heterologous expression of PC synthase from Pseudomonas aeruginosa enabled choline-dependent regulation of PC biosynthesis. This system revealed that even low PC levels are sufficient to restore normal growth and acetic acid fermentation. These findings suggest that PC has diverse physiological roles in AAB and its function does not necessarily depend on its abundance in the membrane.