Acid resistance of E. coli O157:H7 and O26:H11 exposure to lactic acid revealed by transcriptomic analysis

Abstract Shiga toxin-producing Escherichia coli (STEC) strains are classified as important foodborne pathogens and their acid resistance (AR) capability is identified as one of key factors compromising food safety. In this study, we confirmed experimentally that the growth of two STEC strains (O157:H7 and O26:H11) was remarkably inhibited in Luria-Bertani medium (final pH 3.5) supplemented with lactic acid. Transcriptomic analysis indicated that several AR mechanisms employed by these two strains were also reported previously, and represented similar tendency in transcriptomic profiles variation in response to the acid treatment. However, strain O157 showed much more times up-regulation of genes involved in quorum sensing (QS) and biofilm formation as compared to strain O26, indicting the stronger acid resistance capability of the former strain. Most importantly, we first reported that enhanced cysteine biosynthesis might play an essential role in acid resistance of these two strains when treated for longer time, which was not presented in previous studies with short time acid treatment. Our results shed substantial light on following studies deciphering AR mechanisms of microbes with time course, and this will provide profound insights for better control of microbial induced food contamination.