Adenine DNA methylation is involved in regulating ethanol and osmotic stress responses in <i>Lacticaseibacillus paracasei</i> Zhang

Abstract

Abstract As an important feature of epigenetics, DNA methylation is a critical way to regulate gene expression and thus bacterial growth and metabolism. Lacticaseibacillus paracasei Zhang is a probiotic strain originated from koumiss. This study hypothesized that adenine methylation was involved in bacterial regulation of physiological adaptations when grown under environmental stress. Thus, this study compared the growth of an adenine methyltransferase‐inactivated mutant (Δ pglX ) and the wild‐type L. paracasei Zhang when cultured under ethanol and osmotic stress. Transcriptomic and proteomic analyses were implemented to identify their differentially expressed genes/proteins (DEGs/DEPs) when grown under the stressed environments. The membrane fatty acid composition was also determined. Comparing with the wild‐type, the viable counts of the mutant under ethanol and osmotic stress increased by 2.6 times and decreased by half, respectively (ethanol stress: mutant, 4.30 ± 0.0038 × 10 8 CFU/mL; wild‐type, 1.64 ± 0.010 × 10 8 CFU/mL; osmotic stress: mutant, 2.21 ± 0.029 × 10 8 CFU/mL; wild‐type, 4.30 ± 0.13 × 10 8 CFU/mL). Common to both conditions, many identified DEGs and DEPs were involved in carbohydrate metabolism and fatty acid biosynthesis, generally, with more carbohydrate metabolism pathways but fewer fatty acid biosynthesis pathways, accompanied by increases in the membrane fatty acids. Our observations suggested that L. paracasei Zhang maximizes its energy metabolism by enhancing carbohydrate metabolism and improves its membrane strength via increasing the fatty acid content under environmental stress. This is the first report analyzing the epigenetic‐level stress responsive mechanism of L. paracasei Zhang, providing insights into methylation‐based regulation of bacterial adaptive responses.