Comparative transcriptomic analysis of Staphylococcus aureus reveals the genes involved in survival at low temperature. Staphylococcus aureus

In food processing, the temperature is usually reduced to limit bacterial reproduction and maintain food safety. However, Staphylococcus aureus can adapt to low temperature by controlling gene expression and protein activity, although its survival strategies normally vary between dif-ferent strains. The present study investigated the molecular mechanisms of S. aureus with dif-ferent survival strategies in response to low temperature. The survival curve showed that strain BA-26 was inactivated by 6.0 logCFU/mL after 4 weeks of low-temperature treatment, while strain BB-11 only decreased by 1.8 logCFU/mL. Intracellular nucleic acid leakage, transmission electron microscopy and confocal laser scanning microscopy analyses revealed that better cell membrane integrity of strain BB-11 than that of strain BA-26 after low temperature treatment. Regarding oxidative stress, the superoxide dismutase activity and the reduced glutathione con-tent in BB-11 were higher than those in BA-26; thus, BB-11 contained less malondialdehyde than BA-26. RNA-seq showed significantly upregulated expression of the fatty acid biosynthesis in membrane gene (fabG) in BB-11 compared with BA-26 because of the damaged cell membrane. Then, catalase (katA), reduced glutathione (grxC), and peroxidase (ahpC) were found to be sig-nificantly upregulated in BB-11, leading to an increase in the oxidative stress response, but BA-26-related genes were downregulated. NADH dehydrogenase (nadE) and a-glucosidase (malA) were upregulated in cold-tolerant strain BB-11 but were downregulated in cold-sensitive strain BA-26, suggesting that energy metabolism might play a role in S. aureus under low temperature stress. Furthermore, defense mechanisms, such as those involving asp23, greA and yafY, played a pivotal role in the response of BB-11 to stress. The study provided a new perspective for under-standing the survival mechanism of S. aureus at low temperature.