Effects of Na+ adaptation on Bacillus cereus endospore inactivation and transcriptome changes

As Bacillus cereus endospores exist in various vegetables grown in soil, the possibility of contamination in high-salt products cannot be ignored. Recent studies revealed that harsh conditions affect the resistance of bacteria; thus, we investigated the developmental aspect of heat resistance of B. cereus after sporulation with high NaCl concentration. Our data showed that increasing NaCl concentration in sporulation media led to a decrease in heat resistance. Also, cell hydrophobicity, membrane fluidity, and cell density decreased with sporulation at higher NaCl concentrations. When the transcript changes of B. cereus sporulated at NaCl concentrations of 0.5 and 7% were analyzed by transcriptome analysis, it was confirmed that the NaCl 7% endospore cell had significantly lower expression levels (FDR < 0.05) of genes related to sporulation stages 3 and 4, which led to a decrease in expression of spore-related genes such as coat proteins and small acid-soluble proteins. It is concluded that high NaCl concentration blocks sporulation stages 3 and 4 to prevent cell maturation in the forespore and adequate formation of the coat protein and cortex, lowering cell density and hydrophobicity and resulting in the loss of heat resistance. We expect that this study will be utilized as a baseline for further studies and enhanced sterilization strategies