Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence, and Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea.
Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence, and Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea; Institutes of Green Bio Science & Technology, Seoul National University, Pyeongchang-gun, Gangwon-do 25354, Republic of Korea.
Food Res Int. 2024 Nov;195:114975. doi: 10.1016/j.foodres.2024.114975. Epub 2024 Aug 22.
As Bacillus cereus endospores exist in various vegetables grown in soil, the possibility of contamination in food products with high salt concentrations 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. RNA sequencing was conducted for transcriptomic changes when B. cereus endospores formed at high salinity, and membrane fluidity and hydrophobicity were measured to verify the transcriptomic analysis. Our data showed that increasing NaCl concentration in sporulation media led to a decrease in heat resistance. Also, endospore hydrophobicity, membrane fluidity, and endospore 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% endospores 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. Our findings indicated that high NaCl concentrations inhibited sporulation stages 3 and 4, thereby preventing proper cell maturation in the forespores and adequate formation of the coat protein and cortex. This inhibition led to decreased endospore density and hydrophobicity, ultimately resulting in reduced heat resistance.resistanceWe expect that this study will be utilized as a baseline for further studies and enhance sterilization strategies.
由于蜡样芽胞杆菌内生孢子存在于土壤中生长的各种蔬菜中，因此不能忽视高盐浓度食品产品受到污染的可能性。最近的研究表明，恶劣的条件会影响细菌的抵抗力；因此，我们研究了高盐浓度下形成的蜡样芽胞杆菌耐热性的发育方面。当蜡样芽胞杆菌在高盐度下形成内生孢子时进行了转录组变化的 RNA 测序，并测量了膜流动性和疏水性以验证转录组分析。我们的数据表明，在孢子形成培养基中增加 NaCl 浓度会导致耐热性降低。此外，随着较高 NaCl 浓度下的孢子形成，内生孢子疏水性、膜流动性和内生孢子密度降低。当通过转录组分析分析在 NaCl 浓度为 0.5%和 7%的条件下形成的蜡样芽胞杆菌的转录变化时，证实 NaCl 7%内生孢子中与孢子形成阶段 3 和 4 相关的基因的表达水平（FDR<0.05）显着降低，导致与孢子相关的基因如衣壳蛋白和小酸溶性蛋白的表达降低。我们的研究结果表明，高 NaCl 浓度抑制了孢子形成阶段 3 和 4，从而阻止了前孢子的适当细胞成熟和衣壳蛋白和皮质的充分形成。这种抑制导致内生孢子密度和疏水性降低，最终导致耐热性降低。我们希望本研究将作为进一步研究和增强灭菌策略的基础。
