Cronobacter sakazakii CICC 21544 responds to the combination of carvacrol and citral by regulating proton motive force

Response mechanism of Cronobacter sakazakii under stress of combination of citral and carvacrol was investigated by transcriptome sequencing. Twenty-five significantly differentially expressed genes were identified to be closely related to the ability of C. sakazakii tolerating the stress after analysis, mainly involving glycerol metabolism; citrate metabolism; formate metabolism; ribosome function and transmembrane transport system. Combination of carvacrol and citral could cause dissipation of proton motive force (PMF) and the psp regulon is an important switch in the response of C. sakazakii to this condition. To maintain PMF, psp regulated cellular processes to reduce the consumption of cellular energy for cell membrane repair and proton consumption. In T1 group (low concentration group), C. sakazakii remained aerobic metabolism and expression of glycerol metabolism related genes were upregulated for cell membrane repair and proton consumption. In T2 group (high concentration group), bacteria convert from aerobic metabolism to anaerobic metabolism to reduce energy consumption and expression of genes in formate metabolism were upregulated to consume excessive intracellular protons; citrate lyase-related genes were upregulated to decompose citrate, the intermediate of the tricarboxylic acid cycle, to generate acetyl CoA for production of cell membrane phospholipids.