大肠杆菌O157:H7压力反应基因对EGCG和柠檬酸的转录响应

Transcriptional response of E.coli O157:H7 stress related gene to EGCG and citric acid

采用反转录荧光定量PCR技术,检测天然防腐剂表没食子儿茶素没食子酸酯(EGCG)及柠檬酸处理后,大肠杆菌O157∶H7几种压力反应相关基因的转录响应。结果发现,1 mg/mL EGCG处理后,recA转录水平下调,rpoS无明显变化,而oxyR转录水平明显上调;4 mg/mL柠檬酸处理后,recA转录水平小幅上调,rpoS和oxyR转录水平显著上调。1 mg/mL EGCG和4 mg/mL柠檬酸联合作用,recA、rpoS、oxyR基因转录量显著上调,且上调幅度明显大于防腐剂单独处理样本,说明柠檬酸和EGCG具有协同效应。本研究结果证实低浓度的EGCG和柠檬酸均能激活细菌的氧化应激反应,柠檬酸能激活SOS反应,但低浓度EGCG一定程度上能抑制SOS反应。相较柠檬酸,EGCG更适于控制食品中大肠杆菌O157∶H7的污染。

This study aimed at revealing the transcriptional response of stress related genes in Escherichia coil O157 ：H7 when exposed to natural preservatives epigallocatechin gallate （EGCG） and citric acid by RT-real-time PCR. Results showed that when E. coli O157：H7 exposed to 1 mg/ml EGCG, the transcription level of recA reduced, while the transcription level of oxyR increased distinctly. When exposed to 4 mg/ml citric acid, the transcription level of recA improved slightly, while rpoS and oxyR improved significantly. Compared with the samples exposed to EGCG or citric acid, respectively, when E. coli O157：H7 exposed to 1 mg/ml EGCG and 4 mg/ml citric acid, the transcription levels of three genes improved sharply and were much higher. This study demonstrated that both EGCG and citric acid could induce oxidative stress reaction. Citric acid could also induced SOS response but EGCG could slightly inhibited SOS reaction. So compared with citric acid, EGCG was more suitbale in the prevention of E. coli O157：H7 contamination in food production.