The oxyR negatively regulates processing stress resistance in Escherichia coli O157:H7 by reducing ROS scavenging capacity.

Abstract

Escherichia coli O157:H7 has the ability to withstand a wide range of environmental stresses, making it a major challenge to eradicate in the food industry and a threat to food safety. In this study, the effect of oxyR on the ability of E. coli O157:H7 to resist environmental stress was investigated. Firstly, oxyR knockout, complementation and overexpression strains of E. coli O157:H7 were constructed and analysed the survival of wild and mutant strains under conditions of acid, heat, oxidative and osmotic stress. The findings indicate that under the conditions of this experiment, oxyR mainly regulated the resistance of E. coli O157:H7 to oxidative stress, with less effect on the ability to resist osmotic stress, and did not affect the acid stress resistance and heat stress resistance. The role of oxyR in antioxidant stress was then analysed by assessing ROS, MDA levels, cell membrane damage and antioxidant enzyme activities in the four strains under oxidative stress. The results showed that the deletion of gene oxyR reduced the ROS concentration by 54.00±1.24%, the MDA content of oxyR overexpression strain increased to 0.78±0.03 nmol/mL, the overexpression of gene oxyR suffered more severe cell membrane damage (67.83±1.22% for minor damage and 28.88±1.13% for severe damage), and a significant decrease in the activities of SOD, CAT, and GSH-Px (P<0.05), as compared with the wild strain. This study suggests that oxyR regulates bacterial resistance to oxidative stress by affecting intracellular ROS, cell membrane integrity and antioxidant enzyme activities.