The effects of freezing-induced sublethally injury and recovery on adhesion of Escherichia coli O157:H7

Freezing as an effective approach for food storage is commonly used in food industry. Notably, Escherichia coli O157:H7 can survive in a sublethally injured state after freezing and recover under suitable conditions, which is a great threat. This research was to investigate changes and mechanism in adhesion of sublethally injured E. coli O157:H7 during freezing and recovery. Adhesion on stainless steel or lettuce surface showed an increase after 16 h-freezing with sublethal ratio of more than 99%. Adhesion recovered to untreated level in recovery on lettuce while didn’t recover on stainless steel. Motility decreased as freezing time increasing, reached minimum after 12 h-freezing and didn’t recover to untreated level under recovery conditions, which was determined by diameter of motility halo. Extracellular polymeric substances production and carbohydrate to protein ratio both reached minimum after 4 h-freezing and then increased. No significant change of LPS structural feature or gene expression was observed during injury and recovery. Besides, the expressions of flagella, pili and EPS related genes were all down-regulated during freezing while were up-regulated after recovery. The results revealed adhesion behavior of freezing-induced sublethally injured E. coli O157:H7, which provides theoretical basis to bacterial prevention.