酸逆境下本土分離腸出血性大腸桿菌 O157:H7 TWC01之生理反應及蛋白質表現變化

Abstract

Escherichia coli O157:H7 is one of the important food-borne pathogens, and it has unusually higher resistance to acidic environment than other food-borne pathogens. Some researches revealed that acid adapted cells, by exposure to moderately acidic conditions, are more resistant to a subsequent strong acidic challenge or other stress. This study was conducted to understand the growth and the protein regulatory pathways of acid tolerance response (ATR) of local isolated E. coli O157:H7 induced by acidic environment. Six local isolated E. coli O157:H7 were compared the growth under the acid stress and had no difference in acid tolerance. After that, chose the clinical strain TWC01 for further study. By using hydrochloric acid (HCl) or lactic acid as acidifier, E. coli O157:H7 TWC01 were acid adapted to induce ATR. The total protein of adapted cells were extracted for proteomic analysis. Furthermore, the effect of acid adaptation to stx secretion were examined. The result revealed that after acid adaptation, it tended to increase the stx secretion of E. coli O157:H7 TWC01. Image analysis of the gel indicated that a great part of proteins were up-regulation, and lactic acid had more effect on cell than HCl. Analyzed proteins by mass spectrometer, most of proteins were metabolism related protein, and others were related to translation, folding, and membrane proteins. According to protein expression variety under acid stress has found that the induction of many acid tolerance mechanism of E. coli. The metabolism pathway were toward increasing energy production and polypeptide synthesis, in order to provide enough energy and induce ATR. Furthermore, E. coli O157:H7 needed more energy to deal with lactic acid than HCl, revealed that organic and inorganic acid have different stress sensor and response system. This study provide the information of regulation and virulence of E. coli O157:H7 under acid stress, it may help control of this pathogen and improve food safety.