Abstract: The survival characteristics and main influencing factors of common Enterobacteriaceae such as Escherichia coli (Ec10538),  Salmonella enterica subsp. Enterica (sd-51) and Enterobacter cloacae subsp. Cloacae (Ec7256) in river water under freeze-thaw cycles were studied by indoor  simulation experiment method, and the mechanism of freeze-thaw cycle influencing bacterial survival was analyzed. The  results show that the three Enterobacteriaceae in river water is significantly inhibited by freeze-thaw cycles,  and the inhibitory effects gradually stronger with the increase of freeze-thaw frequency. The survival characteristics  of Enterobacteriaceae in river water under freeze-thaw cycle are  related to its tolerance to freeze-thaw stress and water quality. EC7256 is stronger  than the Ec10538 and sd-51  to freeze-thaw stress.   The  better river water quality, the stronger its tolerance  to freeze-thaw cycles. The electrical conductance (EC),  pH value and total organic carbon (TOC) of river water have significant effect on survival of Enterobacteriaceae (P<0.05). The freeze-thaw cycles lead to increase of cell surface hydrophobicity (CSH),  and reach the peak at last freeze-thaw cycles,  which is conducive to the   bacterial agglomeration and resistance to  the freeze-thaw stress. The activities of superoxide dismutase (SOD) and catalase from micrococcus lysodeikticus (CAT) increase with the increase of freeze-thaw frequency,  so as to  reduce the damage of the active oxygen generated by freeze-thaw stress to the bacteria, and then improve the tolerance of bacteria to freeze-thaw stress.

Key words: freeze-thaw cycle,  , river water property,  , Enterobacteriaceae,  , survival,  , influencing factor