室内模拟实验法研究冻融循环下常见肠杆菌在河水中的存活特征及影响因素

Study on Survival Characteristics and Influencing Factors of Common Enterobacteriaceae in River Water under Freeze-Thaw Cycles by Indoor Simulation Experiment Method

通过室内模拟实验法研究冻融循环下常见肠杆菌Escherichia coli(Ec10538),Salmonella enterica subsp.Enterica(sd-51)和Enterobacter cloacae subsp.Cloacae(Ec7256)在河水中的存活特征及主要影响因素,并分析冻融循环影响细菌存活的机理.结果表明:冻融循环显著抑制3株肠杆菌在河水中的存活,随着冻融循环频次的增加,抑制效应增强;冻融循环下河水中肠杆菌的存活特征与其对冻融胁迫的耐受性和水质有关,Ec7256强于Ec10538和sd-51对冻融胁迫的耐受性,河水水质越好,其对冻融循环的耐受性越强;河水pH值、电导率(EC)和总有机碳(TOC)对3株肠杆菌存活(ttd值)具有显著影响(P<0.05);冻融循环导致细菌细胞表面疏水性(CSH)升高,并在最后一个冻融循环达到峰值,有利于细菌团聚抵抗冻融胁迫;超氧化物歧化酶(SOD)和过氧化氢酶(CAT)的活性随冻融频次的增加而增加,从而降低冻融胁迫下活性氧对细菌的伤害,进而提高细菌对冻融胁迫的耐受性.

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.