Survival And The Influence Factors Of Escherichia Coli O157:H7 In Soils Over A Sandy Gradient In Northeastern China

E.coli O157:H7 has become one of the food-borne pathogens that have attracted worldwide attention in the past decade because of its low infectious dose and high pathogenicity.E.coli O157:H7 in soil could migrate to the surface and inside of other environmental media or carriers,so understanding the survival behavior of E.coli O157:H7 in soil and its influencing factors will help reduce environmental organisms caused by such pathogens pollution.To adapt to local conditions,a total of 24 soil samples were collected.According to the soil texture classification standard?USDA?,it can be divided into silt loam,loam,sandy loam,loamy sand,and sandy soil.The sampling locations were collected in Jilin Province-Inner Mongolia Autonomous Region in northeastern China.The sand grain content of soil samples gradually decreased from west to east,showing a natural soil sand grain gradient zone.The study aimed to study the survival behavior of E.coli O157:H7 in sand-gradient soil under natural conditions.E.coli O157:H7 was inoculated into 24 soil samples and the changes in the number of bacteria were continuously recorded.The Weibull model was used to simulate the dynamic changes of the time?ttd?and other survival parameters required for the number of E.coli O157:H7 to drop to the detection limit(100 CFU gdw^-1)in soil.At the same time,the physical and chemical properties of the soil were determined,and the total DNA was extracted.The composition and structure of the soil bacterial community were characterized according to high-throughput sequencing.Finally,the factors affecting the survival behavior of E.coli O157:H7 in soil with different sand content under natural conditions were analyzed.The effects of soil physical and chemical properties,soil microbial community structure,and geospatial variables on the survival behavior of E.coli O157:H7 and their internal relationships are discussed comprehensively.The results showed that the survival time?ttds?of E.coli O157:H7 in soil ranged from 90.52 days to 27.04 days.Among them,soil sand content is one of the important factors affecting the survival behavior of E.coli O157:H7.The regression analysis results show that the soil sand content is significantly negatively correlated with the survival time of E.coli O157:H7?P<0.001?.The soil nutrients?soil carbon and nitrogen,etc.?were significantly positively correlated with survival behavior?P<0.001?.In addition to soil properties,soil indigenous bacterial communities also affect the survival of E.coli O157:H7.Our results indicate that survival time?ttd?is significantly correlated with Acidobacteria,Chloroflexi,and Alphaproteobacteria?P<0.05?.The results of nonmetric multidimensional scaling?NMDS?showed that the bacterial community structure in soils with different sand content was significantly different.Multiple stepwise regression analysis indicated that soil particle size and total carbon may be the most important factors affecting the survival time of E.coli O157:H7.Structural equation model?SEM?showed that the soil bacterial community can directly affect the survival time of E.coli O157:H7,and the soil particle size and geographical distance are more focused on indirectly affecting the survival time by affecting indigenous bacteria communities.Besides,soil physical and chemical properties such as EC?soil salinity?will also affect the survival of E.coli O157:H7.Also,Variation partition analysis?VPA?showed that the bacterial community,physical properties,and chemical properties of the soil explained the survival behavior of 5.63%,12.37%,and 15.38%,respectively.The interaction between biotic and abiotic factors can better explain the dynamics of changes in survival parameters.In summary,the soil collected in this experiment has a long spatial and geographical distance and a large difference in the structure of the bacteria community with physical and chemical properties.When evaluating the survival behavior of E.coli O157:H7,the interaction between biological and non-biological factors should be considered to deepen the understanding of the internal mechanism,and the results should be viewed objectively and comprehensively.