Disentangling survival of Escherichia coli O157∶H7 in soils: From a subpopulation perspective

摘要

Soil physicochemical properties and microbial community have been proved to be correlated to survival behaviors of Shiga toxin-producing Escherichia coli O157∶H7, but the roles of biotic and abiotic factors in the different stages of inactivation process remain unclear. Here, fruit producing soils were collected, and soils physicochemical properties, bacterial and fungal community structure were characterized. Survival experiments were performed by inoculating E. coli O157∶H7 in soils. Double Weibull survival model was found to better fit the experimental data, and two subpopulations with different capability on resistance to stress were identified. The sensitive subpopulation with smaller δ (time needed for first decimal reduction) (i.e., δ_1,) died off faster compared to the more resistant subpopulation with greater δ (i.e., δ_2). Partial Mantel test revealed that red (time needed to reach detection limit) was jointly influenced by physical factors, chemical factors, and bacterial composition (P ＜ 0.05); δ_1 was shaped by physical factors (P ＜ 0.01) and additional bacterial composition (P ＜ 0.05); and δ_2 was strongly steered by bacterial community (P ＜ 0.001). Bacterial co-occurrence network analysis revealed that samples with lower δ_2 were coupled with higher network complexity and closer taxa relationship (e.g. higher average (weighted) degree, higher network diameter, higher graph density, and lower modularity), and vice versa. Taken together, the sensitive subpopulation had difficulty in adapting to coarse particles conditions, while resistant subpopulation might eventually succumb to the robust biodiversity. This study provides novel insights into the E. coli O157∶H7 survival mechanism through subpopulation perspective and sheds light on the reduction of edaphic colonization by pathogens via agricultural management strategy.