| About 10 to 100 billion tons of animal dung are produced in global livestock breeding annually. Most of them are used as manure without correct decontamination resulting in Enterobacteria entering the soil and posing a great threat to human health and food safty. Pathogenic bacteria can form microcolonies biofilm to help them survive in soils, however the molecular mechanisms of the bacterial response to soil minerals remain largely unknown. In the present study, the effects of common soil mineralssuch as iron oxides(goethite and hematite),aluminum oxides(boehmite) and layered silicate minerals(kaolinite, montmorillonite, illite) to E. coli O157:H7 were investigated. The main results are as follows:1. The toxicities of soil minerals to E. coli O157:H7 were explored. Firstly, using the Live/Dead dye to stain the E. coli O157:H7, we find the membrane is damaged when soil minerals interact with E. coli O157:H7. Moreover, E. coli O157:H7 produces more intracellular reactive oxygen species(ROS)when interact with iron aluminum oxide, including goethite,hematite and boehmite than those layered silicate minerals including montmorillonite, illite and kaolinite. However, the colony-forming units(CFU) of E. coli O157:H7 per m L is not significantly influenced by soil minerals.2. The influences of soil minerals on the gene expression of E. coli O157:H7 were clarified. Firstly, q RT-PCR results showed that two toxin encoding genes(stx1 and stx2) are inhibited. While, transcript levels of superoxide dismutase sod B and DNA repair gene rec A are induced by soil minerals. However, soil minerals have no effect on the expression level of the flagella gene, flh D and flagellin gene, fli C. |
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