ATR-FTIR And ATP Studies On Adhesion Of Escherichia Coil O157:H7 To The Surfaces Of Soil Minerals

Escherichia coli O157:H7 is a food-borne pathogen and its minimal infectious dose for human is as few as 10 cells.The carriage of E. coli O157:H7 would most likely result in contamination of the soil environment through manure application or irrigation that pose a serious threat to public health. This dissertation studied the interface interactions between E. coli O157:H7 and the prevalent of primary and secondary minerals(quartz, montmorillonite, illite, goethite, birnessite, and boehmite) in the soil. Attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopy was employed to investigate the adhesion of E. coli O157:H7 to goethite surface over a wide range in solution chemistry. We use ATP as the active index of pathogenic metabolism and explore how different soil minerals may affect bacterial metabolic activity. The main finding are listed as follows:(1)The interaction of viable E. coli O157:H7 at the goethite surface coatings was examined affected by aqueous solution chemistry. In Na Cl and Ca Cl2 solution, surface functional groups of E. coli O157:H7 are similar and composed of amide, carboxylate and phosphate. The carboxyl groups exhibit p H dependent protonation/deprotonation reactions. Major reactive groups found on the cell wall surface are carboxyl and phosphate moieties, which have been identified as active sites in mediating cell attachment to goethite substrates through the formation of covalent bonds. The data also indicate that complexation modes vary with solution chemistry. E. coli O157:H7 are bound to goethite via P-(OFe)2 at p H3, whereas becomes P-OFe with increasing p H. Over a wide range in solution chemical, only monodentate complexes is observed when bacterial cells are bound to goethite. The capacity for bacteria adhesion on goethite surface increased, but the interaction mechanism of molecules is unchanged with action time.(2)To elucidate the influence of soil minerals on bacterial metabolic activity. Quartz enhanced respiration, smectite and illite make bacterial metabolism remained stable, while goethite, birnessite and boehmite inhibit bacterial activity, boehmite exhibits the strongest inhibitory effect.