Relevance of Nontoxigenic Strains as Surrogates for Escherichia coli O157:H7 in Groundwater Contamination Potential: Role of Temperature and Cell Acclimation Time

摘要

Nontoxigenic bacteria are commonly used as indicators for predicting the contamination potential of pathogens in natural or engineered aqueous environments. In this study, column transport experiments were used to examine the relevance of two nontoxigenic strains of Escherichia coli O157:H7 as potential surrogates for the well-known pathogen. Experiments conducted at 11℃ indicate that only one of the nontoxigenic strains may be an appropriate surrogate for predicting the migration potential of the pathogen at low solution ionic strengths. Results of various bacterial characterization methods indicate that differences in cell attachment could qualitatively, but convincingly, be related to differences in cell surface charge. Additional experiments conducted at 22℃ reveal the influence of temperature on bacterial cell surface charge and cell attachment to sand. The role of cell acclimation time to an artificial groundwater solution is also examined, showing little change in the degree of cell attachment over a period of several weeks.