|WALKER, SHARON - University Of California|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2008
Publication Date: 2/10/2009
Citation: Bolster, C.H., Haznedaroglu, B.Z., Walker, S.L. 2009. Diversity of Cell Properties and Transport Behavior Among 12 Enviromental Escherichia Coli Isolates. Journal of Environmental Quality. Vol. 38 p. 465-472
Interpretive Summary: The land application of human and animal wastes can result in the infiltration of pathogenic microorganisms such as bacteria, viruses, and protozoa into underground drinking water supplies. Because testing for specific pathogenic microorganisms is both costly and time consuming, rarely are these pathogens targeted for measurement. Instead, most agencies responsible for monitoring water supplies test for the presence of nonpathogenic microorganisms commonly found in fecal material. A commonly used indicator organism is E. coli. The importance of E. coli as an indicator organism has led to several studies looking at surface characteristics and transport behavior of this particular microorganism in groundwater environments. However, in most studies only a single strain of E. coli was used. In this study we look at the transport behavior of 12 different E. coli isolates obtained from 6 different sources: wildlife, human, horse, beef cattle, dairy cattle, and poultry. We found a large diversity in cell properties and transport behavior for the different E. coli isolates tested suggesting generalizations about the transport behavior of E. coli based on results from a single strain of E. coli should be made with caution. In addition, this large variability suggests that the modeling of E. coli in the environment will require a distribution of bacterial attachment rates, even when modeling E. coli movement from a single fecal source.
Technical Abstract: Escherichia coli is a commonly used indicator organism for detecting the presence of fecal-borne pathogenic microorganisms in water supplies. The importance of E. coli as an indicator organism has led to numerous studies looking at surface characteristics and transport behavior of this important microorganism. In many of these studies, however, a single strain of E. coli was used even though research has shown a significant amount of genetic variability exists among different strains of E. coli. If this genetic diversity results in differences in surface characteristics that control transport, different strains of E. coli may exhibit different rates of transport in the environment. Therefore, the objective of our study was to investigate the variability in surface characteristics and transport behavior of E. coli isolates obtained from six different sources: wildlife, human, horse, beef cattle, dairy cattle, and poultry. Cell properties such as electrophoretic mobility, cell size and shape, hydrophobicity, charge density, and extracellular polymeric substance composition were measured for each isolate. In addition, transport behavior of each strain was assessed by measuring bacterial transport through 10-cm packed beds of clean quartz sand. Our results show large diversity in cell properties and transport behavior for the different E. coli isolates and that the best predictor of breakthrough was cell width and shape. This diversity in transport behavior must be taken into account when making assessments of the suitability of using E. coli as an indicator organism for specific pathogenic microorganisms in groundwater environments as well as modeling the movement of E. coli in the subsurface.