Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2008
Publication Date: 12/1/2008
Publication URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2241.pdf
Citation: Tazehkand, S.S., Torkzaban, S., Bradford, S.A., Walker, S. 2008. Cell preparation methods influence E.coli D21g surface chemistry and transport in saturated sand. Journal of Environmental Quality. 37:2108-2115. Interpretive Summary: The surface of bacterial cells influences their interaction and fate in the environment. Experimental procedures that are used to harvest cells from nutrient solutions can alter their surface properties. In this work, we investigate how experimental procedures for harvesting cell influence their surface properties and interaction with clean sand. The results indicate that cells that were harvested by filtration had a minimal effect on their surface properties and transport behavior compared with cells that were havested by centrifugation.
Technical Abstract: The effect of cell preparation methods on the surface chemistry and deposition of Escherichia coli D21g was investigated over a range of ionic strength conditions. The cell preparation methods, which were considered, included filtration and centrifugation (at various speeds and for different durations). For a given ionic strength condition, it was found that cells prepared by filtration were more negatively charged and hydrophobic than cells prepared by centrifugation. Increasing the force imposed or duration of centrifugation produced cells with increasing zeta potentials (less negative) and decreased hydrophobicity. Column transport experiments were also conducted with ultra pure quartz sand using the same solution chemistries and E. coli D21g. The retention of these cells was quantified by fitting a first-order deposition rate coeffecient (kd) and the maximum deposited concentration (Smax) to the collected effluent concentration curves. The results demonstrate that the rate of the deposition of E. coli D21g increased with increasing force and duration of centrifugation, and was lowest in the case of filtered cells. Moreover, the results show that the influence of cell preparation methods was more pronounced in lower ionic strength solutions.