Transport of Manure-Derived, Tetracycline Resistant Escherichia Coli in Unsaturated Soil

Research Goals
Based on the previously published research findings, the first goal of this research is to specifically evaluate the effects of OMP TolC on the transport of E. coli within saturated sands using mutants that are created through genetic manipulation. The findings from this research will provide valuable insights into the relationship between cell surface structures and E. coli mobility.
In saturated porous media, the transport of bacterial cells is primarily controlled by the kinetics of cell deposition at the solid-water interfaces. When the soil is partially saturated, several mechanisms contribute to cell deposition. In addition to the solid-water interface, bacterial cells may adhere to the air-water interface. Bacterial cells can also be strained at the edges of pendular rings that form around adjacent grains or by the thin water film that stretches between the pendulum rings (Denovio et al. 2004). Published experimental results showed that pore water chemistry and soil moisture content are the most important parameters that control the retention of colloid-sized particles in unsaturated soil (Denovio et al. 2004, Lenhart and Saiers 2002). The second goal of this research is to evaluate the influence of pore water chemistry and soil moisture content on the transport of tetR E. coli in unsaturated soil. It was also reported that chemical perturbation, drainage (i.e. drying front) and imbibitions (i.e. wetting front) could mobilize substantial quantities of colloid-sized particles in partially saturated soil (Cheng and Saiers 2009, Saiers et al. 2003).This proposed research will also examine the release of the retained bacterial cells under transient chemical and flow conditions.