Kinetics of conjugative gene transfer on surfaces in granular porous media

The transfer of genetic material among bacteria in the environment can occur both in the planktonic and attached state. Given the propensity of organisms to exist in sessile microbial communities in oligotrophic subsurface conditions, and that such conditions typify the subsurface, this study focuses on exploratory modeling of horizontal gene transfer among surface-associated Escherichiacoli in the subsurface. The mathematics so far used to describe the kinetics of conjugation in biofilms are developed largely from experimental observations of planktonic gene transfer, and are absent of lags or plasmid stability that appear experimentally. We develop a model and experimental system to quantify bacterial filtration and gene transfer in the attached state, on granular porous media. We include attachment kinetics described in Nelson et al. (2007) using the filtration theory approach of Nelson and Ginn (2001, 2005) with motility of E. coli described according to Biondi et al. (1998).