DNA Partitioning to Soils and Soil Minerals.

The frequency of horizontal gene transfer (HGT) in the soil environment is still in dispute. In many instances, extracellular DNA is subject to rapid degradation by nucleases that are ubiquitous in soil.  Micro-organisms are known to be transformable under natural conditions (i.e. cells taking up free DNA and incorporating it into the genome) and therefore, the acquisition of new heritable information is of concern.  The primary objective of the current research is to improve our understanding of the physicochemical processes controlling the persistence, and transport of extracellular DNA in the soil environment, with a focus on amphoteric soil constituents that readily influence mineral surface properties. The current study focuses on (1) batch sorption experiments designed to evaluate the abiotic partitioning of extracellular DNA to various reactive soil components as a function of chemical conditions; (2) column transport experiments designed to understand the impact of temporal and spatial variability on DNA mobility in soils.  DNA adsorption was compared between pure goethite, kaolinite, mixtures of goethite and kaolinite and a soil collected from The Department of Energy’s Savannah River Site (SRS) under similar pH (~5.5 which is the isoelectric point of DNA) and ionic strength conditions. The adsorption decreased in the order of goethite > kaolinite > mixture of goethite and kaolinite > SDF Soil. DNA sorption was also measured as function of pH (3 to 10) on above materials.