Enhancing Bioremediation by Exploiting Bacterial Chemotaxis: 2-Dimensional Microcosm Studies

In-situ bioremediation is limited by the inability to deliver the bacteria to the source of the chemical contaminant which they will degrade.  Chemotaxis, the ability of some bacteria to sense higher concentrations of chemical attractants and swim toward them, can improve the effectiveness of bioremediation by directing bacteria toward contaminant sources. In this study, a two-dimensional lab-scale model aquifer was used to determine the effect of chemotaxis on the transport of bacteria exposed to a chemoattractant concentration gradient in porous media.   The model was packed with sand and an aqueous medium was pumped across horizontally, simulating groundwater flow in a homogenous aquifer.  Sodium benzoate was injected continuously to generate a steady concentration gradient transverse to flow and chemotactic P.putida F1 or a non-chemotactic mutant of the same species was injected below the attractant.  Samples were collected at the end of the microcosm to provide vertical concentration profiles of the bacteria and attractant.  The chemotactic bacteria center of mass was found to be an average of 1.24 ± 0.86 cm closer to the attractant injection than the non-chemotactic mutant. These results suggest that chemotaxis can improve the transport of bacteria to contaminated zones, enhancing the effectiveness of in-situ bioremediation.