(210e) The Role of Bacterial Chemotaxis in Improving Bioremediation Efficiency

Authors: 
Zhao, X., The University of Virginia
Ford, R. M., University of Virginia
Crude oil components exposure can cause potential health effect to oil spill cleanup workers. An alternative strategy to clean up oil spill is bioremediation. Bioremediation is a technique to use microorganisms to break down environmental pollutants. Microorganisms can accumulate near the oil-water interface, forming biofilms. This accumulation increases the bioavailability of dispersed oil droplets to hydrocarbon-degrading marine bacteria. For low solubility hydrocarbons, such as hexadecane, the formation of biofilm in an oil-water interface is particularly important. A process that contributes to biofilm formation is chemotaxis. In this process, marine bacteria sense the hydrocarbon concentration gradient in the oil-water interface and swim toward the higher concentration gradient. Chemotaxis can compensate for the mass-transfer limitation of the low solubility hydrocarbons, thereby enhancing biodegradation efficiency.

Marine bacteria chemotaxis is not well characterized, therefore, our work is to quantify how much chemotaxis contribute to increasing bioavailability of oil droplets to hydrocarbon-degrading bacteria. To analyze chemotaxis, we exposed marine bacteria to hexadecane in a uniquely designed microfluidic device that ensures the migration of bacteria is solely in response to a constant gradient of hexadecane. This device allows us to readily quantify chemotaxis from the resulting bacterial distribution. Experimental data was then used to quantify parameters in a mathematical model capturing motility and chemotaxis derived from first principles. Specifically, the random motility coefficient was obtained from experiments in a hydrocarbon-free condition and chemotaxis parameters were determined from experiments at different hexadecane concentrations. We found the random motility coefficient for marine bacteria in the model is in the same order of magnitude as that of Escherichia coli, suggesting the model is reasonable. This research enables us to understand the extent to which bacterial chemotactic processes facilitate recycling of dissolved hydrocarbons. Further characterization over different marine bacteria can identify potential bioreporters to sense oil spill in seawater, hence, decreasing human labor and reducing human exposure to crude oil.