| Abstract
| - Bacterial chemotaxis has the potential to enhancebiodegradation of organic contaminants in pollutedgroundwater systems. However, studies of bacterialchemotaxis in porous media are scarce. In this study weuse magnetic resonance imaging (MRI) for the noninvasivemeasurement of changes in bacterial-density distributionsin a packed column at a spatial resolution of 330 μmas a function of time. We analyze both the diffusive andthe chemotactic behavior of Pseudomonas putida F1 in thepresence of the chemical stimulus trichloroethylene(TCE). The migration of motile bacteria in experimentswithout TCE was described using an effective motilitycoefficient, whereas the presence of TCE required additionof a nonzero chemotactic sensitivity coefficient, indicatinga significant response to TCE. The need for a chemotacticsensitivity term was justified by a test for statisticalsignificance. This study represents the first quantificationof bacterial chemotactic parameters within a packedcolumn. For conditions under which chemotaxis occurs inporous media, it may potentially be exploited to significantlyimprove rates of in situ pollutant biodegradation in thesubsurface environment, particularly for pollutants dissolvedin water trapped in low-permeability formations orlenses.
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