Chemotaxis, the ability of bacteria to swim towards higher concentrations of favorable substrates, may expedite movement of introduced bacteria to low-permeability zones (lenses and layers) within aquifers where xenobiotic chemicals often concentrate. However, quantitative informaiton about chemotaxis at the field scale is lacking. In our study, chemotactic migration of Pseudomonas stutzeri, a solvent-degrading, denitrifying bacterium, was measured during an injection-and-recovery experiment involving a solvents-contaminated, granular aquifer (Cape Cod, Massachusetts). The study involved a natural-gradient injection and recovery test in which vertical gradients of an electron donor (acetate) and acceptor (nitrate) were created above an amendment of P. stutzeri. Substantive (0.1m/d) vertical migration (relative to a chemotactically impaired control) of P. sutzeri toward higher acetate and nitrate concentrations was considerably greater than that predicted from laboratory microcosm studies (0.02m/d) with more homogeneous media, suggesting that bacterial chemotaxis may have an important role in remediation of sandy aquifers with cm-scale stratigraphy.

Bacterial chemotaxis as a potential mechanism for enhancing degradation of localized organic contaminants in granular aquifers

243rd National Meeting (2012)

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