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Applied and Environmental Microbiology, June 2007, p. 3865-3876, Vol. 73, No. 12
0099-2240/07/$08.00+0     doi:10.1128/AEM.02933-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Biodegradation Processes in a Laboratory-Scale Groundwater Contaminant Plume Assessed by Fluorescence Imaging and Microbial Analysis{triangledown}

Helen C. Rees,1* Sascha E. Oswald,2 Steven A. Banwart,1 Roger W. Pickup,3 and David N. Lerner1

Department of Civil and Structural Engineering, Kroto Research Institute, North Campus, University of Sheffield, Broad Lane, Sheffield S3 7HQ, United Kingdom,1 UFZ, Helmholtz Centre for Environmental Research, Department of Hydrogeology, Permoserstrasse 15, 04318 Leipzig, Germany,2 Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LA1 4AP, United Kingdom3

Received 19 December 2006/ Accepted 19 April 2007

Flow reactors containing quartz sand colonized with biofilm were set up as physical model aquifers to allow degrading plumes of acetate or phenol to be formed from a point source. A noninvasive fluorescent tracer technique was combined with chemical and biological sampling in order to quantify transport and biodegradation processes. Chemical analysis of samples showed a substantial decrease in carbon concentration between the injection and outflow resulting primarily from dilution but also from biodegradation. Two-dimensional imaging of the aqueous oxygen [O2(aq)] concentration field quantified the depletion of O2(aq) within the contaminant plume and provided evidence for microbial respiration associated with biodegradation of the carbon source. Combined microbiological, chemical, and O2(aq) imaging data indicated that biodegradation was greatest at the plume fringe. DNA profiles of bacterial communities were assessed by temperature gradient gel electrophoresis, which revealed that diversity was limited and that community changes observed depended on the carbon source used. Spatial variation in activity within the plume could be quantitatively accounted for by the changes observed in active cell numbers rather than differences in community structure, the total biomass present, or the increased enzyme activity of individual cells. Numerical simulations and comparisons with the experimental data were used to test conceptual models of plume processes. Results demonstrated that plume behavior was best described by growth and decay of active biomass as a single functional group of organisms represented by active cell counts.

* Corresponding author. Mailing address: Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom. Phone: 44 (0)116 2525366. Fax: 44 (0)116 2523330. E-mail: hcr4{at}le.ac.uk

{triangledown} Published ahead of print on 27 April 2007.

Applied and Environmental Microbiology, June 2007, p. 3865-3876, Vol. 73, No. 12
0099-2240/07/$08.00+0     doi:10.1128/AEM.02933-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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