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Applied and Environmental Microbiology, July 1999, p. 3056-3063, Vol. 65, No. 7
Department of Microbiology, University of
Massachusetts, Amherst, Massachusetts 01003,1
and Waterways Experiment Station, Dyntel Corp., Vicksburg,
Mississippi 391802
Received 15 December 1998/Accepted 19 April 1999
Microbial community composition associated with benzene oxidation
under in situ Fe(III)-reducing conditions in a petroleum-contaminated aquifer located in Bemidji, Minn., was investigated. Community structure associated with benzene degradation was compared to sediment
communities that did not anaerobically oxidize benzene which were
obtained from two adjacent Fe(III)-reducing sites and from methanogenic
and uncontaminated zones. Denaturing gradient gel electrophoresis of
16S rDNA sequences amplified with bacterial or
Geobacteraceae-specific primers indicated significant
differences in the composition of the microbial communities at the
different sites. Most notable was a selective enrichment of
microorganisms in the Geobacter cluster seen in the
benzene-degrading sediments. This finding was in accordance with
phospholipid fatty acid analysis and most-probable-number-PCR
enumeration, which indicated that members of the family
Geobacteraceae were more numerous in these sediments. A
benzene-oxidizing Fe(III)-reducing enrichment culture was established
from benzene-degrading sediments and contained an organism closely
related to the uncultivated Geobacter spp. This genus
contains the only known organisms that can oxidize aromatic compounds
with the reduction of Fe(III). Sequences closely related to the Fe(III)
reducer Geothrix fermentans and the aerobe Variovorax
paradoxus were also amplified from the benzene-degrading enrichment and were present in the benzene-degrading sediments. However, neither G. fermentans nor V. paradoxus
is known to oxidize aromatic compounds with the reduction of Fe(III),
and there was no apparent enrichment of these organisms in the
benzene-degrading sediments. These results suggest that
Geobacter spp. play an important role in the anaerobic
oxidation of benzene in the Bemidji aquifer and that molecular
community analysis may be a powerful tool for predicting a site's
capacity for anaerobic benzene degradation.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Microbial Communities Associated with Anaerobic
Benzene Degradation in a Petroleum-Contaminated Aquifer


*
Corresponding author. Mailing address: 203 N Morrill
Science Center IV N, Department of Microbiology, University of
Massachusetts, Amherst, MA 01003. Phone: (413) 545-9651. Fax: (413)
545-1578. E-mail: dlovley{at}microbio.umass.edu.
Present address: Department of Biological Sciences, University of
Massachusetts, Lowell, MA 01854.
Present address: Environmental Sciences and Engineering,
University of North Carolina, Chapel Hill, NC 27599.
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