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Applied and Environmental Microbiology, April 2002, p. 1728-1734, Vol. 68, No. 4
0099-2240/02/$04.00+0 DOI: 10.1128/AEM.68.4.1728-1734.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Scottish Universities Environmental Research Centre, East Kilbride, Glasgow G75 0QF, Scotland,1 Questor Centre, The Queen's University of Belfast, Belfast BT9 5AG, Northern Ireland, United Kingdom,6 Department of Geology, University of Toronto, Toronto, Canada,2 Woods Hole Oceanographic Institution, Woods Hole, Massachusetts,3 Applied Geology Group, Geological Institute, University of Tübingen, D-72076 Tübingen, Germany,4 Environmental Science, University of California, Berkeley, California5
Received 2 October 2001/ Accepted 3 January 2002
The strain Burkholderia cepacia G4 aerobically mineralized trichloroethene (TCE) to CO2 over a time period of
20 h. Three biodegradation experiments were conducted with different bacterial optical densities at 540 nm (OD540s) in order to test whether isotope fractionation was consistent. The resulting TCE degradation was 93, 83.8, and 57.2% (i.e., 7.0, 16.2, and 42.8% TCE remaining) at OD540s of 2.0, 1.1, and 0.6, respectively. ODs also correlated linearly with zero-order degradation rates (1.99, 1.11, and 0.64 µmol h-1). While initial nonequilibrium mass losses of TCE produced only minor carbon isotope shifts (expressed in per mille
13CVPDB), they were 57.2, 39.6, and 17.0
between the initial and final TCE levels for the three experiments, in decreasing order of their OD540s. Despite these strong isotope shifts, we found a largely uniform isotope fractionation. The latter is expressed with a Rayleigh enrichment factor,
, and was -18.2 when all experiments were grouped to a common point of 42.8% TCE remaining. Although, decreases of
to -20.7 were observed near complete degradation, our enrichment factors were significantly more negative than those reported for anaerobic dehalogenation of TCE. This indicates typical isotope fractionation for specific enzymatic mechanisms that can help to differentiate between degradation pathways.
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