Carbon Isotope Fractionation during Aerobic Biodegradation of Trichloroethene by Burkholderia cepacia G4: a Tool To Map Degradation Mechanisms |
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| Authors: | Johannes A. C. Barth, Greg Slater, Christoph Schü th, Markus Bill, Angela Downey, Mike Larkin, Robert M. Kalin |
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| Affiliation: | Johannes A. C. Barth, Greg Slater, Christoph Schüth, Markus Bill, Angela Downey, Mike Larkin, and Robert M. Kalin |
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| Abstract: | 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 δ13CVPDB), 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, ![[var epsilon]](corehtml/pmc/pmcents/epsiv.gif) , 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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