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Applied and Environmental Microbiology, May 2001, p. 2107-2115, Vol. 67, No. 5
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.5.2107-2115.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Cytotoxicity Associated with Trichloroethylene Oxidation in Burkholderia cepacia G4

Chris M. Yeager,1 Peter J. Bottomley,1,2 and Daniel J. Arp1,3,*

Molecular and Cellular Biology Program,1 Departments of Microbiology and Crop and Soil Sciences,2 and Department of Botany and Plant Pathology,3 Oregon State University, Corvallis, Oregon 97331-2902

Received 26 October 2000/Accepted 19 February 2001

The effects of trichloroethylene (TCE) oxidation on toluene 2-monooxygenase activity, general respiratory activity, and cell culturability were examined in the toluene-oxidizing bacterium Burkholderia cepacia G4. Nonspecific damage outpaced inactivation of toluene 2-monooxygenase in B. cepacia G4 cells. Cells that had degraded approximately 0.5 µmol of TCE (mg of cells-1) lost 95% of their acetate-dependent O2 uptake activity (a measure of general respiratory activity), yet toluene-dependent O2 uptake activity decreased only 35%. Cell culturability also decreased upon TCE oxidation; however, the extent of loss varied greatly (up to 3 orders of magnitude) with the method of assessment. Addition of catalase or sodium pyruvate to the surfaces of agar plates increased enumeration of TCE-injured cells by as much as 100-fold, indicating that the TCE-injured cells were ultrasensitive to oxidative stress. Cell suspensions that had oxidized TCE recovered the ability to grow in liquid minimal medium containing lactate or phenol, but recovery was delayed substantially when TCE degradation approached 0.5 µmol (mg of cells-1) or 66% of the cells' transformation capacity for TCE at the cell density utilized. Furthermore, among B. cepacia G4 cells isolated on Luria-Bertani agar plates from cultures that had degraded approximately 0.5 µmol of TCE (mg of cells-1), up to 90% were Tol- variants, no longer capable of TCE degradation. These results indicate that a toxicity threshold for TCE oxidation exists in B. cepacia G4 and that once a cell suspension has exceeded this toxicity threshold, the likelihood of reestablishing an active, TCE-degrading biomass from the cells will decrease significantly.

* Corresponding author. Mailing address: Department of Botany and Plant Pathology, 2082 Cordley, Oregon State University, Corvallis, OR 97331-2902. Phone: (541) 737-1294. Fax: (541) 737-5310. E-mail: arpd{at}bcc.orst.edu.

Applied and Environmental Microbiology, May 2001, p. 2107-2115, Vol. 67, No. 5
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.5.2107-2115.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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Copyright © 2001 by the American Society for Microbiology. All rights reserved.