Degradation of chlorinated and brominated hydrocarbons by Methylomicrobiumalbum BG8

The degradation kinetics of ten halogenated hydrocarbons by Methylomicrobiu m album BG8 expressing particulate methane monooxygenase (pMMO) and the inh ibitory effects of these compounds on microbial growth and whole-cell pMMO activity were measured. When M. album BG8 was grown with methane, growth wa s completely inhibited by dichloromethane (DCM), bromoform (BF), chloroform (CF), vinyl chloride (VC), 1,1-dichloroethylene (1,1-DCE), and cis-dichlor oethylene (cis-DCE). Trichloroethylene (TCE) partially inhibited growth on methane, while dibromomethane (DBM), trans-dichloroethylene (trans-DCE), an d 1,1,1-trichloroethane (1,1,1-TCA) had no effect. If the cells were grown with methanol, DCM, BF, CF, and 1,1-DCE completely inhibited growth, while VC, trans-DCE, TCE, and 1,1,1-TCA partially inhibited growth. Both DBM and cis-DCE had no effect on growth with methanol. Whole-cell pMMO activity was also affected by these compounds, with all but 1,1,1-TCA, DCM, and DBM red ucing activity by more than 25%. DCM, DBM, VC, trans-DCE, cis-DCE, 1,1-DCE, and TCE were degraded and followed Michaelis-Menten kinetics. CF, BE and 1 ,1,1-TCA were not measurably degraded. These results suggested that the pro ducts of DCM, TCE, VC, and 1,1-DCE inactivated multiple enzymatic processes , while trans-DCE oxidation products were also toxic but to a lesser extent . cis-DCE toxicity, however, appeared to be localized to pMMO. Finally, DBM and 1,1,1-TCA were not inhibitory, and CF and BF were themselves toxic to M. album BG8. Based on these results, the compounds could be separated into four general categories, namely (1) biodegradable with minimal inactivatio n, (2) biodegradable with substantial inactivation, (3) not biodegradable w ith minimal inactivation, and (4) not biodegradable but substantial inactiv ation of cell activity.