05). When acetylene was added in conjunction with ethanol in the presence of mixtures of chlorinated alkenes or alkanes, no significant degradation was observed (Table 1). In the presence of either mixture, the microbial growth rate was significantly reduced as compared with that in the presence of ethanol
and acetylene, i.e., 0.14±0.03 and 0.09±0.04 day−1 for growth on ethanol and acetylene in the presence of chlorinated alkenes and alkanes, respectively, as compared with a growth rate of 0.28±0.0001 day−1 in the presence of ethanol and acetylene only Staurosporine chemical structure (Table 2). The overall growth of Methylocystis strain SB2 in the presence of these mixtures, however, as measured by OD600 nm, was not significantly different from growth in the presence
of ethanol and acetylene (Table 2). Here, it is shown that Methylocystis strain SB2 can degrade a variety of chlorinated hydrocarbons when grown on either methane or ethanol, and that this degradation is due to pMMO activity under both growth conditions. Specifically, the addition of acetylene, a specific inhibitor of pMMO, to Methylocystis strain SB2 grown on ethanol led to no degradation of any compound, but growth still occurred. Further, all the chlorinated hydrocarbons were, individually, potent inhibitors of the growth of Methylocystis strain SB2 on methane. With the exception of 1,1,1-TCA, however, individual chlorinated hydrocarbons had little effect on the growth of this strain on ethanol, indicating that competitive inhibition of pMMO by chlorinated hydrocarbons was at least partly (-)-p-Bromotetramisole Oxalate selleck compound responsible for the reduced growth of Methylocystis strain SB2 on methane. The data also indicated that
not only did the compounds act as competitive inhibitors of pMMO activity, some substrate toxicity was also evident, particularly when combinations of chlorinated hydrocarbons were added. Specifically, although very little degradation of 1,1,1-TCA, DCM, and CF was observed when these compounds were added together for both methane and ethanol-grown cells, growth was substantially reduced. Further, the addition of acetylene to ethanol-grown cells eliminates the possibility of product toxicity as pMMO was inactivated, but reduced growth rates of Methylocystis strain SB2 were still apparent on combinations of both chlorinated alkanes and alkenes, suggesting that the total concentration of chlorinated hydrocarbons is an important issue that can limit the overall methanotrophic activity at high levels. These data extend the previous finding that the facultative methanotroph Methylocystis strain SB2 can degrade chlorinated hydrocarbons when grown on acetate (Yoon et al., 2011) by showing that this strain can also degrade such compounds when grown on ethanol.