Civil and Environmental Engineering, ‡Chemical Engineering, and §Department of Statistics, Stanford University , Stanford, California 94305, United States.
Chemical Engineering & Applied Chemistry, and ⊥Cell and Systems Biology, University of Toronto , Toronto, Ontario M5S 3E5, Canada.
Environ Sci Technol. 2016 Nov 15;50(22):12187-12196. doi: 10.1021/acs.est.6b02957. Epub 2016 Nov 3.
Bioremediation of groundwater contaminated with chlorinated aliphatic hydrocarbons such as perchloroethene and trichloroethene can result in the accumulation of the undesirable intermediate vinyl chloride. Such accumulation can either be due to the absence of specific vinyl chloride respiring Dehalococcoides mccartyi or to the inhibition of such strains by the metabolism of other microorganisms. The fitness of vinyl chloride respiring Dehalococcoides mccartyi subpopulations is particularly uncertain in the presence of chloroethene/chloroethane cocontaminant mixtures, which are commonly found in contaminated groundwater. Therefore, we investigated the structure of Dehalococcoides populations in a continuously fed reactor system under changing chloroethene/ethane influent conditions. We observed that increasing the influent ratio of 1,2-dichloroethane to trichloroethene was associated with ecological selection of a tceA-containing Dehalococcoides population relative to a vcrA-containing Dehalococcoides population. Although both vinyl chloride and 1,2-dichloroethane could be simultaneously transformed to ethene, prolonged exposure to 1,2-dichloroethane diminished the vinyl chloride transforming capacity of the culture. Kinetic tests revealed that dechlorination of 1,2-dichloroethane by the consortium was strongly inhibited by cis-dichloroethene but not vinyl chloride. Native polyacrylamide gel electrophoresis and mass spectrometry revealed that a trichloroethene reductive dehalogenase (TceA) homologue was the most consistently expressed of four detectable reductive dehalogenases during 1,2-dichloroethane exposure, suggesting that it catalyzes the reductive dihaloelimination of 1,2-dichloroethane to ethene.
地下水受氯代脂肪烃（如氯乙烯和三氯乙烯）污染后，可采用生物修复技术进行处理，但可能会导致不良中间产物 vinyl chloride 的积累。这种积累可能是由于缺乏特定的 vinyl chloride 呼吸型 Dehalococcoides mccartyi，也可能是由于其他微生物的代谢物对这种菌株的抑制。在含有氯乙烯/氯乙烷共污染物混合物的情况下，氯乙烯呼吸型 Dehalococcoides mccartyi 亚群的适应性尤其不确定，而这种混合物在受污染的地下水中很常见。因此，我们在一个连续进料的反应器系统中，研究了在不断变化的氯乙烯/乙烷进料条件下 Dehalococcoides 种群的结构。我们观察到，随着 1,2-二氯乙烷与三氯乙烯进料比的增加，相对于含有 vcrA 的 Dehalococcoides 种群，含有 tceA 的 Dehalococcoides 种群在生态上得到了选择。尽管氯乙烯和 1,2-二氯乙烷都可以同时转化为乙烯，但长时间暴露于 1,2-二氯乙烷会降低培养物的氯乙烯转化能力。动力学测试表明， consortium 对 1,2-二氯乙烷的脱氯作用受到顺式-二氯乙烯的强烈抑制，而不受氯乙烯的抑制。原生聚丙烯酰胺凝胶电泳和质谱分析表明，在 1,2-二氯乙烷暴露期间，四种可检测的还原脱卤酶中，一种三氯乙烯还原脱卤酶（TceA）同工酶的表达最为一致，表明它催化 1,2-二氯乙烷的还原二卤代消除反应，生成乙烯。
