Division of Environmental Science and Engineering, National University of Singapore, Singapore.
ISME J. 2010 Jan;4(1):88-97. doi: 10.1038/ismej.2009.90. Epub 2009 Aug 6.
In the microbial reductive dechlorination of tetrachloroethene (PCE) and trichloroethene (TCE), dechlorinators usually produce cis-1,2-dichloroethene (cis-DCE) as the predominant product or an intermediate. This study shows that dechlorination of PCE and TCE can also lead to the generation of trans-1,2-dichloroethene (trans-DCE) by a co-culture MB. During its enrichment process, the ratio of trans- to cis-DCE increased from 1.4 (+/-0.1):1-3.7 (+/-0.4):1, whereas the TCE reductive dechlorination rate went up from approximately 26.2 to approximately 68.8 micromol l(-1) day(-1). PCR-denaturing gradient gel electrophoresis (PCR-DGGE) revealed that the increased ratio of trans- /cis-DCE was well correlated with the increased proportions of Dehalococcoides and the disappearance of Desulfuromonas during the enrichment process. As shown by PCR-DGGE, similar Dehalococcoides species were consistently present in another three sediment-free cultures with various trans- /cis-DCE ratios. The 16S rRNA gene sequence of this Dehalococcoides sp. in co-culture MB is 100% identical (over 1489 bp) to that of Dehalococcoides ethenogenes strain 195 (CP000027), which belongs to the Cornell subgroup of the Dehalococcoides cluster. The other bacterium in this co-culture MB was a Sedimentibacter species, which showed no PCE or TCE dechlorination activity. Results from this study show that microbial dechlorination of chloroethenes by this particular subgroup of Dehalococcoides could result in significant accumulation of trans-DCE in the environment if no trans-DCE dechlorinators coexist in the contaminated sites.
在四氯乙烯 (PCE) 和三氯乙烯 (TCE) 的微生物还原脱氯过程中，脱氯菌通常会将顺式-1,2-二氯乙烯 (顺式-DCE) 作为主要产物或中间产物产生。本研究表明，PCE 和 TCE 的脱氯反应也可以通过共培养 MB 产生反式-1,2-二氯乙烯 (反式-DCE)。在其富集过程中，反式-DCE 与顺式-DCE 的比例从 1.4(+/-0.1):1-3.7(+/-0.4):1 增加到 26.2 增加到约 68.8 µm l(-1) day(-1)。聚合酶链反应-变性梯度凝胶电泳 (PCR-DGGE) 显示，反式-DCE 比例的增加与 Dehalococcoides 比例的增加以及富集过程中 Desulfuromonas 的消失密切相关。如 PCR-DGGE 所示，在另外三个无沉积物培养物中，始终存在具有不同反式-DCE 比例的类似 Dehalococcoides 种。共培养 MB 中这种 Dehalococcoides sp. 的 16S rRNA 基因序列与 Dehalococcoides ethenogenes 菌株 195(CP000027)完全相同(超过 1489 bp)，属于 Dehalococcoides 聚类的 Cornell 亚群。共培养 MB 中的另一种细菌是 Sedimentibacter 种，它没有表现出 PCE 或 TCE 的脱氯活性。本研究结果表明，如果污染地点没有共存的反式-DCE 脱氯菌，这种特定的 Dehalococcoides 亚群对氯代烯烃的微生物脱氯反应可能会导致反式-DCE 在环境中的大量积累。
