Microbial Diversity of Chlorinated Compounds Degrading Bacteria by Molecular Biological Techniques

Abstract

Tetrachloroethene (PCE) and trichloroethene (TCE) are common groundwater contaminants that also impact river flats, especially near urban and industrial areas. However, very little is known about dechlorinating microbial communities in river flats. Titanium pyrosequencing, 16S rRNA gene clone libraries, and dechlorinator-targeted PCR characterize the reductive dechlorinating activities and populations in river sediments collected from Wonju River in South Korea. Four times enrichment process were performed to obtain a more enriched dechlorinating bacteria community, and the final enrichment culture was studied in detail. 2-Bromoethanesulfonic acid was added in B2 but not in B3. The chlorinated ethenes were detected by gas chromatography with a HP-5 column. The dechlorinating mechanism was different between the two enrichment cultures B2 and B3. In the microcosms of B2, PCE dechlorination to TCE began within 10 days, and nearly 100% of the initial amount of PCE was converted to TCE after 12 days. In addition, cis-1,2-Dichloroethene (cis-DCE) was observed after TCE transformed. In B3, PCE was almost directly transformed to cis-DCE with no detectable TCE formation. cis-DCE was observed as the dechlorination end product in both of the enrichment cultures. Pyrosequencing of bacterial 16S rRNA genes revealed that Desulfovibrio populations were predominant in B2 and that Desulfotomaculum populations were predominant in B3. Other abundant groups included Geobacter, Treponema, Denitrobacterium, Tepidimicrobium, Zunongwangia in the B2 and B3 enrichment cultures. The results suggest that BES accounts for the different pathways of these two enrichment cultures, which were from the same originator. Moreover, titanium pyrosequencing provides more detailed insight into the community structure dynamics of dechlorinating microcosms than conventional 16S rRNA gene sequencing. A total of seventeen strains were isolated from B2 and B3. Two of seventeen belonged to Desulfovibrio a...