Phylogenetic Analysis of TCE-Dechlorinating Consortia Enriched on a Variety of Electron Donors

Abstract

Two rapidly fermented electron donors, lactate and methanol, and two slowly fermented electron donors, propionate and butyrate, were selected for enrichment studies to evaluate the characteristics of anaerobic microbial consortia that reductively dechlorinate TCE to ethene. Each electron donor enrichment subculture demonstrated the ability to dechlorinate TCE to ethene through several serial transfers. Microbial community analyses based upon 16S rDNA, including terminal restriction fragment length polymorphism (T-RFLP) and clone library/sequencing, were performed to assess major changes in microbial community structure associated with electron donors capable of stimulating reductive dechlorination. Results demonstrated that five phylogenic subgroups or genera of bacteria were present in all consortia, including Dehalococcoides sp., low G+C Gram-positives (mostly Clostridium and Eubacterium sp.), Bacteroides sp., Citrobacter sp., and delta Proteobacteria (mostly Desulfovibrio sp.). Phylogenetic association indicates that only minor shifts in the microbial community structure occurred between the four alternate electron donor enrichments and the parent consortium. Inconsistent detection of Dehalococcoides spp. in clone libraries and T-RFLP of enrichment subcultures was resolved using quantitative polymerase chain reaction (Q-PCR). Q-PCR with primers specific to Dehalococcoides 16S rDNA resulted in positive detection of this species in all enrichments. Our results suggest that TCE-dechlorinating consortia can be stably maintained on a variety of electron donors and that quantities of Dehalococcoides cells detected with Dehalococcoides specific 16S rDNA primer/probe sets do not necessarily correlate well with solvent degradation rates.

Biostimulation of Indigenous Microbial Communities for Anaerobic Transformation of Pentachlorophenol in Paddy Soils of Southern China

“…33 Lactate is a good electron donor for the respiration of a wide range of microorganisms in contaminant transformation. 34 The dechlorinating and iron-reducing bacteria identified in the present study can also utilize lactate as an electron donor to stimulate the reductive dechlorination of PCP. The continuous dechlorination in lactate-fed systems with higher electron concentration transferred and increased the amount of generated active Fe(II) species, as shown in the MFC results (Figure 4).…”

“…2,3,5,6-TeCP and 2,3,5-TCP, with one and two chlorines, respectively, dechlorinated in the PCP molecular structure, were determined in PCP transformation, and the concentrations were continuously increased, accompanied by PCP concentration decreasing, suggesting that the transformation processes underwent reductive dechlorination reaction under anaerobic conditions. 34 The two soils used in the present study have high Fe 2 O 3 contents and relatively high ratios of iron minerals (Table 1S of the SI). Iron cycle reactions may affect the transformation process, and the reduced Fe(II) in soils enhances the transformation of PCP in soil minerals.…”

Enrichment and Characterization of a Trichloroethene-Dechlorinating Consortium Containing Multiple “Dehalococcoides” Strains

“…Bacteroidetes populations have been identified in many dechlorinating mixed cultures, including the KB-1 and ANAS cultures. [41][42][43] Spirochaetes populations have been also detected in chloroethenes-dechlorinating consortia. [43][44][45][46] The RDP SeqMatch analysis for the Spirochaetes representative showed the highest score (0.833) to the genus Treponema, specifically, Spirochaetes bacterium SA-8 (AY695839).…”

Distribution of Dehalococcoides 16S rRNA and Dehalogenase Genes in Contaminated Sites

“…Bacterial 16S rRNA was quantified using the primers BAC338F and BAC805R, and the probe BAC516F (Yu, Lee, Kim, & Hwang, 2005). We used primers and probes specific for the Dehalococcoides 16S rRNA gene published by Freeborn et al (2005). To assay reductive dehalogenase genes, specific primers and probe were used: the primers TceA1270F and TceA1336R and the quenching antisense probe TceA1294 (Johnson, Lee, Holmes, & Alvarez-Cohen, 2005) for tceA; the primers Bvc925F and Bvc1017R and the antisense probe Bvc977 for bvcA; and the primers Vcr1022F and Vcr1093R and antisense probe Vcr1042 for vcrA.…”