Potential Role of Methanogens in Microbial Reductive Dechlorination of Organic Chlorinated Pollutants In Situ

Abstract

Previous studies often attribute microbial reductive dechlorination to organohalide-respiring bacteria (OHRB) or cometabolic dechlorination bacteria (CORB). Even though methanogenesis frequently occurs during dechlorination of organic chlorinated pollutants (OCPs) in situ, the underestimated effect of methanogens and their interactions with dechlorinators remains unknown. We investigated the association between dechlorination and methanogenesis, as well as the performance of methanogens involved in reductive dechlorination, through the use of meta-analysis, incubation experiment, untargeted metabolomic analysis, and thermodynamic modeling approaches. The meta-analysis indicated that methanogenesis is largely synchronously associated with OCP dechlorination, that OHRB are not the sole degradation engineers that maintain OCP bioremediation, and that methanogens are fundamentally needed to sustain microenvironment functional balance. Laboratory results further confirmed that Methanosarcina barkeri (M. barkeri) promotes the dechlorination of γ-hexachlorocyclohexane (γ-HCH). Untargeted metabolomic analysis revealed that the application of γ-HCH upregulated the metabolic functioning of chlorocyclohexane and chlorobenzene degradation in M. barkeri, further confirming that M. barkeri potentially possesses an auxiliary dechlorination function. Finally, quantum analysis based on density functional theory (DFT) indicated that the methanogenic coenzyme F430 significantly reduces the activation barrier to dechlorination. Collectively, this work suggests that methanogens are highly involved in microbial reductive dechlorination at OCPcontaminated sites and may even directly favor OCP degradation.

Long-Term Dechlorination of Polychlorinated Biphenyls (PCBs) in Taihu Lake Sediment Microcosms: Identification of New Pathways, PCB-Driven Shifts of Microbial Communities, and Insights into Dechlorination Potential

“…Our previous studies found that PCB71 and PCB149 could be extensively dechlorinated in Hudson and Grasse River sediments with similar levels of Dehalococcoides but with a more prevalent methane production. , It was reported that methanogens might assist dechlorination through the activity of coenzyme F430 . The methanogenic coenzyme F430 was demonstrated to significantly reduce the energy barrier to dechlorination …”

“…66 The methanogenic coenzyme F430 was demonstrated to significantly reduce the energy barrier to dechlorination. 67 The response of microbes to PCB dechlorination was further demonstrated through the analysis of the microbial community composition. PCBs remarkedly decreased the microbial community richness and evenness and drove the shifts of the microbial community composition.…”

Quantitative Extraction and Evaluation of Tomato Fruit Phenotypes Based on Image Recognition

“…Quantitative phenotyping tools also allow researchers to delve deeper into the mechanisms behind the formation of certain traits in tomato fruit at the genetic level ( Marefatzadeh-Khameneh et al, 2021 ). Research on the association network analysis between tomato fruit color and metabolic pathways would possibly be accelerated further as well ( Hu et al, 2020 ; Yuan et al, 2021 ).…”

Offshore Marine Sediment Microbiota Respire Structurally Distinct Organohalide Pollutants

“…Despite the changes in taxonomic composition during enrichment (Figure a), fermentative (e.g., Petrimonas, Sedimentibacter, and Anaerolineaceae), methanogenic (e.g., Methanosarcina and Methanofollis), and sulfate-reducing microorganisms (e.g., Desulfomicrobium and Desulfobulbus), together with Dehalococcoides, were present in the enrichments and original sediment microcosms alike. Some of these none-OHRB microbial populations may contribute to enhancing robustness of dehalogenation, for example, by supplying beneficial nutrients and maintaining anerobic conditions …”

“…Some of these none-OHRB microbial populations may contribute to enhancing robustness of dehalogenation, for example, by supplying beneficial nutrients and maintaining anerobic conditions. 47 Identification of Known Obligate OHRB and RDase Genes. To further quantify the growth of obligate OHRB and identify putative RDase genes responsible for the observed dehalogenation in marine enrichment cultures E, F, and P, qPCR was performed.…”