Growth inhibition of methanogens for the enhancement of TCE dechlorination

Wei

Water Science and Technology

et al. 2022

Complete dechlorination of trichloroethene (TCE) by Dehalococcoides mccartyi is catalyzed by reductive dehalogenases (RDases), which possess cobalamin as the crucial cofactor. However, virtually all D. mccartyi isolated thus far are corrinoid auxotrophs. The exogenous addition of commercially available cobalamin for TCE-contaminated site decontamination is costly. In this study, TCE reduction by a D. mccartyi-containing microbial consortium utilizing biosynthetic cobalamin generated by interior corrinoid-producing organisms within this microbial consortium was studied. The results confirmed that subcultures without exogenous cobalamin in the medium were apparently unaffected and were able to successively metabolize TCE to nonchlorinated ethene. The 2-bromoethanesulfonate and ampicillin resistance tests results suggested that ampicillin-sensitive bacteria rather than methanogenic archaea within this microbial consortium were responsible for biosynthesizing cobalamin. Moreover, relatively stable carbon isotopic enrichment factor (ɛ-carbon) values of TCE were obtained regardless of whether exogenous cobalamin or selective inhibitors existed in the medium, indicating that the cobalamin biosynthesized by these organisms was absorbed and utilized by D. mccartyi for RDase synthesis and eventually participated in TCE reduction. Finally, the Illumina MiSeq sequencing analysis indicated that Desulfitobacterium and Acetobacterium in this microbial consortium were responsible for the de novo cobalamin biosynthesis to fulfill the requirements of D. mccartyi for TCE metabolism.

Section: -Bes and Ampicillin Resistance Tests Of The Exogenous Cobala...mentioning

confidence: 99%

Interspecies transfer of biosynthetic cobalamin for complete dechlorination of trichloroethene by Dehalococcoides mccartyi

Wei

Water Science and Technology

et al. 2022

“…As for bacterial isolates, organohalide-respiring bacteria (OHRB) have been confirmed to be highly effective TCE degrading strains ( Fincker and Spormann, 2017 ), including species from Dehalococcoides ( Maymo-Gatell et al, 1997 ; Maymó-Gatell et al, 1999 ; Gushgari-Doyle and Alvarez-Cohen, 2020 ; Asai et al, 2022 ) and Candidatus Dehalogenimonas ( Chen et al, 2022 ), which can dechlorinate TCE to benign ethene. Besides, strains from Dehalobacter ( Holliger et al, 1998 ; Rupakula et al, 2015 ), Enterobacter ( Kang et al, 2012 ), Clostridium ( Lo et al, 2020 ; Lin et al, 2021 ), and Acidimicrobiaceae ( Ge et al, 2019 ) were also observed to effectively dechlorinate TCE ( Table 3 ). In addition, immobilization technique has been used to alleviate the toxic effect of TCE on cells ( Lo et al, 2020 ), and the advantages including: (1) cells are well protected from adverse conditions, which can be easily recovered from bulk solutions; (2) cells can maintain high density for long time; (3) fixed cell can alleviate the inhibitory effects of high TCE concentrations to cells by avoiding delay times ( Chen et al, 2007 ; Yang et al, 2019 ; Lo et al, 2020 ).…”

Section: Biodegradation Of Tcementioning

confidence: 99%

Recent advances and trends of trichloroethylene biodegradation: A critical review

Man

Niu

et al. 2022

Front. Microbiol.

Trichloroethylene (TCE) is a ubiquitous chlorinated aliphatic hydrocarbon (CAH) in the environment, which is a Group 1 carcinogen with negative impacts on human health and ecosystems. Based on a series of recent advances, the environmental behavior and biodegradation process on TCE biodegradation need to be reviewed systematically. Four main biodegradation processes leading to TCE biodegradation by isolated bacteria and mixed cultures are anaerobic reductive dechlorination, anaerobic cometabolic reductive dichlorination, aerobic co-metabolism, and aerobic direct oxidation. More attention has been paid to the aerobic co-metabolism of TCE. Laboratory and field studies have demonstrated that bacterial isolates or mixed cultures containing Dehalococcoides or Dehalogenimonas can catalyze reductive dechlorination of TCE to ethene. The mechanisms, pathways, and enzymes of TCE biodegradation were reviewed, and the factors affecting the biodegradation process were discussed. Besides, the research progress on material-mediated enhanced biodegradation technologies of TCE through the combination of zero-valent iron (ZVI) or biochar with microorganisms was introduced. Furthermore, we reviewed the current research on TCE biodegradation in field applications, and finally provided the development prospects of TCE biodegradation based on the existing challenges. We hope that this review will provide guidance and specific recommendations for future studies on CAHs biodegradation in laboratory and field applications.

“…In contrast, methanogens consume a large amount of H 2 (an electron donor for both methanogenesis and dehalogenation) , and may compete with OHRB for corrinoids in mixed dehalogenating cultures . Further, the growth inhibition of methanogens is beneficial to trichloroethene dechlorination and the enrichment of OHRB . Solid evidence of the relationship between methanogenesis and dehalogenation (especially for widespread HOCs) is currently insufficient, but still essential because methanogenesis is an ecological hotspot issue.…”

Section: Introductionmentioning

confidence: 99%

“…23 Further, the growth inhibition of methanogens is beneficial to trichloroethene dechlorination and the enrichment of OHRB. 24 Solid evidence of the relationship between methanogenesis and dehalogenation (especially for widespread HOCs) is currently insufficient, but still essential because methanogenesis is an ecological hotspot issue. At present, traditional cultivation techniques combined with multiomics and statistical methods (e.g., model-based gene prediction and expression and correlation analyses) can provide an accurate and in-depth understanding of the metabolic potential and environmental adaptation of microorganisms as well as interspecies synergistic interactions.…”

Section: Introductionmentioning

confidence: 99%

Marine Dehalogenator and Its Chaperones: Microbial Duties and Responses in 2,4,6-Trichlorophenol Dechlorination

Deng

Chen²,

Wang³

et al. 2023

Environ. Sci. Technol.

Marine environments contain diverse halogenated organic compounds (HOCs), both anthropogenic and natural, nourishing a group of versatile organohalide-respiring bacteria (OHRB). Here, we identified a novel OHRB (Peptococcaceae DCH) with conserved motifs but phylogenetically diverse reductive dehalogenase catalytic subunit (RdhAs) from marine enrichment culture. Further analyses clearly demonstrate the horizontal gene transfer of rdhAs among marine OHRB. Moreover, 2,4,6-trichlorophenol (TCP) was dechlorinated to 2,4-dichlorophenol and terminated at 4-chlorophenol in culture. Dendrosporobacter and Methanosarcina were the two dominant genera, and the constructed and verified metabolic pathways clearly demonstrated that the former provided various substrates for other microbes, while the latter drew nutrients, but might provide little benefit to microbial dehalogenation. Furthermore, Dendrosporobacter could readily adapt to TCP, and sporulation-related proteins of Dendrosporobacter were significantly upregulated in TCP-free controls, whereas other microbes (e.g., Methanosarcina and Aminivibrio) became more active, providing insights into how HOCs shape microbial communities. Additionally, sulfate could affect the dechlorination of Peptococcaceae DCH, but not debromination. Considering their electron accessibility and energy generation, the results clearly demonstrate that bromophenols are more suitable than chlorophenols for the enrichment of OHRB in marine environments. This study will greatly enhance our understanding of marine OHRB (rdhAs), auxiliary microbes, and microbial HOC adaptive mechanisms.