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

Abstract

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.

Effects of Bacterial Growth Conditions on Carbon and Chlorine Isotope Fractionation Associated with TCE Biotransformation

“…Similar observations regarding a robust enrichment factor were made for a microbial consortium containing a tceA -D. mccartyi strain regardless of whether biosynthesized cobalamin or exogenous cobalamin was supplied …”

“…17 Similar observations regarding a robust enrichment factor were made for a microbial consortium containing a tceA-D. mccartyi strain regardless of whether biosynthesized cobalamin or exogenous cobalamin was supplied. 51 Effect of Microbial Interaction. In this setup, we investigated whether the transformation activity of strain Y51 grown in coculture with a second OHR bacterium is affected and whether interspecies interactions result in variations of the observable isotope fractionation.…”

Whole genome sequence and 16S rRNA gene amplicon metagenomics of enhanced in-situ reductive dechlorination at a tetrachloroethene-contaminated superfund site

“…Geobacter is known for interactions with other microbes, including the transfer of electrons along specialized pili and the production of cobalamin that can be transferred to cobalamin auxotrophs, such as Dhc [12, 49]. Sulfurospirillum , Acetobacterium and Desulfitobacterium are also cobalamin producers that increase at NRAP [13, 14]. Desulfomonile is a validated OHRG [50].…”

“…Geobacter can produce cobalamin that can be transferred to Dhc , a cobalamin auxotroph [12]. Sulfurospirillum , Acetobacterium and Desulfitobacterium are also cobalamin producers found in dechlorinating consortia [13, 14], exemplifying the importance of syntrophy in the utilization of OH as an energy source [15].…”