Vitamin B12 effects on chlorinated methanes-degrading microcosms: Dual isotope and metabolically active microbial populations assessment
Author(s)
Rodriguez-Fernandez, Diana
Guivernau, Miriam
Vinas, Marc
Soler, Albert
Domenèch, Christina
Rosell, Mònica
Date issued
October 2017
In
Science of the Total Environment
No
621
From page
1615
To page
1625
Subjects
Carbon tetrachloride Chloroform CSIA Carbon chlorine isotope plot MiSeq high-throughput sequencing Pseudomonas stutzeri
Abstract
Field-derived anoxic microcosms were used to characterize chloroform (CF) and carbon tetrachloride (CT) natural
attenuation to compare it with biostimulation scenarios in which vitamin B12 was added (B12/pollutant
ratio of 0.01 and 0.1) by means of by-products, carbon and chlorine compound-specific stable-isotope analysis,
and the active microbial community through 16S rRNA MiSeq high-throughput sequencing. Autoclaved slurry
controls discarded abiotic degradation processes. B12 catalyzed CF and CT biodegradation without the accumulation
of dichloromethane, carbon disulphide, or CF. The carbon isotopic fractionation value of CF (ƐCCF) with B12
was −14 ± 4‰, and the value for chlorine (ƐClCF) was −2.4 ± 0.4‰. The carbon isotopic fractionation values
of CT (ƐCCT) were−16±6 with B12, and−13±2‰without B12; and the chlorine isotopic fractionation values
of CT (ƐClCT)were−6±3and−4±2‰, respectively. Acidovorax, Ancylobacter, andPseudomonaswere themost
metabolically active genera,whereas Dehalobacter and Desulfitobacteriumwere below0.1% of relative abundance.
The dual C-Cl element isotope slope (Λ = Δδ13C/Δδ37Cl) for CF biodegradation (only detected with B12, 7 ± 1)
was similar to that reported for CF reduction by Fe(0) (8 ± 2). Several reductive pathways might be competing
in the tested CT scenarios, as evidenced by the lack of CF accumulation when B12 was added, which might be
linked to a major activity of Pseudomonas stutzeri; by different chlorine apparent kinetic isotope effect values
and Λ which was statistically different with and without B12 (5 ± 1 vs 6.1 ± 0.5), respectively. Thus, positive
B12 effects such as CT and CF degradation catalyst were quantified for the first time in isotopic terms, and confirmedwith
themajor activity of species potentially capable of their degradation.Moreover, the indirect benefits
attenuation to compare it with biostimulation scenarios in which vitamin B12 was added (B12/pollutant
ratio of 0.01 and 0.1) by means of by-products, carbon and chlorine compound-specific stable-isotope analysis,
and the active microbial community through 16S rRNA MiSeq high-throughput sequencing. Autoclaved slurry
controls discarded abiotic degradation processes. B12 catalyzed CF and CT biodegradation without the accumulation
of dichloromethane, carbon disulphide, or CF. The carbon isotopic fractionation value of CF (ƐCCF) with B12
was −14 ± 4‰, and the value for chlorine (ƐClCF) was −2.4 ± 0.4‰. The carbon isotopic fractionation values
of CT (ƐCCT) were−16±6 with B12, and−13±2‰without B12; and the chlorine isotopic fractionation values
of CT (ƐClCT)were−6±3and−4±2‰, respectively. Acidovorax, Ancylobacter, andPseudomonaswere themost
metabolically active genera,whereas Dehalobacter and Desulfitobacteriumwere below0.1% of relative abundance.
The dual C-Cl element isotope slope (Λ = Δδ13C/Δδ37Cl) for CF biodegradation (only detected with B12, 7 ± 1)
was similar to that reported for CF reduction by Fe(0) (8 ± 2). Several reductive pathways might be competing
in the tested CT scenarios, as evidenced by the lack of CF accumulation when B12 was added, which might be
linked to a major activity of Pseudomonas stutzeri; by different chlorine apparent kinetic isotope effect values
and Λ which was statistically different with and without B12 (5 ± 1 vs 6.1 ± 0.5), respectively. Thus, positive
B12 effects such as CT and CF degradation catalyst were quantified for the first time in isotopic terms, and confirmedwith
themajor activity of species potentially capable of their degradation.Moreover, the indirect benefits
Publication type
journal article
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