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Investigations of potential microbial methanogenic and carbon monoxide utilization pathways in ultra-basic reducing springs associated with present-day continental serpentinization: the Tablelands, NL, CAN.

Morrill PL, Brazelton WJ, Kohl L, Rietze A, Miles SM, Kavanagh H, Schrenk MO, Ziegler SE, Lang SQ - Front Microbiol (2014)

Bottom Line: Ultra-basic reducing springs at continental sites of serpentinization act as portals into the biogeochemistry of a subsurface environment with H2 and CH4 present.The average isotopic enrichment factor resulting from this microbial utilization of CO was estimated to be 11.2 ± 0.2‰.This indicates that in our experiments, CO was used primarily as an energy source, but not for biomass growth.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Sciences, Memorial University St. John's, NL, Canada.

ABSTRACT
Ultra-basic reducing springs at continental sites of serpentinization act as portals into the biogeochemistry of a subsurface environment with H2 and CH4 present. Very little, however, is known about the carbon substrate utilization, energy sources, and metabolic pathways of the microorganisms that live in this ultra-basic environment. The potential for microbial methanogenesis with bicarbonate, formate, acetate, and propionate precursors and carbon monoxide (CO) utilization pathways were tested in laboratory experiments by adding substrates to water and sediment from the Tablelands, NL, CAD, a site of present-day continental serpentinization. Microbial methanogenesis was not observed after bicarbonate, formate, acetate, or propionate addition. CO was consumed in the live experiments but not in the killed controls and the residual CO in the live experiments became enriched in (13)C. The average isotopic enrichment factor resulting from this microbial utilization of CO was estimated to be 11.2 ± 0.2‰. Phospholipid fatty acid concentrations and δ(13)C values suggest limited incorporation of carbon from CO into microbial lipids. This indicates that in our experiments, CO was used primarily as an energy source, but not for biomass growth. Environmental DNA sequencing of spring fluids collected at the same time as the addition experiments yielded a large proportion of Hydrogenophaga-related sequences, which is consistent with previous metagenomic data indicating the potential for these taxa to utilize CO.

No MeSH data available.


Average δ13C of PLFAs from live 13C-labeled CO (13C Live) and live non-labeled CO (Live) treatments. The values reported for the live 13C-labeled treatments are average values of replicate experiments, while the values reported for the live treatments are an average of two bottles, as one broke during freezing. The error bars are the standard deviations of the averages.
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Figure 6: Average δ13C of PLFAs from live 13C-labeled CO (13C Live) and live non-labeled CO (Live) treatments. The values reported for the live 13C-labeled treatments are average values of replicate experiments, while the values reported for the live treatments are an average of two bottles, as one broke during freezing. The error bars are the standard deviations of the averages.

Mentions: For the most part the δ13C of the PLFAs were similar in the live 13C-labeled CO compared to the live non-labeled CO experiments [i.e., incubated with CO with a natural abundance of 13C/12C (δ13CCO = −44.4‰)] with the majority of individual PLFA (i.e., cy17:0, 18:1ω 7, 18:1ω 9, and cy19:0) having well constrained δ13C values between −27.2 and −24.2‰ in all treatments (Table 2, Figure 6). However, the uptake of the 13C into two individual PLFAs was detected, indicating that some microbial taxa incorporated CO into their biomass while others did not (Table 2, Figure 6). The PLFA associated with gram negative bacteria, 16:1ω 7, had more negative δ13C than other PLFA in live non 13C CO-labeled experiments (−38.0 ± 3.5‰ and −34.1 ± 0.4‰), likely due to the very negative δ13C of the CO used for the experiment (−44.4‰), and less negative but variable δ13C values in live microcosms incubated with 13C-labeled CO (−29.5 ± 0.5‰, −26.0 ± 0.5‰, and −11.8 ± 0.5‰). The same trend was present in the non-specific PLFA, 16:0, but to a much lesser extent (Table 2, Figure 6). Additionally, the δ13C of 16:0 and 16:1ω 7 were highly correlated (R = 0.94, p = 0.0005). However, the difference in δ13C between labeled and non-labeled experiments (up to 26‰) was very low compared to the high concentration in 13C in CO in the labeled microcosms which was greater than 2800‰, indicating that carbon that resulted from CO fixation made up <1% of PLFA.


Investigations of potential microbial methanogenic and carbon monoxide utilization pathways in ultra-basic reducing springs associated with present-day continental serpentinization: the Tablelands, NL, CAN.

Morrill PL, Brazelton WJ, Kohl L, Rietze A, Miles SM, Kavanagh H, Schrenk MO, Ziegler SE, Lang SQ - Front Microbiol (2014)

Average δ13C of PLFAs from live 13C-labeled CO (13C Live) and live non-labeled CO (Live) treatments. The values reported for the live 13C-labeled treatments are average values of replicate experiments, while the values reported for the live treatments are an average of two bottles, as one broke during freezing. The error bars are the standard deviations of the averages.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230201&req=5

Figure 6: Average δ13C of PLFAs from live 13C-labeled CO (13C Live) and live non-labeled CO (Live) treatments. The values reported for the live 13C-labeled treatments are average values of replicate experiments, while the values reported for the live treatments are an average of two bottles, as one broke during freezing. The error bars are the standard deviations of the averages.
Mentions: For the most part the δ13C of the PLFAs were similar in the live 13C-labeled CO compared to the live non-labeled CO experiments [i.e., incubated with CO with a natural abundance of 13C/12C (δ13CCO = −44.4‰)] with the majority of individual PLFA (i.e., cy17:0, 18:1ω 7, 18:1ω 9, and cy19:0) having well constrained δ13C values between −27.2 and −24.2‰ in all treatments (Table 2, Figure 6). However, the uptake of the 13C into two individual PLFAs was detected, indicating that some microbial taxa incorporated CO into their biomass while others did not (Table 2, Figure 6). The PLFA associated with gram negative bacteria, 16:1ω 7, had more negative δ13C than other PLFA in live non 13C CO-labeled experiments (−38.0 ± 3.5‰ and −34.1 ± 0.4‰), likely due to the very negative δ13C of the CO used for the experiment (−44.4‰), and less negative but variable δ13C values in live microcosms incubated with 13C-labeled CO (−29.5 ± 0.5‰, −26.0 ± 0.5‰, and −11.8 ± 0.5‰). The same trend was present in the non-specific PLFA, 16:0, but to a much lesser extent (Table 2, Figure 6). Additionally, the δ13C of 16:0 and 16:1ω 7 were highly correlated (R = 0.94, p = 0.0005). However, the difference in δ13C between labeled and non-labeled experiments (up to 26‰) was very low compared to the high concentration in 13C in CO in the labeled microcosms which was greater than 2800‰, indicating that carbon that resulted from CO fixation made up <1% of PLFA.

Bottom Line: Ultra-basic reducing springs at continental sites of serpentinization act as portals into the biogeochemistry of a subsurface environment with H2 and CH4 present.The average isotopic enrichment factor resulting from this microbial utilization of CO was estimated to be 11.2 ± 0.2‰.This indicates that in our experiments, CO was used primarily as an energy source, but not for biomass growth.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Sciences, Memorial University St. John's, NL, Canada.

ABSTRACT
Ultra-basic reducing springs at continental sites of serpentinization act as portals into the biogeochemistry of a subsurface environment with H2 and CH4 present. Very little, however, is known about the carbon substrate utilization, energy sources, and metabolic pathways of the microorganisms that live in this ultra-basic environment. The potential for microbial methanogenesis with bicarbonate, formate, acetate, and propionate precursors and carbon monoxide (CO) utilization pathways were tested in laboratory experiments by adding substrates to water and sediment from the Tablelands, NL, CAD, a site of present-day continental serpentinization. Microbial methanogenesis was not observed after bicarbonate, formate, acetate, or propionate addition. CO was consumed in the live experiments but not in the killed controls and the residual CO in the live experiments became enriched in (13)C. The average isotopic enrichment factor resulting from this microbial utilization of CO was estimated to be 11.2 ± 0.2‰. Phospholipid fatty acid concentrations and δ(13)C values suggest limited incorporation of carbon from CO into microbial lipids. This indicates that in our experiments, CO was used primarily as an energy source, but not for biomass growth. Environmental DNA sequencing of spring fluids collected at the same time as the addition experiments yielded a large proportion of Hydrogenophaga-related sequences, which is consistent with previous metagenomic data indicating the potential for these taxa to utilize CO.

No MeSH data available.