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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.


Related in: MedlinePlus

The kinetic isotope effect (KIE) of microbial CO utilization using a Rayleigh Distillation Equation (RDE) (Mariotti et al., 1981). The fractionation factor (α) is equal to 1 plus the slope of a linear regression of ln(R/Ro) vs. ln(C/Co) determined from experimental data, where Ro is the initial isotopic ratio (13C/12C) of the CO and R is the isotopic ratio of the CO at time t, and Co is the initial concentration of CO and C is the concentration of CO at time t (Scott et al., 2004). Fractionation factors are often reported as enrichment values [ε = 1000 × (α − 1)].
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Figure 7: The kinetic isotope effect (KIE) of microbial CO utilization using a Rayleigh Distillation Equation (RDE) (Mariotti et al., 1981). The fractionation factor (α) is equal to 1 plus the slope of a linear regression of ln(R/Ro) vs. ln(C/Co) determined from experimental data, where Ro is the initial isotopic ratio (13C/12C) of the CO and R is the isotopic ratio of the CO at time t, and Co is the initial concentration of CO and C is the concentration of CO at time t (Scott et al., 2004). Fractionation factors are often reported as enrichment values [ε = 1000 × (α − 1)].

Mentions: The results from the CO utilization experiments demonstrated that CO was utilized by microorganisms from the WHC2 pool. In the non-labeled CO experiments, the residual CO concentration decreased on average 62% over 60 days in live experiments. At the same time, the residual CO became on average 10.1 ± 1.5‰ more enriched in 13C in the live non-labeled CO experiments. Therefore, there was most likely a biological process occurring whereby CO containing 12C was utilized faster than CO containing 13C causing the 13C/12C ratio of the residual CO to increase over time. The kinetic isotopic fractionation can be determined using the Rayleigh Distillation Equation (RDE) (Figure 7). The isotopic enrichment factor determined for both live non-labeled CO addition experiments were fairly consistent (−11.3 and −11.0‰) (Figure 7), demonstrating that the isotopic fractionations in both experiments were consistent. The correlation coefficients for the regression lines were 0.8792 and 0.8970, indicating that the data were well described by the RDE in both experiments; however, the high R2 values are driven by binomial dispersion of the data (Figure 7). Additional experiments should be performed to continue to quantify the kinetic isotope fractionation of the microbial CO utilization in these systems. The RDE applied to the killed controls had very poor correlation coefficients for the regression lines (averaging 0.1608). This is not surprising as the δ13C of CO remained fairly constant in the killed controls, while the concentrations varied.


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)

The kinetic isotope effect (KIE) of microbial CO utilization using a Rayleigh Distillation Equation (RDE) (Mariotti et al., 1981). The fractionation factor (α) is equal to 1 plus the slope of a linear regression of ln(R/Ro) vs. ln(C/Co) determined from experimental data, where Ro is the initial isotopic ratio (13C/12C) of the CO and R is the isotopic ratio of the CO at time t, and Co is the initial concentration of CO and C is the concentration of CO at time t (Scott et al., 2004). Fractionation factors are often reported as enrichment values [ε = 1000 × (α − 1)].
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: The kinetic isotope effect (KIE) of microbial CO utilization using a Rayleigh Distillation Equation (RDE) (Mariotti et al., 1981). The fractionation factor (α) is equal to 1 plus the slope of a linear regression of ln(R/Ro) vs. ln(C/Co) determined from experimental data, where Ro is the initial isotopic ratio (13C/12C) of the CO and R is the isotopic ratio of the CO at time t, and Co is the initial concentration of CO and C is the concentration of CO at time t (Scott et al., 2004). Fractionation factors are often reported as enrichment values [ε = 1000 × (α − 1)].
Mentions: The results from the CO utilization experiments demonstrated that CO was utilized by microorganisms from the WHC2 pool. In the non-labeled CO experiments, the residual CO concentration decreased on average 62% over 60 days in live experiments. At the same time, the residual CO became on average 10.1 ± 1.5‰ more enriched in 13C in the live non-labeled CO experiments. Therefore, there was most likely a biological process occurring whereby CO containing 12C was utilized faster than CO containing 13C causing the 13C/12C ratio of the residual CO to increase over time. The kinetic isotopic fractionation can be determined using the Rayleigh Distillation Equation (RDE) (Figure 7). The isotopic enrichment factor determined for both live non-labeled CO addition experiments were fairly consistent (−11.3 and −11.0‰) (Figure 7), demonstrating that the isotopic fractionations in both experiments were consistent. The correlation coefficients for the regression lines were 0.8792 and 0.8970, indicating that the data were well described by the RDE in both experiments; however, the high R2 values are driven by binomial dispersion of the data (Figure 7). Additional experiments should be performed to continue to quantify the kinetic isotope fractionation of the microbial CO utilization in these systems. The RDE applied to the killed controls had very poor correlation coefficients for the regression lines (averaging 0.1608). This is not surprising as the δ13C of CO remained fairly constant in the killed controls, while the concentrations varied.

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.


Related in: MedlinePlus