Effect of dilution on methanogenesis, hydrogen turnover and interspecies hydrogen transfer in anoxic paddy soil

Conrad, Ralf; Babbel, Monika

doi:10.1111/j.1574-6968.1989.tb03654.x

Cited by 42 publications

(17 citation statements)

References 12 publications

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“…Here, we showed by using the gas diffusion probe that H 2 concentrations in two methanogenic systems were in a range of 10-80 nM. Since this range is comparable to earlier determinations by us, testing various methanogenic environments [10], and is also consistent with measurements applying techniques other than extraction such as gas bubble analysis [34,35] or analysis of gas equilibria under steady-state conditions [22,33], we are confident that H~ concentrations > 10 nM are realistic for methanogenic environments. Furthermore, these H 2 concentrations allow exergonic methanogenesis in a range of Gibbs free energies of -7 to -11 kJ mo1-1 H 2 [3,36].…”

Section: Measurement Of Vertical Profilessupporting

confidence: 87%

“…Dissolved H 2 increased with depth and reached values of about 50-80 nM (equivalent to 70-115 ppmv H 2 in the gas phase) below 3 cm depth. These H 2 concentrations are within the range of those obtained from the analysis of the steady-state H 2 mixing ratios in the headspace of incubated anoxic paddy soil slurries [22,33]. The H 2 mixing ratios in gas bubbles (10-110 ppmv H 2) retrieved from rice fields are in a similar range [34,35].…”

Section: Measurement Of Vertical Profilessupporting

confidence: 70%

“…This is the same range of Gibbs free energies that are observed in pure culture of hydrogenotrophic methanogens [37] or in H2-syntrophic cocultures [5,38]. On the other hand, H 2 concentrations in methanogenic environments < 10 nM were often found to be too low to allow exergonic methanogenesis [15,33].…”

Section: Measurement Of Vertical Profilessupporting

confidence: 56%

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Measurement of dissolved H2 concentrations in methanogenic environments with a gas diffusion probe

Krämer

Conrad

1993

FEMS Microbiology Ecology

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A probe for the measurement of dissolved H2 in anoxic methanogenic environment was developed. The probe was based on the diffusion of dissolved H2 through a silicone membrane into a gas space at the end of the probe. This gas space was flushed with N2 and analyzed gaschromatographically for H2. The probe was calibrated in aqueous solutions of the known gas space was flushed The detection limit was about 7 nM H2, the depth resolution of vertical profiles was about 5–10 min. The probe could also be used to measure dissolved CH4 and CO. The probe allowed the measurement of in situ concentrations of dissolved H2 that were unbiased by eventual effects of an extraction procedure on the steady state between production and consumption of H2. However, it could not be implanted into the environment for periods longer than hours because of dramatically increased H2 signals due to microbial growth on the silicon membrane. The probe was used to measure vertical profiles of dissolved H2 and CH4 in cores of the deep sediment of Lake Constance and of anoxic paddy soil. The vertical CH4 profiles measured with the probe compared well with those measured by extraction. In the lake sediment, concentrations of H2 increased with depth and reached values in the range 10–60 nM H2 within the methanogenic zone, below about 2–5 cm depth. In the anoxic paddy soil, H2 concentrations also increased with depth reaching values of 40–100 nM H2. Dissolved CO was about 5–20 nM. The turnover of H2 was very dynamic as revealed when starch powder was added to the flooding water. Within 1 day, H2 concentrations increased to 80 μM H2 in the upper 2 cm of the soil core, but after 5–7 days decreased again to the lower values measured previously.

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Section: Measurement Of Vertical Profilessupporting

confidence: 87%

Section: Measurement Of Vertical Profilessupporting

confidence: 70%

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Measurement of dissolved H2 concentrations in methanogenic environments with a gas diffusion probe

Krämer

Conrad

1993

FEMS Microbiology Ecology

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“…There is numerous evidence for disequilibrium of H 2 between soil microsites and the gas phase (e.g. [20,21]). Unfortunately, it is not possible to permanently agitate soil suspensions because of adverse a¡ects on microorganisms and microbial aggregates [22] and thus, it is not possible to keep the H 2 within microsites in equilibrium with the gas phase.…”

Section: Discussionmentioning

confidence: 99%

How specific is the inhibition by methyl fluoride of acetoclastic methanogenesis in anoxic rice field soil?

Conrad

Klose

1999

FEMS Microbiology Ecology

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Acetoclastic methanogens have been described to be inhibited at much lower concentrations of methyl fluoride, CH3F, than H2/CO2‐utilizing methanogens. Therefore, we tested whether CH3F inhibition may be used to determine, in anoxic rice field soil, the contribution of H2/CO2‐dependent methanogenesis to the total CH4 production by comparing this technique with the incorporation of 14CO2 into CH4. In general, addition of 0.01–1% CH3F to the gas phase resulted in an immediate partial inhibition of the total CH4 production which lasted for at least 200 h. Inhibition increased with the logarithm of the initial CH3F concentration up to about 0.2–0.6%. The initial CH3F concentration slowly decreased with time, probably due to decomposition. CH4 production sometimes completely recovered during the course of the experiment. The presence of CH3F resulted in the accumulation of acetate, the final concentration of which was usually stoichiometrically related to the deficit in CH4 production and increased with the initial CH3F concentration. In some experiments, acetate accumulation was larger than expected from the CH4 deficit and a substantial incorporation of 14CO2 into acetate was observed. Hydrogen, on the other hand, was only slightly elevated in the presence of CH3F. Addition of increasing CH3F resulted in an increase of the percentage of H2‐dependent methanogenesis (measured by conversion of 14CO2 to 14CH4) demonstrating that acetoclastic methanogenesis was preferentially inhibited by CH3F. However, the conversion of 14CO2 to 14CH4 was also slightly inhibited by CH3F. Apparently, CH3F inhibited the H2‐dependent methanogenesis to some extent, depending on the concentration of CH3F applied. Indeed, the ratio between the residual CH4 production rate and the fraction of CH4 produced from 14CO2 decreased with an increasing CH3F concentration. A ratio of unity was obtained at initial CH3F concentrations of 0.2–0.6% (58–174 μM). Both methods, i.e. inhibition using 0.5% CH3F and conversion of 14CO2 to 14CH4, were applied to determine the temporal change of the contribution of H2/CO2‐dependent methanogenesis to the total CH4 production in two different batches of Italian rice field soil during a 120‐days anoxic incubation period. The results of the two methods agreed well within the error of the methods and showed a relatively constant contribution of H2/CO2‐dependent methanogenesis of about 25–30% as soon as CH4 was produced at a steady rate and H2 partial pressures had stabilized at about 1.5–2.5 Pa.

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“…When CH4 production started, the soil slurries showed pH values of 6.8-7.3. This procedure has been used in several studies and proved to result in fairly reproducible population sizes of methanogenic bacteria and in fairly reproducible rates of methanogenesis and of turnover of H 2, glucose and other metabolites [3,4,[9][10][11].…”

Section: Preparation Of Anoxic Paddy Soilmentioning

confidence: 99%

Bicarbonate-dependent production and methanogenic consumption of acetate in anoxic paddy soil

Thebrath¹,

Mayer²,

Conrad³

1992

FEMS Microbiology Ecology

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Effect of dilution on methanogenesis, hydrogen turnover and interspecies hydrogen transfer in anoxic paddy soil

Cited by 42 publications

References 12 publications

Measurement of dissolved H2 concentrations in methanogenic environments with a gas diffusion probe

Measurement of dissolved H2 concentrations in methanogenic environments with a gas diffusion probe

How specific is the inhibition by methyl fluoride of acetoclastic methanogenesis in anoxic rice field soil?

Bicarbonate-dependent production and methanogenic consumption of acetate in anoxic paddy soil

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