Carbon Monoxide, Hydrogen, and Formate Metabolism during Methanogenesis from Acetate by Thermophilic Cultures of Methanosarcina and Methanothrix Strains.

Section of Microbiology, Wing Hall, Cornell University, Ithaca, New York 14853.
Applied and Environmental Microbiology (Impact Factor: 3.67). 11/1992; 58(10):3323-9.
Source: PubMed


CO and H(2) have been implicated in methanogenesis from acetate, but it is unclear whether they are directly involved in methanogenesis or electron transfer in acetotrophic methanogens. We compared metabolism of H(2), CO, and formate by cultures of the thermophilic acetotrophic methanogens Methanosarcina thermophila TM-1 and Methanothrix sp. strain CALS-1. M. thermophila accumulated H(2) to partial pressures of 40 to 70 Pa (1 Pa = 0.987 x 10 atm), as has been previously reported for this and other Methanosarcina cultures. In contrast, Methanothrix sp. strain CALS-1 accumulated H(2) to maximum partial pressures near 1 Pa. Growing cultures of Methanothrix sp. strain CALS-1 initially accumulated CO, which reached partial pressures near 0.6 Pa (some CO came from the rubber stopper) during the middle of methanogenesis; this was followed by a decrease in CO partial pressures to less than 0.01 Pa by the end of methanogenesis. Accumulation or consumption of CO by cultures of M. thermophila growing on acetate was not detected. Late-exponential-phase cultures of Methanothrix sp. strain CALS-1, in which the CO partial pressure was decreased by flushing with N(2)-CO(2), accumulated CO to 0.16 Pa, whereas cultures to which ca. 0.5 Pa of CO was added consumed CO until it reached this partial pressure. Cyanide (1 mM) blocked CO consumption but not production. High partial pressures of H(2) (40 kPa) inhibited methanogenesis from acetate by M. thermophila but not by Methanothrix sp. strain CALS-1, and 2 kPa of CO was not inhibitory to M. thermophila but was inhibitory to Methanothrix sp. strain CALS-1. Levels of CO dehydrogenase, hydrogenase, and formate dehydrogenase in Methanothrix sp. strain CALS-1 were 9.1, 0.045, and 5.8 mumol of viologen reduced min mg of protein. These results suggest that CO plays a role in Methanothrix sp. strain CALS-1 similar to that of H(2) in M. thermophila and are consistent with the conclusion that CO is an intermediate in a catabolic or anabolic pathway in Methanothrix sp. strain CALS-1; however, they could also be explained by passive equilibration of CO with a metabolic intermediate.

Full-text preview

Available from:
  • Source
    • "As discussed previously, heterotrophic respiration with TEAs likely played a minor role in C mineralization in the present study and hence was not a significant source of acetate production. Acetate can also be produced through the process of homoacetogenesis (i.e., acetate formation from CO 2 and H 2 ), but thermodynamics suggests that hydrogenotrophic methanogens should outcompete homoacetogens for their common substrate, H 2 (Zinder and Anguish, 1992), except possibly at low temperature when H 2 is sufficient (Hoehler et al., 1999; Kotsyurbenko et al., 2001). In the present study, we did not measure H 2 concentrations , but we did determine rates of homoacetogenesis in samples near their native pHs by quantifying the incorporation of 14 CO 3 À into acetate (unpublished data). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Methane (CH4) production varies greatly among different types of peatlands along an ombrotrophic–minerotrophic hydrogeomorphic gradient. pH is thought to be a dominant control over observed differences in CH4 production across sites, and previous pH manipulation experiments have verified the inhibitory effect of low pH on CH4 production. In this experiment, we asked (i) if the major effect of low pH is direct inhibition of one or both pathways of methanogenesis and/or inhibition of ‘upstream’ fermentation that provides substrates for methanogens, and (ii) to what extent is pH sufficient to explain differences in CH4 production relative to other factors that co-vary across the gradient. To address these questions, we adjusted the pH of peat slurries from 6 peatlands to 4 levels (3.5, 4.5, 5.5, and 6.5) that reflected their range of native pH, maintained these pH levels over a 43-day anaerobic laboratory incubation, and measured a suite of responses within the anaerobic carbon cycle. Higher pH caused a significant increase in CO2 production in all sites. Regardless of site, time, and pH level, the reduction of inorganic electron acceptors contributed to <12% of total CO2 production. Higher pH caused acetate pooling by Day 7, but this effect was greater in the more ombrotrophic sites and lasted throughout the incubation, whereas acetate was almost completely consumed as a substrate for acetoclastic methanogenesis by Day 43 in the minerotrophic sites. Higher pH also enhanced CH4 production and this process was up to 436% more sensitive to changes in pH than CO2 production. However, across all sites and pH levels, CH4 production accounted for <25% of the total gaseous C production. Fermentation appeared to be the main pathway for anaerobic C mineralization. Our results indicate that low pH inhibits CH4 production through direct inhibition of both methanogenesis pathways and indirectly through its effects on fermentation, but the direct effects are stronger. The inability of acetoclastic methanogenesis to fully compensate for acetate pooling in ombrotrophic peats at higher pH suggests that CH4 production is inhibited by some factor(s) in addition to pH in these sites. We examine a variety of other potential inhibitory mechanisms and postulate that humic substances may provide an important inhibitory effect over CH4 production in ombrotrophic peatlands.
    Full-text · Article · Nov 2012 · Soil Biology and Biochemistry
  • Source
    • "In addition, CO is consumed by both aerobic (Bartholomew and Alexander 1979; King 1999a, 2003; Rich and King 1999; King and Hungria 2002) and anaerobic (Zinder and Anguish 1992; Davidova et al. 1994; Rich and King 1999) microbial processes in soils and sediments. Furthermore, some soil bacteria, including human pathogens of the genus Mycobacterium, are capable of growth on CO as a carbon and energy source (King 2003). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Dissolved carbon monoxide (CO) is present in ground water produced from a variety of aquifer systems at concentrations ranging from 0.2 to 20 nanomoles per liter (0.0056 to 0.56 microg/L). In two shallow aquifers, one an unconsolidated coastal plain aquifer in Kings Bay, Georgia, and the other a fractured-bedrock aquifer in West Trenton, New Jersey, long-term monitoring showed that CO concentrations varied over time by as much as a factor of 10. Field and laboratory evidence suggests that the delivery of dissolved oxygen to the soil zone and underlying aquifers by periodic recharge events stimulates oxic metabolism and produces transiently high CO concentrations. In between recharge events, the aquifers become anoxic and more substrate limited, CO is consumed as a carbon source, and CO concentrations decrease. According to this model, CO concentrations provide a transient record of oxic metabolism affecting ground water systems after dissolved oxygen has been fully consumed. Because the delivery of oxygen affects the fate and transport of natural and anthropogenic contaminants in ground water, CO concentration changes may be useful for identifying predominantly anoxic ground water systems subject to periodic oxic or microaerophilic conditions.
    Full-text · Article · May 2007 · Ground Water
  • Source
    • "M. thermophila has a rapid growth rate (12-h doubling time), which allows synthesis to proceed more rapidly than isotope exchange. The culture also produces little hydrogen (H 2 ) as a metabolic byproduct (Zinder and Anguish, 1992), avoiding any problems with H 2 oxidation confusing the CH 4 oxidation rate measurements. M. thermophila is also capable of utilizing acetate more completely (10 –20 ␮M threshold) than other aceticlastic methanogens (Min and Zinder, 1989), which allows the synthesis to be performed with small quantities of radioactivity, but at high specific activity. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The role of methane clathrate hydrates in the global methane budget is poorly understood because little is known about how much methane from decomposing hydrates actually reaches the atmosphere. In an attempt to quantify the role of water column methanotrophy (microbial methane oxidation) as a control on methane release, we measured water column methane profiles (concentration and δ13C) and oxidation rates at eight stations in an area of active methane venting in the Eel River Basin, off the coast of northern California. The oxidation rate measurements were made with tracer additions of 3H-CH4.Small numbers of instantaneous rate measurements are difficult to interpret in a dynamic, advecting coastal environment, but combined with the concentration and stable isotope measurements, they do offer insights into the importance of methanotrophy as a control on methane release. Fractional oxidation rates ranged from 0.2 to 0.4% of ambient methane per day in the deep water (depths >370 m), where methane concentration was high (20–300 nM), to near-undetectable rates in the upper portion of the water column (depths <370 m), where methane concentration was low (3–10 nM). Methane turnover time averaged 1.5 yr in the deep water but was on the order of decades in the upper portion of the water column. The depth-integrated water column methane oxidation rates for the deep water averaged 5.2 mmol CH4 m−2 yr−1, whereas the upper portion of the water column averaged only 0.14 mmol CH4 m−2 yr−1; the depth-integrated oxidation rate for deep water in the 25-km2 area encompassing the venting field averaged 2 × 106 g CH4 yr−1. Stable isotope values (δ13C-CH4) for individual samples ranged from −34 to −52‰ (vs. PDB, Peedee belemnite standard) in the region. These values are isotopically enriched relative to hydrates in the region (δ13C-CH4 about −57 to −69‰), further supporting our observations of extensive methane oxidation in this environment.
    Preview · Article · Aug 2001 · Geochimica et Cosmochimica Acta
Show more