Showing papers on "Methanogen published in 1982"

Kinetic analysis of competition between sulfate reducers and methanogens for hydrogen in sediments.

Abstract: The competition between sulfate-reducing and methanogenic bacteria for hydrogen was investigated in eutrophic lake sediments that contained low in situ sulfate concentrations and in sulfate-amended sediments. Sulfate reduction and methane production coexisted in situ in lake surface sediments (0 to 2 cm), but methane production was the dominant terminal process. Addition of 10 to 20 mM sulfate to sediments resulted in a decrease in the hydrogen partial pressure and a concomitant inhibition of methane production over time. Molybdate inhibition of sulfate reduction in sulfate-amended sediments was followed by an increase in the hydrogen partial pressure and the methane production rate to values comparable to those in sediments not amended with sulfate. The sulfate reducer population had a half-saturation constant for hydrogen uptake of 141 pascals versus 597 pascals for the methanogen population. Thus, when sulfate was not limiting, the lower half-saturation constant of sulfate reducers enabled them to inhibit methane production by lowering the hydrogen partial pressure below levels that methanogens could effectively utilize. However, methanogens coexisted with sulfate reducers in the presence of sulfate, and the outcome of competition at any time was a function of the rate of hydrogen production, the relative population sizes, and sulfate availability.

Isolation and characterization of an anaerobic syntrophic benzoate degrading bacterium from sewage sludge

Abstract: An anaerobic, motile, gram-negative, rod-shaped bacterium is described which degrades benzoate in coculture with an H2-utilizing organism and in the absence of exogenous electron acceptors such as O2, SO 4 = or NO 3 - . The bacterium was isolated from a municipal primary, anaerobic sewage digestor using anaerobic roll-tube medium with benzoate as the main energy source and in syntrophic association with an H2-utilizing sulfate-reducing Desulfovibrio sp. which cannot utilize benzoate or fatty acids apart from formate as energy source. The benzoate utilizer produced acetate (3 mol/mol of substrate degraded) and presumably CO2 and H2, or formate from benzoate. In media without sulfate and with Methanospirillum hungatei (a methanogen that utilizes only H2−CO2 or formate as the energy source) added, 3 mol of acetate and 0.7 mol of methane were produced per mol of benzoate and CO2 was probably formed. Low numbers of Desulfovibrio sp. were present in the methanogenic coculture and a pure coculture of the benzoate utilizer with M. hungatei was not obtained. The generation times for growth of the sulfate-reducing and methanogenic cocultures were 132 and 166h, respectively. The benzoate utilizer did not utilize other common aromatic compounds, C 3 - −C7 monocarboxylic acids, or C4-C6 dicarboxylic acids for growth, nor did it appear to use SO 4 = , NO 3 - or fumarate as alternative electron acceptors. Addition of H2 inhibited growth and benzoate degradation.

Acetylene as an Inhibitor of Methanogenic Bacteria

Abstract: SUMMARY: Growth of six pure cultures of methanogens was inhibited by low concentrations of dissolved acetylene (C2H2); other archaebacteria (three Halobacterium species) and several eubacteria were not similarly affected. The minimum concentration of dissolved C2H2 required to inhibit growth of Methanospirillum hungatei completely was about 8 mu;m; dissolved ethylene at 20 mu;m had little effect on growth. Dissolved acetylene (33 mu;m) did not alter the E h of the medium, or result in a loss in viability of M. hungatei after 16 h exposures. In anaerobic cell extracts of M. hungatei, activities of hydrogenase, NADP reductase, methyl-coenzyme M reductase and ATP hydrolase were not inhibited by C2H2 concentrations several times higher than those required for growth inhibition. The intracellular ATP content of all of the methanogens dropped dramatically on exposure to C2H2. Moreover, cells of M. hungatei and Methanobacterium bryantii on exposure to C2H2 lost their ability to maintain a transmembrane pH gradient. We suggest that exposure to C2H2 results in a decline in methanogen functions which require a H+-flux, including ATP synthesis, Ni2+ uptake and methanogenesis.

Colonisation of polyurethane reticulated foam biomass support particle by methanogen species

Abstract: The ability of methanogen species to colonise reticulated polyurethane foam biomass support particles (BSP) in a continuous culture system using formate as carbon source was investigated. Scanning electron micrograph evidence and biomass measurements indicate that two methanogen species effectively colonised within the the matrix of the support particle. The freely suspended colonised BSP are resistant to washout, and a comparison of methane output of the immobilised culture and a liquid culture of the methanogens indicates the potential for process intensification of methane production.