Hydrogen turnover by psychotrophic nomoacetogenic and mesophilic methanogenic bacteria in anoxic paddy soil and lake sediment.
Wasserstoff-Umsatz durch psychotrophe homoacetogene und mesophile methanogene Bakterien in anoxischem Reisboden und Seesediment
The effect of temperature on CH4 production, turnover of dissolved H2, and enrichment of H2-utilizing anaerobic bacteria was studied in anoxic paddy soil and sediment of Lake Constance. When anoxic paddy soil was incubated under an atmosphere of H2/CO2, rates of CH4 production increased with time at temperatures higher than 25 degree C, but decreased at temperatures lower than 20 degree C. Chloroform completely inhibited methanogenesis in anoxic paddy soil and lake sediment, but did not or only partially inhibit the turnover of dissolved H2, especially at low incubation temperatures. Cultures with H2 as energy source resulted in the enrichment of chemolithotrophic homoacetogenic bacterial whenever incubation temperatures were lower than 20 degree C. Hydrogenotrophic methanogens could only be enriched at 30 degree C from anoxic paddy soil. A homoacetogen (strain HP4) and a methanogen (strain Bab1) were isolated from enrichtment cultures with lake sediment at 4 degree C and with anoxic p addy soil at 30 degree C, respectively. The two strains greatly differed in cardinal temperatures of growth. Whereas the methanogen was mesophilic, the homoacetogen was psychrotrophic. This adaptation possibly allows homoacetogenic bacteria to contribute to the turnover of dissolved H2 at low in situ temperatures of anoxic soils and lake sediments.