Temporal change of gas metabolism by hydrogen-syntrophic methanogenic bacterial associations in anoxic paddy soil |
| |
Authors: | Ralf Conrad Hans-Peter Mayer Monika Wüst |
| |
Institution: | Universität Konstanz, Fakultät für Biologie, Konstanz, F.R.G. |
| |
Abstract: | Abstract Interspecies H2 transfer within methanogenic bacterial associations (MBA) accounted for 95–97% of the conversion of 14CO2 to 14CH4 in anoxic paddy soil. Only 3–5% of the 14CH4 were produced from the turnover of dissolved H2. The H2-syntrophic MBA developed within 5 days after the paddy soil had been submerged and placed under anoxic atmosphere. Afterwards, both the contribution of MBA to H2-dependent methanogenesis and the turnover of dissolved H2 did not change significantly for up to 7 months of incubation. However, while the rates of H2-dependent methanogenesis stayed relatively constant, the rates of total methanogenesis decreased. The contribution of MBA to H2-dependent methanogenesis was further enhanced to 99% when the temperature was shifted from 30°C to 17°C, or when the soil had been planted with rice. This enhancement was partially due to an increased utilization of dissolved H2 by chloroform-insensitive non-methanogenic bacteria, most probably homoacetogens, so that CH4 production was almost completely restricted to H2-syntrophic MBA. The activity of MBA, as measured by the conversion of 14CO2 to 14CH4, was stimulated by glucose, lactate, and ethanol to a similar or greater extent than by exogenous H2. Propionate and acetate had no effect. |
| |
Keywords: | H2 concentration H2 turnover Interspecies H2 transfer Homoacetogenic bacteria Fermenting bacteria Rice |
|
|