水田土壌中のメタン生成・酸化細菌の特徴と生態

抄録

Paddy fields are one of the main sources for methane emission of a global scale. The magnitude of methane emission is a net result of methane production and the oxidation rate. Methanosarcina sp., Methanothrix sp., Methanobacterium sp. and Methanobrevibacter arboriphilicus have been isolated from paddy field soils. Populations of methanogens in paddy soil are about 10³∼10⁶/g dry soil, and stay almost constant during entire season of flooded rice field soil and drained soil. A large number of sulfate reducers are present in paddy soils. In the absence of sulfate, sulfate reducers are important anaerobic bacteria to degrade organic acids and alcohols to acetate by syntrophic association with hydrogenotrophic methanogens. The bacterial number of methanotrophs are about 10⁴∼10⁵cells/g dry soil in paddy field soils. The methanotrophs isolated were gram-negative, oxidase-positive and rod- shaped bacteria, and belonged to type II methanotrophs.