グラニュール汚泥の高硫酸塩条件への馴致過程におけるメタン生成菌と硫酸還元菌の空間分布の変遷

抄録

Competitive interaction between methane producing bacteria and sulfate reducing bacteria in UASB granules was investigated by applying fluorescence in situ hybridization (FISH) of DNA-targeted probes specific to five different bacterial groups. Granules grown in an UASB reactor were imposed on a stepwise perturbation of feed sulfate strength from 33 to 1, 000 mg SO₄-S·L^-1. Under the low sulfate condition, Methanobacterium and Methanosaeta were found to be predominant, respectively, at the outer surface layer and at the internal portion of granules. Relatively small amounts of Desulfovibrio and Desulfobulbus were observed dispersively at the outer surface layer in the form of individual singular cell. Under the high sulfate fed condition Desulfobulbus became thin layered form to cover the whole granule surface. Hydrogen consumers, mainly such as Methanobacterium and Desulfovibrio, entirely disappeared in the granules, and completely-oxidizing sulfate reducing bacteria were abundantly observed.