Activity and distribution of methanogenic bacteria in a lake sediment.

Methane production in the environment has been recognized as an important factor for the global warming. It is also important as a process for self-purification in the polluted environment. In this study, the author isolated methanogenic bacteria which live in a lake sediment and investigated the methanogenic activity of the isolated bacteria. The author also studied the distribution of methanogenic activity in a lake sediment by using sediment samples which were obtained from each depth of the sediment, and temperature effects to the methanogenic activities. One coccus bacterial strain of methanogenic bacteria isolated from the lake sediment was a hydrogen utilizing methanogen. It was impossible to isolate acetate utilizing methanogen from the lake sediment because of the coexisting bacteria other than methanogens. There were many differences between hydrogen utilizing methanogenesis and acetate utilizing methanogenesis. Methanogenesis from hydrogen dominated in the lake sediment, especially in the deeper sediment. This methanogenic activity was also observed at low temperature. Methanogenesis from acetate was active at the upper sediment which contained much organic compounds, but not so high as methanogenesis from hydrogen.