Which of the following microbes plays an important role in the nutrition of cattle by digesting the cellulose-rich food material in its rumen?

Certain bacteria, which grow anaerobically on cellulosic material, produce large amounts of methane along with CO₂ and H_2. These bacteria are collectively called methanogens, and one such common bacterium is Methanobacterium. These bacteria are commonly found in the anaerobic sludge during sewage treatment. These bacteria are also present in the rumen (a part of the stomach) of cattle. A lot of cellulosic material present in the food of cattle is also present in the rumen. In rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle.