Methanobrevibacter smithii is the predominant archaeon in the human gut. M. smithii has a cocobacillus shape. It plays an important role in the efficient digestion of polysaccharides (complex sugars) by consuming the end products of bacterial fermentation. Accumulation of hydrogen in the gut reduces the efficiency of microbial fermentation as well as the yield of energy. Methanogenic archaea are therefore particularly significant for the human gut, because they are pivotal in the removal of excess hydrogen. M. smithii is the most common methanogenic archaeon in the human gut flora.