Archaea human intestine prokaryote (Methanobrevibacter smithii), illustration. Methanobrevibacter smithii is the main human gut (intestine) archeon (from the Archaea domain) that is a methanotroph (methanogen). It recycles the hydrogen in methane and allows for an increase in energy extraction for nutrients. It plays a role in the digestion of polysaccharides (complex sugars) by consuming the end products of bacterial fermentation. The human gut flora consists of three main groups of hydrogen consuming microbes: methanogens; a polyphyletic group of acetogenic bacteria; and sulphate reducing bacteria.