Protozoa, much like fungi, have close relationships with methanogens in the rumen. Methanogens, as you remember, are the archaea in the rumen and the producers of methane, which comes out in the burps that are killing us all. 8/?

A brief digression: most methane in the rumen comes from hydrogen and formate, and methanogenesis is SEVERELY uncompetitive for these molecules, in a thermodynamic sense. Concentrations of these molecules that support methanogenesis require energy input. 9/?