Methane formation and cellulose digestion - biochemical ecology and microbiology of the rumen ecosystem

In postulates 1 on the Earth's origin, gaseous chemical elements combined with each other during cooling; compounds with the highest boiling points condensed first, followed by those containing lighter elements. Living material, formed gradually by chemical reactions of the lighter elements and traces of the heavy ones, was peculiar in its tendency to revert to nonliving material unless chemical work maintained its living state. Abundant non-living compounds of C, H, and 0 also formed in various proportions. The relatively large energy changes involved in the oxidoreduction of these elements equipped them to be agents for the chemical work. Because the Earth was initially anaerobic, with insufficient oxygen to combine completely with the available carbon and hydrogen, much of the carbon must have been in an intermediate state of oxidation. In the absence of 02, energy was not available through the oxidation of carbon to CO2 and H20, but it could be derived by converting C atoms at an intermediate state of oxidation to CO2 and CH4. These molecules are in a low energy state anaerobically, incapable of further redox reactions except that CO2 can be reduced with H2 to CH4. Thus methane was, presumably, an important waste product of early metabolism, and methanogenesis was a primitive phenomenon, accomplished by possibly many diverse forms.