I just saw this paper in PNAS that’s pretty interesting. The authors from MIT and the Chinese Academy of Sciences suggest that huge pools of acetate were present in the oceans about 250 million years ago. Archaea in the oceans were unable to utilize this carbon, until they obtained genes for acetoclastic methanogenesis via gene transfer. Suddenly, this acetate was available for growth and respiration, resulting in ‘super-exponential’ increases in methane on Earth. It was this methane that killed off a large portion of life on Earth.
Well worth a read anyway…