Vibrio spp. Methylococcus spp. sugar + O 2 O 2 + CH 4 CO 2 + H 2 O CO 2 Methanosarcina spp. Desulfovibrio spp. CO 2 + H 2 or alcohol SO 4 + alcohol CH 4 H 2 S Cyanobacteria spp. Rhodopseudomonas spp. Clostridium spp. light + H 2 O light + H 2 S sugar O 2 SO 4 CO 2 + H 2 + alcohol