8→83-3→3 (a) Individual Population Microorganisms in Nature Community 2 Community 1 6 CO+6H. O Oxic zone. Photic zone- cyanobacteria and c.H.O.+60 Chemoorganotrophic algae bacteria c.H.O.+60 6CO+6H. O A microbial community Sediments Anoxic zone structure in a lake ecosystem Community 3 1. Guild 1: methanogenic bacteria(co CH) homoacetogenic bacteria(Co,--acetate) 2. Guild 2: sulfate-reducing bacteria(SO-H,S) sulfur-reducing bacteria(S H S) 3. Guild 3: denitrifying bacteria (NO ferric iron-reducing bacteria (Fe Fe) 4: Guild 4: fermentative bacteria (fermenting sugars, amino and fatty acidsMicroorganisms in Nature A microbial community structure in a lake ecosystem