Microbial interactions regulated by the dosage of ferroferric oxide in the co-metabolism of organic carbon and sulfate.

Effects of ferroferric oxide (Fe3O4) and organic carbon on co-metabolism of sulfate and organic carbon were investigated. With Fe3O4, the degradation of acetate and sulfate was inhibited when fed with acetate, while the degradation of acetate and propionate produced from ethanol was promoted when fed with ethanol. The dominant sulfate reducing bacteria (SRB) of acetate-fed reactors were Desulfobacteraceae (complete oxidizing SRB, CO-SRB) and Desulfurmonas (incomplete oxidizing SRB, IO-SRB). IO-SRBs of Desulfobulbus and Desulfomicrobium were dominant in ethanol-fed reactors. CO-SRB had higher competitiveness than methanogens to utilize acetate, while IO-SRBs might cooperate with methanogens to produce methane when dosed with ethanol and Fe3O4. The dosage of Fe3O4 changed the dominant methanogen from Methanosarcina to Methanosaeta with acetate as the organic carbon, while increased the relative abundance of Methanosaeta with ethanol as the organic carbon.