Geobacter bremensis sp. nov. and Geobacter pelophilus sp. nov., two dissimilatory ferric-iron-reducing bacteria.

Two strictly anaerobic, dissimilatory ferric-iron-reducing bacteria, strains Dfr1T and Dfr2T, were isolated from freshwater mud samples with ferrihydrite as electron acceptor. Both strains also grew by reducing Mn(IV), S0 and fumarate. Electron donors used by strains Dfr1T and Dfr2T for growth with ferric iron as electron acceptor included hydrogen, formate, acetate, pyruvate, succinate, fumarate and ethanol. An affiliation with the family Geobacteraceae was revealed by comparative analysis of 165 rRNA gene sequences. Strains Dfr1T and Dfr2T shared 92.5% sequence identity and their closest known relative was Geobacter sulfurreducens, with approximately 93% sequence identity. Cultures and colonies of strains Dfr1T and Dfr2T were intensely red in colour, due to the presence of c-type cytochromes. On the basis of physiological and phylogenetic data, strain Dfr1T (= DSM 12179T = OCM 796T) is described as Geobacter bremensis sp. nov. and strain Dfr2T (= DSM 12255T = OCM 797T) as Geobacter pelophilus sp. nov.