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

Two strictly anaerobic, dissimilatory ferric-iron-reducing bacteria, strains Dfr1(T) and Dfr2(T), were isolated from freshwater mud samples with ferrihydrite as electron acceptor. Both strains also grew by reducing Mn(IV), SO and fumarate. Electron donors used by strains Dfr1(T) and Dfr2(T) 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 16S rRNA gene sequences. Strains Dfr1(T) and Dfr2(T) shared 92.5% sequence identity and their closest known relative was Geobacter sulfurreducens, with approximately 93% sequence identity. Cultures and colonies of strains Dfr1(T) and Dfr2(T) were intensely red in colour, due to the presence of c-type cytochromes. On the basis of physiological and phylogenetic data, strain Dfr1(T) (= DSM 12179(T) = OCM 796(T)) is described as Geobacter bremensis sp. nov. and strain Dfr2(T) (= DSM 12255(T) = OCM 797(T)) as Geobacter pelophilus sp. nov.