Geobacter uraniireducens sp nov., isolated from subsurface sediment undergoing uranium bioremediation

A Gram-negative, rod-shaped, motile bacterium, strain Rf4(T), which conserves energy from dissimilatory Fe(III) reduction concomitant with acetate oxidation, was isolated from subsurface sediment undergoing uranium bioremediation. The 16S rRNA gene sequence of strain Rf4(T) matched sequences recovered in 16S rRNA gene clone libraries constructed from DNA extracted from groundwater sampled at the same time as the source sediment. Cells of strain Rf4(T) were regular, motile rods, 1.2-2.0 mu m long and 0.5-0.6 mu m in diameter, with rounded ends. Cells had one lateral flagellum. Growth was optimal at pH 6.5-7.0 and 32 degrees C. With acetate as the electron donor, strain Rf4(T) used Fe(III), Mn(IV), anthraquinone-2,6-disulfonate, malate and fumarate as electron acceptors and reduced U(VI) in cell suspensions. With poorly crystalline Fe(Ill) oxide as the electron acceptor, strain Rf4(T) oxidized the following electron donors: acetate, lactate, pyruvate and ethanol. Phylogenetic analysis of the 16S rRNA gene sequence of strain Rf4(T) placed it in the genus Geobacter. Strain Rf4(T) was most closely related to 'Geobacter humireducens' JW3 (95.9 % sequence similarity), Geobacter bremensis Dfr1(T) (95.4 %) and Geobacter bemidjiensis Bem(T) (95.1 %). Based on phylogenetic analysis and phenotypic differences between strain Rf4(T) and closely related Geobacter species, this strain is described as a representative of a novel species, Geobacter uraniireducens sp. nov. The type strain is Rf4(T) (=ATCC BAA-1134(T) = JCM 13001(T)).