Rhodoferax ferrireducens sp nov., a psychrotolerant, facultatively anaerobic bacterium that oxidizes acetate with the reduction of Fe(III)

To further investigate the diversity of micro-organisms capable of conserving energy to support growth from dissimilatory Fe(III) reduction, Fe(ill)-reducing micro-organisms were enriched and isolated from subsurface sediments collected in Oyster Bay, VA, USA. A novel isolate, designated T118(T), was recovered in a medium with lactate as the sole electron donor and Fe(III) as the sole electron acceptor. Cells of T118(T) were Gram-negative, motile, short rods with a single polar flagellum. Strain T118(T) grew between pH 6.7 and 7.1, with a temperature range of 4-30degreesC. The optimal growth temperature was 25degreesC. Electron donors utilized by strain T118(T) with Fe(III) as the sole electron acceptor included acetate, lactate, malate, propionate, pyruvate, succinate and benzoate. None of the compounds tested was fermented. Electron acceptors utilized with either acetate or lactate as the electron donor included Fe(III)-NTA (nitrilotriacetic acid), Mn(IV) oxide, nitrate, fumarate and oxygen. Phylogenetic analysis demonstrated that strain T118(T) is most closely related to the genus Rhodoferax. Unlike other species in this genus, strain T118(T) is not a phototroph and does not ferment fructose. However, phototrophic genes may be present but not expressed under the experimental conditions tested. No Rhodoferax species have been reported to grow via dissimilatory Fe(III) reduction. Based on these physiological and phylogenetic differences, strain T118(T) (= ATCC BAA-621(T) = DSM 15236(T)) is proposed as a novel species, Rhodoferax ferrireducens sp. nov.