Studies on the microorganisms living in hydrocarbon-contaminated sediments in San Diego Bay, California led to the isolation of a novel Fe(III)-reducing microorganism. This organism, designated strain SDBY1, was an obligately anaerobic, non-motile, non-flagellated, gram-negative rod. Strain SDBY1 conserves energy to support growth from the oxidation of acetate, lactate, succinate, fumarate, laurate, palmitate, or stearate. H2 was also oxidized with the reduction of Fe(III), but growth with H2 as the sole electron donor was not observed. In addition to various forms of soluble and insoluble Fe(III), strain SDBY1 also coupled growth to the reduction of fumarate, Mn(IV), or S0. Air-oxidized minus dithionite-reduced difference spectra exhibited peaks at 552.8, 523.6, and 422.8 nm, indicative of c-type cytochrome(s). Strain SDBY1 shares physiological characteristics with organisms in the genera Geobacter, Pelobacter, and Desulfuromonas. Detailed analysis of the 16S rRNA sequence indicated that strain SDBY1 should be placed in the genus Desulfuromonas. The new species name Desulfuromonas palmitatis is proposed. D. palmitatis is only the second marine organism found (after D. acetoxidans) to oxidize multicarbon organic compounds completely to carbon dioxide with Fe(III) as an electron acceptor and provides the first pure culture model for the oxidation of long-chain fatty acids coupled to Fe(III) reduction.