A petroleum assimilating facultative anaerobic bacterium (strain HD-1) was isolated from an oil field in Shizuoka. The cells were anaerobically grown on CO2 as the sole carbon source in the presence of H-2, and the growth was markedly enhanced by the addition of aromatic or aliphatic hydrocarbon [Morikawa, M, and Imanaka, T. : J. Ferment. Bioeng., 76, 280-283, 1993]. The strain degraded tetradecane (C14) under anaerobic conditions and one of the major metabolic intermediates was identified as 1-dodecene (C12). This result demonstrates that alkanes are biodegradable in the absence of molecular oxygen via a pathway different from that of beta-oxidation. The strain was found to grow on CO2 in the presence of tetradecane and absence of H-2 gas and Light. These findings strongly indicate that the bacterium is capable of anaerobically utilizing alkane as an energy source.