Characterization of two oil-degrading bacterial groups in the Nakhodka oil spill

In January 1997, a heavy oil spill from the Russian tanker Nakhodka occurred in the Japan Sea. We have isolated two bacterial groups, ODB-G1 and ODB-G2, from the spilled oil. Using physiological analysis, electron microscopy, and 16S rDNA sequence analysis, ODB-G1 were shown to contain two genera, Caulobacter sp. and Alcanivorax sp. ODB-G2 also contained two genera, Halomonas sp. and Alcanivorax sp. Their abilities to degrade oil components were examined by TLC/FID method or by the change in the dry weight of the heavy oil with which they were incubated. The results obtained by the TLC/FID method showed that ODB-G1 and ODB-G2 degraded the saturate fraction and the aromatic fraction very well. They were also able to degrade the resin and the asphalten fraction, although the quantity was less. The Alcanivorax sp. degraded heavy oil well, but the Caulobacter sp. and the Halomonas sp. were found unable to degrade heavy oil as assessed by the change in the dry weight of heavy oil. Interestingly, ODB-G1 (a mixture of Caulobacter sp. and Alcanivorax sp.) and ODB-G2 (a mixture of Halomonas sp. and Alcanivorax sp.) displayed a higher degradation rate than Alcanivorax sp. alone.