Oil Degrading Ability and Mechanisms in Oil Degrading Bacterial Groups Isolated from NAKHODKA Oil Spill

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We have isolated 5 oil degrading bacterial groups (ODB-SG1〜5) from NAKHODKA oil spill, and tried to identify their species and to measure their oil degradation rate about all the bacteria which are included in each isolated group. [RESULTS AND DISCUSSION] 1. Identification of species of bacteria in each group: From DNA sequence of the 16SrRNA gene, BioLog test and the observation of fine structures, the species of bacteria in each group were identified as followed, ODB-SG1 : Caulobacter sp. and Alcanivorax sp. ; ODB-SG2 : Halomonas sp. and Alcanivorax sp. ; ODB-SG3 : Deleya sp. and Alcanivorax sp. ; ODB-SG4 : unidentified; ODB-SG5 : unidentified and Alcanivorax sp. Especially, Alcanivorax sp. existed in all identified groups. All of these bacteria were gram-negative. 2. Comparison of the cell composition of each bacterium: SDS-PAGE showed that bacterial protein band pattern were clearly different among Caulobacter sp. , Halomonas sp. , and Alcanivorax sp. The band patterns of 4 Alcaniv … More orax sp. (in ODB-SG1, 2, 3, 5) were similar, but there were some difference. From this result, we speculated that 4 Alcanivorax sp. are distinct species or strains of Alcanivorax sp. 3. Degradation rates of each bacterium and group: Their abilities to degrade oil were examined by the change in the dry weight of the heavy oil with which they were incubated. The degradation rates of each group were as followed, ODB-SG1 : 10.7%, ODB-SG2 : 13.1%, ODB-SG3 : 15.0%% ODB-SG4:13.3%, ODB-SG5 : 12.4%. The Alcanivorax sp. degraded heavyoil well (4.9〜7.8%), but the Caulobacter sp. and the Halomonas sp. were found unable to degrade heavy oil. Thus ODB-SG1 and ODB-SG2 displayed a higher degradation rate than Alcanivorax sp. alone. From these results, we suppose that Caulobacter sp. and Halomonas sp. can help and accelerate the degradation of heavy oil. 4. The mechanisms of oil degradation by bacteria: We have observed the heavy oil was emulsified by the concentrated culture medium of Alcanivorax sp. SDS-PAGE showed that lipopolysaccharides were secreted in the medium. Less