Diversity Of PAHs-Degrading Bacteria From Deep Sea Water Column At Indian Ocean Middle Ridge

Polycyclic aromatic hydrocarbons (PAHs) are a group of compounds composed of two or more fused aromatic rings. They are persistent in the environment, and are toxic, mutagenic and carcinogenic. Aims of this study were to detect the diversity of PAHs-degrading bacteria from deep sea water near Kairei hydrothermal vents at southwest ridge of the Indian Ocean.Ten PAHs-degrading consortium were obtained by enrichment with a mixture of naphthalene, phenanthrene, anthracene and pyrene as carbon sources from the deep sea water of the Indian Ocean. Structure of bacterial communities was analyzed by 16S library and DGGE (V3 region of 16S rDNA) combined with isolation of culturable strains. Total of 94 strains were isolated from ten consortia, they were identified to be 31 genus and 39 species. Most of them belong to a andγProteobacteria. The predominant genus were Alcanivorax, Marinobacter, Kaistia, Thalassospira, Maricaulis and Nitratireductor. There were five strains belonging to new genus and ten strains to new species for their low 16S rDNA sequence similarity to the known type strains.After analyzed by DGGE and sequence of 16S library, the results showed that the predominant degrading bacteria in the ten consortium were Alcanivorax, Marinobacter, Novosphingobium, Alteromonas, Cycloclasticus and Parvularcula. And there were many clones that didn't have the corresponding isolates.The growth and dynamics of bacteria composition of the ten consortium were determined at different culture time. The results indicated that the consortium reached a steady-going state after a month. There was a little of naphthalene and phenanthrene were detected in the medium after 40 days, but half of anthracene and pyrene still remained.The consortium of 2PC121 was growing well when transferred to the medium with the mixture of different carbon source. The pyrene and fluoranthene were degraded effectively when combined with phenanthrene.Thalassospira were found in many PAHs-degrading consortium in our lab, but they could not degrade PAHs by themselves. There was not any report to show their function. Total of 52 strains of genus Thalassospira were isolated by our lab from different ocean, three type strains additional, were first studied based on 16S, gyrB and BOX-PCR. The results showed that some strains which had high 16S similarity had a low gyrB similarity, and this was found to be related to their isolation place. After phylogenetic analysis based on gyrB, seven potential new species were separated from the total 52 strains. The result of BOX-PCR comparison also supported the result analysed by gyrB. And we found that the strains had the same fingerprint of BOX-PCR when they had the same gyrB sequence. When the strains had difference in gyrB sequence, they had different fingerprint of BOX-PCR product. Furthermore, the strains had more difference in gyrB sequence, and then they had more distinction in the latter. This study proved that the BOX-PCR was reliable and sensitive in the identification of different strains.Five type strains of Alcanivorax genus and strain P40 which was existed in ten PAHs-degrading consortium were study based on housekeeping gene gyrB. The results indicated that strain had high 16S similarity 99% to Alcanivorax dieselolei B-5~T, but only 87% similarity of gyrB nucleotide sequence and 96% similarity of gyrB protein sequence. The other strain Alcanivorax dieselolei NO1A which was isolated from deep sea had high similarity with P40 at 99%, 99%, 100% of 16S, gyrB nucleotide sequence and gyrB protein sequence, respectively. Therefore, we speculated that P40 and NO1A were a deep-sea ecotype of Alcanivorax dieselolei.