Oil-Degrading Bacterial Community Structure In Mangrove Surface Sediment Of The Jiulong River Estuary, China

Research about mangrove areas as well as their microbial resources for the bioremediation of oil pollution in marine environment has become a hot spot in the twenty-first century by environmentalists.This study was set out to determine the ability of oil-degrading bacteria in mangrove ecosystem to utilize diesel oil and crude oil as a carbon source in an in-situ condition in both non-transfer and transfer enrichment samples and determine their community structure.Sediment samples were collected from three stations in Fugong mangrove swamp of the Jiulong River Estuary,Fujian,China and the microorganism were enriched in MSM supplemented with crude oil and diesel oil.The metabolic activities of microorganism were analyzed and the changes in microbial community structure were evaluated using PCR- DGGE analysis of amplified 16S rDNA gene fragment during batch culture enrichment.The results obtained are as follows:1.The mangrove sediments harbored abundant cultivatable bacteria.In the non-transfer sample,there was a constant bacteria number between the first 1st to the 5th week of enrichment and the number start declining in the 6^th to the 8^th weeks of enrichment in all the stations with little variation.In the transfer sample there was a decrease in the cultivatable bacteria number from the first week of enrichment in all the stations.2.The Electron Transport System Activity(ETSA) of sediment samples and enrichment cultures were tested in both non-transfer and the transfer enrichment sample.In the non-transfer sample.there was a constant ETSA number between the first 1-5 weeks as shown by their OD value and the number started to decline in the 6^th to the 8^th weeks of enrichment in all the stations.In the transfer sample,the result showed a decrease in the ETSA value and station 15 exhibited high activity rate followed by the sea water enrichment,station 14 and the least was recorded at station 12.3.The DGGE profile demonstrated that there was no remarkably shift in bacteria community from first subculture to the eighth subculture.DGGE bands were successfully sequenced and eight dominant species were identified.They were closely related to Vibrio natriegens,Vibronaceae bacterium,Vibrio campbellii, Uncultured marine bactyerium,Vibrio parahaemolyticus,Pseudomonas sp., Vibrio sp.and Vibrio alginolyticus respectively.4.Eleven strains were isolated from the cultivatable culture dependent bacteria from both the crude oil and diesel oil enrichment culture and 16S rDNA library analysis showed that the vast majority of the corresponding sequences of cultured bacteria are microorganisms that have been previously identified as potential polycyclic aromatic hydrocarbons(PAHs) degraders,Furthermore, when the corresponding sequences were compared with the GeneBank database revealed the following populations of bacteria capable of utilizing petroleum product as a carbon source as follows;Pseudomonas sp.,Flexibacteraceae bacterium,Rhodobacteraceae bacterium,Marinobacter sp.,Alteromonas sp., Marine CFB-group bacterium,Marinobacter aquaeolei,Thalassospira sp., Alteromonas sp.,Muricauda sp.,and Uncultured Alteromonas sp.respectively.