Diversity And Degradation Characteristics Of Oil-degrading Bacteria In Hydrothermal Area Of Southwest Indian Ocean

With the rapid improvement of marine petroleum exploitation technology and the boom of maritime transport,petroleum spill accidents in the ocean have occurred frequently.At present,the oil-degrading bacteria for the bioremediation of marine oil pollution has been widely studied in the world,but the adaptability of oil-degrading bacteria is poor in the environment,leading to the lack of degradation ability.As an extreme environment in the deep sea,the hydrothermal area is characterized by high pressure,oligotrophic,and high salinity.In recent years scientists around the world committed to the microbiological and microbial metabolic potential study of the hydrothermal area.Therefore,this research is devoted to screening out the high efficient oil-degrading bacteria with strong environmental adaptability from the extreme environment of the deep-sea hydrothermal area,in order to apply it to the bioremediation of oil pollution.The main research results are as follows:(1)Eight sediments from different sites were collected from the deep-sea hydrothermal areas(Longqi,Tiancheng and Tianzuo hydrothermal areas)and non-hydrothermal areas of the Southwest Mid-Indian Ocean.The oil-degrading bacteria in sediments were enriched and cultured.High-throughput sequencing technology and oil degrading methods are used to evaluate the composition of oil-degrading bacteria communities,as well as their degradation capacity and potential.The results show that the alpha diversity index(Shannon and Simpson)of the oil-degrading bacteria is larger than that in the non-hydrothermal area as a whole.There are obvious differences in abundance and diversity of oil-degrading bacteria between the three hydrothermal areas and the non-hydrothermal area.The oil-degrading bacteria in the Tiancheng hydrothermal area is tend to the community of non-hydrothermal area due to the cessation of the hydrothermal vent.Therefore,the hydrothermal vent system may be the key factor to from the diversity of oil-degrading bacteria in hydrothermal.It is studied in this project that alphaproteobacteria is a class of culturable oil-degrading bacteria with significant differences in microbial communities between hydrothermal and non-hydrothermal areas.There is no significant difference in oil degradation rate between the communities from three hydrothermal areas and that from the non-hydrothermal area.The community is good at n-alkanes degradation,but the degradation effect of polycyclic aromatic hydrocarbons is poor.(2)A total of 162 culturable oil-degrading bacteria are isolated from the enrichment culture with crude oil as the only carbon source and energy.The bacteria are belonged to 16 genera,being mainly Microbacterium(38.89%),Pseudomonas(20.37%)and Acinetobacter(14.20%),and two suspected new strains are found,namely Gramellasp.GCO3-9 and Qipengyuania sp.LQ02-29.By calculating the Shannon-Wiener and Shannon indices,it is found that the oil-degrading bacteria obtained from the Longqi hydrothermal area are relatively abundant.By testing the oil degradation ability of the strains obtained from the hydrothermal areas(Longqi,Tiancheng,and Tianzuo hydrothermal areas),it is found that eight strains have a better crude oil degradation effect,and the oil degradation rates are higher than 40%.Weathering rates have been improved by more than 20%.Among them,Pseudomonas sp.LQ01-5 has the best oil degradation ability,and the oil degradation rate is 47.87%.The degradation rate of n-alkanes(C10-C35)is above 59.53%,and the degradation ability of middle and long chains(C16-C35)is higher than that of short chain C16-C35.Moreover,the degradation rates of pristane(PR)and phytane(PH)are 58.56% and58.37%,respectively.(3)Whole genome sequencing and analysis of the oil-degrading bacterium Pseudomonas sp.LQ01-5 is carried out.The whole genome size of the strain LQ01-5is 5074194 bp,with 4674 coding genes and 1 chromosome.Two oil degradation-related genes are found in the gene annotation results,namely alk B and bam A,as well as genes related to the production of biosurfactants and biofilms.In addition,17 sulfur metabolism genes,7 salt tolerance genes,5 low temperature tolerance genes,and abundant heavy metal resistance genes are found,which shows potential in future practical applications and this strain can be further studied.In conclusion,the diversity of culturable oil-degrading bacteria varies in different hydrothermal areas.Screening oil-degrading bacteria from hydrothermal areas containing a large number of hydrocarbons is a way to obtain abundant oil-degrading bacteria resources.