Diversity Of Anaerobic Hydrocarbon Degrading Bacteria In Offshore Sediments And Degradation Characteristics Of Desulfovibrio Subterraneus ND17

The offshore coast,as the junction of land and sea,is vulnerable to oil pollution from the ocean,and the degradation process of various types of petroleum hydrocarbons entering the sediment is not clear.Microorganisms can effectively decompose organic matter accumulated from land and sea.Research on petroleum hydrocarbon degrading bacteria under aerobic conditions has been carried out earlier and more intensively,while research on anaerobic petroleum hydrocarbon degradation in offshore coastal sediments,including microbial species,degradation mechanisms and related functional genes,is at the initial stage.In order to investigate the bacterial groups involved in anaerobic hydrocarbon degradation in offshore coastal sediments,and to select efficient hydrocarbon degrading bacteria from them,we investigated their degradation characteristics and functional genes.In this paper,the diversity of anaerobic hydrocarbon degrading bacteria was analyzed and single bacteria were isolated by anaerobic enrichment of deep sediments in the intertidal area of Qingdao Nvdao Bay using mixed hydrocarbons(medium and long chain alkanes and polycyclic aromatic hydrocarbons)as carbon sources and sulfate as electron acceptors.The bacterial diversity of the enriched community showed that under the effect of mixed hydrocarbons as carbon source,the dominant flora changed to Desulfosarcinaceae,Desulfobacteraceae and other sulfate-reducing bacteria with petroleum hydrocarbon degradation potential,and the abundance in the enriched samples could reach more than 30%.An anaerobic hydrocarbon-degrading strain ND17 was obtained by isolation and purification,with 99.93%similarity to the 16S rRNA gene sequence of the model species Desulfovibrio subterraneus HN2T.Further experiments showed that ND17 could utilize medium and long chain alkanes,polycyclic aromatic hydrocarbons and halogenated hydrocarbons for growth,and was able to reduce various electron acceptors such as sulfate,thiosulfate,AQDS,MnO2,and oxidize long chain alkanes(C24-C32)under the condition of coupled trivalent iron reduction.The degradation of eicosanoids and phenanthrene by strain ND17 could reach 53.9%and 35.7%,respectively,under anaerobic conditions,which is the first study of petroleum hydrocarbon degradation by pure culture of Desulfovibrio genus under anaerobic conditions.The sequencing and analysis of the whole genome of ND17 showed that ND17 has a complete sulfate reduction pathway and can perform nitrogen fixation,which plays a great role in coupling the carbon,nitrogen and sulfur cycle.As a widely distributed bacterium in anaerobic environments,Desulfovibrio has been found in anaerobic environments such as oil reservoirs,marine sediments,mangrove sediments and oil-contaminated areas,and this study provides support for further understanding of its remediation potential in marine oilcontaminated environments.