Screening And Degradation Characteristics Study Of Phenanthrene In Acinetobacter.sp AC

Polycyclic aromatic hydrocarbons(PAHs)are a kind of hydrophobic pollutants with large quantity and wide distribution.It usually comes from the decomposition of organic matter,incomplete combustion of fossil fuels,oil spills,factory emissions and volatile hydrocarbons from sediment erosion.Phenanthrene is a typical representative of PAHs,with low molecular weight and simple PAHs containing three angular fusion rings,which is widely found in industrial waste.Because of its widespread presence in nature,it is often used as a preferred model compound for PAHs biodegradation.This study is to screen a strain that has high degradation efficiency to phenanthrene,and to study the degradation characteristics to phenanthrene.Taken from the soil near the abandoned oil production plant in Baicheng(China).Phenanthrene is the only carbon source.Screenings use traditional methods.The characteristics of a single colony was detected by morphology,and 16 S rRNA sequencing results showed that the strain was Acinetobacter sp.named Strain AC.Study the growth of strain AC under different conditions and found to be a highly degradable strain of phenanthrene.Nevertheless the mechanism of degradation is not clear.Therefore,transcriptome sequencing was used to study the different gene expression of Strain AC in degradation of phenanthrene in the presence and absence of phenanthrene for 24 hours(logarithmic growth phase).The different degradation genes and action patterns were identified by RNA-Seq and qRT-PCR.RNA-Seq results showed that there were 4876 transcripts and 2502 differentially expressed genes(log 2 ≥ 2,Q ≤ 0.001),and 880 genes were up-regulated.The Unigenes were annotated into the KEGG database.The main metabolic pathways were "Amino acid metabolism" and "Carbohydrate metabolism".The up-regulated genes involved in "degradation and metabolism of Xenobiotics" were annotated into the KEGG and GO database,verified by qRT-PCR.It was found that anthranilate 1,2-dioxygenase,3-hydroxyacyl-CoAdehydrogenase,alcohol dehydrogenase and cytochrome P450 were the main enzymes involved in the biodegradation of phenanthrene.The degradation intermediates of phenanthrene,such as 1-hydroxy-2-naphthalene and 1,2-dinaphynaphthalene were analyzed by GC-MS.The results of showed that oxygenase and dehydrogenase were the key expression genes in phenanthrene degradation.On the basis of the aforementioned study,the possible degradation pathway of phenanthrene was further determined.This information will help further our understanding of the detailed mechanisms of Acinetobacter sp.degrading phenanthrene.