Mineralization Of Anthacene In Soil And Its Functional Microbiology

According to the survey,farmland soils are facing more serious pollution problems of PAHs in China.PAHs are structurally stable,have poor water solubility,and can enter the soil for long periods of time,threatening human health.Therefore,the restoration of PAH-contaminated soil is a hot topic in the academic community.Microbial remediation is an effective way to remove PAHs in soil.Anthracene is a typical PAHs,which contain 3 benzene rings.To further clarify the mechanism of mineralization of PAHs by microorganisms in the soil,this study used anthracene as the tested PAH,and analysised by using radio isotope probing technology,selective inhibition technology,high-throughput sequencing,and stable isotope probing technology.Firstly the effects of highly degradable fungus Pycnoporus sanguineus H1 on the mineralization of anthracene and its water solubility were analyzed;secondly,the relative contribution of fungi and bacteria in the soil to mineralization of anthracene was ascertained;finally,the participation of functional microbiology about mineralization in the soil was identified.The results provide a theoretical basis for understanding the microbial mineralization process of PAHs in the soil and improving the recovery effect of polycyclic aromatic hydrocarbons.The main findings are as follows:(1)The effects of the degradation by Pycnoporus sanguineus,mineralization rate and water solubility of the degradation products of Pycnoporus sanguineus H1 were studied by shaking flask culture experiments.The results showed that the degradation rate of Pycnoporus sanguineus H1 to anthracene was 83.0%and the main degradation product was anthraquinone,but the mineralization rate was only 0.5%.The rate and its products were washed with different polar eluents.As a result,the intensity of radioactivity in the polar eluent was increased,while the radioactivity of the nonpolar eluent was decreased compared to the control,indicating that the white rot fungus mainly converted anthracene to a more polar intermediate product.Therefore,it is believed that although Pycnoporus sanguineus H1 has a low mineralization rate,the water solubility of its degradation products was enhanced,which was conducive to the continued mineralization of anthracene in the soil by indigenous bacteria.(2)Bacteria and fungi in the soil were studied by adding fungal(cycloheximide,captan)and bacterial inhibitors(streptomycin,bronopol)to soil in soil micro-culture conditions,as well as the relative contribution to niobium mineralization and the microbial groups participating in mineralization.The results showed that the cycloheximide and bronopol,both at a concentration of 2 mg g'1,specifically inhibited the growth of fungi and bacteria,respectively.The mineralization rates of these two treatments were 3.9%and 0.1%,respectively,below the control(20.0%),indicating that bacteria and fungi were involved in the mineralization of anthracene;further copy number analysis of the bacterial PAH-RHD gene found that the copies in the cycloheximide and bronopol treatment was 2.9×104 and 0,also lower than the control(2.2 × 106),and the analysis showed that PAH-RHD gene copies and mineralization rate fit a higher degree(R2 = 0.89),indicating that bacteria play a major role in the mineralization of anthracene;through high-throughput Sequencing found that,compared with the control,the bacterial community in the phylum,class,and OTU levels were significantly different after treatment with cycloheximide and bronopol,and 9 types of OTUs were found to be significantly reduced,mainly belonging to the beta proteobacteria and acidobacilli.Therefore,it is believed that bacteria and fungi in the soil were involved in the mineralization of anthracene,but bacteria played a major role.(3)In the soil micro-culture conditions,stable isotope probing technology was applied to further study the microorganisms involved in the mineralization of anthracene in farmland soils.The results showed that the PAH-RHD gene migrated to the CsCl layer at 28 days,which was a suitable time for sampling,and the mineralization rate of anthracene was 12.2%.and through ultra high-speed density gradient centrifugation combined with high-throughput sequencing analysis,It was found that five OTUs were successfully labeled at 28d,which belonged to the class Betaproteobacteria(Cuvriavidus)and Alphaproteobacteria Sphingomonas(Sphingomonas).Rhodoplanes;Geobacter of Delaproteobacteria;Mycobacterium of Actinobacteria.Therefore,it is believed that the diversity of microorganisms involved in mineralization of anthracene in the soil,and at least five of OTUs may involved in the mineralization of anthracene in farmland soil.