Isolation And Characterization Of Degradable Microbes Against Polychlorinated Biphenyls From Mangrove Sediments In Zhanjiang

Polychlorinated biphenyls(PCBs)are kinds of persistent organic pollutants widely distributed around the world.They are difficult to be degraded in the environment,cause wide-spreading and persistent pollution to the environment.PCBs are highly hydrophobic,and easy to accumulate in organisms,particle phase and adipose tissues.They also have a variety of biological toxicity.This poses threats to human and animal health.Mangrove is an extremely unique ecosystem in the coastal intertidal zone.It has varieties of microorganism species and luxuriant microbial resources with great potential.Studies have shown that,isolated microorganisms can degrade harmful pernicious pollutant from mangrove environment.At present,PCB pollution is a major problem in environmental pollution.To find a highly efficient PCB degradation strain for microbial remediation is key to eliminating PCBs pollutions.The study includes the following test:(1)Taking the soil sample from Zhanjiang Mangrove National Nature Reserv high-tide zone,medium-tide zone and low-tide zone to analyse the microbial diversity.(2)To isolate and identify the PCBs degradation bacterial by MM30 medium;(3)Verified the degradation effects and characteristics by GCMS.The results were as follows:(1)The results of high-throughput sequencing showed that the sequence number,diversity index and coverage rate in the high-throughput sequencing result were all in higher level from three habitats.According to the statistics of the OTUs number,we got a total of 10054 OTUs(S1:6761,S2:7866 and S3:8073)from the soil samples and belonged to 60 different bacterial families.For diversity analysis,both the Chao1 curve and the Shannon curve tended to be flat in the following stage.It indicated that the amount of sequencing data in sample is large enough,and the microorganisms'diversity of sample tended to be saturated,which is enough to reflect the species information of most microorganisms in the sample.The Shannon index were distributed from 4.94 to 6.03,and the Simpson in the range from 0.004775 to 0.021409.The index has a larger span to show the better species diversity.It was observed that,most OTUs were classified into phylum and many were classified into order level,but there were still many that could not be classified,indicating that mangroves are rich in diversity and the large number of bacteria have not been sequenced and found.Proteobacteria,Chloroflexi,Actinobacteria,Bacteroidetes and Acidobacteria all have quantitative advantages among the samples and play the dominant role in the sample environment.The total proportions were over 80%,and there exist slight difference in various groups.(2)To enrich,domesticate and separate the degrading bacteria,we used the MM30medium which add BP or PCBs as the sole carbon source in turn.Finally,we got three pseudo-degrading strains,they are S3-1,S2-2 and LW3.The sequence result showed that S3-1 strain is a gram positive(G~+)bacteria and the homologous arrive 99.26%with the KU163265.1(Proteobacteria Aquamicrobium defluvii strain TLA-7 16S.LW3 also is a gram negative(G~—)and had a 98%homology with the NC?016845.1(Klebsiella pneumoniae subsp.Pneumoniae HS11286.It may be a new species under the genus Klebsiella.S2-2 is a gram negative(G~—)and had 99.09%similarity with NZ?CP009553.3(Pandoraea pnomenusa strain DSM 1653).It belonged to the genus Pandora and fermented glucose to produce gas.(3)Degradation system verification:We inoculated the system to C1(5 mg/L),C2(10 mg/L),C3(20 mg/L),C4(40 mg/L)and C5(60 mg/L)five groups at 10%bacterial amount.The GCMS result showed that three strains had good degradation effect.after 96 hours,the final degradation rate was over to 96%.In summary,the above results indicate that the Zhanjiang mangrove soil had good diversity.S3-1(Proteobacteria Alphaproteobacteria),S2-2(Pandoraea pnomenusa strains)and LW3(Klebsiella pneumoniae subsp)can degrade PCBs under definite condition,which had a positive guiding effect on the actual restoration of polluted soil.It provides a basis for the complete elimination of PCBs pollution in the environment and the exploration of mangroves'potential ecological functions.