Study On The Evaluation Of Microbial Community In The Mangroves Sediment Under Estradiol Stress

In recent years,industrial wastes have resulted in undesirable effects in the various ecosystems.Endocrine disrupting compounds(EDCs)is a sort of harmful product in the wastewater,which can accumulate in the organisms through food chain.Microbial remediation of EDCs contaminants is considered as a effective and ecological friendly method which gaining attention of researchers globally.However,the biodegradation of EDCs is still not well known.Mangrove is an important coastal wetland in with abundant microbial diversity and activities,driving geochemical cycles of various elements such as carbon,nitrogen,phosphorus.Estrogens(E2),a type of ECDs,were detected at high level in the six mangroves along Southern Sea of China.Therefore,up-layer sediments in these mangroves were applied for enrichment culture using E2 as sole carbon source.After several transfers,16S rRNA gene high-throughput sequencing and metagenomics technology were used to evaluate the enriched microbial communities,the interaction network of functional genes,and the prediction of E2 metabolic pathways.The results of this study are as follows:1)The results of 16S rRNA gene high-throughput sequencing revealed that microbial community had an obvious shift after enrichment.The dominant communities evolved from Gammaproteobacteria and Deltaproteobacteria to Alphaproteobacteria and Gammaproteobacteria.In enriched cultures,Proteobacteria dominated the communities in the range of 70.0%to 90.2%at the Phylum level;At the Class level,the abundances of Alphaproteobacteria and Gammaproteobacteria were increased while the abundances of Betaproteobacteria and Deltaproteobacteria were decreased;At the Family level,unclassified bacterial communities were accounting 58.3%?70.9%,but the high abundance of Chitinophagaceae,Rhizobiaceae,Methylophagaceae and Rhodanobacteraceae indicated that they might involve in transformation of E2.2)Collaborative metabolic network of microbiota revealed that the unclassified Alphaproteobacteria and Gammaproteobacteria had a significant positive correlation with Rhizobiaceae,Methylophagaceae,Rhodanobacteraceae and Chitinophagaceae.It indicated that these bacteria had a cooperation in degradation of E2.3)In the enrichment culture,the abundance of genes involve in transcription were increased,while those involve in replication,signal transduction and energy metabolism showed a downward trend.Along E2 degradation pathways,the abundances of functional genes in metabolizing amino acid,phenylacetic acid,benzoyl-CoA,phthalate and catechol were increased.4)Metagenomic analysis revealed a predicted biodegradation pathway of E2.Firstly,E2 was dehydrogenated to E1 by OecA or 17?-HSD.Secondly,the oxygenation of B,C and D rings of E2 producing 4-hydroxyphenylpyruvate which could entered the phenylacetic acid metabolic pathway to yield energy and CO₂.4-hydroxyphenylpyruvate could also enter the amino acid metabolic pathway by ammonification of aminotransferase.Moreover,oxygenases such as OecB and OecC could degrade A ring of E2 to yield 9,17-Dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid(HIP) which entered the HIP metabolic pathway.