Structure Analysis Of Decabromodiphenyl Ether Degrading Bacterial Consortium GY1 And The Degradation Mechanisms Of Its Predominant Strain Microbacterium Y2

Decabromodiphenyl ether?BDE-209?was one of the widely used Polybrominated diphenyl ethers?PBDEs?,Due to its long half life,BDE-209 was frequently detected in environment.In addition,human health and ecological safty were strongly threatened by BDE-209 on account of its bioaccumulation and biotoxicity.Thus,It is vital to explore effective method to eliminate BDE-209 in polluted environment.A novel microbial consortium GY1 was obtained after extensive screening,the degradation ability,transformation mechanism and microbial community shift were further analyzed.Microbacterium Y2 was isolated from GY1,the studies of degradation ability,BDE-209metabolites,physiological response and cell membrane characteristic changes were conducted.i TRAQ?isobaric tags for relative and absolute quantitation?and High-throughput sequencing technologies were applied to deeply analyze the the alteration of protein of Microbacterium Y2 under BDE-209 stress and the relationship between Microbacterium Y2 and indigenous populations during water-sediment system remediation.The major results in our study were as follows:The sequence results showed that Hyphomicrobium,Pseudomonas,Aminobacter,Chryseobacterium,Bacillus,Pseudaminobacter,Stenotrophomonas,Sphingobacterium and Microbacterium were the core genera in GY1,and the functional prediction results revealed that the improve of BDE-209 degradation efficiency during enrichment process was attributed to the overexpression of function genes related to BDE-209 transformation.GY1 could utilize BDE-209 as the carbon and energy source.Biodegradation efficiency of 1 mg/L BDE-209achieved 51.3%within 7 days under optimal conditions?p H 7,2 g/L of GY1,30??,which mainly relied on their intracellular enzyme.The 12 debrominated metabolites were identified,containing BDE-208,BDE-207,BDE-206,BDE-205,BDE-190,BDE-181,BDE-155,BDE-154,BDE-99,BDE-47,BDE-17 and BDE-7,suggesting that BDE-209 was degraded by GY1 could be consider as a successive process of debromination.The toxicity of BDE-209reduced after treatment by GY1,indicating that the reaction of BDE-209 with GY1 was a detoxification process.Moreover,Cells viability changed and MDA content increased obviously under BDE-209 stress,meanwhile,low levels of BDE-209??3 mg/L?showed a significant promotion of SOD and CAT activity,but a noticeable decrease was observed at higher concentrations?>3 mg/L?.Microbial community analysis results showed that the predominated strains have changed obviously and some genera were even lost after GY1 was incubated in enriched medium.The major genera in GY1 have changed to Stenotrophomonas,Microbacterium and Sphingobacterium and these three strains might were the major BDE-209 degraders in GY1.Using traditional culture-dependent method,a strain named Y2 was isolated,and phylogenetic tree analysis suggested that the strain was closely related to Microbacterium sp.Approximately 57.6%of 1 mg/L BDE-209 has been degraded after 5 days under optimal conditions?p H 7,2 g/L of Microbacterium Y2,30?,?NH₄?₂SO₄?,and intracellular enzyme might paly key roles in BDE-209 degradation.Eleven debrominated congeners were detected during BDE-209 degradation,including BDE-208,BDE-207,BDE-206,BDE-205,BDE-181,BDE-154,BDE-99,BDE-47,BDE-17,BDE-15 and BDE-7.Cell membrane permeability and cell surface hydrophobicity were altered under BDE-209 stress,meanwhile,BDE-209 induced excess ROS generation,causing lipid peroxidation and membrane potential declined.SOD and CAT enzymes were activated to mitigate oxidative stress induced by BDE-209.In addition,BDE-209 could disturb the Microbacterium Y2 normal cell cycle and cause the programmed apoptosis to adapt to the severe environment.Proteomics results showed that haloacid dehalogenases and glutathione S-transferases were the key functional proteins in BDE-209 biodegradation,also,the expression of ABC transporter proteins could help BDE-209 degradation and reduce toxicity by promoting the export of BDE-209 and its metabolites.The up-regulation of SOD,CAT,heat shock protein90 homolog,ribonuclease E,oligoribonuclease,30S ribosomal protein,50S ribosomal protein L1 and multi-drug resistant associate protein indicated a protective strategy for Microbacterium Y2 to counter the BDE-209 stress.Pyruvate dehydrogenase E1 component beta subunit and dihydrolipoamide dehydrogenase also increased to accelerate the synthesis of pyruvate dehydrogenase complex to support the glucose metabolism,fatty acid metabolism and tricarboxylic acid cycle.Alanine dehydrogenase could catalyze a reversible oxidative deamination of alanine to pyruvate,and provide energy though tricarboxylic acid cycle.The overexpression of prephenate dehydratase could help the synthesis of proteins related to L-phenylalanine to affect the cells viability of Microbacterium Y2.Moreover,glutamate dehydrogenase,isoleucyl-t RNA synthetase and valyl-t RNA synthetase were down-regulated simultaneously during BDE-209 degradation,inferring that the synthesis of proteins in Microbacterium Y2 were inhibited to a certain extent.Toxicity evaluation experimet demonstrated that the reaction of BDE-209 with Microbacterium Y2 was a detoxification process,which was help to the bioremediation of BDE-209 polluted environment.Compare to the control,a remarkable improvement in BDE-209 degradation was achieved in actual water-sediment system after incubation of Microbacterium Y2 with an approximate 40.0%of BDE-209 being degraded at the 7th week.Microbacterium Y2 could successfully colonize and survive in water-sediment system,and Luteimonas,Methylovorus,Hyphomicrobium,Methylobacillus and Ramlibacter might also be involved in BDE-209 biodegradation in water-sediment system.The functional prediction results further revealed that cytochrome P450/NADPH-cytochrome P450 reductase,Catechol2,3-dioxygenase,haloalkane dehalogenase,2-haloacid dehalogenase and glutathione S-transferase might be involved in BDE-209 removal in water-sediment system,suggesting that the diminution of BDE-209 observed in remediation system was probably related to not only the introduced bacterial activity but also the function of indigenous microbial populations stimulated by introduced bacteria.