Mutants Construction Of Shewanella Decolorationis S12 Outer Membrane Transporters And Their Functions On The Degradation Of Decabromodiphenyl Ether (BDE-209)

With electronic products widely used and electronic waste largely abandoned, the concentration of bromine flame retardants deca polybrominated diphenyl ether(BDE-209) in the environment is increasing day by day. Because BDE-209 has the strong hydrophobicity and biological toxicity, easy accumulation in soil and sediment, and easier accumulation along the food chain, causing a great threat to human health. More and more studies showed that some bacteria, such as Shewanella decolorationis S12, can degrade BDE-209, but the bioavailability of BDE-209 and the degradation mechanism is still not clear.In the context, transposon mutagenesis,in-frame gene deletion and gene complementation in combination with physiological characteristic were used to explore the role of outer membrane proteins of Shewanella decolorationis S12 in degradation decabromodiphenyl ether(BDE-209).The main conclusions are following:Firstly, the in-frame gene deletion mutants b21,H and P of tbdr(TonB-dependent receptor),fadl(long chain fatty acids) and p were constructed and the complementation strains of the mutants also constructed.Secondly, althtrough TonB-dependent receptor(TBDR) and long chain fatty acid transporter(Fad L) have contrast substrates spectrum — TBDR transport hydrophilic substrates and Fad L transport hydrophobic ones, both of them involve in BDE-209 degradation.The BDE-209 degradation rate of b21,H were lower than wild strain S12.Thirdly, acording to the recent studies and experimental results: BDE-209 degradation ability of tbdr gene deletion mutant strain b21 was lower than wild stran S12,which was recovered by complement strain Cb21;fadl gene deletion mutant strain H lost the ability to degrade BDE-209,then complement strain CH recovered the ability;in contrast,p gene mutant strain P had no effect on BDE-209 degradation,but the degradation rate of complement strain CP decreased,so we infer that Fad L may involve in BDE-209 tansportation, TBDR may be responsible to transport coenzyme vintamin B12 of dehalogenase indirectly impairing BDE-209 degradation and P proteins play negative role in BDE-209 degradation.In summary, the study not only helps us recognize the role and the mechanism of outer membrane proteins in BDE-209 uptake and degradation, but also improve the degradation rate of hydrophobic substrates.