| A strain with high-efficiency in degrading decabromodiphenyl ether (BDE-209)was isolated from sediment samples collected from Guiyu town in Shantou city,Guangdong Province, an e-waste recycling area. The strain was identified asEnterococcus casseliflavus. The BDE-209degradation mechanism was expected to beclarified from a biological point of view through revealing the biodegradability ofBDE-209and the biological characteristics of bacteria in the process of degradation,and through analyzing the differential proteins of the bacteria in the process ofdegradation of BDE-209by two-dimensional electrophoresis.The optimum culture conditions for BDE-209were as follows: the initialmedium pH7, incubation time48h, incubation temperature30℃. Time, bacterialdosage and cell age had a certain influence in degradation of BDE-209byE.casseliflavus.The degradation efficiency of about56.7%within4d was achieved,when dealing with1mg·L-1BDE-209under initial natural pH at30℃by1g·L-1E.casseliflavus. The utilization of BDE-209by E. casseliflavus occurred mainly in theintracellular environment, and the residual amount of BDE-209was around0.5mg·L-14days later. E. casseliflavus presented high cell surface hydrophobicity (CSH),which offered the possibility for better absorption of BDE-209.Then the CSHdecreased with increasing time. Under the stress of BDE-209, a response frombacteria happened on the fourth day as follows: the increasing of cell membranepermeability, that resulted in the augment of BDE-209in intracellular environmentand the outflow of the cytoplasm. Diauxic growth made the group structure of the cellreturn to normal structure, and mycelial morphology was short rod.The biological activity of E. casseliflavus changed having added BDE-209andcell cycle was disrupted. Besides, the degradation of BDE-209by E. casseliflavus wasrealized by apoptosis pathway. In the process of degradating BDE-209byE.casseliflavus, protein composition of the bacteria had changed. BDE-209could induce a new class of extracellular protein, while the increase of BDE-209leaded tothe change of the amount of intracellular protein and some unexpressed protein whichhappened because of the inhibition due to BDE-209. After4days’ degradation of1mg·L-1BDE-209,31differentially expressed proteins were identified in totalcompared with the control. Among them,5protein spots were new and13spotsdisappeared. The change indicated that the conformation of protein associated withthe degradation had changed, which resulted in the changes of the protein type andexpression quantity. |
