Characteristics Of Pyrene Degrading Strain Brevibacillus Brevis And The Analysis Of Associated Differential Proteins

Pyrene is a typical high- molecular weight polycyclic aromatic hydrocarbon(PAH). Due to its environmental persistency, bioaccumulation potential in organism and toxic effects on human and organisms, investigations on the pollution control have rapidly increased in recent years. The objective of the current study is to explore the relative contributions of biosorption, transport, biodegradation and accumulation to the removal of pyrene by Brevibacillus brevis and the effect of rhamnolipid on biodegradation of pyrene, along with the biological characteristics of bacteria in the process of degradation, and analyze the differential proteins of B. brevis under pyrene stress by means of two-dimensional electrophoresis, aiming to reveal pyrene degradation mechanism from a biological point view.The results showed that pyrene was initially adsorbed by B. brevis and subsequently transported across the plasma membrane into the cell. Then, most of pyrene was degraded under the action of related enzymes. When rhamnolipid was 9 mg/L, the pyrene degradation efficiency was up to 64%, which increased by 15% compared with the control without rhamnolipid.The cell surface morphology was affected severely by pyrene, with cytoadherence, cell surface corrugation and cell invagination. However, cells regrowth after 96 h treatment was observed, and proportion of necrotic cells in pyrene containing system was only 2.8% after 120 h. This result revealed that intact cells still accounted for the vast majority of B. brevis after 120 h, and these intact cells continued to produce corresponding enzymes to degrade pyrene. In the pyrene degradation process, cell response from bacteria was caused. The cell apoptosis was signi?cantly induced, which results in the change of the cell surface groups. Moreover, cell membrane potential was evidently depolarized, thus promoting the uptake and degradation of pyrene.After pyrene was added, the main compositions of B. brevis had changed, as lipid peroxidation improved, leading to malondialdehyde(MDA) content increasing. And the unsaturated fatty acids significantly increased to enhance the membrane fluidity. In the pyrene degradation process, proteins composition of the bacteria had changed. After pyrene degradation for 120 h, 44 differentially expressed proteins were ide ntified in comparison with the control. Moreover, 72 protein spots were new and 7 spots disappeared. These findings revealed that pollutant stress led to the changes of the protein type and expression quantity.