| dc.description.abstract | Octylphenol polyethoxylates (OPEOn) are nonionic surfactants that have been used for more than 40 years in household and industrial detergents, crop protection agents, chemical, plastics and textiles manufacturing. The degradation metabolites of OPEOn and octylphenol (OP) have become ubiquitous in the aquatic environment and can serve as environmental hormones. The ultimate fate of OPEOn and their metabolites is not adequately understood. A bacterial strain, Pseudomonas putida TX2, was previously isolated in the microcosm of farm soil with addition of OPEOn followed by 2 month of adaptation. It can grow effectively on 0.05%~20% OPEOn as the sole carbon source. This study was aimed to use functional proteomic approach to identify the TX2 proteins up- and down-regulated under 0.5% OPEOn, 0.02% OPEOn or 0.02% OP and the same concentration of succinate as control. 1D-SDS-PAGE and 2D-SDS-PAGE were used for protein separation, and those protein changing by more than 4-fold were identified by MALDI-Q-TOF or ESI-MS/MS. There are 64 up-regulated proteins and 46 down-regulated proteins in the proteome of P. putida TX2 grown in 0.5% OPEOn; 25 up-regulated proteins and 16 down-regulated proteins in 0.02% OPEOn, and 47 up-regulated proteins and 9 down-regulated proteins in 0.02% OP. The physiological responses of P. putida TX2 to environmental stress under 0.5% or 0.02% OPEOn and 0.02% OP are very similar. Take enzymes responsible for alcohol hydrolysis under OPEOn stress as example, the up-regulated responses in 0.5% OPEOn is alcohol dehydrogenase while in 0.02% OPEOn are methanol dehydrogenase and benzoate 1,2- dioxygenase. There is another strain named P. nitroreducens TX1 studied and cultured as previously described. P. nitroreducens TX1 also degrades OPEOn but is not able to further degrade OP, a product with estrogen activity. However, the small molecular transportation protein in 0.02% OPEOn is ABC transporter while transportation protein in 0.02% OP is outer membrane protein and branched-chain amino acid ABC transporter. Increases of protein expression under 0.5% OPEOn of both P. putida TX2 or P. nitroreducens TX1 are heat-shock proteins, protective proteins for antioxidants and structural protection as well as small transportation proteins, metabolic enzymes for protein, peptides and nitrogen. However, the main metabolic enzymes for amino acids in P. putida TX2 are glutamate、histidine and methionine but in P. nitroreducens TX1 is aspartate. The breakthrough of biodegradation in OPEOn or OP is that P. putida TX2 is able to cleave ethoxylate chain and to oxidize the alcohol terminal into aldehyde and then to carboxyl group. Also, the existence of enzyme for digesting benzene ring structure equally contributes to biodegradation in OPEOn or OP. In conclusion, the biotransformation performed by P. putida TX2 to OPEOn or OP is through the oxidation of alcohol into aldehyde. Intriguingly, enzyme responsible for benzene ring cleavage seemed to be necessary in 0.5% OPEOn, but is not detected in 0.02% OP, and which is the key for further study. | en_US |