Effects Of Surfactant On Bacterial Interfacial Behaviors Of Phenanthrene Biodegradation By Citrobacter Sp.SA01and Arthrobacter Sp. SA02

The organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs) coexist in the environment with surfactant, where occurred complex physical, chemical and biological interaction. Surfactant played an important role of the migration, transformation and biodegradation of PAHs, Most studies focused on the interactions between surfactants and PAHs, but studies have suggested that the effectiveness of surfactants in the biodegradation of PAHs involve modifications of the cell surface, and the underlying mechanisms are not been well understood. Therefore, Tween80and SDBS were selected to investigate the affects and underlying mechanisms of surfactant on bacterial cell surface properties and membrane fludity, as well as those effects on phenanthrene metabolism. The main results were as follows:(1) The mechanisms of surfactant-enhanced bacterial cell surface hydrophobicity (CSH) were explored. The CSH of Gram-negative Citrobacter sp. SA01and Gram-positive Arthrobacter sp. SA02was increased by enhancing the release of lipopolysaccharide (LPS) and lipid teichoic acid (LTA), respectively. The partion coefficients of phenanthrene on both strains’ cells were related linearly to the CSH.(2) The enhanced membrane fludity of both strains was revealed by increasing unsaturated fatty acid content in the present of Tween80and SDBS. The enhanced membrane fludity promoted partition of phenanthrene between liquid phase and cell membrane (K1-m), and partition between cell membrane and cytochylema (Km-c). When Tween80and SDBS were applied in50mg/L, K1-m is5.32-fold and12.50-fold of that without surfactants, respectively, and Km-c is separetly1.44-fold and10.59-fold of that in the absent of surfactants.(3) Tween80and SDBS increased bacterial electronic chain transfer system (ETS) activity and catechol1,2-dioxygenase (C12) activity, which in turn promoted phenanthrene metabolism. For strain SA01, the ETS activities, C12activities, and poly β-hydroxybutyrate (PHB) content separately increased23.46-26.51times,3.21-3.28times and1.33-2.07times in the presence of50mg/L of surfactants as compared to in their absence. The comparative CT method of RT-qPCR was used to investigate effect of Tween80and SDBS on the expression changes of1H2Nase gene. Tween80and SDBS were applied in30mg/L, the expression amount of1H2Nase gene is separetly45.99-fold and60.01-fold of that in the absent of surfactants. The expression plasmid pET21(+)b-lH2Nase was constructed. Recombinant protein1H2Nase-His6, with its molecular weight of45.3kD, was overexpressed in E. coli (Origami B) express system at22℃for12h when the amount of IPTG was0.2μmol/L. Tween80and SDBS, in the range of10-30mg/L, could significantly increase its activity. The modiefied Mond model validation showed that the surfactant-enhanced partition of phenanthrene on cells can increase the metabolic processes of phenanthrene.