| Tetracycline (TC) was one of the common antibiotic, the residue tetracycline in the environment will accelerate the proliferation of tetracycline resistant bacteria (TRB) and tetracycline resistant genes (TRGs). The occurrence and spread of TRB and TRGs were the huge threaten to human health, which have been paid attention. EPS was high-molecular polymer which surrounding the cells, tetracycline must across the EPS layer then enter into cells. However, It is not clear that the impact of EPS on the formation of TRB and TRGs. In the dissertation, the aerobic activated sludge in four SBR reactors which running under the same conditions was taken as the subject investigated, by using heating method to extracted activated sludge EPS. Polysaccharides, protein and DNA were detected respectively. Then, variations of the numbers of EPS, TRB and TRGs under different concentrations of tetracycline and metal ions were studied, then the correlation between them by SPSS software were analyzed. Results showed that the total EPS increased when the TC concentration in four SBR reactors increased.As running time went on, EPS firstly increased then reduced. The number of TRB CFU was soar, especially when interaction with TC20d to25d, and TRB CFU in sludge phase increased significantly.3group tet genes was determined by RT-qPCR, the order of them was:(EFF)>(RPP)>(DEE).TRGs in the sludge phase increased significantly. The correlation between EPS and TC, TRB were R2=0.795(p<0.05),0.995(p<0.01), but the correlation between EPS and TRGs was low (R2=0.223, p>0.05), under the pressure of tetracycline coexistence with several metal ions, EPS were reduced as TC and metal ions concentration increased, Ca2+, Mg2+coexistence with TC play a bigger part on EPS than Cd2+, Cu2+, Cr6+done. CFU numbers of TRB was reduced as Ca2+, Mg2+and TC increased, and the CFU numbers of TRB first increased then declined as Cd2+,Cu2+, Cr6+and TC increased.TRGs variation trend was that firstly increased at small range then increased at large range. Under the pressure of tetracycline and several metal ions coexistence, EPS to TC and metal ions was negative correlations (R2=-0.800(p<0.05);R2=-0.799(p<0.05)), EPS to TRGs was negative correlations (R2=-0.604(p<0.05); R2=-0.629(p<0.05)), however the correlation between EPS and TRB was close.(R2=0.763(p<0.05);R2=0.808(p<0.05)).The structure characteristics of EPS were observed by CLSM and FTIR. When TC concentration in four SBR reactors increased, EPS and main component protein, β-ploysaccharide variation trend was similar to chemical method consequence. FTIR spectroscopy can show the content of EPS main component which can correspond to chemical method and CLSM image. According to the displacement situation before TC interaction with TC and after TC interaction with TC, the main function group EPS to TC was-OH, C-O-C、C=O and C-N.Finally, the effect of different concentration TC on activated sludge microbial community form interaction mechanism was studied. Trace TC changed microbial community significant succession in SBR reactor. As TC concentration increased and running time went on, the microbial which can’t adjust to TC was replaced by those adjusted to TC.TC had impact on the stability activated sludge microbial community. Diversity index of Shannon’s index (H) and Simpson’s (D) were increased then reduced. |
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