Effects Of Norfloxacin On Intracellular Polymers And Community Structure Of Microorganisms During Biological Phosphorus Removal

Norfloxacin has strong antibacterial,has widely used in the prevention and treatment of various infectious diseases,So a lot of abuse leads to high detection frequency of norfloxacin in sewage treatment plants,but the biotoxicity of norfloxacin will affect the growth of microorganisms in sewage treatment plants and their intracellular polymers anabolism,reduce the effect of sewage treatment.In current,there are few studies on the mechanism of norfloxacin on microorganisms and intracellular polymers during biological phosphorus removal.Therefore,the effects of different concentrations of norfloxacin（0mg/L,5μg/L,100μg/L,500μg/L,1 mg/L,5 mg/L）to the anabolism and structure of intracellular polymers during biological phosphorus removal by chemical method and Fourier transform infrared spectrometer.In addition,high-throughput sequencing technology was used to analyze the diversity of microbial population structure based on Bray Curtis distance algorithm.Asymmetric correlation matrix was used to analyze the correlation between environmental factors and microorganisms.The co-occurrence network was constructed to reveal the effect of norfloxacin on microbial interactions during biological phosphorus removal.The main conclusions are as follows:（1）SBR reactor was used to study the effect of norfloxacin on biological phosphorus removal system.The concentration of 5μg/L have no adverse effect on the removal of phosphorus and COD,while upon exposure to a high concentration of norfloxacin,the concentration of effluent phosphorus and COD gradually increased.It showed that norfloxacin inhibited the pollutant removal effect of microorganisms in the biological phosphorus removal system and was dose-dependent.（2）The effects of norfloxacin on the contents of intracellular polymers in typical cycles were studied by chemical method.At the concentration of 0 mg/L,5μg/L,100μg/L,500μg/L,1 mg/L and 5 mg/L,the reactor gradually decreased with the increase of the infusion concentration.In addition,the synthetic degradation of intracellular PHB and poly-P in the typical cycle are inhibited,but the intracellular glycogen metabolism gradually increases.（3）Fourier transform infrared spectroscopy（FTIR）was used to analyze the effect of norfloxacin on the structure of intracellular polymers.The results show that with the increase of the concentration of norfloxacin,the transmittance of the functional group P-O-P increases gradually,indicating that the addition of norfloxacin may reduce the chain length and degree of polymerization of intracellular poly-P.When the concentration of norfloxacin is greater than 500μg/L,the absorption peak of intracellular PHB carbonyl becomes blue shift.The PHB sample may contain PHV copolymers,but norfloxacin will not affect the structure of intracellular PHB.The intracellular glycogen samples belong to pyran polysaccharide.When the concentration of norfloxacin is greater than 1 mg/L,the intracellular glycogen may have esterified with norfloxacin and addedβ-glycosidic bond.Therefore,norfloxacin may also change the way the glycogen is connected,thus changing its spatial structure.（4）Changes in microbial species between reactors before and after tosormalization of norfloxacin were analyzed by OTU clustering.As the concentration of norfloxacin increases,the number of species that disappear in the biological phosphorus removal reactor gradually increases.（5）The microbial community composition and characteristics of microbial communities under the influence of phosphorus removal system under the influence of norfloxacin were analyzed by microbial abundance bubble map and diversity.The abundance of P-removing microorganisms gradually decreased with increasing norfloxacin concentration,and the abundance of microorganisms associated with glycogen degradation gradually increased with increasing norofloxacin concentration,becoming one of the dominant bacterial genera.The abundance of microorganisms associated with denitrification and organic degradation showed different trends with increasing norfloxacin concentration.In addition,when the concentration of norfloxacin is greater than 100μg/L,the microbial abundance and diversity in the biological phosphorus removal reactor gradually decrease with the increase of norfloxacin concentration.the microbial community structure under the concentration of 5μg/L was changed little,and the microbial community structure under the concentration of greater than 5μg/L norfloxacin was obviously different.（6）The correlation of microorganisms with norfloxacin,PO₄^3-,COD,DO and p H in the biological phosphorus removal system was analyzed by the Spearman rank correlation heatmap of environmental factors.The results show that under this experimental condition,the microorganisms in the system have no correlation with p H and DO,and the correlation with other environmental factors shows different degrees of positive and negative correlation with different species functions.（7）The interaction between microorganisms in biological phosphorus removal system was analyzed by constructing microbial co-occurrence network.After norfloxacin was added,the microbial co-occurrence network contained only 26 points and 60 edges,and the network density and positive correlation ratio were reduced to 0.185 and 51.66%,respectively.Therefore,norfloxacin would reduce the symbiotic relationship between microorganisms in the bioreactor of biological phosphorus removal,and the ecological network structure was simpler,and the microbial community became unstable.In addition,some microorganisms with low abundance also play a key role in biological phosphorus removal systems.The effects of norfloxacin on the anabolism and structure of intracellular polymers in the process of biological phosphorus removal were studied,and the changes of microbial diversity and community structure under the action of norfloxacin were explored by high-throughput sequencing,for the phosphorus removal rate increased the theoretical basis,further improve the influence of fluoroquinolone antibiotics on biological phosphorus removal system,has certain theoretical and application value.Figure[28]Table[10]Reference[123]...