Effects Of Oxytetracycline On Intracellular Substances And Microbial Communities Of Biological Phosphorus Removal Microorganisms

Antibiotics has been widely used in medical,animal husbandry and other fields because of their good promotion of growth and antibacterial effects,and their extensive use has also led to higher detection rates and content in the environment.Biological phosphorus removal is the main method of phosphorus removal in sewage treatment plants,and the treatment process involves a variety of microorganisms.However,the biological toxicity of antibiotics can inhibit microbial activity,thereby reducing the effect of sewage treatment.At present,there are fewer comprehensive and systematic studies on the effects of antibiotics on microbial intracellular substances and microbial communities in biological phosphorus removal.Therefore,it is im portant investigate the effect of oxytetracycline on microbial intracellular substances and microbial communities in biological phosphorus removal and its mechanism of action.In this study,the content of intracellular substances and the activity of functional enzyme were measured by chemical methods.The interaction between oxytetra cycline and functional enzymes activity was studied by molecular docking technology.The effects of different concentrations of oxytetracycline on microbial communities in biological phosphorus removal were analyzed by High-throughput sequencing te chnology.The abundances of functional enzymes and functional gene were predicted on the Kyoto Encyclopedia of Genes and Genomes database.The main conclusions of this study are as follows:（1）The effects of different concentrations of oxytetracycline on biological phos phorus removal system were studied by sequencing batch reactor.Studies have shown that after adding different concentrations of oxytetracycline,the concentrations of orthophosphate and COD in the effluent of each reactor gradually increased,and the removal rate gradually decreased.Moreover,the higher the concentration of oxyt etracycline,the more significant the effect was,and the worse the removal effect of orthophosphate and COD.（2）The effects of different concentrations of oxytetracycline on the changes of COD content,phosphate content,intracellular polymer content and functional enzyme activity in the typical cycle of biological phosphorus removal system were studied by chemical methods.Studies have shown that after adding different concentrations of oxytetracycline,the COD consumption and phosphate removal anaerobic stage were severely inhibited in the typical cycle.The maximum synthesis amount of PHB and the maximum degradation amount of poly-P gradually decrease with the in crease of oxytetracycline concentration,and the maximum degradation amount of glycogen gradually increases with the increase of oxytetracycline concentration.In the aerobic stage,the maximum degradation of PHB and the maximum synthesis of poly-P were less affected by oxytetracycline,and the maximum synthesis of glycogen gradually has increased.（3）The interaction of oxytetracycline with PPK and PPX was studied by molecular docking technology.Studies have shown that the binding energies of oxytetra cycline,PPX and PPK proteins were-7.4 and-7.9 kcal/mol,respectively.The main forces were hydrogen bonds,Van der Waals and hydrophobic interaction Pi-Pi bond,respectively.The formation of van der Waals force between oxytetracycline and amino acid residues His378 and Arg405 of PPX and PPK active sites is the main reason for the decrease of enzyme activity.（4）The effects of different concentrations of oxytetracycline on microbial community in biological phosphorus removal reactors was studied by high-throughput sequencing technology.The results of species composition showed that with the number of microorganisms in the reactor decreased with the increase of oxytetracycline concentration.At the phylum level,the relative abundance of Proteobacteria has gradually decreased,while that of Bacteroides gradually has increased.At the genus level,the relative abundance of Acinetobacter,Dechloromona and Candidatus＿Accumu libacter gradually have decreased,while that of Candidatus＿Competibacter gradually has increased.The results of the microbial Alpha diversity analysis showed that with the increase of oxytetracycline concentrations,the microbial diversity index of species showed a decreasing trend.The results of microbial Beta diversity analysis showed that oxytetracycline concentrations of 0 mg/L and 1 mg/L had high species similarity,and oxytetracycline concentrations of 5 mg/L and 10 mg/L had higher species similarity.（5）The interrelationship between microbial species and environmental factors were studied by redundancy analysis.Studies have shown that oxytetracycline is negatively correlated with Candidatus＿Accumulibacter,Acinetobacter and Dechloromona,and positively correlated with Candidatus＿Competibacter and Zoogloea.There was a positive correlation between oxytetracycline,COD and PO₄^3-.（6）PICRUSt2 was used to predict community function.Studies have shown that he highest abundance in the primary metabolic pathway was metabolism,and the highest abundance in the secondary metabolic pathway was Amino Acid Biosynthesis,Carbohydrate metabolism and Energy metabolism.The functional enzyme histog ram showed that the abundance of functional enzymes involved in poly-P metabolism,PHA metabolism and Energy metabolism gradually decreased with the increase o f oxytetracycline concentration.The abundance of functional enzymes in the HMP and ED pathway changed less.The abundance of functional enzymes in EMP and TCA cycles pathways have increased.The abundance of functional enzymes in gluconeogenesis pathway have increased.The functional gene heatmap showed that the relative abundances of functional genes ppk,ppx,Pst A,pst B,pst C,pst S,Pho R,Pho P,Pho B,pha C and adk involved in poly-P metabolism,PHA metabolism and Energy metabolism gradually decreased with the increase of oxytetracycline concentration.The relative abundance of functional gene edd and zwf in the HMP and ED pathway changed less.The relative abundances of functional genes pfk,pyk,gap A,pgi,f ba A,pgk,eno in the EMP pathway and glt A,icd,suc B,mdh,sdh A,ace A in the T CA pathway were higher than that of low concentration of oxytetracycline.The relative abundances of functional genes pcca and fbp in gluconeogenesis pathway have increased.The experiment comprehensively and systematically analyzed the effects of oxyt etracycline on the intracellular substances and microbial communities of biological phosphorus removal microorganisms in sewage,which provided important data refere nce for the removal of oxytetracycline in sewage and the scientific evaluation of its biological hazards.Figure[33]Table[16]Reference[161]...