摘要Excessive ammonia nitrogen has been demonstrated to cause a serious hazard to water environments.Bacteria performing simultaneous nitrification and denitrification(SND)can be effective biological instruments to remove ammonia nitrogen completely from effluents.For the first time,Pseudomonas oleovorans QS-7 with SND function,isolated from the biogas treatment system of a pig farm,was found to efficiently remove ammonia nitrogen.Through the determination of key enzymes and functional genes related to the nitrogen metabolism of strain QS-7,combined with nitrogen balance measurements of the nitrogen metabolic process,it was speculated that the SND pathway of the novel strain is NH4+→NH2OH→NO2-→NO3-→NO2-→NO→N2O→N2.QS-7 exhibited 98.6％ammonia nitrogen removal and a maximum ammonia degradation rate of 9.2 mg/(L·h)at 18 h in 100 mg/L ammonia nitrogen solution.This strain also has a certain capacity to remove nitrate and nitrite nitrogen;the maximum removal efficiencies were 54.22％and 73.93％,respectively,in systems with 100 mg/L of nitrate or nitrite nitrogen as the sole nitrogen source.Nitrogen metabolic balance analysis for QS-7,using ammonia(100 mg/L)as the sole nitrogen source,demonstrated that assimilation(56.1％)is the main mode of nitrogen removal,followed by conversion to N2(43.6％).Meanwhile,NO-2 was not detected,and almost no NOx was produced,which indicates that the nitrogen removal process of QS-7 is environmentally friendly.The optimal environmental conditions for QS-7 were found to be sodium citrate as the carbon source,C/N=10,pH=7.0,150 r/min,and 30℃.The above results indicate that QS-7 may provide a material and conceptual basis for the advancement of SND technology.