Effect of sulfamethoxazole on aerobic denitrification by strain Pseudomonas stutzeri PCN-1

Sulfamethoxazole (SMX), as a common sulfonamide antibiotic, was reported to affect conventional anaerobic denitrification. This study presented effects of SMX on aerobic denitrification by an aerobic denitrifier strain Pseudomonas stutzeri PCN-1. Results demonstrated serious inhibition of N₂O reduction as SMX reached 4μg/L, leading to higher N₂O emission ratio (251-fold). Increase of SMX (∼8μg/L) would induce highest nitrite accumulation (95.3mg/L) without reduction, and severe inhibition of nitrate reduction resulted in lower nitrate removal rate (0.15mg/L/h) as SMX reached 20μg/L. Furthermore, corresponding inhibition of SMX on denitrifying genes expression (nosZ>nirS>cnorB>napA) was found with a time-lapse expression between nosZ and cnorB. Meanwhile, the decline in electron transport activity and active microbial biomass of strain PCN-1 was revealed. The insight into mechanism of SMX influence on aerobic denitrifier is of particular significance to upgrade nitrogen removal process in antibiotics-containing wastewater treatment plant.