Nitrogen removal characteristics and predicted conversion pathways of a heterotrophic nitrification–aerobic denitrification bacterium, Pseudomonas aeruginosa P-1

In this study, the heterotrophic nitrification–aerobic denitrification activity of Pseudomonas aeruginosa (P-1) strain was investigated, and the N transformation pathway was revealed. The highest removal rates of NH 4 + , NO 3 − , and NO 2 − (9.29, 6.12, and 3.72 mg L −1 h −1 , respectively) by this strain were higher than those by most reported bacteria and were achieved when the carbon source was glucose, C/N ratio was 15, pH was 8, temperature was 30 °C, and shaking speed was 200 rpm. The removal order and characteristics of three N sources were investigated in Pseudomonas aeruginosa for the first time. The results revealed that P-1 preferentially nitrified NH 4 + and only began to denitrify NO 2 − and NO 3 − when NH 4 + was almost entirely depleted. Isotopic labeling of N sources revealed that P-1 uses both partial and complete nitrification/denitrification pathways that can operate either simultaneously or independently, depending on the availability of different types of N compounds, with N 2 as the final gaseous product and virtually no NO 2 − accumulation. Moreover, the P-1 strain could convert various nitrogen compounds under high salinity (40 g L −1 ) and high concentrations of Cu 2+ , Zn 2+ , Cr 6+ , Pb 2+ , and Cd 2+ (50 mg L −1 ). Therefore, P-1 could be used as an alternative of inorganic N-removal bacteria in practical applications.