Characterization and metabolic pathway of Pseudomonas fluorescens 2P24 for highly efficient ammonium and nitrate removal

The ammonium and nitrate removal performance and metabolic pathways of a biocontrol strain, Pseudomonas fluorescens 2P24, were investigated. Strain 2P24 could completely remove 100 mg/L ammonium and nitrate, with removal rates of 8.27 mg/L/h and 4.29 mg/L/h, respectively. During these processes, most of the ammonium and nitrate were converted to biological nitrogen via assimilation, and only small amounts of nitrous oxide escaped. The inhibitor allylthiourea had no impact on ammonium transformation, and diethyl dithiocarbamate and sodium tungstate did not inhibit nitrate removal. Intracellular nitrate and ammonium were detectable during the nitrate and ammonium transformation process, respectively. Moreover, the nitrogen metabolism functional genes (glnK, nasA, narG, nirBD, nxrAB, nirS, nirK, and norB) were identified in the strain. All results highlighted that P. fluorescens 2P24 is capable of assimilatory and dissimilatory nitrate reduction, ammonium assimilation and oxidation, and denitrification.