Characterization and genomic insights into the nitrogen metabolism of heterotrophic nitrifying and aerobic denitrifying bacterium Pseudomonas aeruginosa WS-03.

Abstract

To achieve effective removal of various inorganic nitrogen in aquatic ecosystems, while expanding the applicability of existing heterotrophic nitrifying-aerobic denitrifying (HN-AD) strains and enhancing their stress tolerance, we isolated the Pseudomonas aeruginosa WS-03 from a sewage treatment plant. The results of parameter optimization indicated that the following were the most favorable conditions for nitrogen removal: using sodium citrate as the carbon source, a C/N ratio of 9, a pH of 7, a temperature of 30 °C and an NH₄⁺-N concentrations below 300 mg/L. The maximum reduction rates of nitrogen are 8.96 mg/(L·h), 4.64 mg/(L·h) and 5.12 mg/(L·h) of NH₄⁺-N, NO₃^--N and TN, respectively. The result of genome analysis and polymerase chain reaction (PCR) amplification electrophoresis revealed the presence of genes related to nitrogen metabolism, which involves nitrification, denitrification, and assimilation pathways. It also verified that absence of key nitrification genes in strain WS-03, suggesting it operates via a unique denitrification mechanism. Notably, nitrogen assimilation has been identified as the predominant pathway for nitrogen removal by the strain. The strain demonstrated an impressive efficiency of 54.28% in reducing the concentration of NH₄⁺-N in untreated landfill leachate, highlighting its potential for application in practical wastewater treatment. This study comprehensively explored the denitrification characteristics and showed its significant role in environmental remediation.