Simultaneous aerobic nitrogen and phosphate removal by Pseudomonas aeruginosa SNDPR-01: Comprehensive insights on metabolic potential and mechanisms

Versatile metabolic bacteria with simultaneous nitrification–denitrification and phosphate removal (SNDPR) capabilities are promising to reduce the wastewater treatment process from a multi-unit system to a single unit system. Due to the limited study, the metabolic potential and mechanisms of nitrogen (N) and phosphate (P) removal for any SNDPR bacteria remain unknown. In this study, genomic analysis revealed various genes were present in an SNDPR isolate, Pseudomonas aeruginosa SNDPR-01, establishing diverse N- and P-metabolism potential, such as aerobic and anoxic denitrification; dissimilatory nitrate reduction to ammonia; polyphosphate (polyP) metabolism; and utilization of organic P. Phylogenetic analysis predicted that key functional genes related N and P metabolism may co-evolve with chromosomal genes, except for the norB gene, which may originate from horizontal gene transfer. Transcriptomic analysis revealed a partial nitrification and denitrification pathway (NH4+ → NO2– → NO → N2O → N2) to aerobically remove N without the involvement of conventional amoA, hao and napA genes. Unknown genes were confirmed to mediate the oxidation of ammonium to nitrite. Excellent P removal ability was aided by the synthesis of adenosine triphosphate (ATP) and polyP. The formed polyP was utilized under aerobic conditions without accumulation, which is different from traditional polyP accumulation organisms in wastewater treatment plants (WWTPs). This study will deepen the roles of SNDPR bacteria in aerobic ecological niches and enhance their application in WWTPs.