Evidence for Propioniciclava as a novel polyphosphate-accumulating organism and construction of its metabolic profile

Enhanced biological phosphorus removal (EBPR) relies on polyphosphate-accumulating organisms (PAOs). This study identifies Propioniciclava as a novel putative PAO. High phosphorus release and uptake rates were achieved in two lab-scale Propioniciclava-dominated sequencing batch reactors (SBRs), reaching up to 2.37 and 2.10 mmolP/(gVSS·h), respectively. Metabolic pathway reconstruction for Propioniciclava was based on its most abundant metagenome-assembled genome (bin70), which accounted for 28.8% in SBR1 and 45.5% in SBR2. Functional annotation of bin70 revealed genes for phosphorus and glycogen metabolism but not for polyhydroxyalkanoate synthesis, suggesting a distinct storage strategy. Fluorescence in situ hybridization combined with 4',6'-diamidino-2-phenylindole (FISH-DAPI) staining provided evidence for intracellular polyphosphate granules. Metatranscriptomic analysis further highlighted genes related to phosphorus and glycogen synthesis being actively transcribed by Propioniciclava. The enrichment of Propioniciclava was crucially dependent on glucose. These findings expand the known diversity of PAOs and elucidate the metabolic profile of Propioniciclava, enhancing our understanding of EBPR microbiology.