Metagenomic characterization of Candidatatus Defluviicoccus tetraformis TFO71, a tetrad-forming organism, predominant in an anaerobic-aerobic membrane bioreactor with deteriorated biological phosphorus removal
In an acetate-fed anaerobic-aerobic membrane bioreactor with deteriorated enhanced biological phosphorus removal (EBPR), Defluviicoccus-related tetrad-forming organisms (DTFO) were observed to predominate in the microbial community. Using metagenomics, a partial genome of the predominant DTFO, “Candidatus Defluviicoccus tetraformis TFO71,” was successfully constructed and characterized. Examining the genome confirmed the presence of genes related to the synthesis and degradation of glycogen and polyhydroxyalkanoate (PHA), which function as energy and carbon storage compounds. Both TFO71 and Candidatus Accumulibacter phosphatis (CAP) UW-1, a representative polyphosphate-accumulating organism (PAO), have PHA metabolism-related genes with high homology, but TFO71 has unique genes for PHA synthesis, gene regulation, and granule management. We further discovered genes encoding DTFO polyphosphate (polyP) synthesis, suggesting that TFO71 may synthesize polyP under untested conditions. However, TFO71 may not activate these genes under EBPR conditions because the retrieved genome does not contain inorganic phosphate transporters that are characteristic of PAOs (CAP UW-1, Microlunatus phosphovorus NM-1, and Tetrasphaera species). As a first step in characterizing EBPR-associated DTFO metabolism, this study identifies important differences between TFO and PAO that may contribute to EBPR community competition and deterioration