Context. Phosphate is an important, but scarce resource. Recycling of phosphate from wastewater is one way to solve this problem, a process where polyphosphate-accumulating organisms(PAOs), such as the well-known genera Candidatus Accumulibacter, Tetrasphaera, along with the recently confirmed Dechloromonas store phosphate intracellularly for further removal and recovery. These genera show a diverse metabolism but are all dependend on alternating anaerobic and aerobic conditions.
Gap. Recent mass balance studies of biomass from full-scale plants with enhanced biological P-removal indicate that several unknown PAO exists in some plants and that they may be important for the removal of P.
Aim. To investigate the ecophysiology of several genera of putative polyphosphate-accumulating organisms, including the genera Rhodoferax, Tessaracoccus, and Sulfuritalea, to determine whether they are PAO or not.
Methods. We utilized 16S rRNA gene sequencing to investigate the abundance of the genera, metagenomics to retrieve high-quality metagenome assembled genomes(MAGs) for annotating metabolic pathways, and quantitative FISH-Raman analysis of polyphosphate and other intracellular storage polymers in probe-defined cells.
Findings. Rhodoferax and Sulfuritalea were observed in variating relative read abundances in both Danish and global plants comprising up to 5.8% and 2.3%, respectively. Tessaracoccus was not so abundant globally, but was found to contribute up to 2.6% in Danish wastewater treatment plants. FISH-Raman analysis of Tessaracoccus and Rhodoferax showed signs of intercellular stored polyphosphate. The possibility of these two genera being polyphosphate-accumulating organisms was further supported by the retrieved MAGs, where important genes indicating polyphosphate storage such as Pit, PstSCAB, and PhoU were present in both genera.
Utilization. By elucidating the remaining unknown polyphosphate-accumulating organisms and their ecophysiology, we can get a comprehensive understanding of all microorganisms that contribute to enhanced biological phosphorus removal, thereby enable surveillance and possibly better management of the wastewater treatment plants.
