Context. The genus Tetrasphaera belongs, along with Ca. Accumulibacter and Dechloromonas, to the most abundant polyphosphate accumulating organisms (PAOs) worldwide in wastewater treatment plants with enhanced biological removal (EBPR). Several Tetrasphaera species are isolated, showing some diversity in their physiology, and the available data indicates a clear niche differentiation to the two other PAO genera, possibly explaining their co-existence in many EBPR plants.
Gap. None of the Tetrasphaera isolates represent the abundant species actually present in WWTPs worldwide, so our knowledge about the "important" Tetrasphaera is very limited.
Aim. To investigate the phylogeny, metabolic potential, and global distribution of the Tetrasphaera actually present in full-scale plants.
Methods. We analyzed 11 new high-quality metagenome assembled genomes (MAGs) from uncultured Tetrasphaera and other genomes from the Dermatophilaceae family, which includes Tetrasphaera isolates. The global distribution was investigated in the framework of the MIDAS global survey.
Findings. Phylogenomic analysis of the MAGs revealed that the former "Tetrasphaera" consist of several distinct genera that are not properly resolved in 16S rRNA gene trees. The most abundant genus was given the name Ca. Phosphoribacter, and it was detected across the globe in high numbers with two abundant species, Ca.P. baldrii and Ca. P. hodrii. Species-specific FISH probes were designed for visualization. FISH-Raman microspectroscopy in combination with phosphate cycling experiments confirmed that both species are indeed PAOs. They seem to have a very diverse physiology but, in contrast to other PAOs, do not accumulate PHA or glycogen.
Utilization. It is important to include Ca. Phosphoribacter in future investigations of the EBPR process as it represents the most abundant former Tetrasphaera lineage and PAO in EPBR systems in Denmark and globally.
Acknowledgement. We thank the Villum foundation for funding
