The Saprospiraceae family is a very diverse family within the phylum Bacteroidetes, commonly present in high abundance in wastewater treatment plants (WWTPs) worldwide, such as the genus OLB8, but little is known about their function and importance. The genera described are characterized by rod-shaped or filamentous morphology and an aerobic heterotrophic metabolism with their potential involvement in nutrient removal in WWTPs. Here, we used the MiDAS4 global survey, including samples from 480 WWTPs located in 30 countries, to analyze the abundance and global distribution of members of the Saprospiraceae family. In addition, we retrieved 32 high-quality metagenome assembled genomes (MAGs) from Danish WWTPs for metabolic reconstruction, and designed novel fluorescence in situ hybridization (FISH) probes for visualization and in combination with Raman microspectroscopy to detect and confirm important physiological features. FISH revealed rod-shaped morphologies for the three most abundant genera, present mostly inside the flocs. The genomic potential reveled diverse metabolism for genus OLB8 and other genera with possible degradation of polysaccharides, other carbon complexes and partial denitrification. FISH-Raman showed a presence of glycogen and PHA, also confirmed by the metabolic potential of MAGs, while none of the genera contained polyphosphate. These results provide the first overview of some of the most abundant Saprospiraceae genera present across the world and their potential involvement in polysaccharides and other carbon complex degradation and nutrient removal in WWTPs.
