Metabolic potential of superphylum Patescibacteria reconstructed from activated sludge samples in a municipal wastewater treatment plant

Patescibacteria are widely distributed in a variety of environments and are often detected in activated sludge. However, little is known about its detailed phylogeny, morphology, ecophysiological role in activated sludge, and interactions with other microorganisms. In this study, we identified microorganisms correlated with Patescibacteria in activated sludge by correlation analysis using 16S rRNA gene, and predicted the metabolic potentials of Patescibacteria by metagenomic analysis. The metagenome assembled genomes (MAGs) of Patescibacteria consisted of three Saccharimonadia, three Parcubacteria, and one Gracilibacteria, and showed strong positive correlation of relative abundances with Chitinophagales. The metabolic prediction from 10 recovered Patescibacterial MAGs and five Chitinophagales MAGs supports the mutualistic interactions between a member of Saccharimonadia and Chitinophagales via N-acetylglucosamine, between a member of Parcubacteria and Chitinophagales via nitrogen compounds related to denitrification, and between Gracilibacteria and Chitinophagales via phospholipids in activated sludge. The findings obtained in this study indicate that various interactions of Patescibacteria with Chitinophagales were important for their survival in activated sludge ecosystem.