Planctopirus ephydatiae, a novel Planctomycete isolated from a freshwater sponge.

The microbiome of freshwater sponges is rarely studied, and not a single novel bacterial species has been isolated and subsequently characterized from a freshwater sponge to date. A previous study showed that 14.4% of the microbiome from Ephydatia fluviatilis belong to the phylum Planctomycetes. Therefore, we sampled an Ephydatia sponge from a freshwater lake and employed enrichment techniques targeting bacteria from the phylum Planctomycetes. The obtained strain spb1T was subject to genomic and phenomic characterization and found to represent a novel planctomycetal species proposed as Planctopirus ephydatiae sp. nov. (DSM 106606 = CECT 9866). In the process of differentiating spb1T from its next relative Planctopirus limnophila DSM 3776T, we identified and characterized the first phage - Planctopirus phage vB_PlimS_J1 - infecting planctomycetes that was only mentioned anecdotally before. Interestingly, classical chemotaxonomic methods would have failed to distinguish Planctopirus ephydatiae strain spb1T from Planctopirus limnophila DSM 3776T. Our findings demonstrate and underpin the need for whole genome-based taxonomy to detect and differentiate planctomycetal species.