Isolation and Characterization of Microsphaera multipartita gen. nov., sp. nov., a Polysaccharide-Accumulating Gram-Positive Bacterium from Activated Sludge

A new gram-positive bacterium was isolated from activated sludge acclimated with sugar-containing synthetic wastewater. This organism, designated strain Y-104T (T = type strain), was a coccus-shaped, aerobic chemoorganotroph that had a strictly respiratory type of metabolism with oxygen as the terminal electron acceptor. This strain accumulates large amounts of polysaccharide in its cells. Strain Y-104T has the following chemotaxonomic characteristics: it contains menaquinone MK-8(H4), its DNA G+C content is 67.5 mol%, and it contains meso-diaminopimelic acid. No previously described high-G+C-content gram-positive coccus contains both MK-8(H4) as a major quinone and meso-diaminopimelic acid in its cell wall. A phylogenetic analysis based on 16S rRNA sequences showed that strain Y-104T represents a line of descent distinct from those of previously described species of high-G+C-content gram-positive bacteria and that members of the genus Frankia are the nearest neighbors. Therefore, we concluded that our isolate should be assigned to a new genus and species, for which we propose the name Microsphaera multipartita. The type strain is strain Y-104.