Millisia brevis gen. nov., sp. nov., an actinomycete isolated from activated sludge foam

Abstract

The taxonomic position of two mycolic-acid-producing actinomycetes, isolates J81Tand J82, which were recovered from activated sludge foam, was clarified. Comparative 16S rRNA gene sequence studies indicated that the organisms formed a distinct lineage within theCorynebacterineae16S rRNA gene tree. The taxonomic integrity of this group was underpinned by a wealth of phenotypic data, notably characteristic rudimentary right-angled branching. In addition, isolate J81Tcontained the following:meso-diaminopimelic acid, arabinose and galactose;N-glycolated muramic acid residues; a dihydrogenated menaquinone with eight isoprene units as the predominant isoprenologue; a fatty acid profile rich in oleic and palmitoleic acids and with relatively small proportions of myristic, stearic and tuberculostearic acids; mycolic acids with 44–52 carbons; and diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannosides as major polar lipids. Strain J81Twas found to have a chemotaxonomic profile that serves to distinguish it from representatives of all of the other taxa classified as belonging to the suborderCorynebacterineae. In the light of these data, it is proposed that the two isolates be classified in a novel monospecific genus. The name proposed for this taxon isMillisia brevisgen. nov., sp. nov.; strain J81T(=DSM 44463T=NRRL B-24424T) is the type strain ofMillisia brevis.