The genus Saccharothrix is phylogenetically heterogeneous on the basis of analysis of almost complete 16S rDNA sequences. An evaluation of chemotaxonomic, morphological and physiological properties in the light of the molecular phylogeny data revealed that several species are misclassified. Saccharothrix aerocolonigenes NRRL B-3298T and Saccharothrix flava NRRL B-16131T constitute a lineage distinct from Saccharothrix and separate from Lentzea. The genus Lechevalieria gen. nov. is proposed for these species. Lechevalieria aerocolonigenes comb. nov. is the type species and S. flava is transferred as Lechevalieria flava comb. nov. Although Lentzea albidocapillata, the type species of the genus Lentzea, was transferred recently to the genus Saccharothrix, the revival of Lentzea is clearly supported by molecular phylogenetic and chemotaxonomic data. The description of the revived genus is emended to include galactose, mannose and traces of ribose as diagnostic whole-cell sugars and MK-9(H4) as the principal menaquinone and elimination of tuberculostearic acid as a diagnostic component in the fatty acid profile. Saccharothrix waywayandensis NRRL B-16159T, S. aerocolonigenes NRRL B-16137 and 'Asiosporangium albidum' IFO 16102 are members of the amended genus Lentzea on the basis of phylogenetic and chemotaxonomic properties. S. waywayandensis is transferred to Lentzea as Lentzea waywayandensis comb. nov., while the new species Lentzea californiensis sp. nov. and Lentzea albida sp. nov. are described for S. aerocolonigenes NRRL B-16137 and 'A. albidum' IFO 16102, respectively. Nucleotide signatures in the 16S rDNA sequences are defined that are diagnostic for the genera Lechevalieria, Lentzea and Saccharothrix.

The generic position of two isolates from soils inside a gold mine cave in Kongju, Korea, was determined by 16S rDNA sequencing and chemotaxonomic characteristics. Phylogenetic analysis indicated that both of the isolates formed a clade with Lentzea albidocapillata and members of the genus Saccharothrix of the family Pseudonocardiaceae. The chemical composition of the isolates and of Lentzea albidocapillata was consistent with that of the genus Saccharothrix, which is characterized by a type III cell wall (the meso-isomer of diaminopimelic acid, and galactose and rhamnose as characteristic whole-cell sugars), MK-9(H4) as the major menaquinone, and a phospholipid type PII pattern (phosphatidylethanolamine as a diagnostic phospholipid). The combination of morphological features, chemotaxonomic characters and phylogenetic data supported the proposal that Lentzea albidocapillata, the only and type strain of the genus Lentzea, should be transferred to the genus Saccharothrix. On the basis of physiological properties, cellular fatty acid composition and DNA-DNA hybridization data, two new species within the genus Saccharothrix are proposed: Saccharothrix violacea sp. nov., type strain LM 036T (= IMSNU 50388T), and Saccharothrix albidocapillata comb. nov., type strain DSM 44073T (=IMSNU 21253T).