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The glycopeptide antibiotic A40926 is produced by the actinomycete strain ATCC 39727, originally classified, on the basis of morphology and cell-wall composition, as a member of the genus Actinomadura1). In the last decade, 165 rRNA gene (16S rDNA) sequence-based phylogenetic analysis has been widely applied for classification of bacteria. To this respect, actinomycete taxonomy has been subjected to revisions allowing the clarification of relationships at various taxonomic levels2). In 1990 KROPPENSTEDT et al.3) proposed the transfer of several Actinomadura species to the genus Microtetraspora and the taxonomic revision of the two genera. The latter genus, however, has later been emended and several species (namely, all those originally included in the genus Actinomadura) transferred to the new genus Nonomuraea on the basis of 16S rDNA sequence analysis4). Strain ATCC 39727 is industrially important as the producer of A40926, the precursor of the antibiotic dalbavancin, currently under clinical development5). Thus, it was important to classify this strain according to the most recent taxonomy. Previously, 1147nt of the 16S rDNA sequence of strain ATCC 39727 were deposited to GenBank (AF135374). Following published procedures6), we expanded this sequence to 1460nt (corresponding to 94.6% of the E. coli sequence, accession number AJ582011). Database searches revealed that the most closely related sequences corresponded to the 16S rDNA of several Nonomuraea species, all having over 98% identity with that of ATCC 39727. Pairwise comparison with the 165 rDNA sequences of Actinomadura madurae DSM 43067T and Microtetraspora glauca DSM 43311T (type species of these two genera) showed much lower identities, i.e. 93.4% and 95.5% respectively. The 16S rDNA sequence of strain ATCC 39727 was then aligned with the 16S rDNA sequences of the type species of all genera within the suborder Streptosporangineae, to which Actinomadura, Microtetraspora and Nonomuraea belong, as well as with that of several Nonomuraea species. The resulting phylogenetic tree (Fig. 1) clearly shows that strain ATCC 39727, together with all the Nonomuraea strains, forms a distinct clade within the family Streptosporangiaceae. In this tree, the three validly described Microtetraspora species form a coherent cluster, clearly distinguished from Nonomuraea. The data from the fatty acid profile are in agreement with this assignment. The major fatty acids of Actinomadura spp. are hexadecanoic, 14-methylpentadecanoic (iso-16:0) and 10-methyl-octadecanoic acid, while Nonomuraea and Microtetraspora contain high amounts of iso-16:0 with a significant fraction of 10-methyl-heptadecanoic acid (10Me-17)3). In Microtetraspora the amount of iso-16:0 is more than twice that of 10Me-17, while for Nonomuraea the levels of iso-16:0 and 10Me-17 are either comparable or the latter is more abundant4). The major fatty acid of strain ATCC 39727 is 10Me-17, with a slightly smaller amount of iso-16:07). From the phylogenetic analysis and the fatty acid profiles we can thus conclude that strain ATCC 39727 belongs to the genus Nonomuraea.

Reclassification as a Nonomuraea sp. of the Strain ATCC 39727, Producing the Glycopeptide Antibiotic A40926.