Summary auto-generated
This study proposes reviving the genus Kitasatospora as a separate taxon from Streptomyces. The authors analyzed 16S ribosomal DNA sequences and 16S-23S rRNA gene spacer sequences from 12 actinomycete strains. Phylogenetic analyses using neighbor-joining and maximum-parsimony methods consistently showed that Kitasatospora species formed a stable, distinct monophyletic clade separate from Streptomyces. The 16S-23S spacer analysis was particularly informative, clearly distinguishing the two genera as separate lineages regardless of outgroup selection. Beyond molecular evidence, the genera differ chemotaxonomically: Kitasatospora contains substantial amounts of meso-diaminopimelic acid and galactose in whole-cell hydrolysates, while Streptomyces lacks these characteristics. Additionally, Kitasatospora species exhibit unique phenotypic features including formation of submerged spores in liquid culture and resistance to polyvalent Streptomyces phages. Based on phylogenetic, chemotaxonomic, and phenotypic evidence, the authors recommend restoring Kitasatospora as a valid genus and transferring three previously designated Streptomyces species to Kitasatospora.
Key findings
- Kitasatospora species form a stable, distinct monophyletic clade separate from Streptomyces in phylogenetic analyses of 16S rRNA and 16S-23S spacer sequences
- Kitasatospora contains major amounts of meso-diaminopimelic acid (49-89%) and galactose in cell walls, contrasting with Streptomyces (1-16% meso-DAP) and lacking galactose
- 16S-23S rRNA gene spacers consistently segregate Kitasatospora and Streptomyces into distinct clades with high bootstrap values, independent of outgroup selection
- Kitasatospora species share unique phenotypic features including formation of submerged spores and resistance to Streptomyces phages, rarely observed in Streptomyces
- Nine nucleotide signatures specific to Kitasatospora in the spacer region enable PCR-based discrimination between the two genera
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Abstract
We determined almost complete 16S ribosomal DNA sequences for 12 actinomycete strains which were either previously classified as Kitasatospora strains or defined as Streptomyces strains but shown to contain major Amounts of meso-diaminopimelic acid in their whole-cell hydrolysates. These sequences were subjected to phylogenetic analyses together with the sequences of 34 Streptomyces species. Phylogenetic trees were reconstructed by using both neighbor-joining and maximum-parsimony methods. The Kitasatospora species always formed a stable monophyletic clade. However, the genus Kitasatospora appeared to be either a sister taxon of the genus Streptomyces or a lineage that originated from within Streptomyces species, depending on the outgroup used. Phylogenetic trees were also constructed by using the sequences of the 16S-23S rRNA gene spacers. Sereptomyces and Kitasatospora species were consistently recovered as two distinct clades independent of the outgroup used. On the basis of phylogenetic, chemotaxonomic, and phenotypic evidence, we propose that the genus Kitasatospora Omura et al. 1982 should be revived.