RESUMEN
Actinomycetes are antibiotic-producing filamentous bacteria that have a mycelial life style. The members of the three genera classified in the family Streptomycetaceae, namely Kitasatospora, Streptacidiphilus and Streptomyces, are difficult to distinguish using phenotypic properties. Here we present biochemical and genetic evidence that helps underpin the case for the continued recognition of the genus Kitasatospora and for the delineation of additional Kitasatospora species. Two novel Kitasatospora strains, isolates MBT63 and MBT66, and their genome sequences are presented. The cell wall of the Kitasatospora strains contain a mixture of meso-and LL-diaminopimelic acid (A2pm), whereby a single DapF surprisingly suffices to incorporate both components into the Kitasatospora cell wall. The availability of two new Kitasatospora genome sequences in addition to that of the previously sequenced Kitasatospora setae KM-6054(T) allows better phylogenetic comparison between kitasatosporae and streptomycetes. This showed that the developmental regulator BldB and the actin-like protein Mbl are absent from kitasatosporae, while the cell division activator SsgA and its transcriptional activator SsgR have been lost from some Kitasatospora species, strongly suggesting that Kitasatospora have evolved different ways to control specific steps in their development. We also show that the tetracycline-producing strain "Streptomyces viridifaciens" DSM 40239 not only has properties consistent with its classification in the genus Kitasatospora but also merits species status within this taxon.