Streptomyces tacrolimicus sp. nov., a low producer of the immunosuppressant tacrolimus (FK506)

Abstract

The number of tacrolimus (FK506)-producing isolates has increased remarkably because of the clinical importance of tacrolimus as an immunosuppressant. However, the taxonomy of several of these isolates has not been studied. The taxonomic status of strain ATCC 55098T, a tacrolimus-producing strain, was determined in this study. The genotypic, phenotypic and chemotaxonomic properties were consistent with the inclusion of strain ATCC 55098T in the genus Streptomyces. The 16S rRNA gene sequence of strain ATCC 55098T was determined and used to generate phylogenetic trees with corresponding sequences of the most closely related type strains (≥98 % 16S rRNA gene sequence similarity) of species of the genus Streptomyces. Strain ATCC 55098T formed a distinct phylogenetic branch adjacent to a cluster comprising Streptomyces fulvissimus NBRC 13482T and Streptomyces flavofungini NBRC 13371T. However, morphological and physiological tests and DNA–DNA relatedness distinguished strain ATCC 55098T from its closest phylogenetic neighbours. On the basis of these results, strain ATCC 55098T represents a novel species of the genus Streptomyces, for which the name Streptomyces tacrolimicus sp. nov. is proposed. The type strain is ATCC 55098T ( = CECT 7664T).