Instituto Biomar SA

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).

Three new cytotoxic 3,6-disubstituted indoles (1-3) were isolated from the mycelium of a strain identified as Streptomyces sp. (BL-49-58-005), which was separated from a Mexican marine invertebrate, and their structures established by analysis of NMR and mass spectral data. GI(50) values for 1 and 2 in cytotoxic bioassays against a panel of 14 different tumor cell lines were estimated at micromolar range, while compound 3 showed no activity in the same assays.

A new poplycyclic xanthone, IB-00208 (I), was isolated from the culture broth of a marine Actinomadura sp.I contains a xanthone unit and is structurally related to a small family of polycyclic antibiotics including cervinomycins, simaomycins and actinoplanones.