| The genus Streptomyces produces a large number of clinically important natural products. The biosynthesis of many of these products has been studied in detail, leading to a body of knowledge that is now being explored to produce new metabolites via genetic manipulation. In an effort to add to this bioinformatic "toolbox" an ongoing program to isolate novel secondary metabolite-producing Streptomyces species and clone their biosynthetic pathways has been established. As part of this program, Streptomyces strain CIT0036 was isolated from beach sand collected on Crown Island, Papua New Guinea. Initial assays of the fermentation products from this organism revealed strong activity against leukemia p388 cells. Subsequent investigation revealed the primary bioactive metabolite to be bafilomycin B1. The genes involved with the biosynthesis of this molecule were cloned and sequenced. A novel Acyltransferase (AT) domain specific for isobutyrate was identified. In vitro analyses of enzymes involved in tailoring of the macrolactone bafilomycin core was conducted to confirm their role in producing an unusual pendant moiety. A second natural product biosynthesis cluster was found adjacent to the bafilomycin biosynthesis genes. This cluster, which was also sequenced and annotated, appears to encode enzymes involved in the biosynthesis of a siderophore, tentatively named lohichelin. An alignment of the 16S sequence of strain CIT0036 indicated that it was most likely a member of the Streptomyces anulatus subgroup. However, the melanin production observed by this strain is a minority characteristic within this subgroup. Therefore a rigorous, polyphasic, characterization of this strain was undertaken. The results of this study indicate that CIT0036 is unique within the Streptomyces anulatus subgroup and has prompted the designation of this strain as a new species, Streptomyces lohii sp. nov. |
