BIOSYNTHESIS OF 1-N-METHYLALBONOURSIN BY AN ENDOPHYTIC STREPTOMYCES SP ISOLATED FROM PERENNIAL RYEGRASS

A Streptomyces sp. has been isolated from perennial ryegrass seedling tissues from which it emerged in liquid culture after surface sterilization of seed. In submerged fermentation the Streptomyces produced 1-N-methylalbonoursin [1], a fluorescent and weakly antibiotic metabolite which was identified by ms and X-ray crystallography and further characterized by, uv, H-1-, and C-13-nmr spectroscopy. The biosynthesis of the diketopiperazine skeleton of compound 1 from leucine and phenylalanine was demonstrated. A close affinity of the Streptomyces sp. with Streptomyces albus, from which this metabolite was first isolated, is implied. The possibility that the Streptomyces sp. should be recognized as an endophyte of ryegrass is discussed.