PRODUCTION OF ACTINORHODIN-RELATED BLUE PIGMENTS BY STREPTOMYCES-COELICOLOR A3(2)

The genetically well-known strain Streptomyces coelicolor A3(2) produc es the pH indicator (red/blue) antibiotic actinorhodin, but not all th e ''blue pigment'' produced by this strain is actinorhodin. When the o rganism was subjected to various nutrient limitations (ammonium, nitra te, phosphate, or trace elements), and also during growth cessation ca used by a relatively low medium pH, blue pigment production was initia ted but the pigment and its location varied. At pH 4.5 to 5.5, signifi cant formation of actinorhodin occurred and was Located exclusively in tracellularly. At pH 6.0 to 7.5 a different blue pigment was produced intracellularly as well as extracellularly. It was purified and identi fied as gamma-actinorhodin (the lactone form of actinorhodin). Analysi s of act mutants of S. coelicolor A3(2) confirmed that both pigments a re derived from the act biosynthetic pathway. Mutants with lesions in actII-ORF2, actII-ORF3, or actVA-ORF1, previously implicated or sugges ted to be involved in actinorhodin export, were impaired in production of gamma-actinorhodin, suggesting that synthesis of gamma-actinorhodi n from actinorhodin is coupled to its export from the cell. However, e ffects on the level of actinorhodin production were also found in some mutants.