Streptomyces glaucescens, strain Tü 49 = ETH 22794, produces hydroxystreptomycin as well as the tetracenomycins, a mixture of several lipophilic antibiotics. The main component and the most active one is tetracenomycin C. Tetracenomycin C has a molecular formula C23H20O11 and is chemically related to tetracyclines and anthracyclinones. The pale yellow antibiotic is active against some gram-positive bacteria, especially against streptomycetes. Gram-negative bacteria and fungi are not inhibited. In considering the differences of biological activity and the functional groups of the molecule, tetracenomycin C is not a member of the tetracycline or anthracyclinone group of antibiotics.