M-81, a new peptide antibiotic produced by Streptomyces griseus subsp. Psychrophilus at moderate temperature.

M-81, a new water-soluble basic peptide antibiotic, was isolated from the culture filtrate of Streptomyces griseus subsp. psychrophilus AKU 2881, which produces cryomycin only at low temperatures. M-81 was produced at 20-37°C, but not below 20 C. M-81 was active against some Gram-positive bacteria. Its antimicrobial spectrum is more limited than those of cryomycin. It darkens at 208°-213°C with decomposition. The LD50 in mice by intraperitoneal injection is more than 300 mg/kg.