[Directed search for streptomycetes that are producers of ionophoric antibiotics].

Streptomyces producing ionophore antibiotics were searched for in various natural substrata, such as soil, sea water, and coastline sea mud, in many geographical regions. A total of 393 Streptomyces strains were isolated, 308 of which proved to be capable of producing antibiotics; 135 of these contained water-insoluble antibiotically active substances in the mycelium. Studies by radioindication, spectrophotometry, and potentiometry demonstrated that these partially purified hydrophobic antibiotics possessed ionophore properties.