A streptomycete was isolated from an Easter Island soil sample and found to inhibit Candida albicans, Microsporum gypseum and Trichophyton granulosum.The antibioticproducing microorganism was characterized and identified as Streptomyces hygroscopicus. The antifungal principle was extracted with organic solvent from the mycelium, isolated in crystalline form and named rapamycin. Rapamycin is mainly active against Candida albicans; minimum inhibitory concentration against ten strains ranged from 0.02 to 0.2 pg/ml.Its apparent activity against Microsporum gypseum and Trichophyton granulosum is lower because of its instability in culture media on prolonged incubation required by these fungi. No activity was observed against gram-positive and gram-negative bacteria. Acute toxicity in mice is low.Cultures of a streptomycete isolated from an Easter Island (Rapa Nui) soil sample were found to inhibit the yeast, Candida albicans, and the dermatophytes, Microsporum gypseum and Trichophyton granulosum; antibacterial activity was only marginal and limited to some grampositive species, such as Sarcina lutea and Staphylococcus aureus; all gram-negative bacteria tested were resistant. The active principle was isolated from the mycelium of the streptomycete and the crystalline material obtained after purification was found to inhibit mainly Candida albicans; lesser activity was observed against the dermatophytes and no activity was demonstrated against any of the gram-positive and gram-negative bacteria tested. The antibiotic was named rapamycin [Etymol.: Rapa-(Rapa Nui=Easter Island), -mycin]. Its structure is still unknown. This paper deals with the characterization of the producing streptomycete, the isolation and purification of the antibiotic and some of its biological properties. Identification of the Rapamycin-Producing StreptomyceteStreptomycete strain AY B-994 was isolated from a soil sample collected in Easter Island (Rapa Nui): the soil was diluted in distilled water and the resulting suspensions were plated on yeast-starch agar according to the double-layer technique of PORTER et al.".After one week of incubation at 28°C the streptomycete colonies were purified by repeated streaking and the pure strains grown separately on yeast-starch agar plates to yield confluent growth. After 4-,-10 days of incubation, discs (7 mm in diameter) were cut and transferred onto the surface of plates of Bacto-Blood Agar Base (Difco Laboratories, Detroit, Mich.) inoculated with test bacteria and SABOURAUD dextrose agar inoculated with test yeast and dermatophytes.The Blood Agar Base plates were inoculated with a standardized bacterial inoculum grown at 37"C for 5 hours in Bacto-Nutrient broth; the SABOURAUD dextrose agar plates were inoculated with a standardized inoculum consisting of cells of yeast or spores of dermatophytes.Plates were

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A streptomycete was isolated from a Guatemala soil sample and found to inhibit Grampositive bacteria including mycobacteria. The antibiotic-producing microorganism was characterized, identified as a new species and named Streptomyces ravidus. The antibiotic principle was extracted with organic solvent from the mycelium, isolated in crystalline form and named ravidomycin. Ravidomycin is mainly active against Gram-positive bacteria including mycobacteria. It shows only weak activity against Gram-negative organisms and no activity against fungi. Ravidomycin exhibits potent antitumor activity against P388 lymphocytic leukemia, Colon 38 tumor and CD8F1 mammary tumor. Acute toxicity in mice is low.

Increase in antimycin A production was achieved through a parallel strain and medium improvement program: a 125-fold augmentation (75 to 9,500ug/ml) was obtained. The selective system included antimycin A productivity, conidiation, sensitivity to ultraviolet radiation, growth rate and yield,