Endospore formation by Streptomyces avermitilis in submerged culture

摘要

The ability of streptomycetes to form endospores during their life cycle was studied in submerged cultures of Streptomyces avermitilis. Submerged S. avermitilis spores were most intensely formed (1) during the culture development cycle on synthetic medium CP1 with glucose under phosphate limitation and (2) in autolysing cell suspensions of high density obtained by tenfold concentration in phosphate buffer (pH 7.2) with 0.2% CaCl2 of stationary-phase cells grown in synthetic medium. Endospores of S. avermitilis formed in submerged cultures shared the major characteristics of specialized microbial resting forms: heat resistance, resistance to lysozyme, ability to retain the main species-specific features, and ultrastructural organization characteristic of endospores. They can be considered a resting form of streptomycetes alternative to the spores formed exogenously on aerial mycelium in surface cultures.