Morphological changes accompanying actinomycin production in Streptomyces antibioticus

Abstract

The fine structure of the actinomycin producing bacterium Streptomyces antibioticus has been studied. The typical appearance of freshly inoculated cells is one of a generally electron dense cytoplasm. As cellular protein synthesis ceases and secondary metabolism (actinomycin biosynthesis) is initiated, a gradual loss of cytoplasmic density occurs, revealing in many cells membrane enclosed vesicles and an extensive cytoplasmic membrane system. Vesicles are seen to be compartmented by cell wall and may be released into the medium by a subsequent breakdown of the cell wall. The data suggest that the appearance of these internal structures is not due to a differentiation of S. antibioticus cells related to the initiation of secondary metabolism, but rather that these vesicles and membrane systems may be normal subcellular structures which become visible only after a loss of cytoplasmic material due to aging of the cells.