Small cells in pure cultures of Agromyces ramosus and in natural soil

Previously, transmission electron-microscopic observations of thin-sectioned and frozen-etched preparations of microorganisms concentrated directly from soil showed many cells that were considerably smaller than the cells found in pure cultures isolated from soil. The present study shows that pure cultures of the soil bacterium Agromyces ramosus can produce cells as small as those observed in natural soil. Growth on a nutritionally limiting medium and the presence of an agar surface contributed to the occurrence of these small cells.