Induction and Isolation of a Minicell-Producing Strain of Salmonella typhimurium

Summary A mutant of S. typhimurium which produces small spherical anucleate bodies (minicells) was induced and isolated after treatment of a normal strain of S. typhimurium with increasing amounts of triethylenemelamine (TEM). No differences were observed in growth characteristics or colonial morphology between the minicell-producing strain and the normal strain of S. typhimurium. The minicells were shown to be approximately onetenth the size of normal cells of S. typhimurium and were easily isolated from the larger parent cells by a combination of differential and density-gradient centrifugations. Purified minicell preparations contained about 0.007 the amount of DNA per cell as normal cells. They utilized glucose linearly with time, and were serologically indistinguishable from normal cells.