Cryptic Plasmids in a Minicell-Producing Strain of Salmonella typhimurium

A minicell-producing strain of Salmonella typhimurium contains two cryptic plasmids. One has a molecular weight of 2.6 x 10(6) to 2.8 x 10(6), is present in multiple copies per cell, and segregates into minicells. The other has a molecular weight of 130 x 10(6), is present in few copies per cell, and probably does not segregate into minicells.