Minicells of Bacillus subtilis

Abstract

After nitrosoguanidine (N methyl N' nitro N nitrosoguanidine) mutagenesis, two B. subtilis mutants (div IV A1 and div IV B1) were isolated that are defective in the location of division site along cell length. Both mutations were transferred into strain CU403 by transformation, and their properties were studied in the CU403 genetic background. Location of divisions in close proximity to cell pole regions in both mutants results in minicell production. Purified minicells contain a ratio of ribonucleic acid to protein comparable to that found in the parent cells. Autoradiographs of 3H thymine incorporation into deoxyribonucleic acid (DNA), thymine 2 14C incorporation into DNA, electron micrographs, and chemical analyses for DNA all fail to demonstrate DNA in the minicells. Minicells produced by both mutants are highly motile, an indication of functional energy metabolism. Electron micrographs reveal that minicells are produced by a structurally normal division mechanism and that minicells contain a normal cell surface. The div IV A1 mutation has been mapped by PBS1 transduction linked to ura. The div IV B1 mutation is closely linked to pheA by both PBS1 transduction and by co transformation.