The multiplicity of bacterial DNA methylases has been shown for new microorganisms, Mycobacteria and Shigella, by a double-step procedure including column chromatography followed by isoelectric focusing of the total methylase fraction. The profiles of the DNA methylating activity of Sh. sonnei 47 and M. butyricum strains were studied. Sh. sonnei 47 cells were found to contain five different proteins responsible for DNA methylation and having pI 4.2, 5.3, 6.2, 8.4 and 9.2. Four M. butyricum methylases were represented by proteins with pI 4.2, 6.0, 8.0 and 9.0.