[Sensitivity of E. coli and C. freundii strains to 5-azacytidine].

The sensitivity of E. coli and C. freundii strains to 5-azacytidine and restrictase activity of partially purified cell-free extracts were investigated.

[Methylation of Eco RI (GAm'ATTC) sequences of bacterial DNA].

The methylation of Eco RI (GAm6 ATTC) sequences of DNA of bacteria related to the main branches of their phylogenetic dendrogramme, was studied. It was found that methylation of Eco RI sites is observed in bacteria Caulobacter and in Thermus aquaticus. This finding can be substantiated by the resistance of these DNAs to Eco RI restrictase as well as by the fact that Bam HI fragments of these DNAs cloned within the composition of the vector plasmid pUC8 in E.

[DNA-methylase Sau 3A: isolation and various properties].

DNA-methylase Sau 3A has been isolated for the first time from Staphylococcus aureus 3A cells and purified by column chromatography on phosphocellulose PII, heparin-Sepharose and blue Sepharose. The purified enzyme methylates the GATC sequence with the formation of GATm5C as can be evidenced from the protection of DNA from digestion with restrictases Sau 3A and Bam HI, the lack of the C3H3-group incorporation into Sau 3A DNA-restricts and the formation of a single methylated base m5C. Sau 3A methylase modifies only a two-filament (but not one-filament) DNA.

[Effect of DNA methylation on transformation of Saccharomyces cerevisiae].

To study the action of methylation on transformation efficiency, pA2 was methylated in vitro with M. Sau3A, M. AluI, M.

[DNA methylation in the cells of Escherichia coli MRE 600 in the presence of S-methylmethionine].

The effect of S-methylmethionine (SMM), a methyl group donor, on enzymatic methylation of DNA in E. coli MRE 600 cells was studied. It was found that SMM can be used as a donor of methyl groups during bacterial DNA methylation in vivo without changing the specificity of DNA methylation.