Deoxyribonucleic acid adenine and cytosine methylation in Salmonella typhimurium and Salmonella typhi.

The methylations of adenine in the sequence -GATC- and of the second cytosine in the sequence - [Formula: see text] - were studied in Salmonella typhimurium and in Salmonella typhi. The study was carried out by using endonucleases which restrict the plasmid pBR322 by cleavage at the sequences -GATC- (DpnI and MboI) and - [Formula: see text] - (EcoRII). The restriction patterns obtained for this plasmid isolated from transformed S. typhimurium and S. typhi were compared with those of pBR322 isolated from Escherichia coli K-12. In E. coli K-12, adenines at the sequence -GATC- and the second cytosines at - [Formula: see text] - are met hylated by enzymes coded for by the genes dam and dem, respectively. From comparison of the restriction patterns obtained, it is concluded that S. typhimurium and S. typhi contain genes responsible for deoxyribonucleic acid methylation equivalent to E. coli K-12 genes dam and dcm.