Deoxyribonucleic Acid Adenine and Cytosine Methylation in Salmonella typhimurium and Salmonella typhi

Abstract

The methylations of adenine in the sequence -GATCand of the second cytosine in the sequence -Cc(A)GGwere 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 -ICCQA)GG- (EcoRII). The restriction patterns obtained for this plasmid isolated from transfonned 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 -GATCand the second cytosines at -CC( A )GGare met hylated by enzymes coded for by the genes dam and dcm, 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.on July 31, 2020 by guest

DNA adenine methylation of GATC sequences appeared recently in the Escherichia coli lineage

“…We found that all gram-negative eubacteria of the families Enterobacteriaceae, Parvobacteriaceae, and Vibrionaceae tested are Dam'. Previously, the Dam' phenotype has been reported in other Proteus and Vibrio species, as well as in the related genera Haemophilus, Enterobacter, Escherichia, Erwinia, Klebsiella, Providencia, Salmonella, and Serratia (3,11,33). We found that the five cyanobacteria tested were Darm'.…”

“…For this purpose, we used the isoschizomer enzymes MboI, Sau3A, and DpnI. MboI cleaves unmethylated GATC sequences, Sau3A cuts GATC regardless of the state of methylation, whereas DpnI only cuts methylated GATC sequences (9,16,30 Dam-(3, 6), whereas both Dam' and Dam-bacteria have been detected among gram-negative bacteria (3,11). We have also tested five cyanobacteria, because a cyanobacterium, Anabaena variabilis, has been previously reported to be Dam' (8).…”

“…One can imagine that GATC sequences methylated on the adenine in these archaebacteria are part of longer Schematic representation of the phylogenetic relationships between Dam' and Dam-organisms. The Dam phenotype of various organisms has been deduced from data obtained in this work and from data collected in the literature (3,6,7,11,16,25,31,32). Dam+ organisms are underlined.…”

Bacterial mutagenesis: Review of new insights

“…A possible mechanism that dictates strand selection in mismatch repair events has been outlined by a series of cleverly conceived experiments (M. Meselson [14] , personal communication). E coli and Salmonella [22] contain DNA methylases that methylate adenine residues in the sequence 5' -GATC-3'/3'-CTAG-Sf [23]. E coli infected with lambda phage heteroduplexes containing mismatched base pairs preferentially repair certain mismatches on an unmethylated strand.…”

Mutagenesis, by methylating and ethylating agents, in mutH, mutL, mutS, and uvrD mutants of Salmonella typhimurium LT2

“…The results of transfection experiments with heteroduplex A DNAs that differ in the degree of methylation and carry different genetic markers (28) have led to the suggestion that the presence of N6-methyladenine in the parental strand allows it to be discriminated from the newly synthesized (unmethylated) daughter strand. Such methylation occurs at GATC sequences in both Escherichia coli and Salmonella typhimurium (7,10,17): in E. coli, the product of the dam gene has been identified as being responsible for this methylation (19). Recently, it has been suggested that methylinstructed mismatch repair is carried out by the products of the E. coli mutH, mutL, mutS, and uvrD genes (6,8,9,24,(27)(28)(29).…”