DNA Adenine Methylase Mutants of Salmonella typhimurium and a Novel Dam-Regulated Locus

Mutants of Salmonella typhimurium lacking DNA adenine methylase were isolated; they include insertion and deletion alleles. The dam locus maps at 75 min between cysG and aroB, similar to the Escherichia coli dam gene. Dam- mutants of S. typhimurium resemble those of E coli in the following phenotype...

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Bibliographic Details
Published in:Genetics (Austin) 1996-09, Vol.144 (1), p.15-26
Main Authors: Torreblanca, J, Casadesus, J
Format: Article
Language:English
Subjects:
Bacteria
Chromosome Mapping
Cloning, Molecular
Deoxyribonucleic acid
DNA
DNA Methylation
DNA Transposable Elements
Escherichia coli
Escherichia coli Proteins
Gene Deletion
Genetic Complementation Test
Genetics
Investigations
Mutagenesis, Insertional
Mutation
Salmonella typhimurium
Salmonella typhimurium - enzymology
Salmonella typhimurium - genetics
Salmonella typhimurium - radiation effects
Site-Specific DNA-Methyltransferase (Adenine-Specific) - genetics
Site-Specific DNA-Methyltransferase (Adenine-Specific) - metabolism
Ultraviolet Rays
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Summary:Mutants of Salmonella typhimurium lacking DNA adenine methylase were isolated; they include insertion and deletion alleles. The dam locus maps at 75 min between cysG and aroB, similar to the Escherichia coli dam gene. Dam- mutants of S. typhimurium resemble those of E coli in the following phenotypes: (1) increased spontaneous mutations, (2) moderate SOS induction, (3) enhancement of duplication segregation, (4) inviability of dam recA and dam recB mutants, and (5) suppression of the inviability of the dam recA and dam recB combinations by mutations that eliminate mismatch repair. However, differences between S. typhimurium and E. coli dam mutants are also found: (1) S. typhimurium dam mutants do not show increased UV sensitivity, suggesting that methyl-directed mismatch repair does not participate in the repair of UV-induced DNA damage in Salmonella. (2) S. typhimurium dam recJ mutants are viable, suggesting that the Salmonella RecJ function does not participate in the repair of DNA strand breaks formed in the absence of Dam methylation. We also describe a genetic screen for detecting novel genes regulated by Dam methylation and a locus repressed by Dam methylation in the S. typhimurium virulence (or "cryptic") plasmid.
ISSN:0016-6731
1943-2631
1943-2631
DOI:10.1093/genetics/144.1.15