ABSTRACT
A physical and genetic map of the IncI plasmid R144-drd3 was obtained by determining restriction endonuclease sites and by physical and genetic analysis of cloned fragments, of Tn1 insertion mutants and of deletion mutants.
Subject(s)
Escherichia coli/genetics , Plasmids , Chromosome Mapping , DNA Restriction Enzymes , DNA Transposable Elements , Genes, Bacterial , R Factors , Suppression, GeneticABSTRACT
Transformation of uropathogenic Escherichia coli strains with plasmid DNA was in general unsuccessful or very inefficient. Transformation was much more efficient when galE mutants of such strains, in which the lipopolysaccharide chains appeared shorter, were used as recipients.
Subject(s)
Escherichia coli/genetics , Genes, Bacterial , Lipopolysaccharides/physiology , Plasmids , Transformation, Bacterial , Escherichia coli/pathogenicity , Galactose/metabolism , Lipopolysaccharides/analysis , Mutation , Urinary Tract/microbiology , VirulenceABSTRACT
In Escherichia coli transformation with linear donor deoxyribonucleic acid, the recBC pathway is functional, but genetic analysis shows that the recBC nuclease is deleterious to linear deoxyribonucleic acid.
Subject(s)
Deoxyribonucleases/physiology , Escherichia coli Proteins , Escherichia coli/genetics , Transformation, Bacterial , DNA, Bacterial/genetics , Exodeoxyribonuclease V , Recombination, GeneticABSTRACT
E. coli K12 transformants, selected as leu+ or pyrA+ transformants, were analysed for inheritance of some closely linked unselected markers. Based on the observation that the number of recombinants which require, besides an integration event, one or more crossing-over events was negligible, a simple mapping function was deduced. The function L= e-kd, which directly relates observed linkage of an unselected marker and the relative distance of that unselected marker to the selected marker, gave a consistent interpretation of the experimental results.
Subject(s)
Escherichia coli , Genetic Linkage , Transformation, Genetic , Chromosome Mapping , Chromosomes, Bacterial , Leucine/metabolism , Pyridines/metabolism , Recombination, GeneticABSTRACT
We have developed an experimental system for studying concomitantly the fate of the donor DNA and the process of recombination after conjugation in Escherichia coli. We used a set of Hfr and F-strains carrying complementing lacZ mutations. Expression of the lacZ allele on the chromosomal fragment derived from the donor results in the formation of heat sensitive beta-galactosidase by complementation. By intragenic recombination between the two lacZ mutations a lacZ+ gene may be formed, and wild type beta-galactosidase will be synthesized subsequently. So the assay of heat sensitive and wild type beta-galactosidase enabled us to follow respectively the fate of the donor DNA and the recombination process. Using various recombination deficient recipient strains, we found that the donor DNA is progressively inactivated in recA, rec-34 and recH recipients, although the initial rate of expression is equivalent to that in a Rec+ recipient; no significant recombination was observed. In Rec+, recB or recG recipients there was no inactivation and recombination occurred. The kinetics of recombinant formation in the recB strain seems to differ from the wild type; in a recG recipient the recombination activity is significant, but lower than in the wild type recipient.
