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DNA circle formation in Neisseria gonorrhoeae: a possible intermediate in diverse genomic recombination processes
- Source :
- Molecular and General Genetics MGG. 264:691-701
- Publication Year :
- 2001
- Publisher :
- Springer Science and Business Media LLC, 2001.
-
Abstract
- An important attribute that contributes to the virulence of Neisseria gonorrhoeae is its phenotypic variability, which is based on recombination within complex gene families in the genome. In this study we report on the in vivo amplification of large segments of the genome and the existence of circular DNA intermediates in the cell, which might help to explain the evolution of these gene families and provide possible clues as to how genetic variability is maintained. Using an inserted chromosomal marker (cat) in the N. gonorrhoeae MS11 genome that confers low-level resistance to chloramphenicol (Cm), we isolated variants that express resistance to high levels of Cm. Genetic analysis revealed that virtually all variants harboured single or multiple tandem amplifications of the respective genome segments carrying the cat insert. This process occurred independently of both the location of the cat insertion site and of the presence of a functional recA gene. Analysis of the genetically well characterised pilC region revealed a head-to-tail orientation of the amplified segments, with the junctions being located within direct repeats. Identical junctions were detected in extra-chromosomal circular DNA molecules isolated from non-selected wild-type and recA strains, suggesting that both types of structure arise by related processes. The existence of DNA circles was shown by their banding behaviour in caesium chloride/ethidium bromide density centrifugation and their resistance to digestion by exonuclease. The possible roles of such circles in processes such as pilin gene recombination, chromosomal gene amplification and genetic transformation are discussed.
- Subjects :
- Genetic Markers
Drug Resistance
Cesium
Biology
Polymerase Chain Reaction
Genetic recombination
Genome
Insert (molecular biology)
chemistry.chemical_compound
Chlorides
Gene duplication
Centrifugation, Density Gradient
Genetics
Gene family
Direct repeat
Molecular Biology
Protein Synthesis Inhibitors
Recombination, Genetic
Models, Genetic
Genetic Variation
Sequence Analysis, DNA
Molecular biology
Neisseria gonorrhoeae
Blotting, Southern
Chloramphenicol
Phenotype
chemistry
Tandem Repeat Sequences
Pilin
biology.protein
DNA, Circular
DNA
Plasmids
Subjects
Details
- ISSN :
- 14321874 and 00268925
- Volume :
- 264
- Database :
- OpenAIRE
- Journal :
- Molecular and General Genetics MGG
- Accession number :
- edsair.doi.dedup.....0d875d692a7dd26e7cf48d1f0405462b