Related Experiment Video
Updated: Aug 6, 2026
08:52
Evaluation of Host-Pathogen Responses and Vaccine Efficacy in Mice
Published on: February 22, 2019
Phase variation in Bordetella pertussis is accompanied by changes in DNA modification
1Department of Microbiology, Faculty of Life Sciences, Tel Aviv University, Israel.
Microbial Pathogenesis
|May 1, 1987
Summary
Pathogenic Bordetella pertussis DNA is protected from restriction enzymes by an unknown modification, suggesting phase variation involves DNA modification, not mutation.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Pathogenic Bordetella pertussis strains exhibit phase variation in vitro, losing virulence factors.
- This variation is a stable, non-random, and non-reversible process.
Purpose of the Study:
- To investigate the molecular mechanisms underlying Bordetella pertussis phase variation.
- To characterize DNA modifications associated with virulence and phase variation.
Main Methods:
- Chromosomal DNA isolation from B. pertussis and its variants.
- Restriction enzyme digestion and agarose gel electrophoresis.
- High-performance liquid chromatography (HPLC) and nearest-neighbor analysis for DNA methylation.
Main Results:
- Pathogenic strain DNA resisted digestion by certain restriction enzymes, unlike variant DNA.
- No common methylation-sensitive sequences were identified in resistant DNA.
- A two-fold increase in DNA methylation was observed in the pathogenic strain.
Conclusions:
- Virulent B. pertussis chromosomal DNA possesses an unknown modification protecting it from enzymatic digestion.
- Bordetella pertussis phase variation likely results from alterations in DNA modification, rather than genetic mutation.
Related Concept Videos
02:32Position-effect Variegation
In 1928, a German botanist Emil Heitz observed the moss nuclei with a DNA binding dye. He observed that while some chromatin regions decondense and spread out in the interphase nucleus, others do not. He termed them euchromatin and heterochromatin, respectively. He proposed that the heterochromatin regions reflect a functionally inactive state of the genome. It was later confirmed that heterochromatin is transcriptionally repressed, and euchromatin is transcriptionally active chromatin.
02:04Polytene Chromosomes
Polytene chromosomes are giant interphase chromosomes with several DNA strands placed side by side. They were discovered in the year 1881 by Balbiani in salivary glands, intestine, muscles, malpighian tubules, and hypoderm of larvae Chironomus plumosus. Hence, these are also called "Salivary gland chromosomes." These are found in insects of the order Diptera and Collembola; in certain organs of mammals; and synergids, antipodes of flowering plants. Polytene chromosomes are also regularly...
02:53Conservative Site-specific Recombination and Phase Variation
Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
The recognition sites for Cre recombinase called LoxP...
The recognition sites for Cre recombinase called LoxP...
02:26Comparing Copy Number Variations and SNPs
Sequencing of the human genome has opened up several best-kept secrets of the genome. Scientists have identified thousands of genome variations that exist within a population. These variations can be a single nucleotide or a larger chromosomal variation.
Copy number variations or CNVs are the structural variations that cover more than 1kb of DNA sequence. The single nucleotide polymorphism (SNP), on the other hand, is a single nucleotide change or a point mutation that is found in more than 1%...
Copy number variations or CNVs are the structural variations that cover more than 1kb of DNA sequence. The single nucleotide polymorphism (SNP), on the other hand, is a single nucleotide change or a point mutation that is found in more than 1%...
01:26Bacterial Protein Maturation
Bacterial protein maturation is a tightly regulated process that ensures newly synthesized polypeptides achieve correct functional conformations. This maturation involves a series of modifications, folding events, and quality control steps, often assisted by specialized chaperone proteins.N-Terminal ModificationsThe maturation of bacterial polypeptides begins cotranslationally as the polypeptide exits the ribosome. The first amino acid, N-formylmethionine (fMet), is typically modified at the...
01:28Regulation of Bacterial Virulence
Pathogenic bacteria employ a range of regulatory mechanisms to modulate the expression of virulence genes in response to environmental and host-derived signals. These mechanisms ensure that virulence factors are expressed only under favorable conditions, thereby optimizing infection and survival strategies.Mechanisms of Virulence RegulationKey regulatory strategies include:Two-Component Systems: These consist of a membrane-bound sensor kinase and a cytoplasmic response regulator. Environmental...