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Bacterial Genetics Dr/ Tamer M. El mokadem

Explore the fascinating world of bacterial genetics, including bacterial chromosomes, plasmids, transposons, integrons, and pathogenicity islands. Learn about the structure, function, and importance of these genetic elements in bacterial evolution and pathogenicity.

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Bacterial Genetics Dr/ Tamer M. El mokadem

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  1. Bacterial Genetics Dr/ Tamer M. El mokadem

  2. Bacterial Genome • Chromosome • Plasmid • Transposable genetic elements

  3. Bacterial Chromosome • Single double stranded circular DNA molecule about 1mm long • About 4000 kbp • Divided into about 1000 genes(3 base pairs) • Carry genes essential for growth (Structure or function)

  4. Types of Plasmids (A) Transfer properties • Conjugative (Transmissible) plasmids • Non conjugative (Non transmissible) plasmids (B) Phenotypic properties • Fertility plasmid (F factor) • Bacteriocinogenic (Col) plasmid. • Drug resistance plasmid (R factor) • Virulence plasmid.

  5. Transposons (Jumping genes) • Def:Transposable genetic elements that carry one or more genes in addition to those which are essential for transposition. • Structure : 4 segments • Short DNA inverted repeats (IR) on each end • Transposase gene • Regulator gene • Gene coding for Enzyme or Toxin • Not capable of autonomous replication (Not free). • Multiple different transposons may be present

  6. Integrons • An integron is a two component gene capture and dissemination system found in plasmids, chromosomes and transposons. • The first part: gene coding a site-specific recombinase along with a specific site for recombination • The second part: fragments of DNA called gene cassettes which may contain 5 or more genes coding for antibiotic resistance esp. among gram –ve bacteria • An integron contains an integrase enzyme gene • promoter segments to drive expression.

  7. Pathogenicity islands (PAIs) • Pathogenicity islands (PAIs) : are incorporated in thegenome, chromosomally or extrachromosomally, of pathogenic organisms, but are usually absent from those nonpathogenic organisms • They may be located on a bacterial chromosome or may be transferred within aplasmidor can be found in bacteriophage genomes.

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