Transfer of dna between bacterial cell

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1. TRANSFER OF DNA BETWEEN BACTERIAL CELLS 2. TRANSFER OF DNA BETWEEN BACTERIAL CELLS The transfer of genetic information from one cell to another is occur by three…
  • 2. TRANSFER OF DNA BETWEEN BACTERIAL CELLS The transfer of genetic information from one cell to another is occur by three methods: # CONJUGATION # TRANSFORMATION # TRANSDUCTION
  • 3. Medical Viewpoint From a medical viewpoint, the most important two consequences of DNA transfer are: That antibiotic resistance genes are spread from one bacterial gene to another primarily by CONJUGATION AND That several important exotoxins are encoded by bacterial genes and are transferred by TRANSDUCTION
  • 4. CONJUGATION Definition: It is the process of gene transfer via sex pili between cells of opposite mating types that are in physical contact (cell-to-cell) with each other.
  • 5. CONJUGATION METHODOLOGY: Requires the presence of a special plasmid called the F plasmid. Bacteria that have a F plasmid are referred to as F+ or male. Those that do not have an F plasmid are F- or female. The F plasmid consists of 25 genes that mostly code for production of sex pilli. A conjugation event occurs when the male cell extends his sex pilli and one attaches to the female. This attached pilus is a temporary cytoplasmic bridge through which a replicating F plasmid is transferred from the male to the female. When transfer is complete, the result is two male cells. When the F+ plasmid is integrated within the bacterial chromosome, the cell is called an Hfr cell (high frequency of recombination cell).
  • 6. Conjugation in E. coli
  • 7. Conjugation continued…
  • 8. Conjugation continued…
  • 9. Transduction • Transfer of DNA by mean of bacteriophage. • Bacterial DNA is incorporated into virus particle and is carried into recipient cell during infection. • Phage DNA integrated into cell DNA and cell acquire new trait (lysogenic conversion). • Non-pathogenic change into pathogenic. • Diphtheria toxin, botulinum toxin, cholera toxin and erythrogenic toxin are encoded by bacteriophages and is transferred by transduction.
  • 10. Transduction
  • 11. Transformation • Transformation is a transfer of DNA from one cell to another. • DNA is injected into the nucleus of eukaryotic cell is called transfection. Transfection (used in genetic engineering procedures) • DNA extracted from encapsulated smooth pneumococci transform non capsulated rough pneumococci.
  • 12. Transformation
  • 13. Recombination Once the DNA is transferred from a donor to a recipient cell by one of three processes just described, it can integrate into host chromosome by recombination. Types of Recombination There are two types of recombination:  Homologous recombination  Nonhomologous recombination
  • 14. Homologous recombination, in which two pieces of DNA that have extensive homologous regions pair up and exchange pieces of DNA by breakage and reunion. Homologous Recombination
  • 15. Nonhomologous Recombination Nonhomologous recombination in which little if any homology is necessary.
  • 16. Thank you
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