Understanding Bacterial Transduction Mechanisms

Nov 2, 2024

Lecture Notes: Transduction in Bacteria

Overview of Transduction

  • Definition: Transduction is the process by which a virus transfers DNA from one bacterial cell to another.
  • Types of DNA Transferred: It involves bacterial DNA, not the viral DNA.
  • Textbook Reference: Consistent with OpenStax textbook coverage.

Generalized Transduction

  • Mechanism: Random fragments of bacterial DNA are mistakenly packaged into a phage during its assembly.
    • When this phage infects another bacterium, it transfers bacterial DNA instead of viral DNA.
  • Outcome:
    • Typically, the transferred DNA may have no effect and can be degraded.
    • Occasionally, it includes beneficial genes, e.g., antibiotic resistance genes.
  • Frequency: Rare events but are significant due to the high number of bacteria and phages.

Specialized Transduction

  • Requires Understanding of Phage Cycles:
    • Lytic Cycle: Normal cycle where phages infect, replicate, and lyse the host cell.
    • Lysogenic Cycle: Phage DNA incorporates into the host genome as a prophage.
      • The prophage remains dormant and replicates with the host DNA until triggered to enter the lytic cycle.
  • Mechanism:
    • Involves temperate phages with potential lysogenic cycles.
    • Mistakes during the excision of prophage DNA can result in the inclusion of specific host DNA fragments.
  • Significance: Increases genetic variability by transferring specific bacterial DNA sections.

Prophage and Virulence Factors

  • Prophage Definition: Viral genetic material incorporated into the bacterial genome.
  • Impact on Bacterial Virulence:
    • Many virulence factors are linked to prophage DNA.
    • Examples:
      • Diphtheria toxin
      • Botulinum toxin
      • Cholera toxin
      • Virulence factors in Streptococcus pyogenes
  • Current Implications:
    • Increase in virulence and infections like necrotizing fasciitis.
    • Documented rise in such events over the past decade.

Additional Notes

  • Questions and Clarifications: Reach out via Canvas inbox for queries on transduction, conjugation, and mutation.

This lecture aims to align closely with textbook material for consistency and thorough understanding.