Lecture Notes on Transduction and Viral Gene Introduction to Bacteria

Introduction to Transduction

• Transduction: Introduction of genetic material to bacteria via a bacteriophage.
  • Bacteriophage: A virus specific to bacteria.
  • Not harmful to human cells; only affects bacteria.

Viral Replication Cycles

• Viruses: Not living; require host cells to replicate.
  • Cannot metabolize, maintain homeostasis, or reproduce independently.
  • Obligate intracellular parasites.

Types of Phages

• Virulent Phage:
  • Takes over host cell machinery immediately.
  • Causes lysis of the bacteria.
• Temperate Phage:
  • DNA incorporates into bacterial chromosome without immediate cell death.
  • Called a "prophage" when integrated.
  • Can exist for many generations without bacteria noticing.

Viral Replication Modes

• Lytic Cycle:
  • Quick and violent.
  • Bacteriophage attaches, injects DNA, takes over cell machinery.
  • Assembles new phages, lyses the cell, releasing new phages.
• Lysogenic Cycle:
  • Longer and sneakier.
  • Phage DNA integrates into host genome as a prophage.
  • Can switch to lytic cycle under stress or environmental triggers.

Transduction Types

Generalized Transduction

• Utilizes the virulent phase (lytic cycle).
• Phage injects DNA, takes over host machinery, causing cell lysis.
• New phages may accidentally incorporate bacterial DNA.
• Introduces genetic diversity, e.g., antibiotic resistance genes.

Specialized Transduction

• Involves temperate phage (lysogenic cycle).
• Phage DNA integrates into host genome.
• Under certain conditions, switches to lytic cycle.
• New phages contain both viral and bacterial DNA.
• Can introduce genes like antibiotic resistance into other bacteria.

Conclusion

• Transduction is a mechanism for genetic diversity in bacteria.
• Phages play a significant role in bacterial evolution through gene transfer.