Microbial Genetics: DNA Transfer in Microbes

Bacterial Genome Properties

• Typically a single, circular chromosome.
• Located in the nucleoid region (no nuclear membrane).
• Plasmids: small, circular, self-replicating DNA molecules in the cytosol.

Vertical vs. Horizontal Gene Transfer

• Vertical: from parent to offspring.
• Horizontal: direct transfer from one organism to another.

Key Attributes Transferred Horizontally

• Virulence factors: help bacteria survive (e.g., capsules of Streptococcus pneumoniae).
• Antibiotic resistance: reduces antibiotic effectiveness (e.g., Beta-Lactamase inactivates Penicillin).

Horizontal Gene Transfer Types

• Transformation: uptake of naked DNA.
• Transduction: transfer via bacteriophages (viruses).
• Conjugation: transfer via sexual pilus, requiring cell-to-cell contact.

Phage Therapy

• Uses bacteriophages to target and kill bacteria.
• Advantages: Specific, replicates at infection site, naturally occurring, safe, active against antibiotic-resistant bacteria.
• Disadvantages: further research is required, potential for phage resistance, not accessible to intracellular pathogens, and has difficult administration.