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Bacterial Horizontal Gene Transfer Mechanisms

Flashcards on bacterial horizontal gene transfer — the three mechanisms by which bacteria share genetic material: transformation, transduction, and conjugation. Critical for USMLE Step 1, AP Biology, and microbiology courses, these processes explain how antibiotic resistance spreads between bacterial populations.

Interactive Deck

5 Cards
1
Front

What is bacterial transformation?

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Transformation: a bacterium takes up free DNA from its environment. Competent cells integrate exogenous DNA into the chromosome. Classic example: Griffith's experiment with S. pneumoniae.

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Front

What is bacterial transduction?

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2
Back

Transduction: a bacteriophage accidentally packages bacterial DNA and transfers it to a new host. Can be generalized (any gene) or specialized (genes near phage insertion site).

3
Front

What is bacterial conjugation?

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3
Back

Conjugation: direct cell-to-cell DNA transfer via a sex pilus. The donor (F⁺) transfers a plasmid or chromosomal DNA to the recipient (F⁻) through a mating bridge.

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Locked

Which HGT mechanism requires a phage?

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How does HGT drive antibiotic resistance?

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Frequently Asked Questions

What is the difference between transformation, transduction, and conjugation?

Transformation involves uptake of free environmental DNA. Transduction uses a bacteriophage to transfer DNA between cells. Conjugation requires direct cell contact via a pilus for DNA transfer.

  • No vector needed: transformation
  • Phage vector: transduction
  • Pilus contact: conjugation

Why is horizontal gene transfer clinically significant?

Horizontal gene transfer is the primary driver of antibiotic resistance spread in bacterial populations. Resistance genes on plasmids can transfer between unrelated species through conjugation within hours, making it a critical mechanism in hospital-acquired infections.

Can horizontal gene transfer occur between different bacterial species?

Yes. Conjugation and transformation can occur between distantly related species, while transduction is more host-specific due to phage host range. Cross-species transfer is a major reason resistance genes spread rapidly in clinical settings.