Overview
This lecture explains genetic recombination in bacteria, focusing on the process of transduction, where viruses transfer DNA between bacterial cells.
Genetic Recombination in Bacteria
- Genetic recombination allows bacteria to acquire foreign DNA and new traits.
- Acquired genes can make bacteria antibiotic-resistant or more virulent.
- The three main recombination mechanisms are transformation, conjugation, and transduction.
Introduction to Transduction
- Transduction is genetic recombination mediated by bacteriophages (viruses that infect bacteria).
- Bacteriophages (or "phages") can inject their DNA into bacterial cells.
- Viruses must hijack the host cell's machinery to replicate.
Process of Transduction
- The phage attaches to a bacterial cell and injects its DNA.
- The host's chromosomal DNA may be degraded as phage DNA replicates and phage proteins are made.
- New phages assemble inside the bacterium; some may accidentally package bacterial DNA along with or instead of phage DNA.
- When the bacterial cell lyses, phages are released to infect new cells.
Outcomes of Transduction
- Phages carrying bacterial DNA can inject it into another bacterium.
- In the lytic cycle, phage DNA replicates and leads to cell lysis and more phage production.
- In the lysogenic cycle, bacterial DNA recombines with the new host's chromosome, possibly conferring new traits.
- The recombinant bacterium may gain genes such as those for toxins or antibiotic resistance.
- The inserted phage DNA can remain for many generations before possibly reentering the lytic cycle.
Key Terms & Definitions
- Genetic recombination — The process of exchanging DNA, resulting in new genetic combinations.
- Transformation — Uptake of free DNA by a bacterial cell from its environment.
- Conjugation — Direct transfer of DNA between bacterial cells through physical contact.
- Transduction — Transfer of bacterial DNA from one cell to another via a bacteriophage.
- Bacteriophage (phage) — A virus that infects and replicates within bacteria.
- Lytic cycle — Viral replication process causing cell lysis and release of new viruses.
- Lysogenic cycle — Viral DNA integrates into the host genome and is replicated with it without immediate lysis.
Action Items / Next Steps
- Watch the videos on transformation and conjugation for a complete understanding of all recombination mechanisms.