Learning Objective

Describe the mechanisms of bacterial DNA transfer by bacteriophages, distinguish between generalized and specialized transduction, and understand the role of lytic and temperate phages in these processes.

Transduction is the transfer of bacterial DNA from one cell to another via a bacteriophage vector. It occurs when errors in phage replication incorporate bacterial DNA into the phage particle.

Generalized Transduction

• Occurs with virulent (lytic) phages.
• Any bacterial gene has an equal chance of being packaged into a phage head.
• Mistaken incorporation of bacterial DNA produces a transducing phage.
• Important example: phage P1 in E. coli.

Specialized Transduction

• Occurs with temperate (lysogenic) phages.
• Phage DNA integrates into the bacterial chromosome at a specific site.
• If imprecise excision occurs, adjacent bacterial genes are packaged along with phage DNA.
• Example: λ phage transferring galactose genes in E. coli.

Activity

Bacteriophage Life Cycles

Key Concepts

• Lytic infection: Phage replicates and lyses the bacterial cell; accidental packaging of bacterial DNA produces generalized transduction.
• Lysogenic infection: Phage integrates into the bacterial genome; errors during excision may produce specialized transducing phages.
• Transduction contributes to genetic variation, virulence factors, and antibiotic resistance.

Activity