Genetic Recombination: Transfduction

I. MICROBIAL GENETICS

G. Genetic Recombination in Bacteria

3. Transduction

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Genetic Recombination in Bacteria (def)

Genetic recombination is the transfer of DNA from one organism to another. The transferred donor DNA may then be integrated into the recipient's nucleoid by various mechanisms.

Natural mechanisms of genetic recombination in bacteria include:

a. transformation
b. transduction
c. conjungation

We will now look at transduction.

Transduction (def)

Transduction is the transfer of fragments of DNA from one bacterium to another bacterium by a bacteriophage (def). There are two types of transduction: generalized transduction and specialized transduction.

1. Generalized transduction (def)

During the replication of a lytic phage (def), the capsid (def) sometimes assembles around a small fragment of bacterial DNA. When this phage infects another bacterium, it injects the fragment of donor bacterial DNA into the recipient where it can be exchanged for a piece of the recipient's DNA (see Fig. 1 through 7). Plasmids (def), such as the penicillinase plasmid of Staphylococcus aureus, may also be carried in a similar manner.

GIF animation illustrating generalized transduction.

2. Specialized transduction (def)

This may occur occasionally during the lysogenic life cycle (def) of a temperate bacteriophage (def). During spontaneous induction (def), a small piece of bacterial DNA may sometimes be exchanged for a piece of phage genome (which remains in the nucleoid). This piece of bacterial DNA replicates as a part of the phage genome and is put into each phage capsid. The phages are released, adsorb to recipient bacteria, and inject the donor bacterium DNA/phage DNA complex into the recipient bacterium where it inserts into its nucleoid (see Fig. 8 through 13).

GIF animation illustrating specialized transduction.

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