Transduction - Bacterial Reproduction

TRANSDUCTION

There is a group of viruses, called bacteriophages, which have bacterial cells as their hosts. These bacteriophages inject viral DNA into the host cell. This viral DNA is then replicated and transcribed at the expense of the host and assembled into new viral particles. Under normal circumstances the host cell becomes lysed in order to release the viral progeny, but in exceptional circumstances, rather than enter a replication cycle the viral DNA becomes incorporated, by recombination, into the chromosome of the bacterium. This is known as a temperate phage. The viral DNA thus forms part of the bacterial chromosome and will be copied to all daughter cells.

Temperate phage will become active once again at a low frequency and phasing between temperate and lytic forms ensures the long-term survival of the virus. Occasionally during this transition back to the lytic form the excision of the viral DNA from the bacterial chromosome is inaccurate. The resultant virus may then either be defective, if viral DNA has been lost, or it may carry additional DNA of bacterial origin. Subsequent temperate infections caused by the latter virions will result in this bacterial DNA having moved between cells: a process of gene movement known as transduction. As the host range of some bacteriophages is broad then such processes can move DNA between diverse species.