I’ve talked a lot lately about the use of viruses as vectors for moving genes into new cell lines during gene cloning experiments. When plasmids or other ‘naked’ DNA molecules are taken up by bacterial cells, the process is called transformation or, sometimes, transfection. When a virus is used as the vector for injecting genetic material into a cell, the process is called transduction. Bacteriophages are viruses that infect bacteria.
In a simple example of basic transduction technique, bacteriophage M13 are first inserted into bacterial cells in a manner identical to plasmid DNA transformation (usually heat shock, but certain chemical treatments can also be used). Following this step, single stranded M13 DNA begins replicating in the host cell, using host cell proteins (i.e. the host cell's transcription factors). As part of the lytic life cycle of the phage, however, daughter phage are produced. These lyse the bacterial cells and are released, at which time they infect neighboring bacterial cells, and that process is called transduction.
Bacteriophage are very prevalent microorganisms on our planet, and because of their ability to lyse bacteria, have been used in an antibiotic sense to treat various diseases in humans and animals. The discovery of biochemical antibiotics lead to a decline in interest in phage treatments, but with the rise in antibiotic resistance among pathogenic bacteria, maybe we will see a reversal of focus.
Not all viruses are bacteriophage, nor do all viruses replicate by the same means, or cause lysis of their host cells. Retroviruses are one example of a different type of virus that is released from the host by a different mechanism, called budding. However, these viruses are also very useful in gene and protein engineering research.
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