Biology Question #7

Alexa Clay, a 15 year old female from the Internet asks on April 29, 1999,

How do scientists modify a virus so that it can be beneficial to a host cell? For example, during a lysogenic infection when a virus injects its DNA into the DNA of the host cell, it goes into prophage. Could you keep it in this stage so that it couldn't harm the cell at all? During prophage no other viruses can enter the host cell so if we could make prophage continuous no one would ever get a virus. Is this possible? If not what other theories are being explored? What host cells, and viruses would be good for this sort of project?

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The answer

David Baillie answered on April 29, 1999

The description you provide is for a specific bacteriovirus (a virus which infects bacteria). It applies to only one subclass of virus (in the case described, one called lambda).

Other bacteria infecting virus are not nearly so polite; they just kill the infected cell. As far as I am aware, there is no animal virus that has been demonstrated to behave in the same manner. Retroviruses do integrate into the host DNA but do not confer resistance on the host. So the suggested solution is a reasonable one for protecting some bacteria from getting specific virus infections; however I suspect the person asking the question was not the least bit interested in protecting bacteria from getting a viral infection! The principle is a good one, and might be useful if ever a virus if the type described was found that caused a disease in people.

One other interesting point: when a bacteria with lysogenized lambda virus (integrated into the genome of the host) is mated to a bacteria that does not have the same bacteria integrated in its genome, the bacteria that is mated with is killed by the integrated virus which escapes from the genome after it has been transferred (as a result of bacterial sex) to the sex partner. This is called "zygotic induction" and was described by Jacob and Monod (both Nobel Laureates) in the early 1960s. This discovery lead to the discovery of gene control proteins (repressors and later activators) which is a major area of research by people trying to understand how development is controlled.

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