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Lifecycle F+RNA phages

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Lifecycle F+RNA phages

Postby Sandro » Fri Jan 11, 2008 4:08 am

I'm a bit confused about the life cycle of MS2, GA and other F+ RNA phages. They grow rapidely in host culture so I assume they ususally do have a lytic life cycle. Is it possible that they can have a lysogenic life cycle as well? In that case, which sense (+/-) would have the phage nucleic acid when it has been integrated in the bacterial genome????
This probably sounds quite theoretical but I'm very interested to get an answere or to get a discussion started.
Thanks Sandro
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Re: Lifecycle F+RNA phages

Postby blcr11 » Fri Jan 11, 2008 7:35 pm

Why would they need lysogeny—or even, how could they lysogenize? I can’t speak for them all, but MS2 is a (+)-stranded ssRNA phage. On infection, the RNA can be directly translated into proteins that replicate the phage RNA and direct the synthesis of any capsid proteins required to form new phage particles. The replicase enzyme makes copies of both plus and minus strands, though the latter are only used as a template to make more (+) strand for both translation and packaging into phage. To lysogenize, there needs to be a DNA phase to the replication cycle and there isn’t any such phase for MS2.
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