Question

[Joao Vasconcelos Costa]

Alison Campbell wrote:
> 
> In article <4kpesl$b94_001 at net7b.io.org>, howzit at io.org (Ursula
> Keuper-Bennett) wrote:
> 
> > In article <4krqsb$47e at nms.telepost.no>,
> >    gronvold at telepost.no (Vidar Grønvold) wrote:
> >
> > >      Bacteria can be either deletrious or helpful in an organism. But
> > >what about virus. Is there known any helpful function of virus in
> > >nature? I find it hard to believe they exist as only a deletrious
> > >thing.
> >
> > The only helpful virus I can think of is the one implicated in
> > myxomatosis (disease of rabbits).  As I understand it, Australia was so
> > overrun with rabbits, the disease was purposefully introduced to control
> > their population.
> 
> There's now another one which was accidentally released.  It's
> calicivirus.  It kills rabbits very effectively (~90% death rate).
> Myxomatosis is still in use, however the levels of immunity in wild
> rabbits are rising and so it is losing some of its effectiveness.
> 
> > So for Australians the virus was helpful.  I think the rabbits would
> > assess things a tad differently however.
> 
> mm, probably.  For farmers, however, both viruses are an absolute
> Godsend!  (well, except for rabbit farmers who are rather annoyed by the
> whole thing)
> alison

In both replies, the situations are artificial and do not correspond to 
the original question. The only example of what *may* be helpful,
symbiotic viruses are retrotransposons, assuming that they are almost
viruses or may have derived from viruses (the other way around may also
be true). We don´t know whether they have been evolutionary useful but
at least we can say that they have been conserved.

Joao
 
-- 
*****   JOAO VASCONCELOS COSTA, MD, PhD
*****   Instituto Gulbenkian de Ciencia - Oeiras, Portugal
*****   mailto:jcosta at pen.gulbenkian.pt
*****   http://www.pen.gulbenkian.pt/v2/jvc.html