Are Viruses Living?

[welkin]

ED at molbiol.uct.ac.za ("Ed Rybicki") wrote:
>
> > From:          craigm at sanger.otago.ac.nz (Craig Marshall)
> > Subject:       Re: Are Viruses Living?
> 
> > This seems to be a question with no answer. I would argue that there is
> > some essential difference between the life of say, a bacterium and that
> > of a virus. Viruses have the property of replication under very
> > specific cirmcumstances (ie within a host cell) but I believe there
> > some chemicals are capable of similar activity (but I can give no
> > references for this claim). The property of replication is not
> > equivalent to life in the sense that a bacterium (or whatever) is
> > alive.
> 
> This is snowballing nicely...B-)
> 
> The above does not wash: the only difference between some bacteria and 
> some viruses is that the former have membranes surrounding them and 
> dividing them from the cell, and have their own tRNAs and ribosomes.  
> Otherwise, the smallest bacteria / bacteria with the smallest genomes 
> are as much dependent on being inside living cells (in that they are absolutely 
> dependent on a wide range of substrates that they can't make) as are viruses, 
> some of which (eg. phycodnaviruses, pooxviruses, iridescent viruses) 
> have bigger genomes.  If you don't know WHICH chemicals are capable 
> of self-replication, then it is a little ingenuous to make the 
> claim...!  And do you consider mitochondria or chloroplasts to be a 
> live?  All that separates them and free-living bacteria is a few 
> hundred million years of evolution, after all.
> 
>And what about the endospores of species such
as Bacillus and Clostridium?  They too are nothing
until placed in the right environment.  If they are nlving
they do a remarkable job of propagating themselves
nonetheless.