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Bacteria and Viruses?

Louis van de Zande L.P.W.G.M.van.de.Zande at biol.rug.nl
Tue Sep 10 03:21:17 EST 1996


> > From:          arthurc at crl.com (Arthur Chandler)
> > Subject:       Bacteria and Viruses?
> 
> >  A question from a non-biologist (who has been reading Stephen Gould's 
> > new book, *Full House*). Gould asserts (page 170):
> > 
> >   "...bacteria lie right next to the left wall of minimal conceivable 
> > complexity. Life therefore began with a bacterial mode."
> > 
> >  1) Are viruses more or less complex than bacteria?
> >  2) Are viruses alive?
> 

It is always very tempting when a humble person, beforehand denying 
any expert knowledge, asks fundamental but naive questions, to pick 
up the challenge and become a guru as to enlighten the ignorant.
It is ever so tempting to point to the self-appointed guru that 
things may be not as simple as proposed. So when Rybicki says:

> Yes...B-)...and Yes and no...but both need qualification.  The largest 
> viruses have genomes that are very nearly as large (+300 kb) as the 
> genomes of the smallest cells (eg: mycoplasma, +500 kb); it is no 
> coincidence that both are parasites.  In terms of "genome complexity" 
> one could say that viruses GENERALLY are less complex than cellular 
> organisms, but not necessarily so.  They are all obligate parasites, 
> they lack ribosomes and the machinery of metabolism; however, they 
> can order the cell's machinery to their needs, and some - like 
> poxviruses, phycodnaviruses, and herpesviruses - have highly 
> complicated genome expression strategies.

he is adressing part of the problem and even avoiding a clear answer 
(obviously because there is none). But the worst is yet to come!
 
> As for being alive: yes, viruses in a cell, actively replicating, are 
> engaging in processes indistinguishable from those of a cell going 
> about its normal business - and a cell is most certainly alive if it 
> is metabolising.  However, once the viral genome is encapsidated, it 
> is effectively a quiescent collection of large molecules - much like 
> purified ribosomes - and, as it does not engage in any of the 
> activities associated with living organisms, cannot be termed so.  
> Mind you, neither can a bacterial spore that has been lying around in 
> a dessicator for 50 or so years.  The point is that both a virion - 
> the particle containing a viral genome - and a spore have the 
> POTENTIAL for life, given the appropriate substrate.  Which is 
> nutrients int he case of a spore, and a cell in the case of a virion.

A virus IN a cell, usually is no longer its former entity, but has 
injected its genome into the cell. Now the genome is the living 
thing? I'm not so sure about that. It all ends up a in definition of 
LIFE. But nobody can give that. 

Sorry, but I think that the aswering of the questions posed by Arthur 
Chandler are beyond anybody's reach.




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