Evolution of life and parasites: viruses, bacteria, protists, etc.

Ken Kinman kinman at HOTMAIL.COM
Fri Jul 20 23:53:15 CDT 2001


Curtis,
     In a way, viruses were probably obligate parasites from the very
beginning.  In the organic soup, which was effectively a lagoon, bay, or
even ocean-sized single cell, such parasites had ready access to the
products of more successful viruses (and it was one of the more successful
ones that would have first developed the ability to build a cell membrane to
try and keep such parasites at bay----and that superior virus became the
first true chromosome in a cellular "bacterium").
    In my opinion, all cellular life would probably be descendants of one
successful cellular bacterium that could compete both with parasitic viruses
and other cellular bacteria that might have evolved at about the same time.
And one of its descendants might have been so superior that it
completely outcompeted all the other related cellular lineages, but at some
point we would have the LUCA (Last Universal Common Ancestor) of all living
organisms.
      The LUCA was almost certainly a eubacterium, not a metabacterium
(Woese's so-called "Archaea").  The metabacteria came later, and are
therefore both misnamed and overly ranked (if you have to have "Domains",
there would might be up to a dozen separate eubacterial Domains, and one
metabacterial Domain----the latter being derived and thus there was nothing
particularly "archaeal" about it).
     Anyway, the less successful viruses have been invading their cellular
relatives even since.  It wouldn't surprise if aggressive viruses eventually
help to induce the evolution of the first eukaryote, the nucleus being a
second line of defense against viral invasion.  Small acellular viruses not
only competed with each other, but they probably spurred the development of
their cellular hosts from prokaryotes to eukaryote, and perhaps even to
multicellular levels.
      I don't want to give viruses too much credit, but I think they have
been bugging cells ever since the beginning of cellular evolution.  And
eukaryotic cells have always had both viruses and bacteria to deal with.
And we as metazoans have to fight off viruses, bacteria, protozoans,
protophytes, and fungi.  It's an endless biochemical war that is as old as
life itself, that has just gotten more and more complex over time.
     Then there's all these metazoans pests that often carry these parasites
to infect us (ticks, fleas, flies, mosquitoes, vertebrate feces, food
poisoning, and on and on).  Better stop---am I Howard Hughes worst nightmare
or what?   Even starting to scare myself.   :-)     Thank goodness for the
miracles of modern medicine that keep so many of these parasites at bay (and
the parasites that harbor parasites that harbor parasites.....).
      Enough for tonight.  Need my rest to fight off any potential parasites
tomorrow. Got to keep that immune system in good-working order.
      -----Past my bedtime,
                        Ken
******************************************
>From: Curtis Clark <jcclark at CSUPOMONA.EDU>
>Reply-To: Curtis Clark <jcclark at CSUPOMONA.EDU>
>To: TAXACOM at USOBI.ORG
>Subject: Re: One origin? (viral evolution)
>Date: Fri, 20 Jul 2001 19:39:41 -0700
>
>At 12:27 PM 7/20/01, Ken Kinman wrote:
>>Dear All,
>>     My view is that viruses (sensu lato) preceded cells, and that the
>>earliest living biochemical pathways developed in an acellular "organic
>>soup" (as it is called).
>
>Then why is it that every known virus is an obligate intercellular parasite
>that has no metabolism or replication independent of its host?
>
>
>
>--
>Curtis Clark                  http://www.csupomona.edu/~jcclark/
>Biological Sciences Department             Voice: (909) 869-4062
>California State Polytechnic University      FAX: (909) 869-4078
>Pomona CA 91768-4032  USA                  jcclark at csupomona.edu

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