Path: utzoo!utgpu!water!watmath!uunet!bionet!apple!rutgers!orstcs!bionette!kramerj
From: kramerj@bionette.CS.ORST.EDU (Jack Kramer - CMBL)
Newsgroups: bionet.molbio.evolution
Subject: Re: Origin of mitochondria?
Message-ID: <7034@orstcs.CS.ORST.EDU>
Date: 26 Oct 88 23:18:29 GMT
References: <12441330952.27.LYAGER.HIDE@BIONET-20.BIO.NET>
Sender: usenet@orstcs.CS.ORST.EDU
Reply-To: kramerj@bionette.UUCP (Jack Kramer - CMBL)
Organization: Oregon State University - CMBL
Lines: 51

The origin is still controversial although the work of Lynn Margolis
has swayed most to the serial symbiotic hypothesis.  In this theory
the proto eukaryote progressed to an organism somewhat similar to
present day eukaryotes but lacked mitochondria and plastids.  These
organelles were acquired by by fortuitous persistent invasion by
protomitochondria and protoplastids,  which progressed from obligate
endo cellular symbionts to organelles.  If you start tracing the literature
with Lynn's name you will find probably much more literature on this than
you will want to persue.

I have my own differing theory which can probably be considered way out
in left field.  I call it the coalescent theory.  It goes like this.

Prokaryotes populated the earth for approximately 2 billion years before
the appearance of anything which we would call a eukaryote.  During this
time many symbiotic associations, parasitic, mutual, and commensal, were
formed.  One of the primary obligate commensal associations is the same
as the major biological association in the current world;  that is the
cyclicly dependent photosynthesis/resriration association.  Proto-
mitochondria and protoplastids formed increasingly obligate communal
organisms.  These may at this time still have had an RNA based genome
with its many limitations.  But independently the DNA based prokariote
evolved and being so much more accurate in its genetic control mechanism
that when it became associated with the mitoplastid colony it took over
the master genetic control functions.  The new colonies were even more
successful and prolifferated.  Similarly,  the motile prokaryotes joined in 
with some of the colonies.  This differs form the serial
symbiosis theory in that up to this stage all the elements are still
independent prokariotes joined into colonies.  Since there were many different
kinds of plastids (red, green, yellow-green, golden, etc.) which are still
represented in the many parallel line of existing algae, these lineages
may have been independent before the origin of the eukaryote. Thus the many
morphologically similar lines of organisms which differ ultrastructurally
are really convergent groups which evolved in parallel from the many
combinations  of prokaryotic colonies. These colonies, through increasingly 
obligate association formed an enveloping shell to control the immediate
environment and provide protection.  The most successful of these colonial
lineages became eukariotes.

This is the only theory which fits all thermodynamic, geological, and 
biological evidence that I am familiar with.  I don't talk about it
much any more since all my experimental approaches to date have failed
to provide proof that any of the potential "missing link" organisms would
fit the theory.  I got tired of being told to go to the library and just
look up the way we already know it happened.  If I could only find a way 
to get the @#%**@$#& nuclear ribosomal RNA out of Nanochlorum eukaryotum 
I feel that this may change.

Jack Kramer
Computational Molecular Biology Laboratory
Oregon State University