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From: bchso@uhnix2.UUCP (Dan Davison)
Newsgroups: sci.bio
Subject: Re: Life Classification ...further comments
Message-ID: <382@uhnix2.UUCP>
Date: Fri, 22-May-87 23:55:26 EDT
Article-I.D.: uhnix2.382
Posted: Fri May 22 23:55:26 1987
Date-Received: Tue, 26-May-87 00:39:31 EDT
References: <9543@duke.cs.duke.edu> <1125@ius2.cs.cmu.edu>
Reply-To: bchso@uhnix2.UUCP (Dan Davison)
Distribution: world
Organization: University of Houston
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Summary: chloroplasts look a lot like eubacteria

In article <1991@husc6.UUCP> gallagher@husc4.UUCP (paul gallagher) writes:
>Prokaryotes exchange genetic information
>with plasmids...

And via viruses.  Bacillus sp. also pick up DNA directly from the environment,
ie from those around them that have died and lysed the cell membrane.

>I think it is believed that the Progenotes - the ancestral cells - gave rise
>to the Archebacteria, Eubacteria, and the Urkaryotes (a completely extinct
>kingdom).  

I'm currently working with George Fox, the co-discoverer of the archebacterial
kingdom, and although I don't have my latest Carl Woese paper handy I'm 
pretty sure the Urkaryotes didn't die out...we is them, or they is us, so to
speak.  

>The mitochondria and perhaps the nucleus of the eukaryotic cell
>are thus the descendants of eubacteria, and the cytoplasm of the cell is the
>descendant of urkaryotes.  

This is the distinction as I understand it.  The three kingdoms (not four)
branch *very* deeply and fairly close to one another, although there are some
very strange eukaryotes now being examined.

>Later, another eubacterium containg chlorophyll
>started living inside the cell, and this became the chloroplast of 
>photosynthetic protists and plants.

I am studying the small subunit ribosomal RNA, the 16S rRNA (BTW,
"S" is not a unit of length, it's a hydrodynamic measurement more roughly
proportional to shape and *size*.  12S vs. 16S is meaningful when comparing
two RNAs, but not when comparing an RNA and a protein-RNA complex like the
ribosome (70S in eubacterial and archebacteria, 80S in most eucaryotes).
The secondary structure of that RNA (the way the chain folds back on itself)
is remarkably like the gram-negative eubacteria.  If you did not know it was
a chloroplast you'd put it in with the gram-negatives.

> Paul Gallagher

dr. dan davison/ Dept of Biochemical and Biophysical Sciences/ U. of Houston
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