Re: Nitrogen fixing in higher organisms

To: Plants <Aquatic-Plants at actwin_com>
Subject: Re: Nitrogen fixing in higher organisms
From: "Olive K. Charlsey" <achaudh at emory_edu>
Date: Tue, 2 Jul 1996 20:15:01 -0400 (EDT)
In-Reply-To: <9607022321.AA01285 at sawgrass_hac.com>

Stephen wrote:

> So you mean to say that all of the proteins on the planet are made from
> amino acids constructed by bacteria living on legumes millions of years
> ago (supplemented by the modest amounts they continue to fix now)?

	No, I am sorry if it seemed like I was saying that. I know that
humans can assemble 16 or so of the 20 amino acids by ourselves. The
others we have to consume as parts of the proteins in our food. I am sure
that cows are on similar lines and that they may use the bacteria in their
stomachs to assemble those amino acids for them. I don't know where this
"millions of years ago" came from... This is a continual process, always 
cycling... 

> Where did we get amino acids before legume bacteria evolved? ;-)

	I don't know what you're talking about. Nobody gets nothin'
(pardon me) from these bacteria except for NH3, NO2, NO3. (Well, not
nothing, but nitrogen FIXATION is their primary purpose.) The plants use 
the NH3 to make amino acids. This is one of life's primary sources of 
amino acids, plant matter.

> Seriously though, aren't simple amine acids generated by the action
> of lightning through the air? Blue-green cyano bacteria fix
> nitrogen too. There must be lots of other organic chemical pathways 
> too because there is a fairly substantial loss of nitrogen via
> nitrifying bacteria. Are blue-greens everywhere and are they really
> at the bottom of our food chains (at least for nitrogen building
> blocks for proteins)?

	Miller and Urey's experiment with the lightning bolts was a
scenario that is used to explain the ORIGIN of life. After life existed,
the contribution of lighting to the "soup" was minimal. All amino acids
are essentially "simple." There is really nothing complicated about the
structures of amino acids, it is just that some organisms are auxotrophic
and cannot assemble certain ones. Yes, cyanobacteria fix nitrogen. And,
yes, there are lots of pathways. There is no "loss of nitrogen." The
nitrogen is just converted from a form that is useable for one organism,
to the form that is useable for another. If you want to talk about BOTTOM
of the food chain, then, yes, I guess that nitrogen fixing bacteria are
the bottom. 

					Alok

Reference(s):

Re: Nitrogen fixing in higher organisms

From: Stephen.Pushak at saudan_HAC.COM