nitrogen fixation

Hi Folks,

Some thoughts on Nitrogen fixation...

1.  Nitogen fixation is a VERY expensive process for bacteria to 
perform.  They would rather get their nitrogen from urea or ammonia 
rather than fromt he air.  The primary organisms on the planet that go 
through nitrogen fixation are the cyanobacteria (the pretty blue-green 
buddies in our tanks) and the ones that make root-nodules on plants.  
Bacteria cannot fix nitrogen unless they are able to complete seperate 
themselves from their outside environment.  Cyanobacteria have to make 
modifications of their cell walls to prevent ANY O2 from getting into 
the cell.  Bacteria (Rhizobium) in the root nodules of bean plants have 
to produce chemicals that remove all O2 and they have to live in 
specialized tissues made by the plants and the bacteria!  As you can 
see, this is not a process that is easy.  Besides theys spturcutres many 
different enymes need to be produced by the bacteria and  alot of energy 
must be expended for the process to work.

2.  Free amino acids have always been present.  Someone pointed out that 
there has been amino acids around for a long time.  Lightning is able to 
convert free N2 into NH3 and NH4 within the atmosphere and this was 
probably some of the first amine groups created.  These compounds are 
rarely COMPLETELY broken down by cells.  Amino acids are usually broken 
down to urea or ammonia...but no further..the amine is too expensive to 

That is all....I am sure that you now know more that you ever wanted to 
know about nitrogen fixation :)


    jdavis at bio_tamu.edu
    jmd9261 at tam2000_tamu.edu