How on Earth Did Bacteria Start Fixing Nitrogen?

[jimmydasaint]

A puzzle I have been facing recently is to try to figure out how bacteria managed to capture nitrogen from the atmosphere to incorporate it as ammonia. I suppose I have always considered it similar to the method by which chloroplasts can incorporate atmospheric carbon dioxide into soluble carbohydrates. However, I don't know - it all looks so complicated. Any thoughts...

[ecoli]

I guess if you reduce the scope enough, the proteins are similar in that they involved electron transfer centers and metal cofactors.

[foodchain]

You have in general for metabolism two forms, one is catabolism which breaks down molecules and the other is anabolism which builds them up. So bacteria have evolved to do this from such a standpoint which reflects in the overall metabolism.

 

http://en.wikipedia.org/wiki/Nitrogenase

[CharonY]

You have in general for metabolism two forms, one is catabolism which breaks down molecules and the other is anabolism which builds them up. So bacteria have evolved to do this from such a standpoint which reflects in the overall metabolism.

 

Weird the link is correct, however I do not see any correlation to the sentence above. Anyway the key enzyme of nitrogen fixation is indeed the nitrogenase complex. If you are interested in the evolution, it is a slightly tricky thing as it is not as conserved as one might think. I recommend this paper:

 

Raymond et al 2004

The Natural History of Nitrogen Fixation

 

http://mbe.oxfordjournals.org/cgi/content/abstract/21/3/541

[foodchain]

Weird the link is correct, however I do not see any correlation to the sentence above. Anyway the key enzyme of nitrogen fixation is indeed the nitrogenase complex. If you are interested in the evolution, it is a slightly tricky thing as it is not as conserved as one might think. I recommend this paper:

 

Raymond et al 2004

The Natural History of Nitrogen Fixation

 

http://mbe.oxfordjournals.org/cgi/content/abstract/21/3/541

 

 

I have no idea about the origin of nitrogenase really;) I just know it exists in some microbes and works with the microbes metabolism, being the reaction involves ATP and has by products not to mention being an enzyme or pathway.

[jimmydasaint]

Weird the link is correct, however I do not see any correlation to the sentence above. Anyway the key enzyme of nitrogen fixation is indeed the nitrogenase complex. If you are interested in the evolution, it is a slightly tricky thing as it is not as conserved as one might think. I recommend this paper:

 

Raymond et al 2004

The Natural History of Nitrogen Fixation

 

http://mbe.oxfordjournals.org/cgi/content/abstract/21/3/541

 

Thanks for that link. I read the abstract and the paper which is interesting in its phylogenetic diagrams. However, I still am a little confused. How would you propose that genes can be selected or diverge sufficiently to fix an atmospheric gas? I know that this event must have occurred for fixing carbon dioxide during photosynthesis and preceded animal life in the evolutionary time course, but...it is a hell of a puzzling process even given millions of years. There has to be some sort of advantage for survival in the stages that led up to efficient fixing of carbon dioxide and I cannot think of it at the moment.

[CharonY]

Hmm are you asking about CO2 or nitrogen fixation?

 

Actually it is not that puzzling. Redox enzymes have been around forever (like e.g. in the respiratory chain). While proteins of the respiratory chain most likely first interacted with non gaseous terminal electron acceptors (e.g. iron(III)) It is not that a large jump to reacting with oxygen, or N2.

The paper gets more interesting towards the end.

 

here has to be some sort of advantage for survival in the stages that led up to efficient fixing of carbon dioxide and I cannot think of it at the moment.

 

It is always tricky to think in that long time frames, especially in fast proliferating organisms. Nature does not care about that, of course (or about anything). But as I said it is likely that a redox enzyme "simply" switched substrate.

[jimmydasaint]

It is always tricky to think in that long time frames, especially in fast proliferating organisms. Nature does not care about that, of course (or about anything). But as I said it is likely that a redox enzyme "simply" switched substrate.

 

Now that is very interesting. I am sure that I attended a seminar which stated that enzymes shifted from an aqueous to an ethanolic environment or even in other solvents became efficient with completely new substrates. This is all speculation but I wonder if isolation of enzymes in 'microenvironments' caused the substrate switch?