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Nitroplast is a newly discovered eukaryotic organelle that can perform nitrogen fixation. Like chloroplast, nitroplast was derived from a cyanobacteria species (UCYN-A). Cyanobacteria are the only photosynthetic organisms capable of nitrogen fixation. Because oxygen is very toxic to nitrogenase, cyanobacteria evolved a special photosynthetic pathway which uses the light energy to make ATP without electrolyzing water molecules (cyclic photophosphorylation). Does that mean nitroplast also use this mechanism to fix nitrogen?

I found this question interesting because there is a lot of interest to incorporate nitrogen fixation into plants. However, nitrogen fixation is extremely costly. It’s calculated that it takes two glucose molecules to fix one nitrogen molecule. Even though legumes can fix nitrogen with the help of bacteria, they only do so when nitrogen is scarce. Because the amount of sunlight typically exceeds the requirement of carbon fixation, if nitroplast can use photon energy directly, it can fix nitrogen without consuming organic materials. In another word, the crops can get extra nitrogen without compromising their yields.

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  • $\begingroup$ Please provide a link to information about the "nitroplast". If you know about it and I have never heard of it because of its recent discovery, the chances are that you are as well placed to find out about its biochemistry than anyone on this list. What research have you done? $\endgroup$
    – David
    Commented Apr 28 at 9:18
  • $\begingroup$ I added the link. I can’t provide more details because those papers are paywalled. $\endgroup$
    – 哲煜黄
    Commented Apr 28 at 9:35
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    $\begingroup$ The Wikipedia page Nitroplast has references worth following. New Nitrogen-Fixing Microorganisms Detected in Oligotrophic Oceans by Amplification of Nitrogenase (nifH) Genes is salient. There doesn't seem to be much to indicate that it's an energy-free process though. $\endgroup$ Commented Apr 28 at 9:40
  • $\begingroup$ Ok. I’ll download it and have a glance when I’ve a moment. $\endgroup$
    – David
    Commented Apr 28 at 12:27

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