From SciTechDaily, April 16:
Nitrogen is a nutrient essential for all life on Earth. Despite the abundance of nitrogen gas (N2) in the atmosphere, it remains largely inaccessible to many life forms until it undergoes nitrogen fixation. This vital process transforms dinitrogen into ammonium, an important source of inorganic nitrogen
While there are bacteria that are able to reduce dinitrogen to ammonium, researchers at the University of Rhode Island, Institut de Ciències del Mar in Barcelona, University of California at Santa Cruz, and the Massachusetts Institute of Technology have discovered nitrogen-fixing symbiotic organisms exhibiting behaviors similar to organelles. In fact, researchers posit these symbiotic organisms – UCYN-A, a species of cyanobacteria – may be evolving organelle-like characteristics. Their study was recently published in the journal Cell.
Symbiotic Relationship and Its Implications
UCYN-A live in a symbiotic relationship with a closely related group of marine algae, B. bigelowii, in areas of the open ocean that are often low in nutrients. Most nitrogen-fixing bacteria have mechanisms to regulate dinitrogen use when fixed sources of nitrogen are available, alleviating the high energetic cost of this process. However, UCYN-A have lost the genes allowing this and are able to fix nitrogen gas into ammonium even in nutrient-rich environments. The host, in-turn, provides it with carbon fixed photosynthetically by its chloroplasts....
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