Re: A cyanobacteria may be evolving organelle like characteristics

On 4/11/2024 11:10 PM, Pro Plyd wrote:

 https://www.uri.edu/news/2024/04/evolution-in-action-new-study-finds-possibility-of-nitrogen-fixing-organelles/
 Nitrogen is a nutrient essential for all life
on Earth. Although nitrogen gas (N2) is
plentiful, it is largely unavailable to most
organisms without a process known as nitrogen
fixation, which converts dinitrogen to
ammonium — a major inorganic nitrogen source.
 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.
...
 paper here
 https://www.sciencedirect.com/science/article/pii/S009286742400182X
Metabolic trade-offs constrain the cell size
ratio in a nitrogen-fixing symbiosis
 

My take is that nitrogen fixers are usually anaerobic.  This one likely isn't very efficient at nitrogen fixing, and it gave up on photosynthesis and can't use light to fix carbon so it needs help in order to maintain it's nitrogen fixing ability.  Some how it needs to sequester itself away from oxygen inside an aerobic host.  Legumes help their nitrogen fixers by having leghemoglobin to sop up oxygen and keep the levels low enough in the root nodules so that their nitrogen fixing bacteria can fix nitrogen for them.  In return the plants give the bacteria a carbon source.
Sequestering from oxygen inside of an aerobic cell has to be difficult and is likely the reason that such an endosymbiosis has not occurred.
Ron Okimoto