This is a former bacterium. Scientists Just Discovered How an Algae Connects Another Smaller Cell
This is a significant evolutionary leap, so large that we have only seen it three times in the entire evolution of life.
It is estimated that 8% of human DNA is the legacy of ancient viruses. But there are organisms that steal more than just the DNA of others, organisms that completely assimilate others. The process we just observed between algae and bacteria.
Beyond symbiosis. This merger or assimilation occurred between newly discovered cyanobacteria (which they named UCYN-A) and algae. Braarudosphere of Bigelovia. Bacteria ceased to be an independent organism and became an organelle of algae. This process is called primary endosymbiosis.
As far as we know, this is only the third time this has happened in the entire evolutionary history of the planet.
Blurred border. This “takeover” takes the relationship between algae and bacteria one step beyond symbiosis. Blurred border. Until now, this connection was not completely unknown, and only now did researchers realize that they were not looking at two organisms sharing food, but rather at algae and something that used to be a bacterium.
Scientists have concluded in part that we are dealing with assimilation, rather than a simple symbiotic relationship, because the former cyanobacteria have lost some of their genes responsible for photosynthesis and metabolism. That is, now algae was his main source of energy.
On the other hand, both organisms contained proteins encoded by each other, in addition to the fact that the bacteria were “integrated” into the algal cytoskeleton. Moreover, cell division in both organisms was coordinated.
Recent history.” In evolutionary terms, endosymbiosis between both organisms can be considered to have occurred relatively recently. According to research conducted by the team responsible for the discovery, the symbiosis relationship must have begun about 150 million years ago, and assimilation about 90 million years ago.
Details of this study were published in two scientific journal articles. First in the magazine cell and the second in The science.
From nitrogen to ammonia. And why does algae want to assimilate bacteria in this way? The key is nitrogen fixation, which is the conversion of nitrogen gas into ammonia, which can be used by living organisms.
This chemical reaction is extremely complex because nitrogen gas is very stable. Interestingly, it is the least complex life forms, such as the UCYN-A bacteria, that are the only ones capable of carrying out such a transformation. This is why these prokaryotic cells are so relevant to plants, although until now they have been symbiotic rather than endosymbiotic.
Now Braarudosphaera has become the only complex organism capable of independently carrying out nitrogen transformation. All thanks to its “new organelle,” which its discoverers called nitroplast.
History of (endo)symbiosis. This is only the third time in the billions of years of evolutionary history of our planet. This is actually the third time that we know of. To put the importance of endosymbiosis in context, just remember what the previous two were.
The first of these occurred about 2 billion years ago: the appearance of mitochondria. This cellular organelle is the source of energy for all complex cells today. The absorption of mitochondria allowed the evolution of complex organisms by allowing cells to have a built-in energy source.
The second affected only one of the kingdoms of nature, but it was of decisive importance in its evolution. This is the absorption of chloroplasts by the first plants. Chloroplasts are essentially organelles that allow plants to carry out photosynthesis.
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Image | Valentina Loconte/Berkeley Lab/Tyler Cole