Scientists Witness Rare Evolutionary Event That Happens Once Every Billion Years: The Birth of a New Organism Through Cellular Ingestion
In an extraordinary display of nature's capabilities, scientists from the University of California have observed a rare event in the process of evolution, an occurrence estimated to happen only once every billion years.
This pivotal evolutionary shift, detailed in studies published in the journals Cell and Science, marks the formation of a new life form through the union of two separate entities, a phenomenon that last played a significant role in the emergence of plants on Earth, reports New Atlas.
Dubbed primary endosymbiosis, this process involves one cell engulfing another, then using it as an internal organ. In exchange, the host organism provides nutrients, energy, and protection. This relationship eventually renders the engulfed cell incapable of independent life, transforming it into a functioning part of the host organism.
Throughout Earth's 4 billion-year history, primary endosymbiosis is believed to have occurred only twice before, each time catalyzing a monumental breakthrough in the course of evolution. The first instance occurred around 2.2 billion years ago, when an archaic bacterium (archaea) ingested another bacterium, which evolved into the mitochondrion. This event was crucial for the development of complex life forms, as mitochondria are the powerhouse of the cell.
The second instance happened approximately 1.6 billion years ago. Advanced cells absorbed cyanobacteria capable of harnessing energy from sunlight. These became chloroplasts, the organelles responsible for photosynthesis in plant and eukaryotic algal cells.
The recent observation by researchers involves the algae species Braarudosphaera bigelowii engulfing a cyanobacterium. This acquisition enables them to fix nitrogen directly from the air, a feat not typically possible for algae and plants. Nitrogen fixation is generally achieved through symbiotic relationships with separate bacteria, making this capability particularly noteworthy.
Utilizing X-ray analysis, the researchers examined the algae and found that its growth correlated with the growth of the atelocyanobacterium thalassa (Ucyn-A), a bacterium residing within it. This provided direct evidence of primary endosymbiosis in action.
Further study of a separate Ucyn-A bacterium compared to the one found in the algae revealed that the latter could only produce half of the necessary proteins for its function, relying on the host organism for the remainder.
The scientific team plans to continue their investigation of this newly formed organism to uncover more about the intricacies of evolution. This discovery not only highlights the slow yet astonishingly innovative nature of evolutionary change but also provides insight into the foundational events that have shaped life on our planet.