Scientists have observed a once-in-a-billion-years evolutionary event as they’ve witnessed the phenomenon of primary endosymbiosis in progress. This event is when two lifeforms merge into one organism.

Primary endosymbiosis is a rare phenomenon that occurs only when one microbial organism merges into another, engulfing it in the process.

Eventually, this engulfed organism can no longer exist alone. It needs the organism that it merged with, as it has started to provide so many nutrients that it needs. The organism relies on it.

According to a new study, scientists have discovered this phenomenon is occurring within Braarudosphaera bigelowii, an algae species. 

After discovering this occurrence, scientists have stated that the algae’s consumption of this cyanobacterium has allowed the algae to fix nitrogen from the air.

Algae and plants need nitrogen as a nutrient. Normally, they get the nitrogen through the symbiotic relationships that they form with bacteria. However, this bacteria remains completely separate from the algae or plant itself.

According to this study, scientists took a look at this algae species after first thinking that it had created a symbiotic relationship with UCYN-A, a bacteria. This would be normal, as that’s how algae and plants work.

Therefore, scientists have claimed that these two organisms have linked metabolisms. They’ve also pointed out that the two organisms exchange nutrients. Jonathan Zehr, an author of these new studies, has further explained what they found.

After discovering this initial finding, researchers decided to take a closer look by conducting a follow-up study. In this most recent study, scientists used X-ray imaging to try to view these algae cells.

Most notably, researchers wanted to see if one of the organisms was fully relying on the other after absorption — a major component of primary endosymbiosis.

Scientists have now named the UCYN-A organelle a nitroplast. According to their research, they believe this evolution began about 100 million years ago. 

Scientists also believe that this phenomenon occurred about 1.6 billion years ago for only the second time. This last occurrence happened when cells engulfed cyanobacteria. This bacteria then allowed the cell to better harvest energy from the sun.

Endosymbiosis has reshaped life’s history multiple times, but rarely with documentation. Prior events, like the creation of mitochondria and chloroplasts, underpin much of modern life’s complexity (via Scitable).

The genetic ramifications of the observed primary endosymbiosis are pretty profound. DNA sequencing of both host and engulfed organisms could reveal the specific mutations facilitating this merger, within the realm of what’s known as horizontal gene transfer.

This evolutionary leap by algae could dramatically alter marine ecosystems. By fixing nitrogen, Braarudosphaera bigelowii might shift nutrient dynamics, potentially affecting everything from algae blooms to fish populations.

Nitrogen fixation by algae influences global cycles of carbon and nitrogen, key elements in climate regulation (via Nature Education Knowledge).

Given the rarity of primary endosymbiosis, predicting future occurrences is challenging but crucial.

This discovery also necessitates revisions in the phylogenetic trees of algae and bacteria.

Advanced imaging techniques like X-ray microscopy have been pivotal in uncovering this rare event.

Proposing additional long-term studies to monitor the evolutionary progress of Braarudosphaera bigelowii can provide insights into the stability and adaptability of new traits.

Primary endosymbiosis is an evolutionary rarity, possibly due to the complex conditions required for two distinct organisms to stably merge (via Encyclopedia of Evolutionary Biology).

This recent observation of primary endosymbiosis in Braarudosphaera bigelowii not only highlights its rarity but also its profound implications for evolutionary biology.

The observation of a once-in-a-billion years evolutionary event offers an invaluable window into the processes that shape life on Earth.

Encouraging further studies into how merging organisms can lead to novel biological functions and adaptations, potentially revolutionizing our understanding of evolutionary biology and its applications.