Why the World's Largest Bacterium Is Baffling Scientists


| LAST UPDATE 03/01/2022

By Stanley Wickens
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We used to think of bacteria as some of the smallest living organisms on our planet. That is, until the recent discovery made by scientists, where they found a type of bacterium that has changed the way we study the evolution of lifeforms.

Recent research has found the largest bacterium ever discovered on our planet, consisting of a single cell that measures 2 cm (0.8 in) in length. While most types of bacteria are usually between one and five micrometers long, the recently identified species measures nearly 3,000 times larger than the average bacterium. The new species, which was actually discovered about a decade ago by marine biologist Olivier Gros, lives in the mangroves of Grande-Terre in the Caribbean. However, at the time, Gros didn't recognize the organisms as a bacteria or single-celled organisms at all. It was only after a recent comprehensive analysis that this conclusion was made.

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The massive size of the bacterium has shocked scientists' understanding of the evolutionary development of bacteria. Researchers previously thought that the size of bacteria depended on the distance that molecules exchanged between the organism and its environment could travel. Nutrients must be able to travel into the cell through its membrane, and toxins should be able to leave the cell. Otherwise, the organism couldn't survive. But scientists have recently discovered the trick used by this type of bacterium to manage to survive at such a large size. The organism has a water-filled sac, which constitutes 73% of its overall volume and spreads the cellular contents of the organism out towards the outer membrane. By doing this, the sac shortens the journey that essential molecules need to travel in order to supply vital nutrients to the bacterium.


As strangely large as the size of this bacterium is the size of its genome. It contains 11 million bases and around 11,000 genes, making it nearly three times larger than the genomes of most bacteria. What's more, the team of researchers who studied the bacterium found that its genome is rather repetitive, finding more than half a million copies of some of its sequences. As if all this wasn't bizarre enough, the researchers found that this bacterium's DNA was enveloped in a membrane sac, instead of floating unrestrictedly through the cell-like typical bacteria. Since this phenomenon is normally seen in more complex organisms, the massive bacterium has blurred the lines between different lifeforms. Stay tuned for more on this groundbreaking study!

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