Scientists discover giant bacteria that is visible to the naked eye | Thiomargarita magnifica

When we think of bacteria, we think of microbes, organisms so small that they can’t be seen with the unaided eye. And that’s true. But on June 23, 2022, scientists announced that they’ve identified a species of bacteria that is 50 times larger than the previously largest known bacterium. In fact, it reaches up to about 0.4 inches (1 centimeter) in length, easily seen by the unaided eye!

Bacteria and archaea are the most diverse and abundant organisms on Earth. In 2019, scientists even found bacteria that eat and breathe electricity! So perhaps it’s not too surprising to find bacteria that are a lot bigger than usual, too.

Scientists discovered the bacterium – called Thiomargarita magnifica – in shallow tropical marine mangroves in Guadeloupe, Lesser Antilles, in the Caribbean.

When researchers first found it in 2009, they didn’t realize it was a bacterium. Due to its large size, researchers thought it was possibly a species of eukaryote. Eukaryotes are single-celled or multicellular organisms whose cell contains a distinct, membrane-bound nucleus.

Thiomargarita magnifica is huge for a bacterium, at nearly a centimeter long. Or more specifically, the researchers measured the filaments at up to 9.66 millimeters long.

At such a size, it’s easy to think that these filaments must be made of many individual cells. But no, the filaments of Thiomargarita magnifica are one giant cell. This is similar to other large sulfur bacteria. The researchers used various microscopy techniques, such as hard X-ray tomography, confocal laser scanning microscopy and transmission electron microscopy to study the new bacterium.

While the filaments are one single cell, each cell does contain novel, membrane-bound compartments. Those compartments contain clusters of DNA. The researchers named these compartments “pepins,” after the small seeds found in fruits.

There are still unanswered questions, of course. Do the pepins play a role in the evolution of Thiomargarita magnifica’s extreme size? Are the pepins also present in other bacterial species?

свернуть