You can see it with the naked eye and pick it up with tweezers — not bad for a single bacterium.
Scientists say they’ve discovered the world’s greatest diversity in Guadeloupe’s mangroves – and they’re putting their colleagues to shame.
At up to two centimeters, “Thiomargarita magnifica” is not only around 5,000 times larger than most bacteria, but also has a more complex structure, according to a study published Thursday in the journal Science.
The discovery “shatters a lot of knowledge” in microbiology, Olivier Gros, a professor of biology at the University of the Antilles and a co-author of the study, told AFP.
In his laboratory in the Caribbean archipelago city of Pointe-à-Pitre, he admired a test tube with strands that look like white eyelashes.
“At first I thought it was anything but a bacterium because something two centimeters in size just can’t be one,” he said.
The researcher first spotted the strange filaments in 2009 in a patch of sulfur-rich mangrove sediment.
Techniques like electron microscopy showed it was a bacterial organism, but there was no guarantee it was a single cell.
– “As high as Mount Everest” –
Molecular biologist Silvina Gonzalez-Rizzo from the same lab found that it belongs to the family Thiomargarita, a genus of bacteria known to use sulfides to grow. And a researcher in Paris suggested that they were actually dealing with just one cell.
But a first attempt at publication in a scientific journal a few years later failed.
“We were told, ‘That’s interesting, but we don’t have the information to believe you,'” Gros said, adding that they needed stronger images to provide evidence.
Then a young researcher, Jean-Marie Volland, managed to study the bacterium with the Lawrence Berkeley National Laboratory, operated by the University of California.
With financial backing and access to some of the best tools in the field, Volland and his colleagues set out to get their bearings on the colossal bacteria.
It was clearly huge by bacterial standards — scaled to human proportions, it would be like meeting someone “as tall as Mount Everest,” Volland said.
Finally, special 3D micrographs made it possible to prove that the entire filament was actually a single cell.
But they also helped Volland to make a “completely unexpected” discovery.
Normally, the DNA of a bacterium floats freely in the cell. But in the giant species, it’s condensed into small structures surrounded by a membrane, he explained.
This DNA compartmentalization is “usually a feature of human, animal, and plant cells, complex organisms… but not bacteria,” Volland said.
Future research needs to determine if these properties are unique to Thiomargarita magnifica or if they can be found in other bacterial species, Gros said.
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