The largest bacterium in the world, 5,000 times larger than its “relatives” and with a much more complex structure, was discovered on the Caribbean island of Guadeloupe, according to a study published Thursday in the journal Science. Although the bacterium is normally a single-celled organism that cannot be seen with the naked eye, the newly discovered one is up to 2 centimeters long.
Thiomargarita magnifica It measures up to 2 centimeters, looks like an eyelash and overturns the codes of microbiology, said Olivier Gros, a professor of biology at the Université des Antilles and co-author of the study, according to AFP, taken over by Agerpres.
In his laboratory on the Fouilloles campus in Pointe-a-Pitre, the researcher proudly presents a test tube containing small white filaments. Given that the average size of a bacterium is 2 to 5 micrometers (1 micrometer = 0.001 mm, one thousandth of a millimeter), it “can be seen with the naked eye, I can take it with tweezers!”, He explains. he.
The researcher first observed the bacterium in mangroves in Guadeloupe in 2009.
“At first I thought it was anything but a bacterium, because something 2 inches long can’t be a bacterium,” he said.
Quite recently, however, cell description techniques using electron microscopy showed that it was indeed a bacterial organism. But with such a size, Professor Gros explains, “I had no certainty that it was a single cell” – a bacterium being a single-celled microorganism.
A biologist from the same laboratory revealed that she belongs to the family Thiomargarita, a genus of bacteria already known to use sulfides to grow. And research conducted in Paris by a specialist at the French National Center for Scientific Research (CNRS) suggests that we were dealing with “a single cell,” Gros explained.
Convinced of her discovery, the team tried a first publication in a scientific journal, which she refused. “They told us: It’s interesting, but we need more information to believe youbecause the evidence was not solid enough in terms of the image “, the biologist remembers.
“It’s like meeting a man as tall as Mount Everest”
And here comes Jean-Marie Volland, a young postdoctoral researcher at the Université des Antilles, who will become the first author of the study published in the journal Science. After failing to get a professorship in Guadeloupe, he left for the United States, where he was recruited by the University of California, Berkeley. When he went there, he had in mind studying the “incredible bacteria” he was already familiar with.
“It’s like meeting a man as tall as Mount Everest,” he told himself.
In the fall of 2018, Volland received a first package sent by Professor Gros to the genome-sequencing institute at Lawrence Berkeley National Laboratory, run by the university.
The challenge was, in essence, one of a technical nature: to be able to reproduce an image of the bacterium as a whole, thanks to “three-dimensional microscopic analyzes, at a larger magnification”.
In the American laboratory, the researcher had access to state-of-the-art techniques. Added to this is significant financial support and “access to genome sequencing experts,” acknowledges the scientist, who describes the US-Guadeloupe collaboration as a “success story.”
Its 3D images finally prove that the entire filament is indeed a single cell.
Beyond its “gigantism,” the bacterium also proves to be “more complex” than its “relatives”: a “totally unexpected” discovery that “upsets the knowledge of microbiology,” the researcher said.
Publisher : BP