Discover the largest bacteria in the world

An unprecedented discovery. Can be held with tweezers: the largest bacteria of the world, 5,000 times larger than its peers and more complex in structure, was discovered in GuadeloupeAccording to a study published Thursday in the journal Science.

“Thiomargarita magnifica” measures up to two centimeters, looks like an “eyelash” and rocks the symbols of microbiology, described to AFP by Olivier Gross, professor of biology at the University of West Indiesco-author of the study.

Spotted in 2009

In his laboratory on the Fouillole campus, in Pointe-à-Pitre, the researcher proudly displays a test tube containing tiny white threads. When the average size of the bacteria is 2 to 5 micrometers, “it can be seen with the naked eye, I can pick it up with tweezers!”, it is amazing.

It is located in Guadeloupe Guadeloupe That the researcher first noticed the microbe, in 2009. “At first I thought it was nothing but a germ, because something two centimeters long couldn’t be one.” Very quickly, electron microscopy techniques show that it is nevertheless indeed a bacterial organism. But with this size, Professor Gross says, “we had no confirmation that it was a single cell” – bacteria are a single-celled microorganism.

A biologist from the same laboratory reveals that it belongs to the family Thiomargarita, an already known bacterial genus that uses sulfides for its development. Professor Gross explains that work by a researcher at the National Center for Scientific Research in Paris indicates that we are dealing with “one cell and the same cell”.

As tall as Mount Everest

Convinced of their discovery, the team attempted to publish for the first time in a scientific journal, but that failed. The biologist recalls: “We were told: It is interesting but we lack the information to make us believe you,” and the evidence is not strong enough in terms of photographs.

Enter Jean-Marie Voland, a young postdoctoral student from the University of the West Indies, who will become the first author of the study published in Science. After not obtaining a research position in Guadeloupe, the 30-year-old traveled to the United States, where he was recruited by the University of Berkeley. By leaving there, he was thinking of studying the “amazing bacteria” he was already familiar with. He said to himself, “It would be like meeting a man on Mount Everest.” In the fall of 2018, he received the first package that Professor Gross sent to the Institute of Genome Sequencing at Lawrence Berkeley National Laboratory, which is operated by the university.

The challenge was mainly technical: to succeed in presenting an image of the bacteria as a whole, thanks to “3D microscopic analyses, at high magnification”. In the American laboratory, the researcher possessed advanced technologies. Not forgetting the great financial support and “access to researchers who are experts in genome sequencing,” the scientist admits, calling this US-Guadeloupe collaboration a “success story.” His 3D images finally make it possible to prove that the entire strand is indeed a single cell.

Microbiology disorder

In addition to their “giantness”, bacteria also turned out to be “more complex” than their counterparts: a “completely unexpected” discovery, which “somewhat turns the knowledge of microbiology upside down,” the researcher testifies. “While bacteria are present, the DNA usually floats freely in the cell, in which case it is compressed into tiny structures called dots, a type of small, membrane-enclosed sac that isolates the DNA from the rest of the cell. The cell develops.” Jean Marie Foland.

This division of DNA – the carrying molecule of genetic information – is “a characteristic of human, animal, and plant cells…and not at all bacteria”. Future research should determine whether these properties are specific to Thiomargarita magnifica or if they are present in other types of bacteria, according to Olivier Gros.

“This bacterial giant calls into question many established rules of microbiology” and “provides us the opportunity to observe and understand how complexity arises in living bacteria,” Jean-Marie Volland is excited.