The world’s largest bacterium has been discovered

Unprecedented invention. She can be caught with tweezers: huge Bacteria The world, 5,000 times larger than its counterparts and more complex in structure, was discovered GuadeloupeAccording to a study published Thursday in the journal Science.

The “Theomargarita magnifica” measures up to two centimeters, looks like an “eyelid” and moves the symbols of microbiology, as described by AFP Oliver Cross, professor of biology at the university. West IndiesCo-author of the study.

Seen in 2009

In his laboratory on the Pouillole campus, at Pointe-à-Pitre, the researcher proudly shows a test tube with small white fibers. When the average size of a bacterium is two to five micrometers, it can be “seen with the naked eye and I can pick it up with tweezers! “, He wonders.

It is located in the Guadeloupe swamp The researcher first observed the microbe in 2009. “At first I thought it’s a bacterium, because two centimeters can not be together.” Very quickly, the techniques of cellular interpretation by electronic microscope show that it is actually a bacterial organism. But with this size, Professor Cross says, “we have no certainty that this is a cell” – a bacterium is a single-celled microbe.

A biologist from the same laboratory reveals that it belongs to the Theomargarita family, a type of bacterium that is already being developed using sulfides. The work carried out in Paris by the CNRS researcher says that we are dealing with a “single cell”, explains Professor Cross.

“The height of Mount Everest”

Relying on their discovery, the team attempts the first publication in a scientific journal, which fails. “We were told: this is interesting, but we do not have the information to believe you,” there was not strong enough evidence based on the photos, the biologist recalled.

Enter Jean-Marie Volland, a young graduate student at the University of the West Indies, who will become the first author of a study she has published. Science. The 30-year-old flew to the United States, where he was hired by the University of Berkeley because he did not get a teaching-researcher position in Guadeloupe. By the time he left, he had the idea of ​​reading the “incredible bacteria” he was already familiar with. “It’s like meeting a man as tall as Mount Everest,” he thought to himself. In the fall of 2018, he received the first set sent by Professor Cross to the Institute for Genetic sequencing at the Lawrence Berkeley National Laboratory, which is managed by the university.

The challenge is basically technology: thanks to “three-dimensional microscopic analyzes, at high magnification” succeeded in presenting the overall picture of the bacterium. In the American laboratory, the researcher had advanced techniques. Recognizing the significant funding and “access to researchers who specialize in genetic sequencing”, the scientist acknowledges that this US-Guadeloupe collaboration is a “success story”. Its 3D images help to finally prove that the whole fiber is actually a cell.

Disorder of microbiology

Aside from its “gigantism”, the bacterium is “more complex” than its counterparts: a “completely unexpected” discovery, the researcher testifies, which “turns microbiological knowledge upside down a little bit”. “In bacteria, DNA usually floats freely in the cell, in which it compresses into tiny structures called pips, which are tiny sacs that enclose a membrane that isolates DNA from other cells.” Jean-Marie Woland.

This segmentation of DNA, the carrier molecule of genetic information, is “characteristic of human, animal, and plant cells … not bacteria”. Future research suggests that future research may be needed to determine whether these traits are specific to Theomargarita magnifica or whether they are found in other types of bacteria.

“This bacterium calls into question many established rules in giant microbiology” and “gives us the opportunity to observe and understand how complexity manifests itself in living bacteria,” exclaims Jean-Marie Woland.