Record bacterium discovered as long as human eyelashes

Record bacterium discovered as long as human eyelashes

You should need a microscope to see bacteria, right? Not Thiomargarita magnifica.

This giant cell is clearly visible to the naked eye and is the size and shape of a human eyelash.

Now classified as the world’s largest bacterium, T. magnifica was discovered in the French Caribbean on sunken, decaying leaves of mangrove trees.

Do not worry, the organism is not dangerous and cannot cause disease in humans. But marvel at its proportions.

“These bacteria are about 5,000 times larger than most bacteria. And to put things in perspective, for us humans, meeting another human the size of Mount Everest is tantamount,” says Jean-Marie Volland of the Joint Genome Institute at Lawrence Berkeley National Laboratory in the US .

scale graphic

scale graphic

centimeters long T. magnifica is not the largest unicellular organism on earth. That’s probably called some kind of aquatic alga Caulerpa taxifolia that’s 10 times longer. But the bacterium is definitely impressive considering there are many, much more complex life forms on Earth that require some kind of magnification to be observed. Think of those really tiny worms and flies out there.

T. magnifica was first identified in Guadeloupe in the Lesser Antilles in 2009. But it was initially put aside. Only recently are dr. Volland and colleagues got around to studying it in detail.

A central finding of their investigations relates to the way in which the cell organizes its interior. Bacteria normally have their DNA floating freely in the fluid or cytoplasm that fills their body.

T. magnificaon the other hand, its genetic material is stored in compartments that the researchers call pepins, from the French for fruit seeds.

A significant finding, because until now, the packaging of DNA in a membrane-enclosed compartment was considered the domain of so-called eukaryotic cells, which are the building blocks of higher organisms such as humans, other animals and plants.

mangrove forest

T. magnifica uses the decaying matter in the sediments around the roots of mangroves

and T. magnifica carries a lot of DNA. If you count all the “letters” or bases in its life code or genome, it’s about 12 million. But in every cell there can be half a million copies of the genome.

“Now if you take the genome size of 12 million bases, multiply that by the number of genome copies — so half a million — you end up with about 6,000 giga or billions of bases of DNA. For comparison, a diploid human genome is about six gigabases, so that means our Thiomargarita stores several orders of magnitude more DNA than a human cell,” explains Dr. Tanja Woyke, also of Lawrence Berkeley.

In all of this DNA there are clues to the drivers of the organism’s large size, she added. Some genes associated with elongation appear to be duplicated, and some genes normally involved in division appear to be missing.


The T. magnifica filament is the shape and size of a human eyelash

T. magnifica is a chemosynthetic bacterium. It makes the sugars it needs to support itself by oxidizing the sulfur compounds produced by the decaying organic matter in the mangrove swamp sediments. All it needs is something solid to hold on to.

“I found them on oyster shells, leaves and twigs, but also on glass bottles, plastic bottles or ropes,” said Prof Olivier Gros, a microbiologist at the University of the Antilles.

“They just need some hard substrate to get in contact with the sulfides and with the seawater to get oxygen and CO2. The highest concentration of Thiomargarita I found it on a plastic bag – unfortunately.”

The research team published their description of the bacterium in this week’s issue of Science Magazine. The researchers admit that they still have a lot to learn about how the organism works.

“This project has really opened our eyes to the unexplored microbial diversity that exists. We’re really just scratching the surface and who knows what interesting things we may still have to discover,” commented Dr. Shailesh Date from the Complex Systems Research Laboratory in Menlo Park, USA.

mangrove forest

The mangroves of the Caribbean have the perfect environment for the giant bacterium

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