Scientists have discovered the world’s largest bacterium in a Caribbean mangrove swamp.
Although most bacteria are microscopic, Thiomargarita magnifica is the size of a human eyelash and can be seen with the naked eye.
In fact, the organism is not dangerous to humans, but its size has amazed scientists.
“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 United States states.
The one-centimetre-long bacterium was discovered on decaying leaves of mangrove trees in the Caribbean.
The species belongs to the genus Thiomargarita. Professor Silvina Gonzalez-Rizzo of the University of the Antilles, Guadeloupe, explained how it was named: “Magnifica, because magnus means big in Latin and I think it’s as great as the French word magnifique.
She added, “This type of discovery opens up new questions about bacterial morphotypes that have never been studied before.”
Her colleague Professor Olivier Gros encountered the species during an expedition to the Guadeloupe mangrove swamps in 2009.
He said: “When I saw her, I thought ‘Strange’. At first I thought it was just something weird, a bunch of white fibers that needed to be attached to something in the sediment like a leaf.”
It was initially put aside, but several years later, through scans and the use of a gene sequencing technique, scientists finally identified and classified the prokaryote.
Professor Silvina Gonzalez-Rizzo, who performed the gene sequencing, said: “I thought they were eukaryotes – organisms with a nucleus. I didn’t think they were bacteria because they were so big and seemed to have lots of filaments.
“We realized that they were unique because they looked like a single cell. The fact that they were a ‘macro’ microbe was fascinating.”
Thanks to state-of-the-art scanners, the huge cells could be viewed in three dimensions at high magnification and in exquisite detail.
The images confirmed that they were single cells rather than multicellular filaments.
Novel membrane-bound compartments have also been identified. These contained complex and abundant clusters of DNA – called “pepins” after the small seeds in fruit.
dr Volland said, “The bacteria contain three times more genes than most bacteria and hundreds of thousands of genome copies scattered throughout the cell.”
Scientists determined that T. magnifica is a chemosynthetic bacterium.
It makes its own fuel – sugars – by oxidizing the sulfur compounds produced by the decomposition of organic matter found in the mangrove swamps.
All it takes to grow is find 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.
A full description of the bacterium has been published in science magazine.