In a swampy mangrove forest in the French Caribbean, a strange creature hides among the fallen leaves. Apparently this creature is the largest bacteria that ever existed.
This bacterium, which has the scientific name Thiomargarita magnifica, has a length of 1-2cm, making it a "giant" compared to other microbes. Because of its size, Thiomargarita magnifica is the only bacterium that can be seen without a microscope so far.
"This (bacteria) is about 5,000 times larger than most bacteria. The picture is the same as meeting a human the size of Mount Everest," said lead author Jean-Marie Volland, a microbiologist at Lawrence Berkeley National Laboratory in California.
Finding the biggest bacteria was the thing that crossed Professor Olivier Gros' mind when he was hunting for microbes in the Guadeloupe mangroves in the French Caribbean nearly two decades ago.
While collecting samples from the cloudy water, Professor Gros noticed long white filaments stuck to the leaves. The marine biologist decided to take a closer look, and took the hair-like filaments to his lab at the University of Antilles in Guadeloupe and examined them under a microscope.
"I didn't think it was a bacterium, and the creature was huge for a bacterium. I thought it was a fungus or something," Professor Gros said.
Preliminary genetic analysis revealed that the eccentric organism's makeup matched that of Thiomargarita, a genus that includes sulfur-eating bacteria.
So Professor Gros and his team temporarily named the microbe Thiomargarita magnifica, after "magnus", a Latin word meaning great.
Weird inside and out
When Dr Volland joined Professor Gros's lab a few years later, he focused on studying "microbes" and confirming that they were indeed one-celled bacteria.
The research team collected more samples from the mangroves in Guadeloupe and used a variety of powerful microscopic techniques to view the filaments in three dimensions.
When Dr Volland and his team zoomed in on this single-celled creature and scanned its entire length, he was unable to see a segment normally seen in multicellular organisms.
He also saw a kind of small, seed-like compartment that contained the genetic blueprint of bacteria. This is a curious feature, because bacterial DNA normally floats freely within the cell instead of being neatly packaged in the cell's receptacle as in humans, plants, and animals.
"This has never been observed in bacteria before. This is actually something that characterizes complex organisms," said Dr Volland.
This package of genetic material allows bacteria to grow to enormous sizes, said Ashley Franks, an environmental microbiologist at La Trobe University who was not involved in the study.
"We used to think that bacteria are always spherical in shape and they have a certain size. They all mix together in the middle and that's how you get all of their functions," said Professor Franks.
This is thought to be the reason why most bacteria are micro-sized, because bacteria that grow too large will destroy their internal chemistry.
But because the interior of T. magnifica is relatively regular and somewhat separate, it can grow to a large size without losing its chemical balance.