The largest known bacterium is changing researchers’ ideas about what’s possible for bacteria, Earth’s oldest life form.
The organism was discovered on the Caribbean island of Guadeloupe and is large enough to be seen with the human eye.
Scientists recently said the bacterium, called Thiomargarita magnifica, is unusual for its size — up to about two inches in length. It is also notable because its structure is different from that of other bacteria.
The DNA, the genetic information of an organism, does not move freely in the cell like most bacteria. Instead, the DNA is bound in many small membranes bags† Membrane-bound structures in cells become organelles†
Jean-Marie Volland was a co-leader of the study that appeared in the publication Science†
Volland said of the bacteria: “It is thousands of times larger than normal-sized bacteria. Discovering this bacteria is like meeting a human the size of Mount Everest.”
Researchers have found the bacteria in several places in Guadeloupe, a French island group in the Caribbean.
Research leader Olivier Gros first discovered the bacterium in the sulfur-rich seawater of a Guadeloupe swamp – land that is wet and partially covered with water.
Gros described finding long white materials attached to a sheet of a mangrove tree. He brought the materials back to the lab to study.
“It’s a big surprise to me that such a huge bacteria lives in the mangroves of Guadeloupe,” he said.
A normal bacterium is one to five micrometers long. A micrometer is one millionth of a meter. This one types on average 10,000 micrometers or one cm long. Some Thiomargarita magnifica are twice as long.
Volland said the bacterium is “larger than what we thought the” maximum possible size for a single bacterium.” He added: “They are about the same size and shape as a eyelash†
The largest known bacterium so far had a maximum length of about 750 micrometers.
Bacteria are single-celled organisms that live almost everywhere on Earth. Bacteria are thought to be the first organisms and are still very simple in structure billions of years later. People’s bodies are filled with bacteria. Only a small number of these cause disease.
Caribbean mangrove swamps are filled with organic matter. Microbes break down this material and produce sulfur. The sulfur-rich environment provides an energy source for bacteria such as Thiomargarita magnifica.
The researchers named the DNA-containing organelles “pepinen” after a French word for small seeds in fruit.
“With the exception of two exceptions, no other bacteria were known to keep their DNA within a membrane-bound organelle. That is, in fact, a characteristic from more complex cells that have a membrane-bound nucleus, such as human cells, or animal and plant cells,” Volland said.
A genome map showed that Thiomargarita magnifica has lost some genes necessary for cell division and has more than the usual copy number of genes responsible for cell elongation.
“The genome is also very large, containing three times the average number of genes commonly found in bacteria. We have no idea what half of those genes are for,” Volland said.
This bacterium shows how life on Earth still has surprises waiting to be discovered, he said.
“Life is fascinatingvery diverse and very complex,” adds Volland. “It’s important to stay curious and have an open mind.”
I’m John Russell.
Will Dunham covered this story for Reuters. John Russell adapted it for VOA Learning English.
Words in this story
bag – n. a part in the body of an animal or plant that is in the form of a sac and usually contains liquid or air; a hollow, flexible structure
organelle † n. a specialized cellular part that performs a specific function
mangrove – n. a tropical tree with roots growing from its branches that grows in swamps or shallow salt water
types – n. biology: a group of animals or plants that resemble each other and can produce young animals or plants
maximum †n. the largest number or amount possible
eyelash – n. one of the hairs that grow along the top of the eyelid
characteristic -n. a quality that makes something different from other things
fascinating – adj. very interesting or attractive
#Researchers #discover #worlds #largest #bacteria