Researchers Discover World's Largest Bacterium
2022-06-28
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1The largest-known bacterium is changing researchers' ideas about what is possible for bacteria, Earth's most ancient life form.
2The organism was discovered on the Caribbean island of Guadeloupe and is big enough to be seen with the human eye.
3Scientists said recently that the bacterium, called Thiomargarita magnifica, is unusual for its size -- up to about two centimeters long.
4It is also notable because its structure is unlike other bacteria.
5The DNA, an organism's genetic information, is not free-moving inside the cell like in most bacteria.
6Instead, the DNA is contained within many small membrane-bound sacs.
7Membrane-bound structures in cells are called organelles.
8Jean-Marie Volland was a co-leader of the study that appeared in the publication Science.
9Volland said of the bacteria, "It is thousands of times larger than regular-sized bacteria.
10Discovering this bacterium is like encountering a human being as tall as Mount Everest."
11Researchers have found the bacterium in several places in Guadeloupe, a French island group in the Caribbean.
12Study co-leader Olivier Gros first discovered the bacterium in the sulfur-rich seawater of a Guadeloupe swamp - land that is wet and partly covered with water.
13Gros described finding long white materials attached to a leaf of a mangrove tree.
14He brought the materials back to the lab to study.
15"Big surprise for me to have so huge a bacterium living in the mangroves of Guadeloupe," he said.
16A normal bacteria measures one to five micrometers long.
17A micrometer is one millionth of a meter.
18This species averages 10,000 micrometers or one cm long.
19Some Thiomargarita magnifica are double that length.
20Volland said the bacterium is bigger "than what we thought was the maximum possible size for a single bacterium."
21He added, "They are about the same size and shape of an eyelash."
22The largest-known bacterium until now had a maximum length of around 750 micrometers.
23Bacteria are single-celled organisms that live nearly everywhere on Earth.
24Bacteria are thought to have been the first organisms and remain very simple in structure billions of years later.
25The bodies of humans are filled with bacteria.
26Only a small number of these cause disease.
27Caribbean mangrove swamps are filled with organic material.
28Microbes break down this material and produce sulfur.
29The sulfur-rich environment offers an energy source for bacteria like Thiomargarita magnifica.
30The researchers named its DNA-holding organelles "pepins" after a French word for small seeds inside fruits.
31"Aside from two exceptions, there were no other bacteria known to keep their DNA inside a membrane-bound organelle.
32That is, in fact, a characteristic of more complex cells which have a membrane-bound nucleus, such as human cells, or animal and plant cells," Volland said.
33A genome map showed that Thiomargarita magnifica has lost some genes needed for cell division and has more than the usual number of copies of genes responsible for cell lengthening.
34"The genome is also very big and contains three times the average number of genes that are usually found in bacteria.
35Half of those genes, we have no idea what are they for," Volland said.
36This bacterium shows how life on Earth still has surprises awaiting discovery, he said.
37"Life is fascinating, very diverse and very complex," Volland added.
38"It's important to stay curious and have an open mind."
39I'm John Russell.
1The largest-known bacterium is changing researchers' ideas about what is possible for bacteria, Earth's most ancient life form. 2The organism was discovered on the Caribbean island of Guadeloupe and is big enough to be seen with the human eye. 3Scientists said recently that the bacterium, called Thiomargarita magnifica, is unusual for its size -- up to about two centimeters long. It is also notable because its structure is unlike other bacteria. 4The DNA, an organism's genetic information, is not free-moving inside the cell like in most bacteria. Instead, the DNA is contained within many small membrane-bound sacs. Membrane-bound structures in cells are called organelles. 5Jean-Marie Volland was a co-leader of the study that appeared in the publication Science. 6Volland said of the bacteria, "It is thousands of times larger than regular-sized bacteria. Discovering this bacterium is like encountering a human being as tall as Mount Everest." 7Researchers have found the bacterium in several places in Guadeloupe, a French island group in the Caribbean. 8Study co-leader Olivier Gros first discovered the bacterium in the sulfur-rich seawater of a Guadeloupe swamp - land that is wet and partly covered with water. 9Gros described finding long white materials attached to a leaf of a mangrove tree. He brought the materials back to the lab to study. 10"Big surprise for me to have so huge a bacterium living in the mangroves of Guadeloupe," he said. 11A normal bacteria measures one to five micrometers long. A micrometer is one millionth of a meter. This species averages 10,000 micrometers or one cm long. Some Thiomargarita magnifica are double that length. 12Volland said the bacterium is bigger "than what we thought was the maximum possible size for a single bacterium." He added, "They are about the same size and shape of an eyelash." 13The largest-known bacterium until now had a maximum length of around 750 micrometers. 14Bacteria are single-celled organisms that live nearly everywhere on Earth. Bacteria are thought to have been the first organisms and remain very simple in structure billions of years later. The bodies of humans are filled with bacteria. Only a small number of these cause disease. 15Caribbean mangrove swamps are filled with organic material. Microbes break down this material and produce sulfur. The sulfur-rich environment offers an energy source for bacteria like Thiomargarita magnifica. 16The researchers named its DNA-holding organelles "pepins" after a French word for small seeds inside fruits. 17"Aside from two exceptions, there were no other bacteria known to keep their DNA inside a membrane-bound organelle. That is, in fact, a characteristic of more complex cells which have a membrane-bound nucleus, such as human cells, or animal and plant cells," Volland said. 18A genome map showed that Thiomargarita magnifica has lost some genes needed for cell division and has more than the usual number of copies of genes responsible for cell lengthening. 19"The genome is also very big and contains three times the average number of genes that are usually found in bacteria. Half of those genes, we have no idea what are they for," Volland said. 20This bacterium shows how life on Earth still has surprises awaiting discovery, he said. 21"Life is fascinating, very diverse and very complex," Volland added. "It's important to stay curious and have an open mind." 22I'm John Russell. 23Will Dunham reported on this story for Reuters. John Russell adapted it for VOA Learning English. 24_______________________________________________________________________ 25Words in This Story 26sac - n. a part inside the body of an animal or plant that is shaped like a bag and that usually contains liquid or air; a hollow, flexible structure 27organelle - n. a specialized cellular part that has a specific function 28mangrove - n. a tropical tree that has roots which grow from its branches and that grows in swamps or shallow salt water 29species - n. biology : a group of animals or plants that are similar and can produce young animals or plants 30maximum -n. the largest number or amount that is possible 31eyelash - n. any one of the hairs that grow along the top of the eyelid 32characteristic -n. a quality that makes something different from other things 33fascinating - adj. very interesting or appealing