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Microorganisms are called so because they are so tiny that they can only be seen under a microscope. But in a new study scientists have discovered an extraordinarily huge bacteria that can be seen without a microscope. It dwells in the mangroves of Grande-Terre in the Caribbean.
Its single threadlike cell can grow up to two centimeters in length—as long as a peanut—and is 5000 times larger than many other microbes. Furthermore, unlike other bacteria, this giant has a massive genome that is enclosed in a membrane rather than floating freely inside the cell. This is a feature found in far more complicated cells, such as those found in the human body. This separates the newly discovered microorganism not just from other bacteria, but also from other prokaryotes (organisms with very tiny, basic cell structures).
“When it comes to bacteria, I never say never, but this one for sure is pushing what we thought was the upper limit [of size] by 10-fold,” says Verena Carvalho, a microbiologist at the University of Massachusetts, Amherst.
The discovery straddles the line between prokaryote and eukaryote in that it carries its DNA in a membrane-bound pouch and also carries a second, big pouch filled with water, which accounts for more than 70% of the cell’s total volume. This water-filled pouch squishes all of the contents of the cell up against the cell’s outermost border, which may assist life-sustaining chemicals flow more easily into the cell while poisons pass through more quickly.
The same type of water-filled pouch is carried by a huge sulfur-eating bacteria in the genus Thiomargarita, and the researchers determined that the discovered bacterium likely belongs to the same genus based on this resemblance and a genetic study. They offered the name T. magnifica for the enormous bacterium.
The humongous bacterium “could be a missing link in the evolution of complex cells,” Kazuhiro Takemoto, a computational biologist at Kyushu Institute of Technology, told Science.
“Separating genetic material from everything else allows more sophisticated control and greater complexity,” says Chris Greening, a microbiologist at Monash University, Clayton.
“All too often, bacteria are thought of as small, simple, ‘unevolved’ life forms—so-called ‘bags of proteins,” Greening adds. “But this bacterium shows this couldn’t be much further from the truth.”