Scientists Discover 'Gigantic' Bacteria Visible Without Microscope

Bacteria are so small that we have to use a microscope in order to see them, but a newly discovered bacteria is so big it's visible to the naked eye.

The new bacteria was discovered by marine biology professor Olivier Gros of Université des Antilles, while he was looking for sulfur-oxidizing symbionts in mangrove sediments in Guadeloupe in 2009, Lawrence Berkeley National Laboratory noted in a news release.

They were first observed as thin, "vermicelli-like" strands along with other debris in the petri dish. But microscopy studies revealed that the strands were actually bacteria so large that they can be seen without the help of a microscope.

Specifically, the newly discovered bacteria, which the scientists named Thiomargarita magnifica due to its large size, is about 5,000 times bigger than other bacteria, said study co-author, Jean-Marie Volland of the U.S. Department of Energy Joint Genome Institute (JGI) and the Laboratory for Research in Complex Systems (LRC) in California, as per the news release.

In fact, most bacterial species' cells are about 2 micrometers in length, with the largest specimens being about 750 micrometers, the researchers wrote in their paper describing the find, published Thursday in the journal Science. But the T. magnifica's average cell length is a whopping 9,000 micrometers and it can grow to up to 2 centimeters long.

"To understand how gigantic that is for a bacterium, it is the same as if we were to find a human as tall as Mount Everest," Volland told CNN.

"These cells grow orders of magnitude over theoretical limits for bacterial cell size," the researchers wrote.

Another interesting find about T. magnifica, apart from its relatively gigantic size, is that there are structures within it that contain their DNA. These structures also "compartmentalize" the DNA from the cytoplasm. This, Volland explained, hasn't been seen in bacteria before. In most bacteria, they simply have their DNA floating freely in the cytoplasm.

The T. magnifica is also rather complex.

"The bacteria contain three times more genes than most bacteria and hundreds of thousands of genome copies (polyploidy) that are spread throughout the entire cell," Volland said in the news release.

Taken together, the features of the T. magnifica "challenge traditional concepts of bacterial cells" and open up many more research questions, said the researchers. It also shows how complexity evolved "in some of the simplest organisms," one of the senior authors and the founder and CEO of LRC, Shailesh Date, noted.

"It always strikes me how little we know about the microbial world and how much is out there," another senior author, Tanja Woyke, who heads the JGI program, said in the news release.

"Confirmation bias related to viral size prevented the discovery of giant viruses for more than a century," the authors wrote. "The discovery of Ca. T. magnifica suggests that large and more complex bacteria may be hiding in plain sight."