WASHINGTON : The largest-known bacterium - a vermicelli-shaped organism that was discovered in shallow mangrove swamps in the Caribbean and is big enough to be seen with the naked eye - is redefining what is possible for bacteria, Earth's most ancient life form.
Scientists said on Thursday the bacterium, called Thiomargarita magnifica, is noteworthy not merely for its size - colossal for a single-celled organism at up to about eight-tenths of an inch (2 cm) long - but also because its internal architecture is unlike other bacteria.
The DNA, an organism's blueprint, is not free-floating inside the cell like in most bacteria but contained within numerous small membrane-bound sacs. Membrane-bound structures in cells are called organelles.
"It is thousands of times larger than regular-sized bacteria. Discovering this bacterium is like encountering a human being as tall as Mount Everest," said marine biologist Jean-Marie Volland of the U.S. Department of Energy's Joint Genome Institute and the Laboratory for Research in Complex Systems in California, a co-leader of the study published in the journal Science http://www.science.org/doi/10.1126/science.adc9387.
The bacterium has been found in several locations in Guadeloupe, a French archipelago in the Caribbean. It was first spotted in the sulfur-rich seawater of a Guadeloupe swamp by Université des Antilles microbiologist and study co-leader Olivier Gros.
"In 2009, I found long white filaments attached to a sunken leaf of a mangrove tree. I found such filaments intriguing. I brought them back to the lab to analyze them," Gros said. "Big surprise for me to have so huge a bacterium living in the mangroves of Guadeloupe."
A normal bacterial species measures 1-5 micrometers long. This species averages 10,000 micrometers (four-tenths of an inch/1 cm) long, with some Thiomargarita magnifica twice that length.
"It is orders of magnitude bigger than what we thought was the maximum possible size for a single bacterium," Volland said. "They are about the same size and shape of an eyelash."
The largest-known bacterium until now had a maximum length around 750 micrometers.
Bacteria are single-celled organisms that reside nearly everywhere on the planet, vital to its ecosystems and most living things. Bacteria are thought to have been the first organisms to inhabit Earth and remain quite simple in structure billions of years later. The bodies of people are teeming wi...