World’s largest bacterium found in Caribbean swamps

Christina Larson | Associated Press

WASHINGTON. Scientists have discovered the world’s largest bacterium in Caribbean mangrove swamps.

Most bacteria are microscopic, but this one is so large that it can be seen with the naked eye.

The thin white thread, about the size of a human eyelash, is “by far the largest bacterium known to date,” said Jean-Marie Folland, a marine biologist at Lawrence Berkeley National Laboratory and co-author of the paper announcing the discovery. Thursday in Science.

Olivier Gros, a co-author and biologist at the University of the French West Indies and Guiana, discovered the first specimen of this bacterium, named Thiomargarita magnifica, or “magnificent sulfur pearl”, clinging to sunken mangrove leaves in the Guadeloupe archipelago in 2009.

But he did not immediately realize that it was a bacterium, due to its surprisingly large size, just over a third of an inch (0.9 centimeter) long. It was only later genetic analysis that the organism was a single bacterial cell.

“This is an amazing discovery,” said Petra Levine, a microbiologist at Washington University in St. Louis, who was not involved in the study. “This opens up the question of how many of these giant bacteria exist and reminds us that we should never underestimate bacteria.”

Gross also found the bacterium attached to oyster shells, rocks and glass bottles in the swamp.

Scientists have not yet been able to grow it in laboratory culture, but the researchers say the cell has an unusual structure for bacteria. One key difference: it has a large central compartment, or vacuole, that allows some of the cell’s functions to be performed in this controlled environment rather than the entire cell.