WASHINGTON
Scientists have discovered the world’s largest bacterium in the Caribbean mangrove swamp.
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 “the largest bacterium known to date,” said Jean-Marie Woland, a marine biologist at the Lawrence Berkeley National Laboratory and co-author of the document announcing the discovery. Thursday in the journal Science.
Olivier Gross, co-author and biologist at the University of the French West Indies and Guyana, found the first example of this bacterium – called Thiomargarita magnifica, or “beautiful sulfur pearl” – that clung to a drowned mangrove leaf in the 2009 Guadeloupe archipelago.
But he did not immediately learn that it is a bacterium because of its surprisingly large size – these bacteria reach an average length of a third of an inch (0.9 centimeters). Only later did genetic analysis reveal that the body is a single bacterial cell
“It’s an amazing discovery,” said Petra Levin, a microbiologist at the University of Washington in St. Louis who was not involved in the study. “It raises the question of how many of these giant bacteria are out there – and reminds us that we should never, ever underestimate bacteria.”
Gross also found a bacterium in the swamp attached to the shells of oysters, stones and glass bottles.
Scientists have not yet been able to grow it in laboratory cultures, but researchers say the cell has a structure unusual for bacteria. One key difference: it has a large central compartment, or vacuole, that allows certain cell functions to occur in this controlled environment rather than across the cell.
“Acquiring this large central vacuole definitely helps a cell get around physical limitations … as to how big a cell can be,” said Manuel Compass, a biologist at the National Center for Scientific Research in France who was not involved in the study.
The researchers said they weren’t sure why the bacterium was so large, but co-author Woland suggested it could be an adaptation to help it avoid being eaten by smaller organisms.
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