World’s biggest bacteria discovered in Caribbean mangrove swamp

Gigantic bacteria 50 times larger than any bacterial species previously known to science have been discovered in a Caribbean mangrove swamp, a find that will stimulate new scientific ideas about the size and structure of living cells.

The filaments, which look like fine vermicelli and have individual cells growing up to 1cm long, have been called Thiomargarita magnifica. The discovery was led by researchers from Lawrence Berkeley National Laboratory in California and Université des Antilles in Guadeloupe.

T magnifica grows far beyond the maximum size for bacteria predicted by current theory, said Jean-Marie Volland, lead author of a paper describing the new bacterium in the journal Science.

“It’s 5,000 times bigger than most bacteria,” Volland said. “To put it into context, it would be like a human encountering another human as tall as Mount Everest. . . This is the first opportunity we have to manipulate individual bacteria with tweezers. ”

All T magnifica specimens have so far been free of infection by smaller microbes. Genetic analysis suggests the species makes a range of antimicrobial compounds, which might be a useful source of antibiotics in the future.

Bacteria are by far the most numerous and diverse form of life on Earth. The total number of bacterial species is unknown, with the vast majority still to be described scientifically. Almost all are visible only through microscopes.

Olivier Gros, a marine biology professor in Guadeloupe, originally spotted T magnifica as white threads growing from submerged leaves in a sulfurous mangrove swamp. Genetic analysis in his laboratory revealed their identity as a giant new species within the known bacterial genus Thiomargarita.

The T magnifica bacteria seen next to a one dime coin. Almost all other bacterial species are visible only through microscopes © Tomas Tyml

“I did not think they were bacteria because they were so big,” said Silvina Gonzalez-Rizzo, a molecular biologist at the Université des Antilles.

T magnifica uses sulphides in the water as its energy source. With that metabolism, the bacterium could not infect humans or other animals.

The size of conventional bacteria is limited by the need for all the chemical compounds necessary for life to travel efficiently and speedily within their cells. T magnifica has overcome that limitation by evolving an internal structure that duplicates many biochemical functions within a single cellular filament.

The researchers are still in the early stages of investigating T magnifica. Working out how to cultivate the bacteria in the lab would be an important step forward. So would the discovery of other giant bacteria growing in different conditions. “The discovery of T magnifica suggests that large and more complex bacteria may be hiding in plain sight, ”their scientific paper said.

Petra Levin, a microbiology professor at Washington University in St Louis, who was not involved in the research, called the astonishing discovery. “Bacteria are endlessly adaptable and always surprising – and should never be underestimated,” she said.

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