The world's largest known bacterium was found in a swamp in Guadeloupe.

Thiomargarita magnifica is 50 times larger than all other giantbacteria and the first one to be seen with the naked eye. Thin strands of white were found on mangrove leaves.

According to models of cell metabolism, the bacterium should not grow this large. Scientists used to suggest an upper limit about 100 times smaller than the new species.

Jean-Marie Volland is a scientist at Lawrence Berkeley National Laboratory who co-authored the study.

Thiomargarita magnifica

Thiomargarita magnifica has been found to contain three times as many genes as most other bacteria. Photograph: Vol­lard et al.

A marine biology professor at the Université des Antilles in Guadeloupe discovered the organisms while looking for symbioticbacteria.

Gros thought they were strange when he saw them. The lab made a determination that the strands were single cells with the help of microscopes. A strange internal structure was also discovered. The DNA can be found inside the cell in mostbacteria. The cells of Thiomargarita magnifica seem to keep their DNA more organized. Volland said it's very unexpected for a bacterium.

Hundreds of thousands of genome copies spread throughout each cell and the bacterium has three times the number of genes as mostbacteria.

The scientists don't know how thebacteria evolved to be so large. It's possible that it adapted to avoid being eaten by animals. Volland said that if you grow hundreds or thousands of times bigger than your predator you can't be eaten.

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Being able to move around and colonise new niches would have been lost if it had become big. The way thebacteria interact with their environment has changed as a result of leaving the tiny world.

The researchers went back to the original site recently and found that thebacteria have not yet been found in other places. The discovery suggests that large and more complexbacteria may be hiding in plain sight.