What is the largest known bacterium by cell volume, discovered in a Caribbean mangrove in 2022?

Thiomargarita magnifica is the largest known bacterium by cell volume, reported from a Caribbean mangrove in 2022.

Researchers found thread-like cells that can reach about 2 centimetres long, making them visible to the unaided eye. The species name magnifica refers to its extraordinary size. Its discovery challenged the usual assumption that bacteria are microscopic specks that require magnification to see.

T. magnifica is remarkable not only for length but also for internal organization. Its genetic material and ribosomes are enclosed in membrane-bound structures called pepins, a feature that resembles compartmentalization associated with eukaryotic cells. The cells also contain energy-generating membranes distributed through their large bodies. These adaptations may help overcome the limits imposed by diffusion, which normally restrict bacterial cell size. The organism belongs to the sulfur-oxidizing genus Thiomargarita and was found attached to mangrove leaves and sediment in Guadeloupe. “Largest” here refers to known bacterial cell volume, not necessarily total length in every comparison.