Epulopiscium Fishelsoni

Epulopiscium fishelsoni ("Fishelson's guest at a fish's banquet") is a Gram-positive bacterium that has a symbiotic relationship with the surgeonfish. It is most well known for its large size, ranging from 200-700 μm in length, and about 80 μm in diameter. Until the discovery of Thiomargarita namibiensis in 1999, it was the largest bacterium known.