There are some giant bacteria out there; they’re not common, but they do exist. Two species have been studied in detail. Epulopiscium is known only from the anaerobic hind gut of surgeonfish. It is a battleship of a cell – long and streamlined, about half a millimetre in length, just visible to the naked eye. That’s substantially larger than most eukaryotes, including paramecium (Figure 23). Why Epulopiscium is so big is unknown. Thiomargarita is even larger. These cells are spheres, nearly a millimetre in diameter and composed mostly of a huge vacuole.
