Proc. Natl Acad. Sci. USA 105, 6730–6734 (2008)

A gargantuan bacterium carries tens of thousands of copies of its genome, researchers have found.

One species of the cigar-shaped bacterium Epulopiscium lives in the intestines of the unicornfish Naso tonganus, and can grow to more than half a millimetre in length. Esther Angert of Cornell University in Ithaca, New York, and her colleagues have found that Epulopiscium cells also contain up to 250 picograms of DNA, compared with a human cell's 6 picograms, and have 50,000–120,000 copies of genes believed to occur only once in each genome.

Other bacteria contain multiple copies of their genomes, but so far none has been found to have nearly as many as Epulopiscium.