Spores of E. cuniculi from urine stained with Ryan's modified trichrome (Trichrome blue) courtesy of the Mayo Clinic, Rochester, MN

This genome was sequenced by the Genoscope.

Encephalitozoon cuniculi infects various mammals, including humans, and can cause digestive and nervous clinical syndromes in HIV-infected or cyclosporine-treated people. Its reproduction proceeds as a sequence of two major stages: merogony, involving the multiplication of large, wall-lacking cells (meronts); and sporogony, leading to small, thick-walled spores. The sporal invasive apparatus is characterized by a long polar tube that can be quickly extruded then used for transferring the sporoplasm into the target cell. Consisting of 11 linear chromosomes ranging from 217 to 315 kb, the E. cuniculi genome is remarkably reduced (~2.9 Mb). The nucleotide sequence of the smallest chromosome has been recently reported. The full sequencing of this minimal genome among eukaryotes was expected to provide insight into the metabolism and general biology of microsporidia and to help in the understanding of the evolutionary history of amitochondriate eukaryotes currently considered ‘curious fungi'.