Genome sequencing of cyanobacterium endosymbiont of Epithemia turgida. cyanobacterium endosymbiont of Epithemia turgida isolate EtSB Lake Yunoko

Diatom species of family Rhopalodiaceae possess cyanobacteria-derived intracellular structures called "spheroid body" as well as plastids. Spheroid bodies are thought to be specialized for nitrogen-fixation and presumably lack their photosynthetic ability. This cyanobacteria-derived structure is considered to be highly integrated into the host diatom cell, but the fact that the spheroid body appears only among rhopalodiacean diatoms suggests that acquisition of the spheroid body was quite recent compared to plastids. Thus the spheroid body is considered to exhibit an intermediate stage of transition from an endosymbiotic cyanobacterium to an organelle. In this project we sequenced the complete genome of a spheroid body of a rhopalodiacean diatom species, Epithemia turgida, and tried to grasp a snapshot of genome evolution in the early stage of organellogenesis