diatoms, spheroid bodies, Rhopalodia gibba
The pennate diatom Rhopalodia gibba harbours unusual cell inclusions termed spheroid bodies. These originated from unicellular cyanobacteria and are obligate intracellular endosymbionts with the ability to fix molecular nitrogen. As indicated by the fossil record, this endosymbiosis might be relatively young, thus making R. gibba an interesting model to study early stages of organelle development at the genetic as well as at the physiological level. Here we describe a protocol for the cultivation of Rhopalodia gibba.