Electron micrograph of Candidatus Brocadia anammoxidans, showing membrane-bounded compartments : the outer paryphosomal compartment, the inner compartment with the DNA (dark triangle) and the ribosomes, and a third central compartment, the "anammoxosome," containing the hydrazine-oxidizing enzyme (HZO/HAO). (Kindly provided by John Fuerst, Dept. of Microbiology and Parasitology, University of Queensland, Brisbane, Australia.)