Ultrastructure of Thraustochytrium Aureum, A Biflagellate Marine Phycomycete

SUMMARYElectron microscope studies of logarithmic phase cells of Thraustochytrium aureum showed that the cytoplasm consists of typical endoplasmic reticulum as well as ribosomal and membranous regions which are generally segregated from each other. Another uncommon feature is the presence, in some mitochondria, of concentric membranes which enclose crista-free regions. A feature of possible phylogenetic interest is the occurrence of a Golgi apparatus in this monocentric organism. The latter finding provides added evidence relating thraustochytriaceous forms to the biflagellate series of filamentous Phycomycetes, hitherto the only members of the class reported to possess this structure.