Cell Biology of Organelles

Diatoms are phototrophic, unicellular, and eukaryotic organisms. They originate from secondary endosymbiosis, a specific evolutionary process. Accordingly, their cells and organelles have a typical organisation, as revealed by ultrastructural investigations. Diatoms possess specific compartments and structures, including a silica shell surrounding the diatom cell, the so-called silica deposition vesicles (SDVs), as well as complex plastids that are surrounded by four membranes. Here we provide an overview of diatom organelles, and recapitulate recent information obtained from 3D imaging of whole diatom cells, focusing on the subcellular topology of the model diatom Phaeodactylum tricornutum. This chapter will not discuss issues of the cell wall and the SDVs, which are covered in Chaps. “Structure and Morphogenesis of the Frustule” and “Biomolecules Involved in Frustule Biogenesis and Function”.