Complex Intracellular Structures in Prokaryotes -- Prokaryote Complex Intracellular Structures: Descriptions and Discoveries -- Proteasomes and Other Nanocompartmentalized Proteases of Archaea -- Assembly and Disassembly of Phycobilisomes -- Chlorosomes: Antenna Organelles in Photosynthetic Green Bacteria -- Gas Vesicles of Archaea and Bacteria -- Carboxysomes and Carboxysome-like Inclusions -- Magnetosomes in Magnetotactic Bacteria -- Structure, Function and Formation of Bacterial Intracytoplasmic Membranes -- Membrane-bounded Nucleoids and Pirellulosomes of Planctomycetes -- Anammoxosomes of Anaerobic Ammonium-oxidizing Planctomycetes -- The Enigmatic Cytoarchitecture of Epulopiscium spp. -- Additional Complex Intracellular Structures -- Cytoskeletal Elements in Prokaryotes -- Cryo-electron Tomography Reveals the Architecture of aBacterial Cytoskeleton -- Organization and Assembly of the Mycoplasma pneumoniae Attachment Organelle -- The Junctional Pore Complex: Molecular Motor of Microbial Motility -- Type III Secretion Systems: Bacterial Injection Devices for MicrobeHost Interactions -- Gas Vesicles in Actinomycetes: Not Simply aCase of Flotation in Water-Logged Soil -- Bacterial Endosymbionts in Prokaryotes.

Categorizing organisms as either prokaryotes or eukaryotes was introduced in 1937 and proposed again in 1957 (Beck 2000); however, it was some years later, prompted to a certain degree by a publication by Stanier and van Niel (1962), before the concept became more widely accepted. At this early stage in the late1950s,our complete understanding of the ultra structure of both cell types,but especially prokaryotes,was still initsinfancy and awaited the more common and extensive use of electron microscopy as well as a multitude of other techniques and instrumentation. Prokaryotes were generally viewed as primitive simple cells with little intracellular structure. The existence of some storagebodies had been demonstrated (see Vol. 1 of this series), but littleelse was known about the internal organization (1rst chapter, this volume). The absence of mitochondria orchloroplasts appeared certain, but thes tate of the nucleic acid within the prokaryotic cell and the presence/absence of mitosis were still somewhat controversial subjects. That our concept of a prokaryote has undergone a remarkable transformation during the last 50 years should become readily apparent as one proceeds through thechapters in this volume. Furthermore, the reader should come to realize that the rigid classifcation of an organism as either aprokaryote o reukaryote is not always soclear-cut. We are quite sure that the next 50 years will provide a clearer understanding of the complex intracellular structures presently known as well as bring to light surprising new ones.