Structure, function, and assembly of the terminal organelle of Mycoplasma pneumoniae

Mycoplasmas are cell wall-less bacteria at the low extreme in genome size i n the:known prokaryote world, and the minimal nature of their genomes is cl early reflected in their metabolic and regulatory austerity. Despite this a pparent simplicity, certain species such as Mycoplasma pneumoniae possess a complex terminal organelle that functions in cytadherence; gliding motilit y, and cell division. The attachment organelle is a membrane-bound extensio n of the cell and is characterized by an electron-dense core that is part o f the mycoplasma cytoskeleton, defined here for working purposes as the pro tein fraction that remains after extraction with the detergent Triton X-100 . This review focuses on the architecture and assembly of the terminal orga nelle of M. pneumoniae. Characterizing the downstream consequences of defec ts involving attachment organelle components has made it possible to begin to elucidate the probable sequence of certain events in the biogenesis of t his structure. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Microbiological Societies.