Bacterial cell division: a moveable feast.

Abstract

Recent advances in fluorescence microscopy technologies have revolutionized our views on bacterial cell organization. A prolific area of this revolution in tiny cell visualization has been cell division. Most bacteria divide in their middle, implying that they are aware of at least one particular site of themselves, the midcell division site. This raises the fundamental question: How do bacterial cells identify midcell? It all started with the immunolocalization studies of the FtsZ division protein, which showed that FtsZ assembles at midcell in a ring-like structure (1). Since then, additional cell division proteins have been shown to localize to midcell (2). In a recent issue of the Proceedings , Raskin and de Boer (3) extend this concept of site-specific protein targeting by describing the unique dynamic properties of the localization of the MinD division inhibitor. This discovery adds a new dimension to our exploration of the unexpected complexity in the spatial organization of bacterial cells. One cannot talk about bacterial cell division without considering the FtsZ protein, which shares properties with cytoskeletal molecules. FtsZ, which binds GTP and has a GTPase activity (4–6), plays a central role in cytokinesis as a major component of a contractile ring (1). The assembly of the FtsZ ring at midcell occurs well before the constriction is initiated (1). In addition to ftsZ (7), many more genes are specifically involved in cell division (2, 8). The other cell division proteins are later recruited to the FtsZ ring to form the membrane-associated septal ring that mediates septation. The answer to the problem of midsite selection is still largely unknown, but important insights have come from studies on minicell-producing ( min ) mutants (9). These mutants often divide at the poles (¼ and ¾ sites on the cell), generating small, chromosomeless minicells. Here, we discuss the roles …