A GTP-BINDING PROTEIN (ERA) HAS AN ESSENTIAL ROLE IN GROWTH-RATE AND CELL-CYCLE CONTROL IN ESCHERICHIA-COLI

Era is a membrane-associated GTP-binding protein which is essential for cell growth in Escherichia coli. In order to examine the physiological role of Era, strains in which Era was expressed at 40-degrees-C but completely repressed at 27-degrees-C were constructed. The growth of these strains was inhibited at the nonpermissive temperature, and cells became elongated. Under such conditions, no constrictions or septum formation could be detected by phase-contrast microscopy, and DNA segregation was apparently normal as revealed by fluorescence staining. These data demonstrate that Era has an essential function in cell growth rate control in liquid media and that depletion of Era blocks cell division either directly or indirectly. Thus, the role of GTP-binding proteins as important regulators of cell growth and division may be ubiquitous in nature.