Positive control of cell division: FtsZ is recruited by SsgB during sporulation ofStreptomyces

Abstract

In bacteria that divide by binary fission, cell division starts with the polymerization of the tubulin homolog FtsZ at mid-cell to form a cell division scaffold (the Z ring), followed by recruitment of the other divisome components. The current view of bacterial cell division control starts from the principle of negative checkpoints that prevent incorrect Z-ring positioning. Here we provide evidence of positive control of cell division during sporulation of Streptomyces, via the direct recruitment of FtsZ by the membrane-associated divisome component SsgB. In vitro studies demonstrated that SsgB promotes the polymerization of FtsZ. The interactions are shown in vivo by time-lapse imaging and Fö rster resonance energy transfer and fluorescence lifetime imaging microscopy (FRET-FLIM), and are corroborated independently via two-hybrid studies. As determined by fluorescence recovery after photobleaching (FRAP), the turnover of FtsZ protofilaments increased strongly at the time of Z-ring formation. The surprising positive control of Z-ring formation by SsgB implies the evolution of an entirely new way of Z-ring control, which may be explained by the absence of a mid-cell reference point in the long multinucleoid hyphae. In turn, the localization of SsgB is mediated through the orthologous SsgA, and premature expression of the latter is sufficient to directly activate multiple Z-ring formation and hyperdivision at early stages of the Streptomyces cell cycle.

Taxonomy, Physiology, and Natural Products of Actinobacteria

“…SsgA activates sporulation-specific cell division (312,313), and both ssgA and ssgB are required for sporulation (275,314,315). The symmetrical spacing of the many Z-rings is achieved by SsgB, which directly recruits FtsZ and also stimulates its polymerization (316). SsgB localizes to future division sites prior to and independent of FtsZ (316).…”

Coiled-coil protein Scy is a key component of a multiprotein assembly controlling polarized growth inStreptomyces

“…Moreover, S. coelicolor has no obvi- ous MinC or MinE homologs. Recently, FtsZ positioning in S. coelicolor was shown to be under positive control by an FtsZ partner protein, SsgB, which, in turn, depends on SsgA (39). Interestingly, SsgA localizes at the hyphal tips in a dynamic fashion (40); therefore, it could, in principle, be part of the TIPOC (Fig.…”

Fluorescence Time-lapse Imaging of the Complete <em>S. venezuelae</em> Life Cycle Using a Microfluidic Device

“…Live-cell imaging of Streptomyces development has been challenging because of the complexity of the life cycle and the physiological characteristics of the organism. Previous studies on vegetative growth and the initial stages of sporulation septation have employed oxygen-permeable imaging chambers, or the agarose-supported growth of Streptomyces coelicolor on a microscope stage [11][12][13][14][15] . These methods, however, are limited by a number of factors.…”