| Temporally and spatially regulated gene expression is a key feature in the development of organisms. The spore-forming bacterium Bacillus subtilis provides a simple and accessible model system for studying the role of cell-specific and temporally controlled gene expression in development. Under nutrient-limiting conditions, B. subtilis cells initiate the process of spore formation, which is directed by a cascade of sigma (sigma) factors whose activity is confined to specific compartments at defined times. The final sigma factor in the regulatory cascade is sigmaK, which is active specifically in the mother cell compartment of the sporangium at late stages of sporulation. In this work, I analyze the role of sigma K-controlled gene expression in the final morphogenetic events of sporulation and the reverse process of germination whereby a spore reverts to the vegetative state.;When sigmaK is mutant, sporulation is highly aberrant, resulting in the formation of small, malformed spores that cannot survive environmental insults and that lack the normal protective layers surrounding the spore. Therefore, one or more genes under the control of sigma K must be required for the morphogenetic events of late sporulation that result in a normal, healthy spore. The regulon controlled by sigma K is largely known, but the function of most of its members remains unclear. Here, I attempt to find a gene or genes through which sigma K acts to control morphogenetic events by systematic inactivation of genes in the regulon.;During the course of this work, I discovered and characterized an additional member of the sigmaK regulon, gerT, which plays a role in germination. I show that gerT is induced under the control of sigmaK and that its transcription is subsequently repressed by GerE. I also show that GerT is a component of the protemaceous coat that surrounds the spore and that it localizes to the coat in a dynamic, multi-step process. |
