Studies of Bacterial Endospore Germination

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Abstract Bacterial endospores are the most persistent and resistant forms of life on earth, able to remain in dormancy for decades and to survive a range of potential killing treatments that no other organisms can approach. Amazingly, these dormant cells can sense a growth-supportive environment and return to vegetative growth within hours through the process of germination. Major spore-specific modifications to cell structure and cellular content drive dormancy and resistance to killing treatments, and the dormant spores possess mechanisms to rapidly reverse these modifications during germination. The long-term goal of this study is to fully understand the details of cellular modifications that determine spore properties, the mechanism by which the spore initiates germination, and the cascade of events that lead to a resumption of metabolism and growth Cytoplasmic proteins are highly stabilized in the dehydrated spore core, but most germination-active proteins are on the membrane outer surface, in a hydrated environment, and must be stabilized during long-term dormancy and potential physical assault by other mechanisms. The overriding hypothesis of the proposed work is that the majority of the germination sensing and regulating apparatus is found in very stable multiprotein complexes in or on the inner spore membrane, which serves as a uniquely stable platform due to its minimal membrane fluidity. The specific goals of the proposed work are to define the components of these protein complexes, to examine potentially unique modifications of the membrane structure, and to examine the degradation of spore membrane proteins and effects this has on progression of germination. The proposed work also includes screens for discovery of genes that play previously unknown roles in the germination process. Spores play important roles in the initiation of several human and animal diseases, and in contamination and degradation of food products. Spores are used as the highly stable vehicles for the delivery of desirable metabolic activities in many industrial and agricultural products, and have been developed as stable vehicles for vaccine delivery. In all of these cases, spore germination plays a key role in the success of the process: pathogenesis or delivery of an activity. A full understanding of germination can therefore drive methods to avoid or improve these processes. Blocking germination can prevent pathogenesis, while stimulating highly efficient germination renders the spores susceptible to much simpler decontamination methods. Stimulating higher germination efficiency or rate can improve the effectiveness of a spore-based product.