Morphological Differentiation in a Filamentous Bacterium

点击翻译按钮获取中文摘要

9727234 Losick The goal of this project is to elucidate the nature of the signals and the signaling pathways that govem the process of aerial mycelium formation in the filamentous bacterium Streptornyces coelicolor. The formation of the aerial mycelium depends on so-called bld (i.e., "bald") genes, mutants of which produce smooth, hairless colonies. A striking property of bld mutants is their capacity to regain the ability to form an aerial mycelium when grown near, but not in contact with, certain other bld mutants, a phenomenon known as extracellular complementation. Experiments will be carried out to purify extracellular factors that stimulate the formation of the aerial mycelium. One such factor is transported into cells by a peptide importer, and a gene required for its production will be cloned. In traditional searches for developmental mutants, many bld mutants were probably missed due to extracellular complementation by wildtype colonies under conditions of high colony density. Additional bld mutants will now be sought by carrying out screens at low colony density, and the mutated bld genes will be cloned and characterized. Finally, to facilitate the discovery of additional bld genes, a new procedure for generating insertional mutants will be developed. Aerial mycelium formation is one of the most fascinating and dramatic examples of morphological differentiation in the world of procaryotic organisms. Streptomyces coelicolor and other streptomycetes are filamentous bacteria that grow by the formation of a mold-like, branching network of multinucleoid hyphae. The aerial mycelium consists of hyphae that grow into the air away from the colony surface to form a luxuriant lawn of hair-like filaments that eventually metamorphose into chains of pigmented spores. The colony can be thought of as a kind of community in which the cells are in active communication with one another so as to coordinate the formation of the aerial mycelium. It is anticipated that this project will help elucidate the nature of the intercellular interactions that govern aerial mycelium formation. It is likely that the findings derived from this work will provide insights into signaling systems used by other kinds of bacteria as well as by cells of higher organisms.