csgA Gene and Cell Interactions in Myxococcus xanthus

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Myxococcus xanthus development is regulated by the Csg intercellular communication system. The C signal appears to be the polypeptide product of the csgA gene. The preliminary results suggest four directions for future work. First, random mutagenesis of csgA followed by DNA sequencing of developmental mutants is expected to determine the important functional domains of the protein. Second, examination of the regulation of csgA in response to moderated levels of nutrients is expected to reveal how nutrient levels are assessed in this organism and used to regulate gene expression. This project will involve a) random mutagenesis and DNA sequencing of the regulatory region to identify nucleotides that play a critical role in regulation, b) cloning of genes encoding regulatory proteins using recognition site probes, c) characterization of the protein-DNA interactions with gel mobility shift assays and DNA foot printing, and d) quantitation of the expression levels in vivo using a reporter locus. Third, continued analysis of the csgA suppressor mutations is expected to reveal other steps in the signaling process. Several suppressor alleles have been cloned and these will be sequenced and studied by other functional assays. %%% The life cycle of the myxobacterium, Myxococcus xanthus, contains the basic elements found in the development of higher organisms including directed cell movement, multicellular morphogenesis, regulated gene expression and cellular differentiation. It can therefore serve as an experimentally accessible model for the study of these processes.