Kaiser 9725527 Myxococcus exhibits multicellular gliding movements that are highly coordinated. Coordination spans the range of few to many thousands of cells. While growing, a dozen cells may associate and move as a cohort. In fruiting body development, many thousands of cells move coordinately. The aim of this project is to work out the cellular and molecular basis for movement coordination. Despite the apparent complexity of their movements, myxobacterial cells have the structural, chemical and genetic simplicity of Gram-negative bacteria. Previous work on Myxococcus had distinguished two motility patterns called "adventurous" and "social". This project will seek to identify genes that control social motility and to learn their biochemical functions. For this purpose, mutants defective in social motility will be analyzed. Earlier work had identified pili, long thin hairs that projected from one pole of each cell, as necessary for social motility. This project will investigate the biogenesis of pili and the way that pili support social motility. The finding of mutants that assemble normal pili, yet fail to show social motility shows that pili are necessary but not sufficient for social motility. Steps in transducing a pilus "signal" might be found in this way. Many social motility genes are clustered in one long contiguous continuous stretch of Myxococcus DNA. More motility genes will be sought in the neighborhood of this block. The structure and function of the new genes will be analyzed. Regulation of expression of the pilin gene will be studied. Pilin is the protein monomer of the pilus fiber. The motors responsible for gliding movement have not yet been uncovered in any of the gliding bacteria. The search for new genes and mutants will be structured in a way that should allow mutations which inactivate the gliding engines to be detected. Coordinated multicellular movements are particularly important in early developmental steps of multicellular organisms, but little is known about how they are organized or regulated. Myxobacteria offer a realistic way to begin to investigate this general problem.
