The Gram-negative gliding bacteria have the ability to move over solid surfaces, but not to swim through liquids. The mechanism by which they accomplish this has not been established. With support from a previous NSF grant entitled "Sulfonolipids and Their Functions," Drs. Leadbetter and Godchaux made the fortuitous discovery that sulfonolipid-deficient mutants of the Gram-positive gliding bacterium, Cytophaga johnsonae, are unable to carry out normal gliding motility, and also lack a specific type of non-LPS outer membrane-associated polysaccharide. These mutants phenotypically revert with respect to all three traits (sulfonolipid content, polysaccharide content, and gliding motility) when provided with exogenous L-cysteate, the metabolic precursor of the sulfonolipid "head group." Other nongliding mutants, which are not sulfonolipid-defective, are deficient in this surface polysaccharide, which implicates the polysaccharide in gliding motility, and the sulfonolipids as necessary for the biosynthesis of this polysaccharide. Experiments are planned to biochemically characterize the outer membrane polysaccharides, identify the specific polysaccharides involved in motility, and begin biochemical characterization of the peptidoglycan of the bacterial cell wall. These studies may well result in the unambiguous determination of the biochemical mechanism of gliding motility in Cytophaga.
