Structural specificity of sugars that inhibit gliding motility of Cytophaga johnsonae

It is a common observation that gliding bacteria form raised, smooth-edged colonies on nutrient-rich media, and typical thin, spreading, uneven-edged colonies on nutrient-poor media. An earlier study of the effect of different sugars on colony spreading by Cytophaga johnsonae was expanded to include the effects of several sugars and other organic compounds on the motility of groups of cells (rafts), and latex bead movement on cells' surfaces. When the structures of those sugars that did, or did not, affect raft formation and colony spreading were compared, it was noted that those sugars that inhibited these two manifestations of gliding motility all possessed a common sub-structure, that found in the portion of glucopyranose comprising carbons 3, 4, 5, and 6. If these structural features were altered chemically or stereochemically, the resulting molecule had little to no effect on motility. The differential effects of some compounds on raft formation, colony spreading, and bead movement are noted. A regulatory mechanism that would turn off motility in the presence of an inhibitory sugar is implicated, and the relevance of such a system to the life of the organism is discussed. We report, as well, additional compounds that will serve as carbon and energy sources for C. johnsonae.