The effects of acetate and selected inhibitors on the phenotypic and metabolic traits of {\it Cytophaga johnsonae\/}

Date of Completion

January 1997


Biology, Microbiology




Cytophaga johnsonae belongs to a group of microorganisms known as the gliding bacteria. Characteristically, cells of these bacteria are able to translocate across solid surfaces but are unable to swim through liquids. Their motility is unusual in that it does not arise from detectable organelles, such as flagella, and the mechanism(s) for this motility is unknown. Since these species must make contact with solid surfaces to move, their cell envelope must play an indispensable role in translocation. The membrane of C. johnsonae contains high levels of branched-chain fatty acids, which is unusual for Gram-negative organisms. To ascertain the role that these lipids play in gliding motility, biochemical features of the cell envelope were studied by growing cells with acetate in an attempt to alter their lipid composition. Although cells grown with acetate did not demonstrate any significant differences in the cellular fatty acids, sulfonolipid synthesis did show a proportionate decrease in the presence of acetate.^ Polystyrene latex bead movement on the cell surface is considered by some to be a manifestation of the gliding machinery; however, this relationship has been questioned by others due to contradictory observations. Growth in acetate stopped the movement of beads on the cell surface, while gliding motility was unaffected. The results of this study confirm that bead movement on the cell surface is not a prerequisite for or equivalent to the phenomenon of gliding motility.^ Since acetate is a weak acid, it may act as an uncoupler of oxidative phosphorylation, and thereby decrease the energy supply of the cell. The protonmotive force has been considered to be the source of energy for gliding motility (and presumably, bead movement), and if the electrochemical gradient of the membrane were diminished, the ability of cells to glide could be affected. Intracellular ATP, respiratory activity, and protonmotive force were assessed in cells grown with acetate, as well as select inhibitors of energy-related functions. It was found that ATP and/or O$\sb2$ consumption of the cell could be dramatically decreased without appreciably affecting the protonmotive force. In addition, gliding motility does not depend upon the energy derived from ATP, whereas, bead movement on the cell surface may be influenced by ATP levels. ^