Mechanism of Flavobacterium johnsoniae Gliding Motility

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Gliding motility (the active movement of cells over surfaces without the aid offlagella) is a trait shared by diverse bacteria. Gliding motility was first observed nearly200 years ago, yet the mechanisms responsible for cell movement are still largelyunknown. Flavobacterium johnsoniae is a convenient model organism for studies ofbacterial gliding motility. Techniques to genetically manipulate F. johnsoniae haverecently been developed and used to characterize a number of genes that are requiredfor gliding (gld genes). The proteins encoded by these genes appear to localize to thecell envelope, where the motility apparatus is expected to reside. GldA, GldF, andGldG are thought to interact to form an ATP-binding cassette (ABC) transporter. Mostof the other Gld proteins do not exhibit significant similarity to proteins of knownfunction. The role of the Gld ABC transporter in gliding is not known and will beinvestigated. Wild-type and mutant cells are being biochemically characterized to identifythe cargo of the transporter and determine the role of the transporter in gliding.Additional genes required for gliding will also be identified by cosmid complementationand transposon mutagenesis. These genes will be cloned, sequenced, and analyzed todetermine possible functions for the individual components of the gliding machinery.Mutations will be created in individual gld genes and the effects on cell motility will beassessed. The genes will also be cloned into expression vectors to allowoverproduction of Gld proteins. These proteins will be used to raise antibodies, whichwill allow localization of the Gld proteins by cell fractionation and by immuno-electronmicroscopy. This may allow visualization of the motility machinery at high resolution forthe first time, and will be an important step toward determining the mechanism ofgliding. Bacteriophages that infect only motile cells will also be used as tools to aid inidentification of the outermost components of the motility machinery. These studieswill lead to a better understanding of the mechanism of Flavobacterium gliding motility. In addition to expanding our knowledge on this common but little understood means of bacterial locomotion, these studies could have more practical value since gliding bacteria related to F. johnsoniae are important as pathogens of plants, animals, and humans, as agents of biodegradation, and as producers of enzymes, antibiotics and other secondary metabolites.