Flavobacterium johnsoniae gldN and gldO Are Partially Redundant Genes Required for Gliding Motility and Surface Localization of SprB

Cells of the gliding bacteriumFlavobacterium johnsoniae move rapidly over surfaces. Mutations ingldN cause a partial defect in gliding. A novel bacteriophage selection strategy was used to aid construction of a strain with a deletion spanninggldN and the closely related genegldO in an otherwise wild-typeF. johnsoniae UW101 background. Bacteriophage transduction was used to move agldN mutation intoF. johnsoniae UW101 to allow phenotypic comparison with thegldNO deletion mutant. Cells of thegldN mutant formed nonspreading colonies on agar but retained some ability to glide in wet mounts. In contrast, cells of thegldNO deletion mutant were completely nonmotile, indicating that cells require GldN, or the GldN-like protein GldO, to glide. Recent results suggest thatPorphyromonas gingivalis PorN, which is similar in sequence to GldN, has a role in protein secretion across the outer membrane. Cells of theF. johnsoniae gldNO deletion mutant were defective in localization of the motility protein SprB to the cell surface, suggesting that GldN may be involved in secretion of components of the motility machinery. Cells of thegldNO deletion mutant were also deficient in chitin utilization and were resistant to infection by bacteriophages, phenotypes that may also be related to defects in protein secretion.