Flavobacterium johnsoniae GldH Is a Lipoprotein That Is Required for Gliding Motility and Chitin Utilization

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Abstract
Cells of Flavobacterium johnsoniae move rapidly over surfaces by gliding motility. The mechanism of this form of motility is not known. Six genes ( gldA , gldB , gldD , gldF , gldG , and ftsX ) that are required for gliding have been described. Tn 4351 mutagenesis was used to identify another gene, gldH , which is required for cell movement. GldH mutants formed nonspreading colonies, and individual cells lacked the cell movements and ability to propel latex spheres along their surfaces that are characteristic of wild-type cells. gldH mutants also failed to digest chitin and were resistant to bacteriophages that infect wild-type cells. Introduction of pMM293, which carries wild-type gldH , restored to the gldH mutants colony spreading, cell motility, the ability to move latex spheres, phage sensitivity, and the ability to digest chitin. gldH encodes a predicted 141-amino-acid protein that localized to the membrane fraction. Labeling studies with [ 3 H]palmitate demonstrated that GldH is a lipoprotein. GldB and GldD, which were previously described, also appear to be lipoproteins. GldH does not exhibit significant amino acid similarity to proteins of known function in the databases. Putative homologs of gldH of unknown function are found in motile ( Cytophaga hutchinsonii ) and apparently nonmotile ( Bacteroides thetaiotaomicron , Bacteroides fragilis , Tannerella forsythensis , Porphyromonas gingivalis , and Prevotella intermedia ) members of the Cytophaga - Flavobacterium - Bacteroides group.