Members of this protein family are exclusive to the Bacteroidetes phylum (previously Cytophaga-Flavobacteria-Bacteroides). GldI is a FKBP-type peptidyl-prolyl cis-trans isomerase (pfam00254) linked to a type of rapid surface gliding motility found in certain Bacteroidetes, such as Flavobacterium johnsoniae and Cytophaga hutchinsonii. Knockout of this gene abolishes the gliding phenotype. Gliding motility appears closely linked to chitin utilization in the model species Flavobacterium johnsoniae. This family is only found in Bacteroidetes containing the suite of genes proposed to confer the gliding motility phenotype.