Flavobacterium gliding motility and the type IX secretion system.

Cells of Flavobacterium johnsoniae crawl rapidly over surfaces in a process called gliding motility. These cells do not have flagella or pili but instead rely on a novel motility machine composed of proteins that are unique to the phylum Bacteroidetes. The motility adhesins SprB and RemA are propelled along the cell surface by the still poorly-defined gliding motor. Interaction of these adhesins with a surface results in translocation of the cell. SprB and RemA are delivered to the cell surface by the type IX secretion system (T9SS). T9SSs are confined to but common in the phylum Bacteroidetes. Transmembrane components of the T9SS may perform roles in both secretion and gliding motility.