['Whereas most bacteria move by means of flagella, some prokaryotes move by gliding. In cyanobacteria, gliding motility is a slow uniform motion which is invariably accompanied by a continuous secretion of slime. On the basis of these characteristics, a model has been proposed in which the gliding motility of cyanobacteria depends on the steady secretion of slime using specific pores, as well as the interaction of the slime with the filament surface and the underlying substrate.', 'The structures of the pore apparatus of two different filamentous cyanobacteria have been characterized. In both species, pores are formed by a hitherto uncharacterized type of prokaryotic organelle that spans the entire multilayered cell wall and possesses structural properties expected for an organelle that is involved in the rapid secretion of extracellular carbohydrates. Light microscopic observations of the secretion process provided direct evidence that the pore complexes are the actual sites of slime secretion, that the secreted slime fibrils are elongated at about the same rate as the filament glides (up to 3 micrometer s-1), and that gliding movements are caused directly by the secretion of slime.'] Is the junctional pore complex , a prokaryotic secretion organelle , the molecular motor underlying gliding motility in cyanobacteria?