Biochemistry Questions Biochemistry Questions / Explain the motility mechanisms of cyanobacteria, including the role of pili and nozzles in different species. How do filamentous cyanobacteria move without flagella?

Type IV pili can be found on cyanobacteria. Localised at one pole of the cell, they drag the hormogonia along in a single direction. It is possible to move the pili to a different pole of the cell to allow movement in a different direction.

Slime nozzles are frequently seen in filamentous cyanobacteria. Jet-like nozzles are used to secrete slime, propelling the cells in the desired direction. As filamentous cyanobacteria tend to not have pili, slime nozzles are more common.

Flagella are not seen on cyanobacteria, and so other methods for motility (like those above) must be used.

When a filamentous cyanobacteria is moving, it forms a V shape. This is due to the effect of drag on the extremities of the filament, causing them to move more slowly than the middle of the filament.

Synechocystis, which is not a filamentous cyanobacteria, is capable of ‘running’ and ‘tumbling’ to move in response to a stimulus. This uses retractable type IV pili, allowing response to light and other stimuli.