Gliding Motility in the Blue‐green Alga Oscillatoria Princeps1

SUMMARY Gliding is an active movement displayed by a microorganism in contact with a solid substrate where there is no evidence of a motility organelle or of a conformational change in the organism. Gliding may be accompanied by rotations, reversals, flectional activity, and mucilage sheath production, as well as linear translation. Previous explanations of the mechanism responsible did not consider all these aspects of behavior. The gliding behavior and ultrastructure of the blue‐green alga Oscillatoria princeps Vaucher were examined. O. princeps has a maximum observed gliding rate of 11.1 μm/sec. The trichomes can glide in either longitudinal direction following rapid and occasionally frequent reversals. Right‐handed trichome rotation was always observed, which means that any surface point on these trichomes traces a 60‐deg right‐handed helix. A mucilage sheath envelopes the moving trichomes. The rate of gliding was reduced by viscous substrates, extreme pH, lysozyme, DNP, and cyanide, while sustained darkness had no inhibitory effect. Ultrastructurally, the cell wall is composed of an L‐1 layer which is 10 nm thick and often ill‐defined. The L‐2 layer which is outside this is 200 nm thick and participates in septum formation. The L‐3 layer is outside the L‐2 and is continuous over the trichome surface. The L‐4 “membrane” lies outside the L‐3 layer. Grazing surface sections and freeze‐etch replicas show a parallel and tight array of 6–9 nm wide continuous fibrils in the cell wall on the surface of the distinctive L‐2 layer. Isolated wall fragments were tightly coiled inside out with the fibrils on the inside. The angle of orientation for the fibrils was to the right in a helix with a pitch of 60 deg. O. animalis , a blue‐green alga with a movement tracing a left‐handed helix, showed a similar array of fibrils oriented in a left‐handed helix with a pitch of 60 deg. It is proposed that gliding is produced by unidirectional waves of bending in the fibrils which, act against the sheath or substrate, tints displacing the trichome.