FIG. 6.

Transmission electron micrographs of freeze-etched replicas of Oscillatoria sp. strain A2. (A) Corrugations in the outer membrane, caused by the fibrillar array, can be seen in a transverse view (arrowhead) and in a longitudinal view in the exoplasmic fracture face of the membrane (arrow). (B) Apparent undulations in the fibrillar array are evident. (C) Indentations in the outer membrane, caused by the fibrillar array, can be seen in the exoplasmic fracture face of the membrane, confirming that the fibrillar array itself is external to the cytoplasmic membrane and peptidoglycan. Bars, 400 nm (A) and 200 nm (B and C).