FIGURE 3.

Microcoleus B353 grown under various light conditions on S-solid medium. A, filament bundles (<200 μm in length) consisting of several filaments aligned longitudinally move in rows both forward and backward directions. Bundle width and length increase during exponential growth. Scale bar = 100 μm. B, outermost filaments of bundles grow in random directions, whereas filaments inside bundles grow in parallel. As such, three-dimensional growth of filaments resulted in generation of several layers of bundle strips, forming a mat-like structure. Upper layers of mats form counterclockwise bundles with various thickness viewed during stationary growth phase. Scale bar = 1 cm. C, filaments incubated in the dark condition form few bundles, some of which become yellow in color. Scale bar = 100 μm. D, filaments of Microcoleus B353 move toward unidirectional white (W) light source and sometime penetrate through 0.5% S-solid media. Scale bar = 1 cm.