Scanning electron microscopy of wild type SIN colony on agar plate. Bacilli form filaments expanding on agar towards periphery, leaving wide empty spaces (a). Trunks fuse proceeding together, or separate. Details of the same picture show pioneer filaments proceeding independently (b), going in parallel (c), fusing and separating (d). High magnifications (25–30.000 X) of the SIN cells show no twisting of the structures of the external cell wall (e-f).