Internal structure of colonies formed by Rhizoid, Rough and Soft morphotypes of F. columnare B067. F. columnare cells were grown between a glass slide and Shieh agar and visualised under HR-SEM. Panel A: Rhizoid morphotype, Panel B: Rough morphotype and Panel C: Soft morphotype. A closer view of the cells can be seen underneath each panel marked with a matching lower case letter. Short filaments attaching cells to the surface and connecting cells are indicated by arrows in 3a and 3b. Scale bars in panels A to C 20 μm and in panels a to c 2 μm.