Surface structures and vesicles observed in F. columnare B067 cultured in liquid and on agar. Panels A to C represent the planktonic cells, and panels D to F show cells grown on agar. Panel A: A typical view of the planktonic cells of the Rhizoid morphotype. Vesicles and rope-like structures attaching vesicles to the cells (arrows) were abundant. Panel B: A closer view of the rope-like structure connecting a vesicle (arrow) and a cell from the Rough morphotype. Panel C: Typical clusters of cells with vesicles and long filaments in Rough morphotype. Panel D: An example of the short filaments on the cells of the Rhizoid morphotype. Panels E and F: cells and vesicles in a colony of the Rough morphotype. The scale bar in Panel A was 1 μm, in B, 500 nm, in C, 4 μm, in D, 1 μm, and in Panels E and F, 2 μm.