Transmission electron micrographs (TEM) showing the surface ultrastructure of Calkinsia aureus. A. Tangential TEM section showing conduit-like perforations (arrowheads) embedded within the extracellular matrix (Ex), an array of microtubules, and mitochondrion-derived organelles (MtD). (bar = 1 μm). B. Mitochondrion-derived organelles (MtD) with two membranes (arrow) above the ER. The convoluted appearance of the cell plasma membrane (double arrowhead) and a longitudinal view of a microtubule (arrowhead) are also shown. A glycocalyx (GL) covers the surface of the extracellular matrix (Ex). C. Transverse TEM showing the epibiotic bacteria (B), the glycocalyx (GL), a conduit-like perforation (arrow) through the extracellular matrix (Ex) and the underlying sheet of microtubules (B, C, bars = 500 nm). D. High magnification view showing the epibiotic bacteria (B), the glycocalyx (GL), the extracellular matrix (Ex), the cell plasma membrane (double arrowhead), and the double-layered structure (arrowhead; derived from the dorsal lamina) beneath a sheet of inter-connected microtubules (bar = 200 nm). E. Mitochondrion-derived organelles (MtD) (bar = 500 nm). Inset: High magnification TEM showing the two membranes that surround the mitochondrion-derived organelles (width of inset = 400 nm).