The ingested

material is present in the middle and posterior regions of the cell. B. Surface striations (arrowhead) and a longitudinal rod-like structure (double arrowhead) indicative of a feeding apparatus. C. AF and PF emerging from the anterior opening. The arrowhead shows striation on the surface of the cell. D. Bacteria (arrowheads) that have disassociated Metabolism inhibitor with C. aureus. E. A cell undergoing division showing a longitudinal cleavage furrow starts from the anterior end. The ingested material is present in the middle and posterior regions of the cell. F. Clear cytoplasm extruded from posterior of the cell. G. Bright orange extracellular matrix. H. Bundle of extrusomes (double arrowhead) that have been discharged from extrusomal pocket through the anterior opening. (bars = 10 μm, A-C at same scale). Figure 2 Scanning electron micrographs (SEM) of Calkinsia aureus. A. The ventral side buy Galunisertib of C. aureus showing the anterior opening, a longitudinal groove and epibiotic bacteria. B. The dorsal side of the C. aureus showing the epibiotic bacteria. (A, B bars = 10 μm). C. High magnification SEM of the

anterior vestibular opening showing the absence of epibiotic bacteria on the extracellular matrix (arrow). (bar = 3 μm). Figure 3 Transmission electron micrographs (TEM) showing the general morphology of Calkinsia aureus. A. Sagittal TEM showing the nucleus (N) with condensed chromatin and a conspicuous nucleolus (Nu), a battery of extrusomes (E), the vestibulum (V) located on the dorsal side of the cell, ingested material and epibiotic bacteria on the extracellular matrix. The extrusomal pocket (EP) branched from the vestibulum (V) (bar = 4 μm). B. Ingested material containing diatom frustules (arrow). (bar = 2 μm). IKBKE C. Cross section of the cell through the nucleus (N), the battery of extrusomes (E), the flagellar

pocket (FLP) and the feeding pocket (FdP). (bar = 2 μm). D. High magnification view through the vestibulum (V) that is opened on the ventral side of the cell. E. High magnification view through the anterior opening showing the termination of the extracellular matrix (double arrowhead) and fine somatonemes (S) or hair-like structures on the perforated matrix (arrows) that is not covered with epibiotic bacteria. The arrowhead indicates the supportive microtubular sheet that lines the inside of the cytostome and turns along the cell surface. (D, E, bars = 1 μm). F. Hairs (arrow) on the wall of the vestibulum (V). (bar = 1 μm). G. Cross section showing the battery of tubular extrusomes (E). (bar = 2 μm). Cell Surface and Extracellular Matrix The longitudinally arranged, epibiotic bacteria consisted of only one rod-shaped morphotype (3–5 μm long and 0.350 μm wide) that collectively formed a dense coat over the entire surface of the host cell (Figures 2, 3A, 3C). At least 128 epibiotic bacteria were observed in transverse sections through one cell of C. aureus (Figure 3C).