The cells divided from Pifithrin-�� purchase anterior to posterior along the longitudinal axis (Figure 1D). Cyst formation or sexual reproduction was not observed. Cells of B. bacati were found all year round, although the abundance of

this species decreased significantly during the winter months. Figure 1 Light micrographs (LM) of living cells of Bihospites bacati n. gen. et sp. A. LM showing distinctive black bodies (white arrow) and the prominent nucleus (N) positioned near the anterior end of the cell. B. LM showing the extended dorsal flagellum (Df) that is inserted subapically. C. LM showing the dorsal flagellum (Df) and a contracted cell with raised helically arranged striations (S) on the surface. D. LM showing a cell dividing along the anteroposterior axis. E. LM showing rows of spherical-shaped bacterial episymbionts on the cell surface (arrowheads). F. LM showing the nucleus with a distinct thickening (arrow), providing evidence for the shape and orientation of the C-shaped rod apparatus. Cell Surface The cell surface of B. bacati was covered with two different morphotypes of episymbiotic bacteria: (1) more abundant rod shaped episymbionts and (2) spherical-shaped episymbionts (Figure 1E, 2). The rod-shaped episymbionts were 3-5 μm long and were arranged in bands, about 7 μm wide, along the longitudinal axis of the host cell (Figure 2A). These bands

peeled off when the host Eltanexor in vitro cell deteriorated. The longitudinal bands of rod-shaped episymbionts were separated and defined by single or double rows of spherical episymbionts, each about 0.6 μm in diameter (Figure 2A-E). These longitudinal rows usually extended nearly the entire length of the host cell and were helically organized when the host cells were in a contracted state (Figure 1C, 2A). The rod-shaped episymbionts were connected to the plasma Ergoloid membrane of the host by a glycocalyx-like material (Figure 3A-E). The spherical-shaped episymbionts were attached to the host within a corresponding concavity in the host plasma membrane (Figure 3E). The spherical-shaped

episymbionts were highly organized and possessed an extrusive apparatus consisting of an apical “”operculum”" and a tightly coiled internal thread around a densely stained core (Figure 3D-F). The coiled thread was capable of rapid discharge find protocol through an apical pore when disturbed during chemical fixation for electron microscopy (Figure 2A, D-E); the densely stained core was discharged first, and the coiled thread followed (Figure 3F). Figure 2 Scanning electron micrographs (SEM) of Bihospites bacati n. gen. et sp. A. Ventral view of B. bacati showing a cell covered with rod-shaped and spherical-shaped episymbiotic bacteria (white arrowheads and black arrowheads, respectively), the vestibulum (vt), dorsal flagellum (Df) and ventral flagellum (Vf) (bar = 15 μm). B.