Figure 2. 4×4 tomogram montage of an entire Giardia ventral disc and some of its associated cytoskeletal structures such as flagella and the marginal plate.

A: Approximately 180 nm thick slice through a tomographic reconstruction obtained from a negatively stained, Giardia cytoskeleton preparation (see: Holberton and Ward, 1981). The most prominent features are the highly ordered array of microtubule-microribbon complexes of the ventral disc that start at the dense band MT nucleation zone or the inner disc edge, and end at the outer margin or the ventral overlap zone. Furthermore, four pairs of flagella originate from basal bodies arranged at the center of the spiral. One pair (anterior flagella) points towards the front of the cell, and then curves outwards. All other flagella leave the cell towards the posterior end. The ventral disc microtubules form a large right-handed spiral assembly with an overlap zone at the top right. Distinct regions of the ventral disc are marked with the corresponding color-coding of figure 1B and all figures that follow. B: 3-D reconstructions of Giardia lamblia from Schwartz et al. (2012) by a procedure called 3View (Denk & Horstmann, 2004). This SEM and microtomy 3-D reconstruction approach reveals the overall architecture of the Giardia cell with the ventral disc (pink) the nuclei (cyan), the median body (brown; Woessner & Dawson, 2012), and the four flagellar pairs in green (anterior), blue (caudal), yellow (ventral) and red (post-lateral; Dawson & House, 2010B).