Fig. 1
Complete scanning of a Giardia trophozoite by focused ion beam scanning electron microscopy (FIB-SEM). A, D A whole G. lamblia trophozoite was scanned with an isotropic resolution of 5 nm showing the nucleus (N), the endoplasmic reticulum (ER), cytoskeletal features such as the ventral disc (VD), funis (F) and axonemes (Ax) and mitosomes (m). Peripheral vesicles (PV) are marked by arrowheads. Smaller, electron-dense vesicles (small vesicles (SV)) are also documented (asterisks). B Region of interest of A highlighting PVs of different morphology (arrowheads). C Mitosomes proximal to ER membrane. E Region of interest of D highlighting SVs (asterisks). F Full reconstruction of PVs with ilastik and rendering in Imaris showing at least two PV morphologies: spherical (green) and tubular (violet). Violin plot: 403 spherical and 64 tubular PVs were segmented out. Spherical PVs average a volume of 0.0009243 ± 0.0003322 μm3 with a 95% confidence interval between 9.022 × 10−4 and 9.464 × 10−4 μm3. Tubular PVs average a volume of 0.001067 ± 0.0003322 μm3 with a 95% confidence interval between 0.0009843 and 0.001150 μm3. G Tubular PV lengths are larger than their diameter (p-value < 0.0001) and also larger than spherical PVs (p-value < 0.0001) (values presented in log10 form). H Diameters of spherical PVs average 120.1 ± 9.507 μm (95% CI: [119.2; 121.0]). Tubular PV diameters average 43.01 ± 7.816 μm (95% CI: [41.06; 44.96]). Tubular PV lengths average 771.3 ± 266.2 μm (95% CI: [704.8; 837.8]). I Reconstruction of 269 SVs averages volume at 0.0002525 ± 9.280 × 10-5 μm3 with a 95% confidence interval between 0.0002414 and 0.0002637 μm3 (left violin plot). This equals an average diameter of 77.23 ± 9.666 nm with a 95% confidence interval between 76.07 and 78.40 nm. Spherical PV diameter averages 120.1 ± 9.507 nm with a 95% confidence interval between 119.2 and 121 nm (right violin plot). The difference in the diameter between SVs and spherical PVs is statistically significant (****p-value < 0.0001, t-Student significance test). Scale bars: A, D 2 μm; B, C and E 500 nm. ROI, region of interest