*2.6. Transmission Electron Microscopy*

Samples were fixed with 2.5% (*v*/*v*) glutaraldehyde in 0.1 M cacodylate buffer (pH 7.2) for 1 h at room temperature. After a wash in cacodylate buffer, cells were post-fixed using an osmium-thiocarbohydrazide-osmium (OTO) protocol as already described [39]. Samples were washed in water, dehydrated in an acetone series, and embedded in epoxy resin (EMBED 812 resins, EMS, Hatfield, PA, USA). Ultrathin sections were cut with a UC7 ultramicrotome (Leica, Wetzlar, Germany), stained with 5% (*w*/*v*) uranyl acetate and lead citrate, and observed in an HT7800 transmission electron microscope (Hitachi, Tokyo, Japan) operating at 100 kV.
