FIG. 3.

(A) Swollen conidium inside an AM phagosome after a 24-h in vivo infection in an immunocompetent mouse. In a swollen conidium, the ultrastructure of the conidium organelles is well preserved (whereas fixation and inclusion of a resting conidium is always damaging; see Fig. 1 for comparison). Bar, 350 nm. (B) The cell wall of a swollen conidium has a double electron-lucent layer under the electron-dense outer melanin layer that is in direct contact with the phagolysosome membrane. Bar, 450 nm. (C) Fluorescence view of FITC conidia internalized by AM after 6 h of incubation. Note that the intracellular swollen conidia (long arrows) do not germinate, whereas the extracellular nonphagocytosed conidia produce a germ tube (short arrows). Bar, 12 μm.