FIG. 3.

Transmission electron micrographs of mycelial samples, collected after 3 to 4 days of coculture of P. parasitica (Ph) and P. oligandrum (Po), in the region where the two fungi are interacting. Cellulosic beta-1,4-glucans are labeled with the exoglucanase-gold complex. (a and b) Hyphae of P. oligandrum establish tight binding with the host cells (arrows). Adhesion of P. oligandrum hyphae to the host cells is accompanied by little wall displacement (panel a, arrow). Wall thickening occurs at sites of potential antagonist penetration (panel a, double arrows). CW, cell wall. Bars, 0.75 μm. (c and d) Firm binding of P. oligandrum to its host is associated with local cell wall degradation (arrows). (c) Bar, 1.5 μm; (d) bar, 0.75 μm.