Morphological analysis of the mp65Δ mutant. (A) The wild type (wt), mp65Δ mutant (hom) and revertant (rev) strains were grown in YEPD for 24 h at 28°C with or without Congo red (50 μg/ml) and then observed under a light microscope and SEM, as described in the Methods section. The magnification bar corresponds to 15 μm (Panels 1, 2, 4, 6, 7 and 9), 5 μm (Panel 3), and 60 μm (Panels 5 and 8). (B) Pictures show swelling and clumping of the mp65Δ mutant cells after treatment with Congo red. (C) Flocculation analysis. Following o.n. growth, the cultures were transferred to test tubes and left to stand for 10 min. As shown, the filamentous cells (h) of the mp65Δ mutant precipitated to the bottom of the tube (hom: Tube 2). The yeast cells (y) of the wild type (wt: Tube 1) and revertant strains (rev: Tube 3) remained in suspension.