White-to-opaque switching in natural <i>MTL</i>a/α strains of <i>C. albicans</i> at 37°C.

<p>White cells of two <i>MTL</i><b>a</b>/α strains (CY110 and RVVC10) were plated onto Lee's glucose and Lee's GlcNAc medium plates and cultured in air or 5% CO₂ at 37°C for 3 to 4 days. At this temperature, white cell colonies containing filamentous swollen cells could be stained red. Cellular morphologies were examined to confirm the cellular phenotypes. *, the switching frequencies (% of average ± SD) of these samples represented the percentages of colonies containing opaque cells, including opaque, opaque-sectored, and white-opaque mixed colonies. Swit. Freq., switching frequency. Wh, white cells/colonies. Op, opaque cells/colonies. Scale bar, 10 µm. (A) White-to-opaque switching of CY110 at 37°C. (B) White-to-opaque switching of RVVC10 at 37°C. (C) Expression of GFP in the reporter strains of <i>WOR1/WOR1::WOR1p-GFP</i>, <i>WH11/WH11::WH11p-GFP</i>, and <i>EFG1/EFG1::EFG1p-GFP</i>. The parent strain of these strains was CY110 (<i>MTL</i><b>a</b>/α). Opaque-sectored colonies grown on Lee's GlcNAc medium plates (without phloxine B) were microscopically examined. BF, bright field.