White-opaque switching in a natural <i>MTL</i>a/α strain of <i>C. albicans</i>.

<p>(A) Colony images of SZ306, a clinical <i>MTL</i><b>a</b>/α isolate, grown on Lee's GlcNAc medium in 5% CO₂ (left) for 7 days and on YPD medium in air for 10 days at 25°C. The dye phloxine B, which exclusively stains opaque colonies red, was added to the media. White arrows indicated the opaque colonies on Lee's GlcNAc medium. Pink colonies were opaque on YPD medium. (B) Cellular morphology of white and opaque cells of SZ306 (<b>a</b>/α). Cells were collected from YPD cultures and imaged. Scale bar, 5 µm. (C) SEM images of white and opaque cells of SZ306 (<b>a</b>/α). Cells were collected from YPD cultures and imaged. Scale bar, 5 µm. (D) Northern blot of white and opaque enriched genes in three independent natural <b>a</b>/α isolates and the reference strain WO-1. (E) PCR of <i>MTL</i><b>a</b>1 and α2 genes in the white-opaque switchable SZ306 (<b>a</b>/α). Primers used for PCR are listed in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001525#pbio.1001525.s010" target="_blank">Table S6</a>. The previously characterized strains (SC5314, WUM5A, and GH1013) served as <i>MTL</i><b>a</b>/α, α/α, and <b>a</b>/<b>a</b> controls, respectively. Three independent opaque colonies of SZ306 were tested.