Mutations, Phenotypic Switching, and Colonization by Clinical a/α Strains of Candida albicans.

The transcription factor functions as a suppressor of white-to-opaque and white-to-gray switching in /α strains of In a collection of 27 clinical isolates, 4 of the 17 strains, 1 of the 2 strains, and all 8 of the / strains underwent white-to-opaque switching. The four strains, the one strain, and one of the eight / strains that underwent switching to opaque did not switch to gray and could not be complemented with a copy of Competition experiments in a mouse model for gastrointestinal (GI) colonization confirmed that / cells rapidly outcompete / cells, and in plating experiments, formed colonies containing both gray and opaque cells. Direct microscopic analysis of live cells in the feces, however, revealed that the great majority of cells were opaque, suggesting opaque, not gray, may be the dominant phenotype at the site of colonization. Close to half of a collection of 27 clinical /α isolates of underwent white-to-opaque switching. Complementation experiments revealed that while approximately half of the /α switchers were due to mutations, the remaining half were due to mutations in other genes. In addition, the results of competition experiments in a mouse GI tract colonization model support previous observations that / cells rapidly outcompete strains, but direct microscopic analysis reveals that the major colonizing cells were opaque, not gray.