Variable colonial phenotypic expression and comparison to nuclei number in Blastomyces dermatitidis.

We examined colonial phenotypes of five isolates of Blastomyces dermatitidis at 33, 35 and 37 degrees C on four growth media. Three different colony types were identified: yeast, mycelial, and a mixed type consisting of both yeast and mycelia. Each isolate varied in its ability to grow on the different media and at different temperatures, and in the types of colonies it produced in the various temperature-media combinations. Quantification of the number of nuclei per yeast cell by fluorescent staining revealed no correlation between the number of nuclei per cell and the colonial phenotype. These results indicate that the colonial phenotype of B. dermatitidis varies with the isolate as well as with temperature and culture medium, but is not correlated with the number of nuclei per yeast. These findings could provide a start towards typing B. dermatitidis isolates.