U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska


Date of this Version


Document Type



Mycopathologia 152: 113–123, 2000.


© 2001 Kluwer Academic Publishers


Blastomyces dermatitidis, a pathogenic fungal organism, is able to exist in two differentmorphologies, a multicellular mycelium or a unicellular yeast, according to temperature, 25˚C and 37˚C respectively. The switching between morphologies must be accompanied by a cascade of signaling events in which expression of genes responsible for the change of morphology is increased or decreased. bys1, a gene from B. dermatitidis isolate #58, is expressed at high levels in the unicellular yeast, but gradually diminishes as the temperature is lowered and the organism converts to the mycelial phase where there is no transcription of bys1. We explored if bys1 homologs are found in other B. dermatitidis isolates and if the transcription of the homologs were regulated by temperature. bys1 was identified in all B. dermatitidis isolates tested and could be grouped into two classes by Southern blot, PCR, and DNA sequence. Although the bys1 transcripts of both classes were regulated by temperature, transcription rates varied between the three isolates tested.