The dimorphism and infectivity of Histoplasma capsulatum

Summary By examining mycelial cultures at regular intervals during incubation at 37° C in cysteine-enriched media, it was possible to detect differences in the conversion properties of six isolates ofHistoplasma capsulatum. The organisms varied according to conversion ability, rate and degree of transformation following yeast initiation, and cysteine sensitivity. These findings were unrelated to infectivity of the mycelial phase for mice as determined by percentage recovery of isolates from the cultured organs of inoculated animals.