|Description:||The two test tubes depicted here were being used to carry out a nutritional test involving the identification of various dermatophytic fungal organisms. In this particular instance, the dermatophyte, Trychophyton megninii, was being examined, focusing on its histidine requirements.|
A T. megninii inoculum had been added to the unknown growth medium within each of these two test tubes. On the left, the agar medium contained no histidine, while on the right, to the same agar medium, the ammino acid histidine had been added. Note that with the addition of the nutrient histidine, the T. megninii organsms were thriving, and had created a single, cottony-textured fungal colony atop the medium.