Peptones and mycological reproducibility

The pH reactions, ultraviolet spectra and phosphorus content of solutions of a variety of commercially available peptones all indicated, predictably, considerable differences in the chemical composition of the peptones. The effects of these differences on the outcome of experiments with Candida albicans grown in different peptone media was investigated. The fungus produced germ tubes equally effectively on all such media provided that the inoculum was kept to 10(6) blastospores/ml or less. However, expression of inducible enzyme activities in C. albicans varied extensively from peptone to peptone; there was, for example, an inverse relationship between the inorganic phosphorus content of peptones and the amount of acid phosphomonoesterase detectable in intact blastospores. The results indicated that use of different peptones in "Sabouraud's" media by different laboratories may account for some, but not all, published instances of irreproducibility of experiments with C. albicans.