Growth requirements and nitrogen metabolism of Malassezia furfur

Investigations on the nutrient requirements of Malassezia yeasts led to the preparation of a new minimal medium consisting of an amino nitrogen and a lipid source, which only allowed the growth of the species M. furfur. Carbohydrates, electrolytes, vitamins and trace elements were not required. Using the basal medium, a nitrogen auxanogram for M. furfur was developed, which allowed investigation of the assimilation of 22 amino acids and 9 further nitrogen sources. With the exception of cysteine, all amino acids were metabolized, as were ammonium salts, urea, creatine, creatinine, uric acid and allantoin. KNO3, however, failed to support growth. Depending on the source used, the yeast cells changed micromorphologically: both oval and round forms were induced. Assimilation of several amino acids resulted in dimorphism, especially in the case of glycine and serine. The cell yield differed significantly depending on the nitrogen source; short-chain unbranched amino acids were utilized most readily. Thus, M. furfur can be characterized as a relatively undemanding yeast species which is optimally adapted to the superficial skin environment. All other lipid-dependent Malassezia species seem to require more complex media.