Formation of sulphate, sulphite and S-sulphocysteine by the fungus Microsporum gypseum during growth on cystine.

The dermatophyte Microsporum gypseum was cultivated in media containing 0.5% cystine in suspension, and 0.05% peptone or 1% glucose and 0.05% peptone. During growth on cystine the excess sulphur was oxidized and excreted into the medium not only in the form of sulphate but also in the form of sulphite. Sulphite was produced especially during first phases of growth, where its quantity was higher than that of sulphate and its maximum concentration exceeded 1 mg/ml. S-sulphocysteine, detected chromatographically and determined quantitatively, originated in large quantities by the reaction of sulphite with cystine in the medium. Both sulphite and S-sulphocysteine were further oxidized to sulphate. After exhaustion of cystine 90-93% of the sulphur present was converted to sulphate in the cultivation medium.