A substance toxic for mice has been extracted from the washed mycelia of Mortierella wolfii. This toxin could also be demonstrated in culture fluids after spontaneous autolysis of the fungal hyphae. Purification of the toxin was carried out using Sephadex chromatography (G-200, G-50) and resulted in a single band on sodium dodecyl sulfate polyacrylamide gels. Properties of the toxin included heat lability at 60 C, trypsin sensitivity, activity over a wide pH range, and a molecular weight of

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... 00. The mean lethal dose for 16-week-old male mice was 3.3 ,ug of protein. Mucormycosis is an opportunistic fungal infection which usually occurs in the presence of lowered or altered host resistance and which may affect any organ of the body. Various species of Absidia, Mucor, and Rhizopus were incriminated in the past as the causative agents (3). Recent investigations (1) in which histological observations were supported by cultural studies showed that members of the Mucorales, and in particular the genus Mortierella (e.g., Mortierella wolfii), may be of considerable importance. Apart from the fact that numerous phycomycetes all appear to show a predilection for growth within blood vessels, little is known of the pathogenesis of the disease. This study was undertaken in an attempt to determine if toxins produced during the growth of M. wolfii could be incriminated in the disease process, and, if so, to investigate the properties of the toxin(s). MATERIALS AND METHODS Culture. A strain of M. wolfii (68/4535) obtained