Nitrogen utilisation and growth at reduced water activity by mucoralean fungi present in soil
Nine mucoralean fungal genera including 18 species were examined for their ability to utilise a series of nitrogen containing compounds and to grow at an a(w) of 0.955 on solid media. The nitrogen concentration in the media was 0.1 g/l and the series of nitrogen containing compounds were ammonium chloride, asparagine, sodium glutamate, sodium nitrite and potassium nitrate. The genera were Actinomucor Schostak., Backusella Hesselt. and J.J. Ellis, Cunninghamella Matr., Gongronella Ribaldi, Mortierella Coem., Mucor Fresen., Rhizomucor Lucet and Costantin., Rhizopus Ehrenb. and Thamnostylum Arx and H. P. Upadhyay. Thirty-nine fungal strains obtained from culture collections (CBS, MUFS and PPRI), as well as 12 soil isolates from the Karoo, were tested. All the species and strains tested in this study were able to utilise asparagine and glutamate. Strains belonging to Cunninghamella, Mucor racemosus Fresen., Rhizopus microsporus Tiegh. and Rhizopus stolonifer (Ehrenb.: Fr.) Vuill. were unable to utilise ammonium chloride. Strains of Cunninghamella, Mortierella, Rhizomucor, Rhizopus microsporus and Rhizopus stolonifer were unable to grow on nitrate as sole nitrogen source. Nitrite was found to be toxic to species belonging to Cunninghamella, Mortierella, Rhizomucor, Rhizopus and Thamnostylum. Members of Gongronella, Mortierella, Mucor racemosus, Rhizomucor and Thamnostylum were unable to grow at an a(w) of 0.955.