Growth and sporulation responses of Basidiobolus to changes in environmental parameters

The growth, asexual and sexual reproduction of pathogenic and saprophytic isolates of Basidiobolus haptosporus were studied. Isolates were recovered from amphibian, reptile and wallaby dung, and from woodlice and clinical specimens from the horse. Saprophytic isolates grew poorly or not at all at 40 °C. A pathogenic isolate showed modest growth at this temperature ; reproduction in this isolate was favoured by temperatures about 5° higher than for saprophytic isolates. All forms of biological activity investigated were favoured by slightly acid conditions; however, activity was possible over a wide range of pH values. Conidium production ceased at water potentials lower than around −11 to −16 bar; zygospore formation continued under relatively dry conditions and down to −39 bar. All isolates grew minimally at potentials around −48 to −56 bar. Visible light stimulated conidium production but exerted no observable effect on zygospore formation.