The selection of auxotrophs of<i>Penicillium chrysogenum</i>with nystatin

Abstract

A simple technique for the selection of auxotrophs of Penicilhium chrysogenum after mutagenic treatment has been devised using nystatin. It relies on the differential sensitivity of germinated and dormant conidia to nystatin and on the gradual loss of antibiotic activity which occurs on complex media at laboratory incubation temperatures. After mutagenic treatment, conidia were plated on MM agar to allow germination of prototrophs and then overlaid with CM agar containing enough nystatin to kill germinated conidia but not ungerminated auxotrophic conidia. When nystatin activity had decreased sufficiently the latter germinated and grew and thus were enriched relative to prototrophs.