Aureobasidin A (AbA) is a cyclic depsipeptide anti-fungal antibiotic with a molecular weight of approximately 1.1 kDa. It is isolated from the filamentous fungus Aureobasidium pullulans R106. The yeast selection marker Aureobasidin A inhibits inositol phosphorylceramide (IPC) synthase, a yeast enzyme that is expressed from the AUR1 gene and is toxic to fungi and yeast at low concentrations (0.1–0.5 µg/mL), including Saccharomyces cerevisiae, Schizosaccharomyces pombe and Candida albicans. Aureobasidin A may be used for stringent drug selection of transformed yeast containing a mutant AUR1-C cassette, which confers resistance to Aurobasidin A, and is used to screen for Aspergillus nidulans transformants with the pAUR316 vector from Takara Bio. A major advantage of Aureobasidin A over conventional nutritional selection markers is that Aureobasidin A offers a much more stringent screen by killing non-transformed cells rather than merely retarding their growth.