Candida caseinolytica sp. nov., a new species of yeast occurring in necrotic tissue of Opuntia and Stenocereus species in the southwestern United States and Baja California, Mexico.

We describe Candida caseinolytica, a new yeast species which occurs in rotting tissues of opuntias and other cacti in the North American Sonoran Desert and a few other localities. This small-celled, slowly growing yeast does not ferment any sugar and assimilates a limited number of carbon compounds, including 2- and 5-ketogluconic acids. It exhibits strong extracellular proteolytic activity on casein at pH 6.5, but gelatin is not hydrolyzed or is only weakly hydrolyzed by a few strains. The type strain of C. caseinolytica is strain UCD-FST 83-438.3 (= ATCC 90546 = CBS 7781).