Pichia pseudocactophila, a new species of yeast occurring in necrotic tissue of columnar cacti in the North American Sonoran Desert

Abstract
A description is given of Pichia pseudocactophila, a new species of yeast which is closely related to Pichia cactophila. Pichia pseudocactophila is heterothallic and produces four-spored asci, whereas P. cactophila is homothallic and its asci contain a maximum of two spores. Their morphological and physiological properties and G + C contents of their nuclear deoxyribonucleic acids (DNAs) are similar, but the DNA of P. pseudocactophila shows only 35% homology with the DNA of P. cactophila. In addition, strains of P. pseudocactophila have electrophoretic enzyme patterns for glucose-6-phosphate dehydrogenase, hexokinase-1, hexokinase-2, and phosphoglucomutase that allow them to be distinguished from P. cactophila strains. Lastly, P. pseudocactophila has been found only in rotting tissue of columnar cacti (Pachycereus pringlei and close relatives) in Mexico and southern Arizona, whereas P. cactophila is a host-plant generalist and is distributed worldwide in all cactus species so far investigated.

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