A novel representative of the yeast genus Pichia has been recovered 190 times during the period 1971 to 1976. We regard this organism as belonging to a new species, Pichia cactophila. Strains were found in the necrotic tissue of 16 species of cactus and in the crops of 3 species of Drosophila which utilize the cacti as host plants. Isolates were obtained from widely separate geographic localities (throughout Mexico, Southwestern United States, and Hawaii). The new species forms predominantly two-spored asci. Both homothallic and heterothallic strains were observed. The metabolic capability of P. cactophila, like that of P. membranaefaciens, is limited to oxidative utilization of only a few compounds. P. cactophila can be differentiated from P. membranaefaciens by its strong growth on D-glucosamine and by the lower guanine-plus-cytosine content (36.3 to 37.5 mol%) of its nuclear deoxyribonucleic acid. The type strain of P. cactophila is UCD-FST 76-243A (= ATCC 34932 = CBS 6926).
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