The taxonomy of yeasts found in exudates of certain trees and other natural breeding sites of some species of Drosophila.

Abstract

A survey was made of the yeasts occurring in slime fluxes ofQuercus kellogii (black oak),Abies concolor (red fir) and in certain mushrooms and dead logs in the mountains of the Yosemite region of California. Most of the 134 isolates identified were found to be non-fermentative or poorly fermentative (fermenting glucose only and usually weakly). The isolates were placed in the following genera:Pichia (34),Debaryomyces (35), imperfect forms ofHansenula (39),Endomyces (3),Saccharomyces (2),Candida (11),Trichosporon (7),Torulopsis (1),Cryptococcus (1) andSporobolomyces (1). Four new species have been described,Pichia silvestris, Pichia quercibus, Pichia carsonii andDebaryomyces fluxorum. P. quercibus andP. carsonii are unusual representatives of the genusPichia in that they form a very primitive pseudomycelium and lack pellicles on malt extract. To accommodate such species an amended diagnosis of the genusPichia has been proposed byPhaff in an accompanying paper.Saccharomyces pastori, of which 12 isolates were obtained, has been transferred to the amended genusPichia asP. pastori (Guilliermond) nov. comb.