Validation of the species Pichia guilliermondii.

Many species of yeasts exist in nature in haploid form. If strongly heterothallic, strains of such species produce no ascospores when tested individually. They do mate if sexually reactive strains of opposite sex are mixed on a sporulation medium. In 1952, L. J. Wickerham and K. A. Burton (J. Bacteriol. 63:449, 1952) reported that all strains of an imperfect form known variously as Dematium chodati Nechitch, Candida chodati Berkh., and Sporotrichum anglicum Cast. were capable of reacting with a tester of opposite sex. The perfect stage of this species was validated with a Latin description by J. Boidin et al. (Bull. Soc. Mycol. France 80:396, 1964), who gave it the name Pichia burtonii. The type selected, strain NRRL Y-1933, was isolated from pollen carried by a wild honeybee of a subfamily (Meliponinae) inhabiting tropical America. This strain was received at the Northern Laboratory in 1950 from Cyro G. Teixeira, Campanas, Brazil. This species is frequently isolated from silage and stored grain. Another haploid heterothallic yeast is the ubiquitous species Candida guilliermondii (Cast.) Lang. and Guerra. Sexually reactive strains comprised a minority of those tested (L. J. Wickerham and K. A. Burton, J. Bacteriol. 68:594, 1954). The characteristics of 16 sexually reactive strains are presented in the following description.