A description is given of a new yeast genus, Phaffia, represented by P . rhodozyma sp. nov., to accomodate nine yeast strains isolated in Japan and one in Alaska, all from exudates of deciduous trees. The type strain of P. rhodozyma is UCD (FS&T) 67-210 (= ATCC 24202 = CBS 5905). Phafia, named in recognition of the contributions of Herman Jan Phaff to yeast taxonomy and ecology, is a carotenoid-producing, fermentative yeast of the Deuteromycotina (Blastomycetes) , whose properties indicate a basidiomycetous origin. A comparison is made between Phaffia and other yeast genera to which it might be related.In surveys of yeasts in tree exudates (slime fluxes) in Japan and in the Pacific Northwest of North America (16), we isolated 10 similar yeast strains that belong to a new species which represents a new genus. This yeast produces carotenoid pigments, reproduces vegetatively by budding, and lacks, as far as we have been able to determine, a sexual life cycle. It could not be accommodated in the genus Rhodotorula Harrison because species in that genus are nonfermentative, whereas the isolates from tree exudates ferment several sugars. In an earlier publication (16), this yeast was tentatively named Rhodozyma montanae. However, a Latin diagnosis, as required by the rules of the International Code of Botanical Nomenclature, was not given, and this binomial is therefore a nomen nudum. The intent of this paper is to give a complete description, to discuss the taxonomic relationships of the new organism, and to provide it with a validly published name.
MATERIALS AND METHODSSamples of exudates were collected in new plastic vials or bags. Usually within 6 to 18 h after collection, a loopful of the slimy exudate was streaked directly on 5% malt agar acidified with hydrochloric acid to pH 3.7. If the sample was in a dehydrated condition, it was removed from the tree with a specially made chisel sterilized in alcohol. It was then rehydrated with a small amount of sterile water for a suitable length of time before streaking. The inoculated plates were stored at room temperature ranging from about 15 to 25 C. On most of the plates, relatively few fungi appeared, but many of the samples yielded significant numbers of bacterial colonies in spite of the low pH of malt agar. The plates were inspected with a dissecting microscope after 3 to 6
