Herman J. Phaff

Carotenoids of Phaffia rhodozyma, a red-pigmented fermenting yeast

Abstract The red-pigmented fermenting yeast Phaffia rhodozyma contains astaxanthin as the principal carotenoid pigment. Echinenone, 3-hydroxyechinenone and phoenicoxanthin were also isolated and identified; isocryptoxanthin and canthaxanthin were absent. Evidence is presented for a new carotenoid, 3-hydroxy-3′4′-didehydro-β,ψ-caroten-4-one. A possible biosynthetic scheme for the formation of astaxanthin in P. rhodozyma is suggested.

The life of yeasts

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The taxonomy of yeasts isolated fromDrosophila in the Yosemite region of California

SummaryA survey was made of the yeasts occurring in the intestinal tract of wild species ofDrosophila occurring in the Yosemite Region of California. Two hundred and forty one yeasts, representing 42 species and varieties, were identified. Each isolate was obtained from a different fly. Almost half of the isolates belong toSaccharomyces. The most common species in this genus wereS. montanus (36 isolates),S. veronae (30 isolates),S. cerevisiae var.tetrasporus (22 isolates) andS. drosophilarum (13 isolates). Further species are listed in Table 1.Zygosaccharomyces fermentati Naganishi was shown to be a distinct species and not a synonym ofS. cerevisiae. In order to avoid confusion with another yeast of the same name, it has been proposed to change the nameZ. fermentati toS. montanus Naganishi. Two new species ofSaccharomyces were described,S. wickerhamii andS. kluyveri. S. mangini var.tetrasporus has been renamedS. cerevisiae var.tetrasporus. A non-cellobiose attacking strain ofS. drosophilarum has been designated tentativelyS. drosophilarum var.acellobiosa. A new species of the genusPichia was described asP. xylosa. Saccharomyces pastori andSaccharomyces pini were transferred to the genusPichia on the basis of arguments given in the preceding paper. A new species ofTrichosporon was described asTr. aculeatum on the basis of the presence of characteristic needlelike cells. Common species besides those mentioned inSaccharomyces wereHansenula angusta (19),Kloeckera apiculata (15),Kl. magna (13), andTorulopsis stellata (10). Other genera represented wereHanseniaspora, Cryptococus, Rhodotorula, Candida andOospora. Evidence was obtained that many species of imperfect genera consist of distinctly different physiological types.

An Analysis of the Yeast Flora Associated with Cactiphilic Drosophila and their Host Plants in the Sonoran Desert and Its Relation to Temperate and Tropical Associations

A survey was made in the Sonoran Desert of yeasts living in the decaying arms of five species of cereus cacti and the four species of Drosophila that utilize them as host plants. The most common yeasts among 132 isolates from the cacti and 187 isolates from the files, respectively, were: Pichia membranaefaciens (45% and 67%), Candida ingens (17% and 4%), Torulopsis sonorensis (12% and 11%), and Cryptococcus cereanus (8% and 7%). Eighty—eight percent of the 66 initial isolates of P. membranaefaciens from Drosophila pachea and its host, senita cactus, assimilated D—xylose while only 12% of the remaining 257 initial isolates did so. Nineteen of the 20 isolates of T. sonorensis from files were found in Drosophila mojavensis and 12 of the 14 isolates of Cryptococcus cereanus came from D. pachea. The highest mean number of yeast species per cactus was 2.77 plus or minus 0.68 in organpipe cactus and per fly was 1.63 plus or minus 0.53 in D. pachea. The flies usually carried fewer yeast species than were found in the host plant but D. pachea had almost the same mean and variance as its host, senita cactus, which had 1.64 @+ 0.40. Yeast species diversity and average niche overlap have the following rank order among habitats and localities: temperate trees > temperate flies > tropical flies > desert cacti > desert flies. Habitat diversity and average niche width show: tropical flies > temperate flies and desert cacti > desert flies and temperate trees. The physiological properties of the desert yeasts are most similar to those of the tropical yeast. However, desert yeasts have similarities with yeasts of temperate trees. Both have low fermentative ability and high assimilation ability of several alcohols and acids. The genus Pichia is by far the most common yeast genus associated with Drosophila in all habitats analyzed (36% of 1,426 isolates).

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

SummaryA 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.

Yeasts Isolated from Drosophila and From Their Suspected Feeding Places in Southern and Central California

In 1948 Dobzhansky expressed the view that yeasts are important in understanding some of the forces of natural selection to which popula? tions of Drosophila flies are exposed. Since then there has been an intense interest in the relation of yeast to Drosophila in nature. Al? though certain aspects of this relationship have been studied, information pertaining to the taxonomy of yeast occurring in Drosophila flies is quite limited. Chatton (1913) reported the occurrence of Coccidiascus ligeri as an intestinal parasite of D. funebris. In 1944 Dobzhansky and Epling iso? lated a yeast, which they termed 5\ farinosus (syn. Pichia farinosa), from the crops of D. pseudoobscura. Later, at Dobzhanskys suggestion, Wagner isolated some yeasts from the crops of D. pseudoobscura col? lected at Pinon Flats in the San Jacinto mountains in Southern Cali? fornia. These were identified by Mrak (unpublished data) as species of the genus Zygosaccharomyces. Wagner (1944) also isolated but did not identify 8 types of yeast from Opuntia fruits and demonstrated that the yeasts had different nutritional qualities for certain species of Dro? sophila. Buzzati-Traverso in 1950 3 isolated 15 cultures of Torulopsis from Drosophila flies trapped in the Po Valley in Italy. Hedrick and Burke (1950) and Hedrick and Burke (1952) identified 17 yeasts iso? lated from crop contents, feces, and immediate substrates of two species of flies (D. crucigera and D. pilimana) collected in Hawaii. Shehata and Mrak (1952) compared the intestinal yeast floras of successive populations of Drosophila. In this study emphasis was placed on the relation of the type of yeast to the population cycles of the differ? ent chromosomal types of Drosophila pseudoobscura rather than on the taxonomy of the yeast isolated. In somewhat similar work da Cunha et al. (1951) demonstrated that certain yeasts isolated from the crops

Fungal Glucans — Structure and Metabolism

Glucans constitute important structural or skeletal components of the cell envelope of yeasts and filamentous fungi. Isolation of individual glucan components and elucidation of their chemical structures have presented enormous difficulties. Early investigators generally subjected whole cells of baker’s or brewer’s yeast to more or less drastic treatments with alkali and acid to obtain cell wall glucan residues. It is now recognized that some glucans are extracted by these treatments and their contribution to the cell wall structure was overlooked. In addition, chemical degradation of some polysaccharides occurred as a result of heating with alkali and acids. Thirdly, as will be discussed later on, it was not recognized until the last decade that the alkali-insoluble glucan of baker’s yeast actually consists of two different polysaccharides that are difficult to separate. As a consequence, the value of the early structural investigations on yeast “glucan” was greatly diminished.

Studies on a beta-fructosidase (inulinase) produced bySaccharomyces fragilis

SummaryA study was made of a β-fructosidase, which is produced extracellularly and intracellularly bySaccharomyces fragilis. The enzyme catalyzes the hydrolysis of inulin, bacterial levans, sucrose, and the fructose portion of raffinose, by splitting off terminal fructosyl units. It attacks β-2,1 as well as β-2,6 linkages. The enzyme content of inulin-grown cells is sufficient to allow fermentation of inulin at the same rate as glucose. The ratio of hydrolysis rates with sucrose and inulin was about 25 for the β-fructosidase ofS. fragilis and about 14,000 for invertase.S. fragilis does not contain significant amounts of invertase and it ferments inulin, sucrose and raffinose with the aid of a related, but different enzyme, inulinase.Conditions of growth were established which favor inulinase synthesis. Highest yields were obtained with inulin as the carbon source, and somewhat lower yields with raffinose. Glucose, fructose and sucrose were poor inducers of inulinase. The pH of the medium during growth on inulin had to be in the range where inulinase could act, otherwise growth was tardy and poor. In an inulin containing medium aeration favored enzyme production as a result of stimulation of growth. The inulinase content of the cells in a unit volume was generally greater than that in the culture medium. The intracellular inulinase could be solubilized quantitatively by autolysis. The intra-and extracellular inulinases were concentrated and purified to the same extent. Comparison of the two preparations with respect to substrate specificity, rate of inactivation by heat, pH optima with sucrose (4.2) and with inulin (5.0), and elution patterns from a column of diethylaminoethyl cellulose, indicated that the intra-and extracellular enzymes were identical.

The ecology of the yeast flora in necroticOpuntia cacti and of associatedDrosophila in Australia.

A survey was made of the yeast communities isolated from necrotic tissue of 4 species of prickly-pear cacti (Opuntia stricta, O. tomentosa, O. monacantha, andO. streptacantha) which have colonized in Australia. Yeast communities were sampled from a number of localities and at different times. Cactus specific yeasts accounted for 80% of the total isolates, and the 3 most common species contributed 63% of the total. Comparisons of the species compositions of the yeast communities indicated that the differences among communities were greater betweenOpuntia species than between different localities within a single cactus species, and also that differences between years were greater than average differences between localities within years. Multivariate statistical tests of association between yeast community and physical features of rots indicated that temperature, pH, and age of rot all exerted some influence on the structure of the yeast community. Similar analyses involvingDrosophila species inhabiting these cactus rots suggested the existence of complex associations betweenDrosophila community, yeast community, and physical and chemical attributes of the cactus necroses.

Nucleic Acid Relatedness Among Yeasts

The yeasts are a phylogenetically diverse group of fungi whose teleomorphs are distributed between the Ascomycotina and the Basidiomycotina. The grouping is one of convenience, bound together by the characteristics of predominantly unicellular growth resulting from either budding or fission and a sexual stage unenclosed in a fruiting body. The criteria accepted for use in speciation have, over time, paralleled many other areas of microbiology, first relying on the morphology of vegetative and sexual stages, followed later by definition of taxa through biochemical and genetic tests, and finally, owing to a partial failure of the foregoing to produce definitive results, a reliance on nucleic acid sequence relatedness.