M. W. Miller

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 ecology of yeast flora associated with cactiphilic Drosophila and their host plants in the Sonoran desert

Yeasts were isolated from the rotting stems of 7 species of cereoid cacti and 4 species ofDrosophila which utilize them as host plants. The yeast most common among 132 nonidentical isolates from the cacti and 187 nonidentical isolates from the flies, respectively, were:Pichia membranaefaciens (59 and 126),Candida ingens (22 and 8),Torulopsis sonorensis (16 and 20), andCryptococcus cereanus (11 and 14). Isolates capable of utilizingd-xylose were recovered primarily fromD. pachea andL. schotti. Adult flies were present on the substrates whenP. membranaefaciens was at high concentrations. As the pH of the substrates increased, the percent ofC. ingens cells increased relative to other yeast species. Larvae were detected mainly in alkaline substrates, and since adults did not yieldC. ingens to the extent the substrates did,C. ingens may be important in larval nutrition.Torulopsis sonorensis was recovered mainly fromD. mojavensis and its host plants,M. gummosus andL. thurberi. The concentration ofT. sonorensis in the substrates was negatively correlated with the temperature of the substrate.Cryptococcus cereanus was found in high concentrations in suitable tissues for adult flies but most adults did not yield this species to any extent. The yeast habitat diversities from the substrates had the following order:L. thurberi > C. gigantea > C. gigantea soils ≫ M. gummosus > L. schotti > others. Habitat diversity is discussed in relation to the variation of the physical conditions and chemical composition of the substrates. The yeast habitat diversities from the flies had the orderD. pachea > D. mojavensis ≫ D. nigrospiracula > undescribed Species M. The degree of habitat diversity is possibly a function of the surface feeding behavior of the flies.

Sporulation in Candida pulcherrima, Candida reukaufii and Chlamydozyma species : their relationships with Metschnikowia

Sporulation of Candida pulcherrima, C. reukaufii, Chlamydozyma pulchcrrima, Chl. reukaufii and Chi. zygota was achieved. Ascospores are acicular and 2 per ascus, characteristic of the genus Metschn...

Single‐cell protein: Current status and future prospects

The consumption of microorganisms by man and animals is not a revolutionary new idea. For thousands of years man has consumed, either intentionally or unintentionally, such products as alcoholic beverages, cheeses, yogurt, and soya sauce and, along with these products, the microbial biomass responsible for their production. The rapid growth rate and high protein content of microbes and their ability to utilize inexpensive feedstocks as sources of carbon and energy for growth have made microorganisms prime candidates for use as human food and animal feed protein supplements. Yet, in spite of their promise, only a limited number of commercial-scale, single-cell protein (SCP) processes have been seen. Recently, with the advent of recombinant DNA technology a rebirth of interest in SCP has resulted. This review analyzes the answers to two questions: (1) how far have we come?; and (2) what impact, if any, will the new biotechnologies have in this field?

Pichia opuntiae, a New Heterothallic Species of Yeast Found in Decaying Cladodes of Opuntia inermis and in Necrotic Tissue of Cereoid Cacti

A new heterothallic species of Pichia has been recovered 25 times from widely separated cactus substrates. The organism has been named Pichia opuntiae because the sexually most compatible strains were isolated from Opuntia inermis in Australia. Two varieties are designated based on differences in physiology, habitat, and geographic distribution. P. opuntiae var. opuntiae has a maximum temperature for growth of 30 to 33°C and assimilates citric acid strongly, but assimilation of cellobiose is latent, weak, or negative. P. opuntiae var. thermotolerans grows well at 37°C, but not at 39°C; it assimilates cellobiose strongly but does not assimilate citric acid. Ecologically, P. opuntiae var. opuntiae is associated with Opuntia inermis (tribe Opuntiaeae, subtribe Opuntiinae) in Australia; P. opuntiae var. thermotolerans is associated with species of the cactus tribe Pachycereeae, subtribe Pachycereinae, from various locations in the North American Sonoran Desert. A discussion of the physiological and host-plant shifts for these two varieties and three similar cactophilic yeasts is presented. The base composition of the nuclear deoxyribonucleic acid of P. opuntiae var. opuntiae (average of four strains) is 33.64 ± 0.25 mol% guanine plus cytosine and that of P. opuntiae var. thermotolerans (average of 3 strains) is 33.13 ± 0.23 mol% guanine plus cytosine. The type strain of P. opuntiae and of the type variety, P. opuntiae var. opuntiae, is UCD-FS&T 77-40 (= ATCC 36836 = CBS 7010). The type strain of P. opuntiae var. thermotolerans is UCD-FS&T 76-211 (= ATCC 36834 = CBS 7012).

Pichia amethionina, a New Heterothallic Yeast Associated with the Decaying Stems of Cereoid Cacti

A new species of the genus Pichia has been recovered 38 times in the Sonoran Desert from “rot pockets” of cereoid cacti and from Drosophila species which utilize the cacti. We have named the species Pichia amethionina due to its absolute requirement for methionine or cysteine. P. amethionina is heterothallic and demonstrates an agglutination reaction when opposite mating types are mixed. Two varieties are designated based on the combination of mannitol assimilation and ecological habitat. P. amethionina var. amethionina, the type variety, was recovered from cacti in the subtribe Stenocereinae and cannot assimilate mannitol, whereas P. amethionina var. pachycereana was found in cacti of the subtribe Pachycereinae and can assimilate mannitol. Results are given which demonstrate that the assimilation of mannitol is controlled by a single genetic locus. An evaluation of the interfertility and postmating viability among the two varieties and possibly identical organisms was made. The base composition of the nuclear deoxyribonucleic acid (average of 10 strains) is 33.05 ± 0.19 mol% guanine plus cytosine. The type strain of P. amethionina and of the type variety, P. amethionina var. amethionina, is UCD-FST 76-401B (=ATCC 36080 = CBS 6940). The type strain of P. amethionina var. pachycereana is UCD-FST 76-384A (=ATCC 36079 = CBS 6943).

Enhancement and stabilization of the production of glucoamylase by immobilized cells of Aureobasidium pullulans in a fluidized-bed reactor.

SummaryGlucoamylase production by Aureobasidium pollulans A-124 was compared in free-living cells, cells immobilized in calcium alginate gel beads aerated on a rotary shaker (agitation rate 150 rpm), and immobilized cells aerated in an air bubble column reactor. Fermentation conditions in the bioreactor were established for bead concentration, substrate (starch) concentration, calcium chloride addition to the fermentation medium, and rate of aeration. Production of glucoamylase was optimized at approximately 1.5 units of enzyme activity/ml medium in the bioreactor under the following conditions: aeration rate, 2.0 vol air per working volume of the bioreactor (280 ml) per minute; gel bead concentration, 30% of the working volume; substrate (starch) concentration, at 0.3% (w/v); addition of calcium chloride to the medium at a final concentration of 0.01 M. Productivity levels were stabilized through the equivalent of ten batches of medium with the original inoculum of immobilized beads.

On the occurrence of various species of yeast in nature

A number of yeasts were isolated from various natural sources such as slime fluxes of trees, insects and insect frass, flowers and similar substrata. Several of the isolates represented species described in recent years. The additional isolations reported here contributed additional knowledge regarding the natural habitat of some of the species. Conclusions are offered regarding the ecology ofSaccharomyces kluyveri, S. phaselosporus, S. rosei, S. veronae, S. wickerhamii, Hansenula californica, H. mirakii, H. minuta, Pichia kluyveri, P. pastori, P. rhodanensis, P. silvestris, P. vanriji, Candida albicans, C. claussenii, Torulopsis glabrata, T. candida, Cryptococcus albidus, Cr. diffluens, Cr. laurentii, Rhodotorula graminis, Rh. texensis, andAscocybe grovesii. Various other species are listed in tabular form and by isolation source.