Fourteen genera and 29 species of yeasts were found in the water of three artificial fresh lakes. The lakes, used for recreational purposes and located in the area of the Lowland Záhorie (Slovakia), were sampled in summer and autumn. Aureobasidium, Hansenula, Candida, and Rhodotorula species occurred the most frequently. The composition of yeast species was more heterogeneous in summer than in autumn. Relatively high population levels of fermentative and pellicle-forming yeasts were found, especially of Candida krusei and Hansenula anomala. The "black yeast" Aureobasidium pullulans was frequently isolated in autumn in high counts in contrast with the numbers of other species. Key words: ecology, yeasts, quantitative and qualitative study, freshwater lakes.

In the year 1986, we collected 85 samples of soil, plants and fruits from North Korea. We isolated 30 strains of yeast and yeast-like organisms (11 Ascomycetes, 9 Basidiomycetes, 7 Deuteromycetes and 3 arthroconidial fungi). The following genera were identified:

The ability to grow in liquid media with D-xylose, xylan from decidous trees, and hemicelluloses from conifers was tested in 95 strains of 35 genera of yeasts and yeast-like organisms. Of 54 strains thriving on xylose, only 13 (genera Aureobasidium, Cryptococcus and Trichosporon) utilized xylan and hemicelluloses as growth substrates. The árowth media of these strains were found to contain xylan-degrading enzymes splitting the substrate to xylose and a mixture of xylose oligosaccharides. The ability of these yeasts to utilize the wood components (hitherto unknown in the genus Crytococcus) makes them potential producers of microbial proteins from industrial wood wastes containing xylose oligosaccharides, xylan, and hemicelluloses as the major saccharide components without previous saccharification.

Aureobasidium pullulans (de Bary) Arnaud was isolated from different natural materials plant blossoms in particular. Elements of vegetative multiplication, structure of colonies and cultures in liquid media were analyzed in detail, leading to construction of the life cycle of this organism. Morphological polymorphism was found to be combined with the production of melanin and the polysaccharide pullulan. Morphological analysis served for a directed selection for studies of physiological properties of this organism and its practical application.

No abstract

Anhand der von HEYER (1966) aus Erdolschlamm isolierten, n-Alkane assimilierenden Stamme der farblosen Alge Prototheca wurde die Art Prototheca hydrocarbonea n. sp. beschrieben. Als Typus gilt der nunmehr unter der Nummer CCY 70-1-1 in die Tschechoslovakische Sammlung fiir Hefen (Chemisches Institut der Slovakischen Akademie der Wissenschaften, Bratislava, CSSR) aufgenommene Stamm S6c. Die neue Art unterscheidet sich neben weiteren Merkmalen vor allem durch die GroBe der Autosporen, Wachstum bei +42 "C sowie Assimilation von Xylose und Inosit von den anderen Arten der Gattung. Die zur Differenzierung der Sippe erforderlichen physiologischen Merkmale, allgemeine submikroskopische Strukturen und der Lebenszyklus wurden untersucht.

Nineteen strains of yeasts possessing different characteristics were stored in liquid nitrogen and after 5 years phenotypic characters were evaluated and compared with equivalent strains preserved under paraffin oil. All qualitative characters tested remained stable, and quantitative characters varied only within the range of natural variability.

Nineteen strains of taxonomically diverse yeast species tested survived freezing and subsequent five-year storage in liquid nitrogen at - 196 degrees C, using a medium M 2 composed of malt extract, yeast extract, peptone, calf serum and dimethyl sulfoxide. Viability of the yeast cultures after long-term storage ranged from 5 to 97% (average 62%) compared with the viability of the cultures prior to freezing. The use of liquid nitrogen refrigeration for preserving yeast cultures is strongly advocated.