Elena Sláviková

The occurrence of yeasts in the forest soils

One hundred and eighty one yeast strains were isolated from 180 soil samples collected in three types of forest. The samples were taken during one year. The yeast species found were similar in spite of distinct forest types. Cryptococcus laurentii, Cystofilobasidium capitatum, Leucosporidium scottii, Rhodotorula aurantiaca, and Trichosporon cutaneum were the predominant species in both deciduous and coniferous forests.

Yeasts colonizing the leaves of fruit trees

Yeasts were isolated from leaf surfaces of five species of fruit trees located in southwest Slovakia. One hundred and fifty five yeast strains belonging to 11 genera were isolated from 300 samples of leaves. Seventeen yeast species were identified, but only three occurred regularly:Aureobasidium pullulans, Cryptococcus laurentii, andMetschnikowia pulcherrima. Species such asHanseniaspora uvarum, Pichia anomala, Rhodotorula glutinis, andSaccharomyces cerevisiae, were isolated less frequently. We found only few differences in the yeast community isolated from leaves of different tree species although dominant species occurred regularly on the majority of leaves. Furthermore, yeast species varied throughout years. In spite of the fact that the yeast community occupying the leaves of the fruit trees was studied in the samples harvested in three localities, which are distanced from each other some kilometers, the qualitative representation of the most isolated yeasts was identical. The differences were only in the frequency of the incidence of individual species in the samples.

Geotrichum bryndzae sp. nov., a novel asexual arthroconidial yeast species related to the genus Galactomyces

Ten strains of an asexual arthroconidial yeast species were isolated from Bryndza, a traditional Slovak artisanal sheep cheese, which was manufactured from raw milk during a 4-month summer production period at two Slovakian sites (the northern RuZomberok and the central-southern Tisovec areas). Sequence comparison of the D1/D2 domains of the large-subunit rRNA gene revealed that this yeast represents a novel species of the genus Geotrichum, which contains anamorphs of the ascogenous genus Galactomyces, for which the name Geotrichum bryndzae sp. nov. is proposed (type culture CCY 16-2-1T=NRRL Y-48450T=CBS 11176T). The novel species is most closely related to Geotrichum silvicola NRRL Y-27641T, although yeasts with identical or very similar sequences have been found throughout the world.

The diversity of eukaryotic microbiota in the traditional Slovak sheep cheese — Bryndza

We investigated the occurrence and diversity of yeasts and filamentous fungi in bryndza an artisanal Slovak soft spreadable cheese prepared from raw sheep milk or from a mixture of sheep and cow milk. Samples collected during four months of the summer production period from two locations (northern and southern parts of central Slovakia) contained 10(5)-10(7) (cfu) yeasts and about 10(2) (cfu) of mold per gram of wet weight. Further characterization by conventional taxonomy and sequence comparison of D1/D2 region from 26S rRNA gene revealed Mucor circinelloides v. Tieghem as the predominant filamentous fungus. A novel Geotrichum sp. together with Kluyveromyces (K. lactis/K. marxianus) was identified as the most abundant yeast species. Occasionally other yeasts, such as Candida inconspicua, Candida silvae, Pichia fermentans and Trichosporon domesticum were found. Conventional taxonomy readily identified isolates to the genus level, but DNA sequence comparison was capable of discriminating them at the species level.

Biotransformation of lignin polymers derived from beech wood pulping by Sporobolomyces roseus isolated from leafy material

The ability of the yeast, Sporobolomyces roseus, isolated from leafy material, to modify lignin derived from beechwood pulping was examined by FTIR and 13C NMR spectroscopy, which revealed oxidative cleavage of the Cα-Cβ linkages between lignin units. Using veratryl alcohol as a model substrate confirmed that Sp. roseus could oxidize veratryl alcohol into veratric acid. This yeast might be suitable for the pretreatment of lignocellulosic materials and/or for biotransformation of technical lignins.