Wladyslav I. Golubev

ATP leakage from yeast cells treated by extracellular glycolipids of Pseudozyma fusiformata

The ustilaginaceous yeast Pseudozyma fusiformata secreted glycolipids which were lethal to many yeasts and fungi more active at pH of about 4.0, and in the temperature range of 20-30 degrees C. Purified glycolipids enhanced non-specific permeability of the cytoplasmic membrane in sensitive cells, which resulted in ATP leakage and susceptibility of the cells to staining with bromocresol purple. Cells of Saccharomyces cerevisiae lost the ability to acidify the medium. Basidiomycetous yeasts were more sensitive to the glycolipids than ascomycetous ones. The minimal effective glycolipid concentration was 0.13 and 0.26 mg ml(-1) for Cryptococcus terreus and Filobasidiella neoformans, while for Candida albicans and Saccharomyces cerevisiae it was 1.0 and 1.6 mg ml(-1).

Mycocin production in Trichosporon pullulans populations colonizing tree exudates in the spring.

Mycocin production was demonstrated in Trichosporon pullulans, which is a dominant member of the yeast community in tree exudates released in the early spring (spring sap). Mycocin synthesis was associated with dsRNA-containing virus-like particles. Natural strains of Tr. pullulans free of dsRNA have a sensitive phenotype, and a mycocinogenic strain cured of small dsRNA becomes sensitive to its own mycocin. The mycocin studied was active against isolates from tree exudations only but not against Tr. pullulans strains isolated from other habitats. No activity was found against any other yeast species. The competitive advantage of mycocin production at the population level was exemplified by the predominance of mycocinogenic strains both in laboratory model communities and in natural populations.

The Yeast Pseudozyma fusiformataVKM Y-2821 Producing an Antifungal Glycolipid

The yeast Pseudozyma fusiformata(Ustilaginales) produces an extracellular low-molecular-weight protease-resistant thermostable fungicide, which is active against more than 80% of the 280 yeast and yeast-like species tested under acidic conditions. The fungicide, extracted with methanol and purified by column and thin-layer chromatography, was found to consist of glucose and saturated fatty acids.

Antifungal cellobiose lipid secreted by the epiphytic yeast Pseudozyma graminicola

The yeast Pseudozyma graminicola isolated from plants inhibited growth of almost all ascomycetes and basidiomycetes tested (over 270 species of ca. 100 genera) including pathogenic species. This yeast secreted a fungicidal agent, which was identified as a glycolipid composed of cellobiose residue with two O-substituents (acetyl and 3-hydroxycaproic acid) and 2,15,16-trihydroxypalmitic acid. The release of ATP from the glycolipid-treated cells indicated that this glycolipid impaired the permeability of the cytoplasmic membrane. Basidiomycetes were more sensitive to the cellobiose lipid than ascomycetes.

Mycocin production in Cryptococcus aquaticus

Double-stranded RNA viruses of about 35 nm in diameter were isolated from a mycocin-secreting strain of Cryptococcus aquaticus. A derivative of this strain, lacking small dsRNA, was non-mycocinogenic and sensitive to its own toxin. The killing pattern of this mycocin was restricted to some species of the Cystofilobasidiales clade. Despite the differences in genome size of dsRNA viruses in mycocinogenic strains of Cryptococcus aquaticus, Cystofilobasidium sp. CBS 6569, Cystofilobasidium bisporidii, Cystofilobasidium infirmominiatum, Trichosporon pullulans and Xanthophyllomyces dendrorhous and killing patterns of their mycocins, the viral genomes showed homology in hybridisation experiments.

Killer Activity of Tilletiopsis albescens Gokhale: Taxonomic and Phyloqenetic Implication

Killer activity expressed at pH values ranging from 3.5 to 8.0 was found in the Tilletiopsis albescens VKM-2822. Its killer phenotype was cureless. The toxin excreted with a molecular mass above 10 kDa is fungicidal, thermolabile, sensitive to proteinase K and was specified as a mycocin. The latter does not act against ascomycetous, sporidiobolaceous and tremellaceous yeasts. In contrast to all other Rhodotorula species, Rh. bacarum, Rh. hinnulea and Rh. phylloplana are sensitive to the mycocin studied. Also, its killing pattern includes the species of the genera Exobasidium, Farysia, Protomyces, Pseudozyma, Sporisorium, Taphrina and Ustilago. The host range of T. albescens mycocin is discussed from taxonomic and phylogenetic viewpoints.

Cryptococcus silvicola nov. sp. from nature reserves of Russia and Portugal

Nitrate-positive strains of a filobasidiaceous anamorphic yeast related to Cryptococcus cylindricus were isolated from forest litter in a Russian nature reserve and from a lichen in Portuguese one. Mycocinotyping and rDNA sequence analysis revealed that the strains represent a novel species, for which the name Cryptococcus silvicola (type strain VKM Y-2939=CBS 10099) is proposed.

Mastigobasidium, a new teleomorphic genus for the perfect state of ballistosporous yeast Bensingtonia intermedia.

A new genus, Mastigobasidium, is proposed for teliospore-forming, xylose-lacking, ballistosporogenous, glucuronate-positive yeasts. The distinguishing features of the genus are: germination of the teliospore by several long aseptate hyphae; curved phragmometabasidia development on the apices of these hyphae; and production of basidiospores on a peg in clusters. The type strain of heterothallic, nitrate-negative species Mastigobasidium intermedium is VKM Y-2720T (Bullera intermedia type strain) and the allotype strain is VKM Y-2727AL (Sporobolomyces weijmanii type strain).

Antifungal activity of Bullera alba (Hanna) Derx

A strain ofBullera alba that secretes a killer toxin inhibitory (at pH values ranging from 3 to 7) to many ascomycetous and basidiomycetous yeast-like fungi was discovered. Its killer phenotype was incurable. The toxin was relatively thermostable and resistant to many proteases, and it was identified as a microcin. It inhibited the growth of some pathogenic yeasts and was the most active againstCryptococcus neoformans.

Cryptococcus pinus sp. nov., an anamorphic basidiomycetous yeast isolated from pine litter

A novel species of the genus Cryptococcus, isolated from dead needles of Pinus sylvestris, was identified using mycocinotyping and rDNA sequence data. Phylogenetic analysis showed that the novel species was located in the Kwoniella clade of the Tremellales and was closely related to Cryptococcus dejecticola. The type strain of the novel species, Cryptococcus pinus sp. nov., is VKM Y-2958T (=CBS 10737T).