Ultrastructural characteristics and variability of vegetative reproduction in Fellomyces penicillatus.

The yeast strains VKM Y-2977 and VKM Y-2978, derived from the isolate Pa-202, were examined for their physiological properties and mycocin sensitivities and studied by light, phase-contrast, fluorescence, transmission and scanning electron microscopy. The cells of the first strain produced long stalk-like conidiophores, whereas the cells of the second one had the appearance of a typical budding yeast under the light microscope. Transmission and scanning electron microscopy showed the formation of stalk-like conidiophores and long necks in VKM Y-2977, similar in appearance to Fellomyces fuzhouensis. The actin cytoskeleton, microtubules and nuclei were similar as well, but due to presence of a capsule, they were not clearly visible. The second isolate, VKM Y-2978, had very short stalk-like conidiophores, and the neck, microtubules and actin cables were shorter as well. The actin patches, actin cables, and microtubules were similar in VKM Y-2977 and VKM Y-2978 and not clearly visible. The physiological characteristics and mycocin sensitivity patterns, together with the microscopic structures and ultrastructures, led us to conclude that both strains belong to Fellomyces penicillatus, even though they differ in the lengths of their stalk-like conidiophores and necks.

Rhodotorula rosulata sp. nov., Rhodotorula silvestris sp. nov. and Rhodotorula straminea sp. nov., novel myo-inositol-assimilating yeast species in the Microbotryomycetes.

Three novel species are described as Rhodotorula rosulata sp. nov. (type strain VKM Y-2962(T) =CBS 10977(T)), Rhodotorula silvestris sp. nov. (type strain VKM Y-2971(T) =CBS 11420(T)) and Rhodotorula straminea sp. nov. (type strain VKM Y-2964(T) =CBS 10976(T)) based on the study of eight isolates from needle litter. The new species, phylogenetically located within the Microbotryomycetes, are related to glucuronate-assimilating species of the genus Rhodotorula. Sequencing of the D1/D2 domains of the LSU rDNA gene and the internal transcribed spacer (ITS) region, as well as physiological characterization, revealed their distinct taxonomic positions.

Extracellular cellobiose lipid from yeast and their analogues: structures and fungicidal activities.

Basidiomycetous yeasts Cryptococcus humicola and Pseudozyma fusiformata secrete cellobiose lipids into the culture broth. In the case of Cr. humicola, 16-(tetra-O-acetyl-beta-cellobiosyloxy)-2-hydroxyhexadecanoic acid was defined as major product and 16-(tetra-O-acetyl-beta-cellobiosyloxy)-2,15-dihydrohexadecanoic acid was defined as minor product, while Ps. fusiformata secreted mainly 16-[6-O-acetyl-2'-O-(3-hydroxyhexanoyl)-beta-cellobiosyloxy)-2,15-dihydroxyhexadecanoic acid. These compounds exhibit similar fungicidal activities against different yeasts including pathogenic Cryptococcus and Candida species. The cells of Filobasidiella neoformans causing systemic cryptococcosis completely died after 30-min incubation with 0.02 mg mL(-1) of cellobiose lipids. The same effect on ascomycetous yeast, including pathogenic Candida species, is achieved at 0.1-0.3 mg mL(-1) of cellobiose lipids depending on the test culture used. Cellobiose lipid of Ps. fusiformata inhibits the growth of phytopathogenic fungi Sclerotinia sclerotiorum and Phomopsis helianthi more efficiently than cellobiose lipids from Cr. humicola. Fully O-deacylated analogue, namely 16-(beta-cellobiosyloxy)-2-hydroxyhexadecanoic acid, and totally synthetic compound, 16-(beta-cellobiosyloxy)-hexadecanoic acid, do not inhibit the growth of F. neoformans and Saccharomyces cerevisiae, while 16-(beta-cellobiosyloxy)-2,15-dihydroxyhexadecanoic acid inhibits the growth of both test cultures but at higher concentrations than cellobiose lipids of Cr. humicola and Ps. fusiformata. The amide of 16-(beta-cellobiosyloxy)-2,15-dihydroxyhexadecanoic acid possessed no fungicide activity. Thus, the structures of both the carbohydrate part and fatty acid aglycon moiety are important for the fungicidal activity of cellobiose lipids.

New filobasidiaceous yeasts found in the phylloplane of a fern.

Nitrate-positive strains of anamorphic yeasts representing the genus Cryptococcus were isolated on fern infusion agar from Athyrium filix-femina. Phylogenetic analyses of the D1/D2 domain of the LSU rRNA and of the ITS region placed them in Cylindricus clade in the Filobasidiales. Morphological and physiological characteristics, as well as mycocinotyping and molecular analysis, show a close affinity between strains. Subsequent comparative studies of new isolates revealed that they were not conspecific with any other known Cryptococcus species, and the cultures represented an undescribed species with two varieties, for which the names Cryptococcus filicatus var. filicatus (type strain VKM Y-2954 = CBS 10874) and Cryptococcus filicatus var. pelliculosus (type strain VKM Y-2955 = CBS 10875) are proposed.

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).

Mycocin production in Pseudozyma tsukubaensis.

Killer activity expressed at pH values ranging from 3.5 to 6.0 was found in the ustilaginaceous yeast-like species, Pseudozyma tsukubaensis. Its killer phenotype was incurable, and extrachromosomal genetic elements were not detected. The toxin excreted with a molecular mass above 15 kDa is fungicidal, resistant to proteolytic cleavage, thermolabile and active only against fungi within the Ustilaginomycetes (the orders Microstromatales and Ustilaginales).

Cryptococcus stepposus, a new filobasidiaceous yeast species found in the Prioksko-terrasny biosphere reserve in Russia.

Mycocinotyping of cryptococci from the Prioksko-terrasny reserve (Russia) has revealed three strains that have a unique mycocin-sensitivity profile. Sequencing results of the D1/D2 domain of the 26S rDNA and of the complete ITS region placed them in the Floriforme clade of the Filobasidiales lineage (Hymenomycetes). The three strains had identical sequences, which differed from those of known Filobasidium and Cryptococcus species. A novel species named Cryptococcus stepposus (type strain VKM Y-2918) is proposed to accommodate these isolates. Physiological characteristics distinguishing the novel species from other Cryptococcus species in the Floriforme clade are presented.

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.

Ustilagic acid secretion by Pseudozyma fusiformata strains.

Eight strains of Pseudozyma fusiformata were examined for antifungal activity. All of them had the same spectrum of action and were active against many species of yeasts, yeast-like and filamentous fungi. They secreted glycolipids, which were purified from the culture liquid by column and thin-layer chromatography. According to nuclear magnetic resonance and mass-spectroscopy experiments all strains produced ustilagic acid, a cellobioside-containing 2,15,16-trihydroxypalmitic acid as aglycon, 3-hydroxycaproic acid and acetic acid as O-acylic substituents.

Characterization of an antifungal glycolipid secreted by the yeast Sympodiomycopsis paphiopedili.

An antifungal glycolipid was purified from the culture liquid of the ustilaginomycetous yeast Sympodiomycopsis paphiopedili by column and thin-layer chromatography. According to nuclear magnetic resonance and mass-spectroscopy experiments it was a cellobioside containing 2,15,16-trihydroxypalmitic acid as an aglycon. The minimal effective concentrations leading to ATP leakage and growth inhibition were 45 and 160 microg ml(-1) for Cryptococcus terreus and Candida albicans, respectively.

Curvibasidium cygneicollum gen. nov., sp. nov. and Curvibasidium pallidicorallinum sp. nov., novel taxa in the Microbotryomycetidae (Urediniomycetes), and their relationship with Rhodotorula fujisanensis and Rhodotorula nothofagi.

Strains of Rhodotorula fujisanensis (Basidiomycota, Urediniomycetes, Microbotryomycetidae), including the type strain, are sexually compatible and produce clamped mycelium with teliospores. However, as teliospore germination had not been documented, the complete sexual cycle was not known. During the course of this work, the basidial stage of R. fujisanensis was characterized. In addition, mating studies employing isolates that were identified preliminarily as Rhodotorula nothofagi, a species that is related closely to R. fujisanensis, yielded mycelium with teliospores, which formed basidia and basidiospores. The new data were evaluated by using several criteria, including the available molecular phylogenetic framework for the Microbotryomycetidae. Curvibasidium gen. nov. is described here, to accommodate two teleomorphs: Curvibasidium cygneicollum sp. nov. (CBS 4551T), which is described as the sexual stage of R. fujisanensis, and Curvibasidium pallidicorallinum sp. nov. (CBS 9091T), which is related closely to R. nothofagi, but does not represent its sexual stage.

Cryptococcus paraflavus sp. nov. (Tremellales), isolated from steppe plants in Russia.

Three strains related to Cryptococcus flavus were isolated from plants collected in the Prioksko-terrasny biosphere reserve (Russia). Physiological characterization, mycocinotyping, sequencing of the D1/D2 domain of the 26S rDNA and the ITS region revealed their separate taxonomic position. The name Cryptococcus paraflavus is proposed to accommodate these isolates (type strain VKM Y-2923).

Cryptococcus festucosus sp. nov. a new hymenomycetous yeast in the Holtermannia clade.

Five yeast strains belonging to the genus Cryptococcus Vuillemin were isolated from steppe plants and turf collected in the Prioksko-terrasny biosphere reserve (Moscow region, Russia). Sequence analyses of the D1/D2 domains of the 26S rDNA and of the internal transcribed spacer region revealed that these yeast strains and strain CBS 8016 have almost identical sequences and belong to the Holtermannia clade of the Tremellomycetidae (Basidiomycota, Hymenomycetes). A novel species named Cryptococcus festucosus (type strain VKM Y-2930) is proposed to accommodate these strains. Physiological characteristics and mycocin sensitivity patterns distinguishing Cryptococcus festucosus from the other species of this clade are presented.

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.

Cryptococcus nemorosus sp. nov. and Cryptococcus perniciosus sp. nov., related to Papiliotrema Sampaio et al. (Tremellales).

Three mycocinogenic strains representing the genus Cryptococcus were isolated on glucuronate agar from plants and turf collected in the Prioksko-terrasny biosphere reserve (Russia). These isolates fit the standard description of Cryptococcus laurentii, but differ from its type strain in both their mycocin-sensitivity profiles and the killing patterns of their mycocins. Sequence analyses of the D1/D2 domain of the 26S rDNA and of the internal transcribed spacer region confirmed that these isolates represent two novel species, for which the names Cryptococcus nemorosus sp. nov. (type strain VKM Y-2906(T)) and Cryptococcus perniciosus sp. nov. (type strain VKM Y-2905(T)) are proposed. Morphological, physiological and biochemical characteristics, as well as mycocinotyping and molecular analysis, show a close affinity between these two novel anamorphic species and the teleomorphic species Papiliotrema bandonii (Tremellales).

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).

Double-stranded RNA viruses in a mycocinogenic strain of Cystofilobasidium infirmominiatum.

The viral particles (about 30 nm in diameter) that contain dsRNAs (2.0 and 6.3 kbp) encapsidated by a coat of protein were detected in a mycocin-secreting strain of Cystofilobasidium infirmominiatum isolated from plants in an oak forest (Moscow region). The mycocin with a molecular mass above 15 kDa is fungicidal (maximum activity at pH 4.5) and active mainly against some species of the Cystofilobasidiales and Filobasidiales ('Cryptococcus aerius' clade). Curing by incubation at elevated temperature resulted in the concomitant loss of dsRNAs and mycocinogenic activity, and cured derivatives became sensitive to the mycocin produced by the parent strain.

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.