Polyphasic taxonomy of a novel yeast isolated from antarctic environment; description of Cryptococcus victoriae sp. nov

A Vulvovaginal Yeast Infection Caused by Cryptococcus victoriae in Vietnam: A Rare Case Report

Cases of vulvovaginitis caused by Cryptococcus genus are exceedingly uncommon, with only a handful of instances having been described for this causative species. This report describes a rare case of vulvovaginitis suspected to be caused by Cryptococcus victoriae in a 58-year-old woman residing in an urban area of Hanoi city, Vietnam. The patient with a 10-year history of depression and type 2 diabetes mellitus was admitted to the hospital due to vulvar itching and vaginal discharge. Vaginal swabs confirmed the presence of a yeast infection by direct microscopic examination with 10% KOH and culture on CHROMagar Candida. The yeast was identified as C victoriae using genetic sequencing tools. The patient's treatment plan involved topical clotrimazole and a daily oral dose of 200 mg of itraconazole for 7 days. This comprehensive treatment approach resulted in the patient's full recovery. This is the first reported case of vulvovaginitis attributed to C victoriae in humans worldwide.

Tracking the fecal mycobiome through the lifespan of production pigs and a comparison to the feral pig

IMPORTANCE

This work provides evidence that early-life fungal community composition, or host genetics, influences long-term mycobiome composition. In addition, this work provides the first comparison of the feral pig mycobiome to the mycobiome of intensively raised pigs.

Vishniacozyma pseudocarnescens sp. nov., a new anamorphic tremellomycetous yeast species

Three strains belonging to the basidiomycetous yeast genus Vishniacozyma were isolated from marine water samples collected from intertidal zones in Liaoning province, northeast China. Phylogenetic analyses based on the sequences of the small subunit (SSU) ribosomal DNA (rDNA), the D1/D2 domain of the large subunit (LSU) ribosomal DNA (rDNA), the internal transcribed spacer region (ITS), the two subunits of DNA polymerase II (RPB1 and RPB2), the translation elongation factor 1-α (TEF1), and the mitochondrial gene cytochrome b (CYTB) showed that these strains together with 20 strains from various geographic and ecological origins from other regions of the world represent a novel species in the genus Vishniacozyma. We propose the name Vishniacozyma pseudocarnescens sp. nov. (holotype CGMCC 2.6457) for the new species, which differs phenotypically from its close relatives V. carnescens, V. tephrensis, and V. victoriae by its ability to grow at 30 °C and on 50 % (w/v) glucose-yeast extract agar.

Persisting Cryptococcus yeast species Vishniacozyma victoriae and Cryptococcus neoformans elicit unique airway inflammation in mice following repeated exposure

Background

Allergic airway disease (AAD) is a growing concern in industrialized nations and can be influenced by fungal exposures. Basidiomycota yeast species such as Cryptococcus neoformans are known to exacerbate allergic airway disease; however, recent indoor assessments have identified other Basidiomycota yeasts, including Vishniacozyma victoriae (syn. Cryptococcus victoriae), to be prevalent and potentially associated with asthma. Until now, the murine pulmonary immune response to repeated V. victoriae exposure was previously unexplored.

Objective

This study aimed to compare the immunological impact of repeated pulmonary exposure to Cryptococcus yeasts.

Methods

Mice were repeatedly exposed to an immunogenic dose of C. neoformans or V. victoriae via oropharyngeal aspiration. Bronchoalveolar lavage fluid (BALF) and lungs were collected to examine airway remodeling, inflammation, mucous production, cellular influx, and cytokine responses at 1 day and 21 days post final exposure. The responses to C. neoformans and V. victoriae were analyzed and compared.

Results

Following repeated exposure, both C. neoformans and V. victoriae cells were still detectable in the lungs 21 days post final exposure. Repeated C. neoformans exposure initiated myeloid and lymphoid cellular infiltration into the lung that worsened over time, as well as an IL-4 and IL-5 response compared to PBS-exposed controls. In contrast, repeated V. victoriae exposure induced a strong CD4+ T cell-driven lymphoid response that started to resolve by 21 days post final exposure.

Discussion

C. neoformans remained in the lungs and exacerbated the pulmonary immune responses as expected following repeated exposure. The persistence of V. victoriae in the lung and strong lymphoid response following repeated exposure were unexpected given its lack of reported involvement in AAD. Given the abundance in indoor environments and industrial utilization of V. victoriae, these results highlight the importance to investigate the impact of frequently detected fungal organisms on the pulmonary response following inhalational exposure. Moreover, it is important to continue to address the knowledge gap involving Basidiomycota yeasts and their impact on AAD.

Vishniacozyma victoriae (syn. Cryptococcus victoriae) in the homes of asthmatic and non-asthmatic children in New York City

BACKGROUND

Indoor environments contain a broad diversity of non-pathogenic Basidiomycota yeasts, but their role in exacerbating adverse health effects has remained unclear.

OBJECTIVE

To understand the role of Vishniacozyma victoriae exposure and its impact on human health.

METHODS

A qPCR assay was developed to detect and quantify an abundant indoor yeast species, Vishniacozyma victoriae (syn. Cryptococcus victoriae), from homes participating in the New York City Neighborhood Asthma and Allergy Study (NAAS). We evaluated the associations between V. victoriae, housing characteristics, and asthma relevant health endpoints.

RESULTS

V. victoriae was quantified in 236 of the 256 bedroom floor dust samples ranging from less than 300-45,918 cell equivalents/mg of dust. Higher concentrations of V. victoriae were significantly associated with carpeted bedroom floors (P = 0.044), mean specific humidity (P = 0.004), winter (P < 0.0001) and spring (P = 0.001) seasons, and the presence of dog (P = 0.010) and dog allergen Can f 1 (P = 0.027). V. victoriae concentrations were lower in homes of children with asthma vs. without asthma (P = 0.027), an association observed only among the non-seroatopic children.

Life on the Rocks: First Insights Into the Microbiota of the Threatened Aquatic Rheophyte Hanseniella heterophylla

Little is known about microbial communities of aquatic plants despite their crucial ecosystem function in aquatic ecosystems. Here, we analyzed the microbiota of an aquatic rheophyte, Hanseniella heterophylla, growing at three areas differing in their degree of anthropogenic disturbance in Thailand employing a metabarcoding approach. Our results show that diverse taxonomic and functional groups of microbes colonize H. heterophylla. Proteobacteria, Actinobacteria, Dothideomycetes, and Sordariomycetes form the backbone of the microbiota. Surprisingly, the beneficial microbes reported from plant microbiomes in terrestrial habitats, such as N-fixing bacteria and ectomycorrhizal fungi, were also frequently detected. We showed that biofilms for attachment of H. heterophylla plants to rocks may associate with diverse cyanobacteria (distributed in eight families, including Chroococcidiopsaceae, Coleofasciculaceae, Leptolyngbyaceae, Microcystaceae, Nostocaceae, Phormidiaceae, Synechococcaceae, and Xenococcaceae) and other rock biofilm-forming bacteria (mainly Acinetobacter, Pseudomonas, and Flavobacterium). We found distinct community compositions of both bacteria and fungi at high and low anthropogenic disturbance levels regardless of the study areas. In the highly disturbed area, we found strong enrichment of Gammaproteobacteria and Tremellomycetes coupled with significant decline of total bacterial OTU richness. Bacteria involved with sulfamethoxazole (antibiotic) degradation and human pathogenic fungi (Candida, Cryptococcus, Trichosporon, and Rhodotorula) were exclusively detected as indicator microorganisms in H. heterophylla microbiota growing in a highly disturbed area, which can pose a major threat to human health. We conclude that aquatic plant microbiota are sensitive to anthropogenic disturbance. Our results also unravel the potential use of this plant as biological indicators in remediation or treatment of such disturbed ecosystems.

Vishniacozyma alagoana sp. nov. a tremellomycetes yeast associated with plants from dry and rainfall tropical forests

Plants are important reservoirs of described and undescribed species of yeast. During a study of yeasts associated with bromeliads from the Northeast region of Brazil (collected in 2013-2017), analysis of the D1/D2 domain of the LSU rRNA and internal transcribed spacer (ITS) region identified eleven strains of yeasts as representing an unknown species of the genus Vishniacozyma. The species may have a diverse habitat in Brazil as a strain was collected from a flowering plant (Acanthaceae) in 1994. As a consequence, we propose Vishniacozyma alagoana sp. nov. as a member of the tremellomycetes yeasts (Agaricomycotina, Basidiomycota). Vishniacozyma alagoana sp. nov. was found in Atlantic Forest (a tropical rainforest) and the Caatinga (a seasonally dry tropical forest) associated with bromeliads in northeast and southeastern Brazil. The proposed novel species is related to Vishniacozyma taibaiensis and distinguished by eight nucleotide substitutions in the D1/D2 domain and seventeen in the ITS region. In addition, Vishniacozyma alagoana sp. nov. differs from V. taibaiensis by the ability to assimilate ribitol. The holotype is CBS 15966^T.

Antarctic Cryptoendolithic Fungal Communities Are Highly Adapted and Dominated by Lecanoromycetes and Dothideomycetes

Endolithic growth is one of the most spectacular microbial adaptations to extreme environmental constraints and the predominant life-form in the ice-free areas of Continental Antarctica. Although Antarctic endolithic microbial communities are known to host among the most resistant and extreme-adapted organisms, our knowledge on microbial diversity and composition in this peculiar niche is still limited. In this study, we investigated the diversity and structure of the fungal assemblage in the cryptoendolithic communities inhabiting sandstone using a meta-barcoding approach targeting the fungal Internal Transcribed Sequence region 1 (ITS1). Samples were collected from 14 sites in the Victoria Land, along an altitudinal gradient ranging from 1,000 to 3,300 m a.s.l. and from 29 to 96 km distance to coast. Our study revealed a clear dominance of a 'core' group of fungal taxa consistently present across all the samples, mainly composed of lichen-forming and Dothideomycetous fungi. Pareto-Lorenz curves indicated a very high degree of specialization (F0 approximately 95%), suggesting these communities are highly adapted but have limited ability to recover after perturbations. Overall, both fungal community biodiversity and composition did not show any correlation with the considered abiotic parameters, potentially due to strong fluctuations of environmental conditions at local scales.

Community Profiling of Fusarium in Combination with Other Plant-Associated Fungi in Different Crop Species Using SMRT Sequencing

Fusarium head blight, caused by fungi from the genus Fusarium, is one of the most harmful cereal diseases, resulting not only in severe yield losses but also in mycotoxin contaminated and health-threatening grains. Fusarium head blight is caused by a diverse set of species that have different host ranges, mycotoxin profiles and responses to agricultural practices. Thus, understanding the composition of Fusarium communities in the field is crucial for estimating their impact and also for the development of effective control measures. Up to now, most molecular tools that monitor Fusarium communities on plants are limited to certain species and do not distinguish other plant associated fungi. To close these gaps, we developed a sequencing-based community profiling methodology for crop-associated fungi with a focus on the genus Fusarium. By analyzing a 1600 bp long amplicon spanning the highly variable segments ITS and D1-D3 of the ribosomal operon by PacBio SMRT sequencing, we were able to robustly quantify Fusarium down to species level through clustering against reference sequences. The newly developed methodology was successfully validated in mock communities and provided similar results as the culture-based assessment of Fusarium communities by seed health tests in grain samples from different crop species. Finally, we exemplified the newly developed methodology in a field experiment with a wheat-maize crop sequence under different cover crop and tillage regimes. We analyzed wheat straw residues, cover crop shoots and maize grains and we could reveal that the cover crop hairy vetch (Vicia villosa) acts as a potent alternative host for Fusarium (OTU F.ave/tri) showing an eightfold higher relative abundance compared with other cover crop treatments. Moreover, as the newly developed methodology also allows to trace other crop-associated fungi, we found that vetch and green fallow hosted further fungal plant pathogens including Zymoseptoria tritici. Thus, besides their beneficial traits, cover crops can also entail phytopathological risks by acting as alternative hosts for Fusarium and other noxious plant pathogens. The newly developed sequencing based methodology is a powerful diagnostic tool to trace Fusarium in combination with other fungi associated to different crop species.

Bioprospection of cold-adapted yeasts with biotechnological potential from Antarctica

The aim of this study was to investigate the ability to produce extracellular hydrolytic enzymes at low temperature of yeasts isolated from 25 de Mayo island, Antarctica, and to identify those exhibiting one or more of the evaluated enzymatic activities. A total of 105 yeast isolates were obtained from different samples and 66 were identified. They belonged to 12 basidiomycetous and four ascomycetous genera. Most of the isolates were ascribed to the genera Cryptococcus, Mrakia, Cystobasidium, Rhodotorula, Gueomyces, Phenoliferia, Leucosporidium, and Pichia. Results from enzymes production at low temperatures revealed that the Antarctic environment contains metabolically diverse cultivable yeasts, which represent potential tools for biotechnological applications. While most the isolates proved to produce 2-4 of the investigated exoenzymes, two of them evidenced the six evaluated enzymatic activities: Pichia caribbica and Guehomyces pullulans, which were characterized as psycrotolerant and psycrophilic, respectively. In addition, P. caribbica could assimilate several n-alkanes and diesel fuel. The enzyme production profile and hydrocarbons assimilation capacity, combined with its high level of biomass production and the extended exponential growth phase make P. caribbica a promising tool for cold environments biotechnological purposes in the field of cold-enzymes production and oil spills bioremediation as well.

Microbial communities associated with Antarctic snow pack and their biogeochemical implications

Snow ecosystems represent a large part of the Earth's biosphere and harbour diverse microbial communities. Despite our increased knowledge of snow microbial communities, the question remains as to their functional potential, particularly with respect to their role in adapting to and modifying the specific snow environment. In this work, we investigated the diversity and functional capabilities of microorganisms from 3 regions of East Antarctica, with respect to compounds present in snow and tested whether their functional signature reflected the snow environment. A diverse assemblage of bacteria (Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes, Deinococcus-Thermus, Planctomycetes, Verrucomicrobia), archaea (Euryarchaeota), and eukarya (Basidiomycota, Ascomycota, Cryptomycota and Rhizaria) were detected through culture-dependent and -independent methods. Although microbial communities observed in the three snow samples were distinctly different, all isolates tested produced one or more of the following enzymes: lipase, protease, amylase, β-galactosidase, cellulase, and/or lignin modifying enzyme. This indicates that the snow pack microbes have the capacity to degrade organic compounds found in Antarctic snow (proteins, lipids, carbohydrates, lignin), thus highlighting their potential to be involved in snow chemistry.

Occurrence of Fungal DNA Contamination in PCR Reagents: Approaches to Control and Decontamination

Nucleic acid amplification techniques permitting sensitive and rapid screening in patients at risk for invasive fungal infections are an important addition to conventional fungal diagnostic methods. However, contamination with fungal DNA may be a serious threat to the validity of fungal amplification-based assays. Besides rigorous handling procedures to avoid false-positive test results from exogenous sources, we have implemented protocols for comprehensive assessment of fungal contamination in all materials involved in the analytical process. Traces of fungal DNA were found in different commercially available PCR reagents, including lyophilized primers, TaqMan probes, and master mix solutions. These contaminants resulted in a considerable rate of false-positive tests in panfungal real-time PCR analysis. To address this problem, we have established a decontamination protocol based on the activity of a double-strand specific DNase. Using this approach, we have significantly reduced the frequency of false-positive test results attributable to contaminated reagents. On the basis of our findings, we strongly recommend routine monitoring of all reagents used in fungal PCR assays for the presence of relevant contaminants. As long as fungal-grade reagents are not readily available, pretreatment methods facilitating elimination of fungal DNA are critical for reducing the risk of false-positive results in highly sensitive molecular fungal detection assays.

Small circular single stranded DNA viral genomes in unexplained cases of human encephalitis, diarrhea, and in untreated sewage

Viruses with small circular ssDNA genomes encoding a replication initiator protein can infect a wide range of eukaryotic organisms ranging from mammals to fungi. The genomes of two such viruses, a cyclovirus (CyCV-SL) and gemycircularvirus (GemyCV-SL) were detected by deep sequencing of the cerebrospinal fluids of Sri Lankan patients with unexplained encephalitis. One and three out of 201 CSF samples (1.5%) from unexplained encephalitis patients tested by PCR were CyCV-SL and GemyCV-SL DNA positive respectively. Nucleotide similarity searches of pre-existing metagenomics datasets revealed closely related genomes in feces from unexplained cases of diarrhea from Nicaragua and Brazil and in untreated sewage from Nepal. Whether the tropism of the cyclovirus and gemycircularvirus reported here include humans or other cellular sources in or on the human body remains to be determined.

Cold adaptation of fungi obtained from soil and lake sediment in the Skarvsnes ice-free area, Antarctica

A total of 71 isolates were collected from lake sediment and soil surrounding lakes in the Skarvsnes area, Antarctica. Based on ITS region sequence similarity, these isolates were classified to 10 genera. Twenty-three isolates were categorized as ascomycetous fungi from five genera (Embellisia, Phoma, Geomyces, Tetracladium or Thelebolus) and 48 isolates were categorized as basidiomycetous fungi in five genera (Mrakia, Cryptococcus, Dioszegia, Rhodotorula or Leucosporidium). Thirty-five percent of culturable fungi were of the genus Mrakia. Eighteen isolates from eight genera were selected and tested for both antifreeze activity and capacity for growth under temperatures ranging from -1 to 25 °C. Rhodotorula sp. NHT-2 possessed a high degree of sequence homology with R. gracialis, while Leucosporidium sp. BSS-1 possessed a high degree of sequence homology with Leu. antarcticum (Glaciozyma antarctica), and these two isolates demonstrated antifreeze activity. All isolates examined were capable of growth at -1 °C. Mrakia spp., while capable of growth at -1 °C, did not demonstrate any antifreeze activity and exhibited only limited secretion of extracellular polysaccharides. Species of the genus Mrakia possessed high amounts of unsaturated fatty acids, suggesting that members of this genus have adapted to cold environments by increasing their membrane fluidity.

Influence of abiotic variables on culturable yeast diversity in two distinct Alpine glaciers

The influence of some abiotic variables (pH, dry weight, organic carbon, nitrogen and phosphorous) on culturable yeast diversity in two distinct, but adjacent Alpine glaciers (Glacier du Géant, France, and Miage Glacier, Italy) was investigated. In all, 682 yeast strains were isolated and identified by D1/D2 and ITS sequencing as belonging to species of the genera Aureobasidium, Candida, Bulleromyces, Cryptococcus, Cystofilobasidium, Dioszegia, Guehomyces, Holtermanniella, Leucosporidiella, Mrakia, Mrakiella, Rhodotorula, Sporidiobolus, Sporobolomyces and Udenyomyces. Overall, the most represented genera were Cryptococcus (55% of isolates), Rhodotorula (17%) and Mrakia (10%). About 10% of strains, presumably belonging to new species (yet to be described), were preliminarily identified at the genus level. Principal component analysis (PCA) revealed that organic carbon, nitrogen and phosphorous are apparently mostly related to culturable yeast abundance and diversity. In this context, the hypothesis that the frequency of isolation of certain species may be correlated with some organic nutrients (with special emphasis for phosphorous) is discussed.

Cryptococcus species (Tremellales) from glacial biomes in the southern (Patagonia) and northern (Svalbard) hemispheres

Cryptococcus species (Basidiomycota) were isolated as the predominant yeast from glacial biomes of both Patagonia (Argentina) and the Svalbard archipelago (Norway). For a selected group of Cryptococcus belonging to Tremellales, assimilative profile, production of extracellular hydrolytic enzymes and ribosomal DNA internal transcribed spacer and large subunit (D1/D2) sequences were analysed. Cryptococcus victoriae, which was originally described from Antarctica, was the most frequently found species at both locations. High variability within the species was observed and described at the genotypic and phenotypic levels, two newly described species were found in both Patagonia and Svalbard: Cryptococcus fonsecae and Cryptococcus psychrotolerans. Two other new species were found only in Patagonia: Cryptococcus frias and Cryptococcus tronadorensis. Three additional new taxa were found, but they are not named as they were only represented by single isolates.

Psychrophilic yeasts from worldwide glacial habitats: diversity, adaptation strategies and biotechnological potential

Glacial habitats (cryosphere) include some of the largest unexplored and extreme biospheres on Earth. These habitats harbor a wide diversity of psychrophilic prokaryotic and eukaryotic microorganisms. These highly specialized microorganisms have developed adaptation strategies to overcome the direct and indirect life-endangering influence of low temperatures. For many years Antarctica has been the geographic area preferred by microbiologists for studying the diversity of psychrophilic microorganisms (including yeasts). However, there have been an increasing number of studies on psychrophilic yeasts sharing the non-Antarctic cryosphere. The present paper provides an overview of the distribution and adaptation strategies of psychrophilic yeasts worldwide. Attention is also focused on their biotechnological potential, especially on their exploitation as a source of cold-active enzymes and for bioremediation purposes.

Cryptococcus foliicola sp. nov. and Cryptococcus taibaiensis sp. nov., novel basidiomycetous yeast species from plant leaves

A molecular taxonomic investigation performed on basidiomycetous yeast strains isolated from plant leaves collected in two areas of China revealed two novel species, Cryptococcus foliicola sp. nov. (type strain HS 23.3(T) = AS 2.2471(T) = CBS 9920(T)) and Cryptococcus taibaiensis sp. nov. (type strain ST 7.9(T) = AS 2.2444(T) = CBS 9919(T)), among the non ballistoconidium-forming strains producing cream-colored colonies. These new species differed markedly from closely related species in the internal transcribed spacer (ITS) and 26S rRNA D1/D2 region sequences. They clustered in a strongly supported clade represented by Cryptococcus victoriae in the Tremellales group in the phylogenetic trees drawn from ITS and D1/D2 sequences.

Relative incidence of ascomycetous yeasts in arctic coastal environments

Previous studies of fungi in polar environments have revealed a prevalence of basidiomycetous yeasts in soil and in subglacial environments of polythermal glaciers. Ascomycetous yeasts have rarely been reported from extremely cold natural environments, even though they are known contaminants of frozen foods. Using media with low water activity, we have isolated various yeast species from the subglacial ice of four glaciers from the coastal Arctic environment of Kongsfjorden, Spitzbergen, including Debaryomyces hansenii and Pichia guillermondii, with counts reaching 10(4) CFU L(-1). Together with the basidiomycetes Cryptococcus liquefaciens and Rhodotorula mucilaginosa, these yeasts represent the stable core of the subglacial yeast communities. Other glacial ascomycetous species isolated included Candida parapsilosis and a putative new species that resembles Candida pseudorugosa. The archiascomycete Protomyces inouyei has seldom been detected anywhere in the world but was here recovered from ice in a glacier cave. The glacier meltwater contained only D. hansenii, whereas the seawater contained D. hansenii, Debaryomyces maramus, Pichia guilliermondii, what appears to represent a novel species resembling Candida galli and Metschnikowia bicuspidata. Only P. guilliermondii was isolated from sea ice, while snow/ice in the fjord tidal zone included C. parapsilosis, D. hansenii, P. guilliermondii and Metschnikowia zobellii. All of these isolated strains were characterized as psychrotolerant and xero/halotolerant, with the exception of P. inouyei.

Characterization of outer membrane vesicles released by the psychrotolerant bacterium Pseudoalteromonas antarctica NF3

Pseudoalteromonas antarctica NF3 is an Antarctic psychrotolerant Gram-negative bacterium that accumulates large amounts of an extracellular polymeric substance (EPS) with high protein content. Transmission electron microscopy analysis after high-pressure freezing and freeze substitution (HPF-FS) shows that the EPS is composed of a capsular polymer and large numbers of outer membrane vesicles (OMVs). These vesicles are bilayered structures and predominantly spherical in shape, with an average diameter of 25-70 nm, which is similar to what has been observed in OMVs from other Gram-negative bacteria. Analyses of lipopolysaccharide (LPS), phospholipids and protein profiles of OMVs are consistent with the bacterial outer membrane origin of these vesicles. In an initial attempt to elucidate the functions of OMVs proteins, we conducted a proteomic analysis on 1D SDS-PAGE bands. Those proteins putatively identified match with outer membrane proteins and proteins related to nutrient processing and transport in Gram-negative bacteria. This approach suggests that OMVs present in the EPS from P. antarctica NF3, might function to deliver proteins to the external media, and therefore play an important role in the survival of the bacterium in the extreme Antarctic environment.

Ultrastructural analysis of the extracellular matter secreted by the psychrotolerant bacterium Pseudoalteromonas antarctica NF3

The psychrotolerant strain Pseudoalteromonas antarctica NF3, a Gram-negative bacterium isolated from muddy soil samples of Antarctica, secretes large amounts of a mucoid exopolymer with a high protein content. It has self-assembly properties and capacity to coat and protect liposomes against surfactants. We examined the ultrastructure of P. antarctica and the extracellular matter it secretes by transmission electron microscopy (TEM) after high-pressure freezing, freeze substitution (HPF-FS), and Epon embedding, and compared this with information obtained by conventional methods. The improvements brought about by HPF-FS to the ultrastructural preservation of the extracellular matter allowed us to establish for the first time, in P. antarctica NF3, the presence of two components: a large amount of cell-derived outer membrane vesicles containing proteins and a capsular polymer around the cells.

Endangered Antarctic Environments

The Antarctic continent harbors a range of specialized and sometimes highly localized microbial biotopes. These include biotopes associated with desiccated mineral soils, rich ornithogenic soils, glacial and sea ice, ice-covered lakes, translucent rocks, and geothermally heated soils. All are characterized by the imposition of one or more environmental extremes (including low temperature, wide temperature fluctuations, desiccation, hypersalinity, high periodic radiation fluxes, and low nutrient status). As our understanding of the true microbial diversity in these biotopes expands from the application of molecular phylogenetic methods, we come closer to the point where we can make an accurate assessment of the impacts of environmental change, human intervention, and other natural and unnatural impositions. At present, it is possible to make reasonable predictions about the physical effects of local climate change, but only general predictions on possible changes in microbial community structure. The consequences of some direct human impacts, such as physical disruption of microbial soil communities, are obvious if not yet quantitated. Others, such as the dissemination of nonindigenous microorganisms into indigenous microbial communities, are not yet understood.

Diversity of and yeasts (Basidiomycota) inhabiting arbuscular mycorrhizal roots or spores

The genera Cryptococcus and Dioszegia contain basidiomycetous yeasts found in a wide range of habitats. Primers to amplify the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA (nrDNA) of arbuscular mycorrhizal fungi (AMF) also allow detecting members of this yeast group. Here we report the results of a sequence analysis using maximum parsimony on a set of 50 ITS sequences of yeasts associated with AMF structures (roots of 26 plant species, AM spores) from six field sites in Central Germany. Among 10 separated taxa, respectively five in the Tremellales and two in the Filobasidiales had unknown sequences. Therefore it was not possible to assign these sequences to any known species. The study indicates that exploring the diversity of Cryptococcus and Dioszegia in soil habitats with molecular methods might enlarge the actually estimated biodiversity of the group.

Three new combinations from the Cryptococcus laurentii complex: Cryptococcus aureus, Cryptococcus carnescens and Cryptococcus peneaus

Fifteen strains of the Cryptococcus laurentii complex were reclassified based on sequence analyses of 18S rDNA, the D1/D2 region of the 26S rDNA and the internal transcribed spacer regions, as well as physiological and biochemical properties. The strains were divided into phylogenetic groups I and II. The type strain of C. laurentii (CBS 139T=ATCC 18803T=JCM 9066T=MUCL 30398T=NRRL Y-2536T) was in phylogenetic group I. Phylogenetic group II, which was phylogenetically distant from phylogenetic group I, clustered with Cryptococcus dimennae and Bullera globispora. In phylogenetic group I, the type strain of Torula aurea (CBS 318T=ATCC 32063T=IFO 0372T=NRRL Y-1582T) appeared to be a separate species from C. laurentii, and the designation Cryptococcus aureus comb. nov. is proposed for Torula aurea. Cryptococcus flavescens (formerly Torula flavescens, type strain CBS 942T=ATCC 10668T=DBVPG 6007T=MUCL 30414T) was treated as a synonym of C. laurentii; however, this is a distinct species. The type strains of Torulopsis carnescens (CBS 973T=ATCC 32064T=MUCL 30641T=NRRL Y-1503T), Rhodotorula peneaus (CBS 2409T=ATCC 13546T=MUCL 30643T=NRRL Y-2005T) and Cryptococcus victoriae belonged to phylogenetic group II. Two new combinations, Cryptococcus carnescens comb. nov. (type strain CBS 973T=ATCC 32064T=MUCL 30641T=NRRL Y-1503T) and Cryptococcus peneaus comb. nov. (type strain CBS 2409T=ATCC 13546T=MUCL 30643T=NRRL Y-2005T), are proposed from this group.

Cryptococcus tephrensis, sp.nov., and Cryptococcus heimaeyensis, sp.nov.; new anamorphic basidiomycetous yeast species from Iceland

Two new species from Iceland are described on the basis of physiological profiles and sequence data from the D2 region of LSU rDNA: Cryptococcus tephrensis (type ICE99-IToM Y5, ATCC MYA-1765, CBS 8935, GenBank AF317208) and Cryptococcus heimaeyensis (type ICE99-IToM Y8, ATCC MYA-1759, CBS 8933, GenBank AF370717). The two new species are identifiable from sequence data and can be distinguished from their closest relative, Cryptococcus victoriae, by their higher maximum temperatures for growth, failure to utilize nitrate as sole nitrogen source, and utilization of cadaverine and ethylamine as sole nitrogen sources. Cryptococcus tephrensis is distinguishable from C. heimaeyensis by failure to grow on saccharate as sole source of carbon and energy.