Biodiversity of cold-adapted yeasts from glacial meltwater rivers in Patagonia, Argentina.

The occurrence of culturable yeasts in glacial meltwater from the Frías, Castaño Overo and Río Manso glaciers, located on Mount Tronador in the Nahuel Huapi National Park (Northwestern Patagonia, Argentina) is presented. Subsurface water samples were filtered for colony counting and yeast isolation. The total yeast count ranged between 6 and 360 CFU L(-1). Physiologic and molecular methods were employed to identify 86 yeast isolates. In agreement with yeast diversity data from studies for Antarctic and Alpine glaciers, the genera Cryptococcus, Leucosporidiella, Dioszegia, Rhodotorula, Rhodosporidium, Mrakia, Sporobolomyces, Udeniomyces and Candida were found. Cryptococcus and Leucosporidiella accounted for 50% and 20% of the total number of strains, respectively. Among 21 identified yeast species, Cryptococcus sp. 1 and Leucosporidiella fragaria were the most frequent. The typically psychrophilic Mrakia yeast strain and three new yeast species, yet to be described, were also isolated. All yeast strains were able to grow at 5, 10, and 15 degrees C. Among yeast strains expressing extracellular enzymatic activity, higher proteolytic and lipolytic activities were obtained at 4 degrees C than at 20 degrees C.

Yeasts from glacial ice of Patagonian Andes, Argentina.

Glacial ice and snow are known habitats for cold-adapted microorganisms. Research on cold-adapted yeast biodiversity from Perito Moreno and Mount Tronador glaciers (Patagonia, Argentina), and production of extracellular enzymatic activity at low temperatures (5 and 18 °C), was performed and described in this study. Ninety percent (90%) of the isolates were basidiomycetous; 16 genera and 29 species were identified. Twenty-five percent (25%) of total isolates corresponded to psychrophilic yeasts, whereas 75% were psychrotolerant yeasts. Eighty-five percent (85%) of all isolates had at least one enzymatic activity. Multiple correspondence analysis and cluster classification revealed a relationship between certain genera and some enzymatic activities. Cold-adapted yeast isolates were able to hydrolyze natural compounds (casein, lipids, starch, pectin, and carboxymethylcellulose) at low temperatures, suggesting a significant ecological role of these organisms as organic matter decomposers and nutrient cyclers. These yeasts are especially relevant for metabolic and ecological studies, as well as for yeast-based biotechnological process at low temperatures.

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.

Wickerhamomyces patagonicus sp. nov., an ascomycetous yeast species from Patagonia, Argentina.

Eight strains of a novel yeast species were isolated from tree saps of 'Coihue' (Nothofagus dombeyi, Nothofagaceae) and glacial meltwater (Castaño Overo River) in the Nahuel Huapi National Park, Patagonia, Argentina. The sequences of the D1/D2 domains of the large subunit of the rRNA gene showed that this novel yeast species belongs to the Wickerhamomyces genus (Order Saccharomycetales, Family Wickerhamomycetaceae). The closest related species were Candida ponderosae and Wickerhamomyces chambardii. Wickerhamomyces patagonicus sp. nov. is proposed to accommodate these novel strains, with the type strain CRUB 1724(T) (=CBS 11398(T) =JCM 16381(T)).

Cryptococcus spencermartinsiae sp. nov., a basidiomycetous yeast isolated from glacial waters and apple fruits.

Seven strains representing a novel yeast species belonging to the genus Cryptococcus were isolated from different substrates from Patagonia, Argentina, and The Netherlands. Three strains were isolated from a meltwater river draining from the Frias glacier at Mount Tronador situated in Nahuel Huapi National Park (Patagonia) and four were isolated from apple surfaces in Randwijk, The Netherlands. Analysis of the D1/D2 large-subunit rRNA gene and ITS region sequences indicated that these strains represent a single species that is distinct from other species of the Tremellales clade. The name Cryptococcus spencermartinsiae sp. nov. is proposed to accommodate these strains. The type strain is CRUB 1230(T) (=CBS 10760(T) =DBVPG 8010(T)).

Extracellular enzymatic activities of basidiomycetous yeasts isolated from glacial and subglacial waters of northwest Patagonia (Argentina).

As part of a project aimed at the selection of cold-adapted yeasts expressing biotechnologically interesting features, the extracellular enzymatic activity (EEA) of basidiomycetous yeasts isolated from glacial and subglacial waters of northwest Patagonia (Argentina) was investigated. Ninety-one basidiomycetous yeasts (belonging to the genera Cryptococcus, Leucosporidiella, Dioszegia, Mrakia, Rhodotorula, Rhodosporidium, Sporobolomyces, Sporidiobolus, Cystofilobasidium, and Udeniomyces) were screened for extracellular amylolytic, proteolytic, lipolytic, esterasic, pectinolytic, chitinolytic, and cellulolytic activities. Over 15% of the strains exhibited three or more different EEAs at 4 degrees C and more than 63% had at least two EEAs at the same temperature. No chitinolytic or cellulolytic activities were detected at 4 and 20 degrees C. Cell-free supernatants exhibited significantly higher (P < 0.01) protease and lipase activities at < or = 10 degrees C, or even at 4 degrees C. In light of these findings, cold environments of Patagonia (Argentina) may be considered a potential source of cold-adapted yeasts producing industrially relevant cold-active enzymes.

Molecular characterization of carotenogenic yeasts from aquatic environments in Patagonia, Argentina.

Fifteen aquatic environments (lakes, lagoons and rivers) of glacial origin in the northern Andean Patagonia (Argentina) were surveyed for the occurrence of red yeasts. Subsurface water samples were filtered and used for colony counting and yeast isolation. A preliminary quantitative analysis indicated that total yeast counts ranged between 0 and 250 cells l(-1). A polyphasic approach including physiological and molecular methods was used for the identification of 64 carotenogenic yeast strains. The molecular characterisation of the isolates was based on the mini/microsatellite-primed PCR technique (MSP-PCR) employing the (GTG)5 and the M13 primers. Comparison of representative fingerprints of each group with those of the type strains of pigmented yeasts allowed the expeditious identification of 87.5% isolates. The sequence analysis of the D1/D2 domains of the 26S rDNA was employed to confirm identifications and in the characterization of the unidentified MSP-PCR groups. Teleomorphic yeast species were detected by performing sexual compatibility assays. The isolates corresponded to 6 genera and 15 yeast species, including four new yeast species of the genera Cryptococcus (1), Rhodotorula (1) and Sporobolomyces (2). Rhodotorula mucilaginosa was found in the majority of the samples and represented ca. 50% of the total number of isolates. However, this yeast was not detected in aquatic environments with very low anthropic influence. Other frequent yeast isolates were teleomorphic yeast species of Rhodosporidium babjevae, R. kratochvilovae and Sporidiobolus salmonicolor. This study represents the first report on red yeast occurrence and biodiversity in northwestern Patagonia.

Aflatoxin Production in Soybean Varieties Grown in Argentina.

Natural occurrence of aflatoxin contamination on soybeans was investigated. Thirty four samples from the 1986 crop (5.8% positive samples) and 60 samples harvested in 1987 (11.6% positive samples) were analyzed. Aflatoxin levels in positive samples were low, ranging from traces to 36 µg/kg of total aflatoxins. Aflatoxin production by three isolates of Aspergillus flavus / A. parasiticus in 13 soybean varieties has been studied. Soybeans used for cultures were surface disinfected. Levels of aflatoxin formed were dependent both on the toxicogenic potential of the fungal isolate and on the variety of soybeans. Under laboratory conditions variety Prata was the most susceptible and variety SRF the less susceptible to aflatoxin formation.

Constitutive and UV-inducible synthesis of photoprotective compounds (carotenoids and mycosporines) by freshwater yeasts.

Twelve yeasts isolated from lakes of Northwestern Patagonia, Argentina, belonging to eight genera (Sporobolomyces, Sporidiobolus, Rhodotorula, Rhodosporidium, Cystofilobasidium, Cryptococcus, Torulaspora, and Candida) were analysed for their ability to produce photoprotective compounds. For this purpose, three laboratory experiments were performed to study the effect of photosynthetically active radiation (PAR) and PAR in combination with UV radiation (PAR + UVR) on the production of carotenoids and mycosporines. The synthesis of carotenoid compounds was clearly stimulated in six out of nine red yeast strains tested upon exposure to PAR or PAR + UVR; however, the latter conditions produced a stronger response than PAR alone. The increase in carotenoids in the red strains under PAR + UVR irradiation showed a negative exponential relationship with their basal carotenoid content, suggesting that cells with higher constitutive levels of carotenoids are less responsive to induction by PAR + UVR. Three red yeasts, Rhodotorula minuta, Rh. pinicola, and Rhodotorula sp., and the colourless Cryptococcus laurentii produced a UV-absorbing compound when exposed to PAR or PAR + UVR. This compound showed an absorption maximum at 309-310 nm and was identified as mycosporine-glutaminol-glucoside (myc-glu-glu). In these strains, exposure to PAR or PAR + UVR resulted in elevated concentrations of both carotenoids and myc-glu-glu. This is the first report on the production of mycosporines by yeasts. All strains that developed under PAR + UVR were able to synthesise carotenoids either constitutively or in response to PAR exposure, and a few of them also produced myc-glu-glu when exposed to PAR. Collectively, our results suggest that the presence of carotenoids, either alone or in combination with mycosporines, are required for sustaining growth under exposure to PAR + UVR in the freshwater yeast strains studied.