Occurrence and Diversity of Yeasts in the Mid-Atlantic Ridge Hydrothermal Fields Near the Azores Archipelago

The yeast community associated with deep-sea hydrothermal systems of the Mid-Atlantic Rift was surveyed for the first time. This study relied on a culture-based approach using two different growth media: a conventional culture medium for yeasts supplemented with sea salts (MYPss) and the same medium additionally supplemented with sulfur (MYPssS). For the evaluation of species diversity, a molecular approach involving minisatellite-primed polymerase chain reaction (MSP-PCR) strain typing and sequence analysis of the D1/D2 domains of the 26S rDNA was followed. In the seven water samples that were studied, the number of colony-forming units per liter (cfu/L) ranged from 0 to 5940. The nonpigmented yeasts were much more abundant than the pink-pigmented ones. This disproportion was not observed in studies of other marine systems and may be due to the unique conditions of hydrothermal vents, characterized by a rich animal and microbial diversity and therefore by the availability of organic compounds utilizable by yeasts. Higher counts of nonpigmented yeast were obtained using MYPss, whereas for pink yeasts, higher counts were obtained using MYPssS. Moreover, among pink yeasts, some of the MSP-PCR classes obtained were composed of isolates obtained only on MYPssS, which might be an indication that these isolates are adapted to the ecosystems of the hydrothermal vents. Twelve phylotypes belonged to the Ascomycota and seven phylotypes belonged to the Basidiomycota. The nonpigmented yeasts were identified as Candida atlantica, C. atmosphaerica, C. lodderae, C. parapsilosis, Exophiala dermatitidis, Pichia guilliermondii, and Trichosporon dermatis, whereas the pigmented yeasts were identified as Rhodosporidium diobovatum, R. sphaerocarpum, R. toruloides, and Rhodotorula mucilaginosa. Some of the yeasts that were found belong to phylogenetic groups that include species reported from other marine environments, and eight phylotypes represent undescribed species. The new phylotypes found at Mid-Atlantic Ridge hydrothermal fields represent 33% of the total number of yeast taxa that were found.     

Search for Yeast Producers of Brassylic and Sebacic Fatty Acids

Yeast cultures belonging to the genera Candida, Torulopsis, Saccharomyces, Debaryomyces, Hansenula, Pichia, and Yarrowia, capable of synthesizing brassylic and sebacic fatty acids, were screened. Overall about 200 cultures grown in media containing decane or tridecane as a sole source of carbon were tested. On the medium with tridecane, yeasts synthesized insignificant amounts of brassylic acid. Sebacic acid was produced more intensively in the medium with n-decane. The culture Candida tropicalis, displaying the highest ability to synthesize sebacic acid, was selected.     

Evaluation of fungal and yeast diversity in Slovakian wine-related microbial communities

Since the yeast flora of Slovakian enology has not previously been investigated by culture-independent methods, this approach was applied to two most common cultivars Frankovka (red wine) and Veltlin (white wine), and complemented by cultivation. Model samples included grapes, initial must, middle fermenting must and must in the end-fermentation phase. The cultured isolates were characterized by length polymorphism of rDNA spacer two region using fluorescence PCR and capillary electrophoresis (f-ITS PCR), and some were identified by sequencing. The microbial DNA extracted directly from the samples without cultivation was analysed by f-ITS PCR, amplicons were cloned and sequenced. The use of universal fungal primers led to detection of both yeasts and filamentous fungi. The amplicon of highest intensity and present in all the samples corresponded to Hanseniaspora uvarum. Other species demonstrated by both approaches included Saccharomyces sp., Metschnikowia pulcherrima or M. chrysoperlae, Candida zemplinina, Cladosporium cladosporioides, Botryotinia fuckeliana, Pichia anomala, Candida railenensis, Cryptococcus magnus, Metschnikowia viticola or Candida kofuensis, Pichia kluyveri or Pichia fermentas, Pichia membranifaciens, Aureobasidium pullulans, Alternaria alternata, Erysiphe necator, Rhodotorula glutinis, Issatchenkia terricola and Debaryomyces hansenii. Endemism of Slovakian enological yeasts was suggested on the level of minor genetic variations of the known species and probably not accounting for novel species. The prevalence of H. uvarum over Saccharomyces sp. in the samples was indicated. This is the first culture-independent study of Slovakian enology and the first time f-ITS PCR profiling was used on wine-related microbial communities.     

Yeasts from Tierra Del Fuego Province (Argentina): Biodiversity,Characterization and Bioprospection of Hydrolytic Enzymes

Abstract

Antarctic and sub-Antarctic regions are – with Polar Regions, mountains and the deep sea – the most extreme environments on Earth because of its low temperatures, dryness, high incidence of solar radiation and low nutrient availability. Nevertheless, microorganisms have successfully colonized these regions. In this study, culturable yeasts from soil samples collected from two different locations, a human-impacted area (Encerrada Bay) and a largely pristine and naturally vegetated area near Lago Escondido city (54°39′0″S, 67°46′48″W) from Tierra del Fuego province, Argentina were identified and characterized at different levels. They were characterized and classified as psychrotolerant and were considered as moderately halotolerant because of their ability to grow in the presence of 1.5?M of NaCl. Yeasts from phylum Ascomycota were affiliated to five genera: Candida, Yarrowia, Debaryomyces, Nadsonia, and Wickerhamiella, whereas from phylum Basidiomycota yeasts were affiliated to six genera: Naganishia, Rhodotorula, Leucosporidum, Tausonia, Cystofilobasidium, and Apiotrichum. Most of the yeasts demonstrated at least one extracellular enzymatic activity (mainly β-glucosidase, esterase, and protease activities). One isolate identified as Tausonia pullulans showed significant activity across the eight enzyme types tested. In light of these findings, Tierra del Fuego province could be considered as a cold environment with a potential source of cold-adapted yeasts producing industrially relevant cold-active enzymes.     

Butyrate Activation in Rhodopseudomonas palustris No. 82

Halotolerant killer yeasts which showed killer activity in the presence of NaCl were isolated from fermented foods, such as miso, soy sauce and salted vegetables, and identified as Debaryomyces hansenii, Hansenula anomala, Candida naeodendra and Pichia farinosa. The killer strains of C. naeodendra and P. farinosa were found here for the first time. Seventy-six percent of the salted vegetable samples contained killer yeasts, mainly D. hansenii. On the other hand, killer strains were isolated from 3 of 18 samples of miso and soy sauce. The killer spectra against the standard killer strains, K1 ~ K10, were different from those of other killer strains reported previously.     

A taxonomic study of soil yeasts

Summary Eighty-four samples of Minnesota soils were collected in the spring of the year. All samples yielded yeasts, and a total of 180 cultures were isolated of which 117 were studied taxonomically. Twenty-five cultures were black yeasts. Approximately one-third of the isolates were spore forming yeasts and members of the oxidative and film forming generaHansenula, Pichia, andDebaryomyces, of which a new species (D. mrakii) has been described. Not a single culture ofSaccharomyces was isolated. Perhaps later in the season when fruit was abundant members of this genus would have been present.The greatest number of imperfects belonged to the genusCandida (32 cultures), althoughPullularia (25 cultures),Rhodotorula (20 cultures), andTorulopsis (16 cultures) were well represented.The cultures ofPullularia darkened very slowly if at all, in the asbence of excess sugar. Under these circumstances they were very similar toT. pullulans.A single culture ofTrichisporon cerebriformis was isolated. The culture isolated formed both blastospores and arthrospores.I would like to express my appreciation to Dr.C. E. Skinner of Washington State College, for his help and guidance throughout this entire problem. I would also like to thank Dr.E. M. Mark, of the University of California, Berkeley, for the privilege of working under his direction, and in his laboratory during the study.     

Yeast Microflora Isolated From Brazilian Cassava Roots: Taxonomical Classification Based on Molecular Identification

A rapid molecular identification technique was applied on microbial microflora isolated from Brazilian cassava roots given a yeast profile presented in the samples analyzed. A total of 24 strain isolated from cassava were initially grouped and identified in five groups using restriction-fragment length polymorphism (RFLPs) of 5.8S-ITS rDNA region. Sequencing analysis of the domains D1 and D2 of the 26S rRNA gene or 5.8S rRNA-ITS region were used to identify different groups of yeasts. Representative colonies of yeasts of each group were isolated and identified as Debaromyces hansenii, Kodamaea ohmeri, Candida glabrata, C. haemulonii, and Pichia gullhermondii. It is hoped that these results will contribute toward selecting yeast from this microflora capable to degrade cassava starch in the near future.     

Yeasts associated with algarrobo trees (Prosopis spp.) in northwest Argentina: A preliminary report

Summary Yeasts were isolated from exudates from trees at three sites in northwest Argentina, two between the towns of Amaicha del Valle and Cafayate and one in the Quebrada de Cafayate, a deep river valley north of Cafayate. The majority of the yeasts were identified asCandida famata andRhodotorula graminis, though isolates of other species ofRhodotorula, Candida boidinii, Pichia membranaefaciens, and occasional isolates of other species were obtained. None of the species was the same as those isolated in Crete, from pods of the carob (European algarrobo). Of 96 cultures investigated, 26 utilized methanol as sole carbon source. The frequency of isolation of methylotrophic yeasts from this habitat may prove to be of considerable scientific and technological interest.This paper is dedicated to Professor Herman Jan Phaff in honor of his 50 years of active research which still continues.     

Oral Candida carriage of patients attending a dental clinic in Braga,Portugal

BackgroundThe ability of the Candida species to colonize surfaces can be considered as a risk factor for oral infection.AimsTo establish oral Candida carriage in patients attending a dental clinic in Braga, Portugal.MethodsA total of 97 patients were analysed. Swab samples were collected and directly cultured onto CHROMagar Candida. Representative yeasts were identified by polymerase chain reaction.ResultsFrom the samples analysed 54.6% (n=53) were Candida positive, and Candida albicans was the most frequently isolated species, accounting for 79% of all the species identified. Non-C. albicans Candida (NCAC) species recovered included Candida parapsilosis, Candida glabrata, Candida tropicalis, and Candida guilliermondii. There was a lack of association between the presence of C. albicans or NCAC species, and age, gender, or prostheses wearing in this population. In 17% of the cases (n=9), polymicrobial cultures, with two different Candida species, were identified.ConclusionsThis study shows a high Candida carriage rate among this population, thus pointing to the relevance of an accurate diagnostic approach in Candida species identification.     

Three new species of anamorphic yeasts phenotypically and phylogenetically related toCandida mesenterica: The description ofCandida fungicola sp. nov.,Candida sagamina sp. nov., andCandida fukazawae sp. nov. isolated from fruit bodies of mushrooms

Four strains of anamorphic yeasts isolated from fruit bodies of mushrooms collected in Japan were found to represent three new species of the genusCandida. These species resembleCandida mesenterica in characteristics commonly employed in the classification of yeasts. On the basis of DNA-DNA reassociation, however, they were clearly distinguished fromC. mesenterica and from one another. Three new species,Candida fungicola, Candida sagamina, andCandida fukazawae, are proposed for these yeasts. The analysis of SSU rDNA sequences suggested that these three species were closely related to each other and toC. mesenterica andC. suecica.     

A study of yeast populations in a waste stabilization pond system

Summary From 40 habitats within a waste stabilization pond system for the treatment of sewage from a small institutional dormitory and dining hall, samples of sewage, sludges, pond waters and effluents, and undisturbed and disturbed soils were collected. From these samples and from samples of materials from an adjacent stream, 54 categories of yeasts were isolated in a year-round survey. Although all of the commoner species have been isolated from human clinical materials in past work, none of the species found has been associated with human disease conditions in temperate regions of the northern hemisphere.All of the commoner and some of the less-common species were isolated from shaken cultures in YNB broth, with 1% and 20% glucose used as paired media. Other species, as well as all the commoner species, were obtained on broths made of YCB and YNB media to which were added different nitrogen or carbon sources. For routine surveys of populations the shaken YNB broth cultures seem adequate, but quantitative techniques must be developed for more critical delimitation of populations.In general, within the sets of samples tested,Candida krusei, C. tropicalis, C. parapsilosis, Rhodotorula glutinis, R. mucilaginosa, andSaccharomyces cerevisiae appear indicative of organic enrichment of waters and soils.     

Yeast Diversity in Hydromorphic Soils with Reference to a Grass–Sphagnum Wetland in Western Siberia and a Hummocky Tundra Region at Cape Barrow (Alaska)

The microbiological analysis of 78 samples taken from a high bog in Western Siberia and from a tundra wetland soil in Alaska showed the presence of 23 yeast species belonging to the genera Bullera, Candida, Cryptococcus, Debaryomyces, Hanseniaspora, Metschnikowia, Mrakia, Pichia, Rhodotorula, Saccharomyces, Sporobolomyces, Torulaspora, and Trichosporon.Peat samples from the high bog were dominated by eurytopic anamorphic basidiomycetous species, such as Rhodotorula mucilaginosaand Sporobolomyces roseus, and by the ascomycetous yeasts Candidaspp. and Debaryomyces hansenii.These samples also contained two rare ascomycetous species (Candida paludigenaand Schizoblastosporion starkeyi-henricii), which so far have been found only in taiga wetland soils. The wetland Alaskan soil was dominated by one yeast species (Cryptococcus gilvescens), which is a typical inhabitant of tundra soils. Therefore, geographic factors may serve for a more reliable prediction of yeast diversity in soils than the physicochemical or ecotopic parameters of these soils.     

Transformation of Chlororesorcinol by the Hydrocarbonoclastic Yeasts Candida maltosa,Candida tropicalis,and Trichosporon oivide

The inhibitory effects of chlorinated monoaromatic compounds on three hydrocarbonoclastic yeasts grown on glucose or resorcinol were examined. At concentrations of 1.0 M, all of the monoaromatic compounds were inhibitory. When the concentration of chlororesorcinol was significantly reduced (0.0005 M), the inhibition to each yeast was minimized. Extracts of the cultures of yeasts growing on resorcinol plus chlororesorcinol were analyzed for residual resorcinol and chlororesorcinol with high pressure liquid chromatography. Neither compound was detected in the culture broth of Candida maltosa, but several unidentified compounds were present. Only chlororesorcinol was detected in the culture broth of Trichosporon oivide, and both resorcinol and chlororesorcinol were present in extract from cultures of C. tropicalis. Cultures of C. maltosa grown on resorcinol-yeast nitrogen base, washed and suspended in phosphate buffer and subsequently incubated with chlororesorcinol, turned the culture broth a distinct pink color. The data indicate that C. maltosa has the potential to co-metabolize chlororesorcinol. Received: 28 January 1997 / Accepted: 7 March 1997     

Groups and Sources of Yeasts in House Dust

House dust contains bacteria, mycelial fungi, microarthropods, and yeasts. House dust samples collected in 25 apartments in Moscow and the Moscow region were found to contain yeasts belonging to the genera Candida, Cryptococcus, Debaryomyces, Rhodotorula, Sporobolomyces, and Trichosporon. The most frequently encountered microorganisms were typical epiphytic yeasts, such as Cryptococcus diffluens and Rhodotorula mucilaginosa, which are capable of long-term preservation in an inactive state. The direct source of epiphytic yeasts occurring in the house dust might be indoor plants, which were contaminated with these yeasts, albeit to a lesser degree than outdoor plants. Along with the typical epiphytic yeasts, the house dust contained the opportunistic yeast pathogens Candida catenulata, C. guillermondii, C. haemulonii, C. rugosa, and C. tropicalis, which are known as the causal agents of candidiases. We failed to reveal any correlation between the abundance of particular yeast species in the house dust, residential characteristics, and the atopic dermatitis of the inhabitants.     

Three new,non-fermenting,and nitrate-negative Candida species isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

Three unusual species of yeasts have been isolated from decayed wood palo podrido (12) in the evergreen rainy Valdivian forest of southern Chile. According to their morphological characteristics, they were assigned to the genus Candida Berkhout (8). They differ from all recently accepted Candida species, and are described and illustrated with the names of Candida antillancae, Candida bondarzewiae, and Candida castrensis.     

Chemical signaling and insect attraction is a conserved trait in yeasts

Yeast volatiles attract insects, which apparently is of mutual benefit, for both yeasts and insects. However, it is unknown whether biosynthesis of metabolites that attract insects is a basic and general trait, or if it is specific for yeasts that live in close association with insects. Our goal was to study chemical insect attractants produced by yeasts that span more than 250 million years of evolutionary history and vastly differ in their metabolism and lifestyle. We bioassayed attraction of the vinegar fly Drosophila melanogaster to odors of phylogenetically and ecologically distinct yeasts grown under controlled conditions. Baker's yeast Saccharomyces cerevisiae, the insect‐associated species Candida californica, Pichia kluyveri and Metschnikowia andauensis, wine yeast Dekkera bruxellensis, milk yeast Kluyveromyces lactis, the vertebrate pathogens Candida albicans and Candida glabrata, and oleophilic Yarrowia lipolytica were screened for fly attraction in a wind tunnel. Yeast headspace was chemically analyzed, and co‐occurrence of insect attractants in yeasts and flowering plants was investigated through a database search. In yeasts with known genomes, we investigated the occurrence of genes involved in the synthesis of key aroma compounds. Flies were attracted to all nine yeasts studied. The behavioral response to baker's yeast was independent of its growth stage. In addition to Drosophila, we tested the basal hexapod Folsomia candida (Collembola) in a Y‐tube assay to the most ancient yeast, Y. lipolytica, which proved that early yeast signals also function on clades older than neopteran insects. Behavioral and chemical data and a search for selected genes of volatile metabolites underline that biosynthesis of chemical signals is found throughout the yeast clade and has been conserved during the evolution of yeast lifestyles. Literature and database reviews corroborate that yeast signals mediate mutualistic interactions between insects and yeasts. Moreover, volatiles emitted by yeasts are commonly found also in flowers and attract many insect species. The collective evidence suggests that the release of volatile signals by yeasts is a widespread and phylogenetically ancient trait, and that insect–yeast communication evolved prior to the emergence of flowering plants. Co‐occurrence of the same attractant signals in yeast and flowers suggests that yeast‐insect communication may have contributed to the evolution of insect‐mediated pollination in flowers.     

A study of the polygalacturonase activity of several yeast strains isolated from cocoa

Summary During the traditional fermentation of cocoa, yeasts with pectinolytic activity are involved in the degradation of the pulp. Saccharomyces chevalieri, Torulopsis candila, and Candida norvegensis, as well as Kluyveromyces fragilis included in this study as a control strain all have a pectinolytic activity (endopolygalacturonase E.C. 3.2.1.15). The enzymes studied have the same optimal pH of activity [5] but are different from each other in their optimal temperature and their thermal stability. The enzymes of Torulopsis candida and Kluyveromyces fragilis have the highest optimal temperature (60° C). Among the strains studied, Candida norvegensis produced the greatest amount of exocellular enzyme.     

Studies on the Utilization of Hydrocarbons by Microorganisms

Many strains of the hydrocabon-utilizing yeasts were isolated from various kinds of natural sources by accumulation culture.

Among those yeasts, two strains, S315YI and S131YI, which were identified with Candida tropilcais, assimilated hydrocarbons abundantly. As for type cultures, it was found that many strains of them could utilize hydrocarbons too, especially the strains which belonged to Genus Candida. However, as regards to the ability in utilizing hydrocarbons, no yeast from type culture collections utilized hydrocarbons better than the yeasts newly isolated from nature. Addition of the natural nutrients such as corn steep liquor to the cultural broth of Strain S315Y1 showed no effect on the production of yeast cells.

The yeast Strain S315Y1 assimilated the higher boiling points fraction of n-paraffins in comparison with the hydrocarbon-utilizing bacterium, Pseudomonas aeruginosa S7B1, which had been reported by the authors. Ribonucleic acid contents of dried cells of the yeast Strain S315Y1 and S131Y1 were 5.3 and 4.4% respectively by Schmidt-Thannhauser-Schneider method.     

Oily yeasts as oleaginous cell factories

Oily yeasts have been described to be able to accumulate lipids up to 20% of their cellular dry weight. These yeasts represent a minor proportion of the total yeast population, and only 5% of them have been reported as able to accumulate more than 25% of lipids. The oily yeast genera include Yarrowia, Candida, Rhodotorula, Rhodosporidium, Cryptococcus, Trichosporon, and Lipomyces. More specifically, examples of oleaginous yeasts include the species: Lipomyces starkeyi, Rhodosporidium toruloides, Rhodotorula glutinis, and Yarrowia lipolytica. Yeast do exhibit advantages for lipid production over other microbial sources, namely, their duplication times are usually lower than 1 h, are much less affected than plants by season or climate conditions, and their cultures are more easily scaled up than those of microalgae. Additionally, some oily yeasts have been reported to accumulate oil up to 80% of their dry weight and can indeed generate different lipids from different carbon sources or from lipids present in the culture media. Thus, they can vary their lipid composition by replacing the fatty acids present in their triglycerides. Due to the diversity of microorganisms and growth conditions, oily yeasts can be useful for the production of triglycerides, surfactants, or polyunsaturated fatty acids.     

Characterisation of the diversity and physiology of cellobiose-fermenting yeasts isolated from rotting wood in Brazilian ecosystems

We investigated the yeast species associated with rotting wood samples obtained from Brazilian ecosystems, with a special focus on cellobiose-fermenting species. About 647 yeast strains were isolated from rotting wood samples collected from the areas of Atlantic rainforest, Cerrado, and Amazonian forest. Eighty-six known species and 47 novel species of yeasts were isolated. Candida boidinii, Cyberlindnera subsufficiens, Meyerozyma guilliermondii, Schwanniomyces polymorphus, Candida natalensis, and Debaryomyces hansenii were the most frequently isolated species. Among the cellobiose-fermenting yeasts, 14 known and three novel yeast species were identified. Scheffersomyces queiroziae, Sc. amazonensis, Yamadazyma sp.1, Hanseniaspora opuntiae, C. jaroonii, and Candida tammaniensis were the main ethanol-producing yeasts. These species also produced an intracellular β-glucosidase responsible for cellobiose hydrolysis. In fermentation assays using a culture medium containing 50 g L^?1 cellobiose, ethanol production was observed in all cases; Sc. queiroziae and Sc. amazonensis showed the highest yield, efficiency, and productivity. Candida jaroonii and Yamadazyma sp.1 strains also showed high efficiency in cellobiose fermentation, while C. tammaniensis and H. opuntiae strains produced low amounts of ethanol. This study shows the potential of rotting wood samples from Brazilian ecosystems as a source of yeasts, including new species as well as those with promising biotechnological properties.