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.     

Yeasts from U.S.A. soils

Summary Investigations of yeasts from 38 U.S.A. soils samples show the occurrence of 22 different species (16 sporogenous and 6 asporogenous).The most widespread species were Pichia fermentans and Hansenula anomala. The other isolated species were Saccharomyces ellipsoideus, Torulaspora delbrueckii, Pichia membranefaciens, Saccharomyces smittii, Saccharomyces carlsbergensis, Saccharomyces uvarum, Torulaspora rosei, Zygosaccharomyces rouxii, Zygosaccharomyces n. sp., Hansenula saturnus, Hansenula californica, Hansenula n. sp., Hansenula suaveolens, Debaryomyces n. sp., Torulopsis glabrata, Torulopsis n. sp. Candida tropicalis, Candida robusta, Rhodotorula glutinis, Trichosporon cutaneum and Trichosporon cutaneum var. multisporus.     

Yeast communities in a natural tequila fermentation

Fresh and cooked agave,Drosophila spp., processing equipment, agave molasses, agave extract, and fermenting must at a traditional tequila distillery (Herradura, Amatitan, Jalisco, México) were studied to gain insight on the origin of yeasts involved in a natural tequila fermentations. Five yeast communities were identified. (1) Fresh agave contained a diverse mycobiota dominated byClavispora lusitaniae and an endemic species,Metschnikowia agaveae. (2)Drosophila spp. from around or inside the distillery yielded typical fruit yeasts, in particularHanseniaspora spp.,Pichia kluyveri, andCandida krusei. (3)Schizosaccharomyces pombe prevailed in molasses. (4) Cooked agave and extract had a considerable diversity of species, but includedSaccharomyces cerevisiae. (5) Fermenting juice underwent a gradual reduction in yeast heterogeneity.Torulaspora delbrueckii, Kluyveromyces marxianus, andHanseniaspora spp. progressively ceded the way toS. cerevisiae, Zygosaccharomyces bailii, Candida milleri, andBrettanomyces spp. With the exception ofPichia membranaefaciens, which was shared by all communities, little overlap existed. That separation was even more manifest when species were divided into distinguishable biotypes based on morphology or physiology. It is concluded that crushing equipment and must holding tanks are the main source of significant inoculum for the fermentation process.Drosophila species appear to serve as internal vectors. Proximity to fruit trees probably contributes to maintaining a substantialDrosophila community, but the yeasts found in the distillery exhibit very little similarity to those found in adjacent vegetation. Interactions involving killer toxins had no apparent direct effects on the yeast community structure.     

Two new species ofPichia isolated from slime fluxes of deciduous trees

Two new homothallic species ofPichia, associated with exudates ofPopulus trichocarpa andSalix sp. have been described.Pichia trehalophila sp.n. was isolated from slime exudates in two widely separatedPopulus trichocarpa trees andPichia salictaria sp.n. was isolated from two exudates ofSalix sp. The latter species was previously present as an unidentified strain ofPichia in the culture collection of the Centraalbureau voor Schimmelcultures and had been isolated from a patient in Germany. The natural habitat ofP. salictaria is considered to be in association with willow trees.     

Quantification of different yeasts associated with the bark beetle,Ips typographus,during its attack on a spruce tree

There were different amounts and types of yeasts associated with individuals ofIps typographus spruce bark beetles during different phases of their attack on a healthy spruce tree. The yeasts were isolated on Sabouraud agar medium in order to identify them and estimate their numbers.Hansenula holstii andCandida diddensii type yeasts were most frequently isolated. The increase in number of these two yeast types probably accounted for most of the total yeast increase found during the later attack phases of the bark beetles. Lesser amounts ofHansenula capsulata, Pichia pinus, Candida nitratophila, and twoCryptococcus type yeasts were also found.     

Survey of bovine mycotic mastitis in dairy herds in the State of São Paulo,Brazil

The purpose of this study was to isolate fungi from the quarter milk of cow udders from several dairy herds and to identify the different genera and species involved in mastitis. A total of 2078 milk samples from normal, clinical and subclinical mastitis quarters from 22 dairy herds of 16 districts in the State of São Paulo, Brazil was utilized in this survey. Two hundred and fifty one (12.07%) fungi were isolated from the samples. Two hundred and eight of these (82.86%) were yeasts and 30 (11.95%) were moulds. The fungi were isolated in pure culture (24.77%) or in cultures mixed with bacteria (72.22%). The yeasts isolated were:Cryptococcus spp. (71 strains),Rhodotorula spp. (40),Candida spp. (68),Trichosporon cutaneum (21),Aureobasidium pullulans (7), andPichia ohmeri (1). Moulds classified in following genera were also isolated:Aspergillus (3),Penicillium (3),Alternaria (3),Phoma (3),Epicoccum (2), andGeotrichum (16).     

Identification and characterization of yeasts in sugarcane silages

Aims: To enumerate the micro‐organisms and to identify the yeast species present during the ensilage of different sugarcane (Saccharum spp.) cultivars. Method: Samples of sugarcane silage were collected at 10, 20, 30 and 40 days from the start of fermentation. Population levels of lactic acid bacteria (LAB), mesophilic facultative anaerobic (MFA) bacteria, filamentous fungi and yeasts were determined. Nine species of yeasts were classified according to traditional methods and confirmed using molecular techniques. Conclusions: LAB dominated the ensiling process of sugarcane, although yeasts were present at relatively high population levels throughout the whole fermentation period. The detected species of yeasts varied according to sugarcane cultivar and time of fermentation. Torulaspora delbrueckii was the predominant yeast, followed by Pichia anomala and Saccharomyces cerevisiae. Significance and Impact of the Study: Knowledge of the population of micro‐organisms in general, and of yeasts in particular, present during the fermentation of sugarcane is of fundamental importance in the development of more effective ensiling processes.     

Yeast communities of the cactusPilosocereus arrabidae and associated insects in the Sandy Coastal Plains of Southeastern Brazil

The yeast communities from necrotic tissues, decaying flowers and fruits, and from larval feeding sites of the mothSigelgaita sp. in the cactusPilosocereus arrabidae were surveyed in three restinga ecosystems in Southeastern Brazil. Insects associated with these substrates were sampled to verify the vectoring of yeasts. The cactusPilosocereus arrabidae was shown to have four different yeast communities associated with it. Necrotic stems had a diverse yeast community with the prevalent speciesPichia barkeri, Candida sonorensis, Pichia cactophila, Geotrichum sp.,Myxozyma mucilagina andSporopachydermia sp. A, representing about 80% of the total isolates.Pichia sp. A and aCandida domercqii-like species represented more than 90% of the yeast isolates from decaying flowers. Fruits had a heterogeneous yeast community with typical fruit yeasts of the genusKloeckera, basidiomicetous anamorphs of the genusCryptococcus, the black yeastAureobasidium pullulans, Pichia sp. A, aCandida domercqii-like species, and some cactophilic yeasts, especiallyClavispora opuntiae. The feeding site ofSigelgaita sp. larvae hadClavispora opuntiae as the prevalent species. Insect vectors are suggested as one the most important factors influencing the composition of these yeast communities.     

Fungal diseases of the respiratory tract

The proportion ofCandida and non-Candida species in the clinical material from patients. with respiratory-tract diseases was determined.C. albicans was isolated in 102 cases. An additional 89 strains of yeasts, isolated in association with respiratory diseases, belonged to 10 non-albicans Candida spp. andCryptococcus spp. The prevailing species, which occurred in 47 cases, wasC. parapsilosis. C. tropicalis, C. glabrata, andC. guilliermondii were isolated in 12, 10, and 9 cases, respectively. Four strains ofC. krusei and three strains ofC. lusitaniae and one strain each ofC. freyschussii, C. robusta, C. zeylanoides, andCryptococcus neoformans were also isolated.     

Identification of bacteria and yeasts from <Emphasis Type="Italic">in vitro</Emphasis> and surface-sterilized field samples of <Emphasis Type="Italic">Ensete ventricosum</Emphasis> by rDNA analysis

Bacterial and fungal contaminants of enset (Ensete ventricosum) cultures and microbes associated with surface-sterilized field material were identified by 16S/26S rDNA sequencing. Ten bacterial species were identified in 16 isolates from in vitro cultures and seven in 10 isolates from field clones. Three yeast species and one filamentous fungus were recorded as in vitro contaminants, whereas five yeast species were isolated from the field material. The bacterium, Pseudomonas reactans (6 isolates), and the yeast, Torulaspora delbrueckii (8 isolates), were the most frequent in vitro contaminants. Most of the bacterial species isolated from in vitro enset were Gram-positive and hitherto unrecorded as in vitro contaminants. The difficulty in controlling the in vitro contaminants is due to their apparent endogenous nature and their resistance to antimicrobial drugs.     

The mycology of the freeliving baboon (Papio sp.)

Summary Three field trips were conducted to study the mycoflora of the baboon in its native habitat, East Africa. The flora of the throat, nose, ear, rectum, vagina, and skin of over 300 male and female baboons was studied. A total of 1102 yeast isolates was obtained. None of the molds isolated were of known significant pathogenicity, while yeast isolates were found to belong to the following major genera:Candida, Cryptococcus, Rhodotorula, Saccharomyces, Torulopsis, andTrichosporon. Candida albicans was found to be the yeast most frequently isolated in both 1964 and 1966, while species ofRhodotorula andCryptococcus were more frequently found in 1968. It is our belief that various ecological and geographical conditions have an effect on the mycoflora of the animals, specifically from the quantitative point of view.     

Systematics of the generaDebaryomyces andMetschnikowia: Proton magnetic resonance spectra of their mannans as an aid in classification

The proton magnetic resonance spectra of the mannans of a number ofDebaryomyces andMetschnikowia species (Endomycetales) were determined. The spectra of all of the mannans had several similar characteristics, regardless of the species from which they originated. Pichia vini, a species originally classified asDebaryomyces vini, formed a mannan with a spectrum almost identical with those ofMetschnikowia (Candida) reukaufii andPichia haplophila. Debaryomyces vanrijii, originally placed in the genusPichia, formed a mannan with a spectrum identical with those ofPichia robertsii andCandida (Pichia) guilliermondii mannans.The authors wish to thank Mr. M. Mazurek for the determination of the p.m.r. spectra, and Mr. N. R. Gardner and Mr. R. J. Magus for valuable technical assistance.     

Characterization of early deaths of non-Saccharomyces yeasts in mixed cultures with Saccharomyces cerevisiae

The survival of Kluyveromyces thermotolerans and Torulaspora delbrueckii in mixed cultures with Saccharomyces cerevisiae was examined at low oxygen availability in a defined grape juice medium. In these fermentations, K. thermotolerans and T. delbrueckii died off earlier than S. cerevisiae, and K. thermotolerans and T. delbrueckii exhibited parabolic death kinetics. Furthermore, the early deaths seemed to be non-apoptotic in nature. In order to understand the mechanism causing the early deaths, various single- and mixed-culture fermentations were carried out. The early deaths could not be explained by nutrient depletion or the presence of toxic compounds. Rather, they seemed to be mediated by a cell-to-cell contact mechanism at high cell densities of S. cerevisiae, and to a lesser ability of K. thermotolerans and T. delbrueckii to compete for space, as compared to S. cerevisiae. These results contribute to an increased understanding of why K. thermotolerans and T. delbrueckii die off before S. cerevisiae in wine fermentations.     

Clavispora opuntiae and other yeasts associated with the mothSigelgaita sp. in the cactusPilosocereus arrabidae of Rio de Janeiro,Brazil

Summary Clavispora opuntiae was the prevalent yeast associated with the feeding sites ofSigelgaita sp. larvae in the cactusPilosocereus arrabidae. Also associated with this habitat wereCandida sonorensis, Pichia cactophila, Pichia barkeri, Candida sp. A,Geotrichum sp.,Geotrichum sericeum and the yeast like organismsPrototheca zopfii andAcremonium sp. Atypical yeast biotypes that may represent new species ofPichia, Sporopachydermia andCandida were isolated. Mating types ofClavispora opuntiae were at a ratio 70 h⁺ to 3 h^- and reduced levels of sporulation suggested low pressure for sexual reproduction in this habitat.Sigelgaita sp. probably was not an important vector forClavispora opuntiae because it was not isolated from an adult or eggs of this moth.     

Immunochemical studies on mannans of the genusSaccharomyces

Antigenic mannans isolated from the cells ofSaccharomyces fermentati, Saccharomyces rosei,Saccharomyces delbrueckii, Torulopsis colliculosa, Candida albicans andSaccharomyces cerevisiae were examined for their reactivity withSaccharomyces fermentati andCandida albicans antisera. Mannans ofTorulaspora as well asCandida albicans showed high cross-reactivity with the investigated antisera, which could be due to the presence of long side chains established by the partial acetolysis method. The low specific rotations ofSaccharomyces fermentati, Saccharomyces rosei andTorulopsis colliculosa mannans indicate a predominance of β-glycosidio linkages, whereasSaccharomyces delbrueckii andCandida albicans mannans possess predominantly α-linkages.Saccharomyces cerevisiae mannan showed different structural and immunological properties.     

The mycobiome of Australian tree hollows in relation to the Cryptococcus gattii and C. neoformans species complexes

Cryptococcosis is a fungal infection caused by members of the Cryptococcus gattii and C. neoformans species complexes. The C. gattii species complex has a strong environmental association with eucalypt hollows (particularly Eucalyptus camaldulensis), which may present a source of infection. It remains unclear whether a specific mycobiome is required to support its environmental survival and growth. Conventional detection of environmental Cryptococcus spp. involves culture on differential media, such as Guizotia abyssinica seed agar. Next‐generation sequencing (NGS)‐based culture‐independent identification aids in contextualising these species in the environmental mycobiome. Samples from 23 Australian tree hollows were subjected to both culture‐ and amplicon‐based metagenomic analysis to characterize the mycobiome and assess relationships between Cryptococcus spp. and other fungal taxa. The most abundant genera detected were Coniochaeta, Aspergillus, and Penicillium, all being commonly isolated from decaying wood. There was no correlation between the presence of Cryptococcus spp. in a tree hollow and the presence of any other fungal genus. Some differences in the abundance of numerous taxa were noted in a differential heat tree comparing samples with or without Cryptococcus‐NGS reads. The study expanded the known environmental niche of the C. gattii and C. neoformans species complexes in Australia with detections from a further five tree species. Discrepancies between the detection of Cryptococcus spp. using culture or NGS suggest that neither is superior per se and that, rather, these methodologies are complementary. The inherent biases of amplicon‐based metagenomics require cautious interpretation of data through consideration of its biological relevance.     

The taxonomy of yeasts found in exudates of certain trees and other natural breeding sites of some species ofDrosophila

Summary A survey was made of the yeasts occurring in slime fluxes ofQuercus kellogii (black oak),Abies concolor (red fir) and in certain mushrooms and dead logs in the mountains of the Yosemite region of California. Most of the 134 isolates identified were found to be non-fermentative or poorly fermentative (fermenting glucose only and usually weakly). The isolates were placed in the following genera:Pichia (34),Debaryomyces (35), imperfect forms ofHansenula (39),Endomyces (3),Saccharomyces (2),Candida (11),Trichosporon (7),Torulopsis (1),Cryptococcus (1) andSporobolomyces (1). Four new species have been described,Pichia silvestris, Pichia quercibus, Pichia carsonii andDebaryomyces fluxorum. P. quercibus andP. carsonii are unusual representatives of the genusPichia in that they form a very primitive pseudomycelium and lack pellicles on malt extract. To accommodate such species an amended diagnosis of the genusPichia has been proposed byPhaff in an accompanying paper.Saccharomyces pastori, of which 12 isolates were obtained, has been transferred to the amended genusPichia asP. pastori (Guilliermond) nov. comb.     

Microflora of partially processed lettuce

Bacteria, yeasts, and molds isolated from partially processed iceberg lettuce were taxonomically classified. The majority of bacterial isolates were gram-negative rods. Pseudomonas, Erwinia, and Serratia species were commonly found. Yeasts most frequently isolated from lettuce included members of the genera Candida, Cryptococcus, Pichia, Torulaspora, and Trichosporon. Comparatively few molds were isolated; members of the genera Rhizopus, Cladosporium, Phoma, Aspergillus, and Penicillium were identified.     

Proteomic characterization of extracellular vesicles produced by several wine yeast species

In winemaking, the use of alternative yeast starters is becoming increasingly popular. They contribute to the diversity and complexity of wine sensory features and are typically used in combination with Saccharomyces cerevisiae, to ensure complete fermentation. This practice has drawn the interest on interactions between different oenological yeasts, which are also relevant in spontaneous and conventional fermentations, or in the vineyard. Although several interactions have been described and some mechanisms have been suggested, the possible involvement of extracellular vesicles (EVs) has not yet been considered. This work describes the production of EVs by six wine yeast species (S. cerevisiae, Torulaspora delbrueckii, Lachancea thermotolerans, Hanseniaspora uvarum, Candida sake and Metschnikowia pulcherrima) in synthetic grape must. Proteomic analysis of EV-enriched fractions from S. cerevisiae and T. delbrueckii showed enrichment in glycolytic enzymes and cell-wall-related proteins. The most abundant protein found in S. cerevisiae, T. delbrueckii and L. thermotolerans EV-enriched fractions was the enzyme exo-1,3-β-glucanase. However, this protein was not involved in the here-observed negative impact of T. delbrueckii extracellular fractions on the growth of other yeast species. These findings suggest that EVs may play a role in fungal interactions during wine fermentation and other aspects of wine yeast biology.