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Ecology and Evolution Mar 2018Yeast volatiles attract insects, which apparently is of mutual benefit, for both yeasts and insects. However, it is unknown whether biosynthesis of metabolites that...
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 to odors of phylogenetically and ecologically distinct yeasts grown under controlled conditions. Baker's yeast , the insect-associated species , and , wine yeast , milk yeast , the vertebrate pathogens and , and oleophilic 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 , we tested the basal hexapod (Collembola) in a Y-tube assay to the most ancient yeast, 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.
PubMed: 29531709
DOI: 10.1002/ece3.3905 -
Brazilian Journal of Biology = Revista... Nov 2018Although invasive infections and mortality caused by Candida species are increasing among compromised patients, resistance to common antifungal agents is also an...
Although invasive infections and mortality caused by Candida species are increasing among compromised patients, resistance to common antifungal agents is also an increasing problem. We analyzed 60 yeasts isolated from patients with invasive candidiasis using a PCR/RFLP strategy based on the internal transcribed spacer (ITS2) region to identify different Candida pathogenic species. PCR analysis was performed from genomic DNA with a primer pair of the ITS2-5.8S rDNA region. PCR-positive samples were characterized by RFLP. Restriction resulted in 23 isolates identified as C. albicans using AlwI, 24 isolates as C. parapsilosis using RsaI, and 13 as C. tropicalis using XmaI. Then, a group of all isolates were evaluated for their susceptibility to a panel of previously described killer yeasts, resulting in 75% being susceptible to at least one killer yeast while the remaining were not inhibited by any strain. C. albicans was the most susceptible group while C. tropicalis had the fewest inhibitions. No species-specific pattern of inhibition was obtained with this panel of killer yeasts. Metschnikowia pulcherrima, Pichia kluyveri and Wickerhamomyces anomalus were the strains that inhibited the most isolates of Candida spp.
Topics: Adult; Antifungal Agents; Candida; Candidiasis, Invasive; Humans; Microbial Sensitivity Tests; Polymerase Chain Reaction; Polymorphism, Restriction Fragment Length
PubMed: 29412252
DOI: 10.1590/1519-6984.175635 -
Polish Journal of Microbiology Mar 2017Microbes have evolved ways of interference competition to gain advantage over their ecological competitors. The use of secreted antagonistic compounds by yeast cells is...
Microbes have evolved ways of interference competition to gain advantage over their ecological competitors. The use of secreted antagonistic compounds by yeast cells is one of the prominent examples. Although this killer behavior has been thoroughly studied in laboratory yeast strains, our knowledge of the antagonistic specificity of killer effects in nature remains limited. In this study, yeast strains were collected from various niches and screened for antagonistic activity against one toxin-sensitive strain of Saccharomyces cerevisiae and three pathogenic fungi. We demonstrate that some strains with antagonistic activity against these pathogenic fungi can be found in antagonist culture tests. These yeasts were identified as members of Trichosporon asahii, Candida stellimalicola, Wickerhamomyces anomalus, Ustilago esculenta, Aureobasidium pullulans, and Pichia kluyveri. The results indicated that the antagonistic activity of these killer yeasts has a narrow optimal pH range. Furthermore, we found that the antagonistic activity of some species is strain-dependent.
Topics: Antibiosis; Candida; Hydrogen-Ion Concentration; Pichia; Yeasts
PubMed: 29359688
DOI: 10.5604/17331331.1234997 -
BMC Infectious Diseases Jan 2018Opportunistic infections due to Candida species occur frequently in cancer patients because of their inherent immunosuppression. The aim of the present study was to...
BACKGROUND
Opportunistic infections due to Candida species occur frequently in cancer patients because of their inherent immunosuppression. The aim of the present study was to investigate the epidemiology of yeast species from the oral cavity of patients during treatment for oncological and haematological malignancies.
METHODS
MALDI-TOF was performed to identify yeasts isolated from the oral cavity of 350 cancer patients. Moreover, antifungal susceptibility testing was performed in according to CLSI guidelines (M27-A3).
RESULTS
Among 162 yeasts and yeast-like fungi isolated from the oral cavity of cancer patients, Candida albicans was the most common species (50.6%), followed by Candida glabrata (24.7%), Pichia kudriavzevii (Candida krusei (9.9%)), Candida tropicalis (4.3%), Candida dubliniensis (3.7%), Kluyveromyces marxianus (Candida kefyr (3.7%)) and Candida parapsilosis (1%). In addition, uncommon yeast species i.e., Saprochaete capitata, Saccharomyces cerevisiae, Clavispora lusitaniae (C. lusitaniae) and Pichia kluyveri (C. eremophila) were recovered from oral lesions. Oral colonization by C. albicans, non-albicans Candida species and uncommon yeasts were as follow; 55%, 44% and 1%, whereas oral infection due to C. albicans was 33.3%, non-albicans Candida species 60.6%, and uncommon yeasts 6.1%. Poor oral hygiene and xerostomia were identified as independent risk factors associated with oral yeast colonization. The overall resistance to fluconazole was 11.7% (19/162). Low MIC values were observed for anidulafungin for all Candida and uncommon yeast species.
CONCLUSIONS
This current study provides insight into the prevalence and susceptibility profiles of Candida species, including emerging Candida species and uncommon yeasts, isolated from the oral cavity of Iranian cancer patients. The incidence of oral candidiasis was higher amongst patients with hematological malignancies. The majority of oral infections were caused by non-albicans Candida species which were often more resistant to anti-fungal agents. Our findings suggest that anidulafungin should be used as antifungal of choice for prophylaxis in clinically high-risk patients with documented oral colonization or infection.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Antifungal Agents; Candida; Candidiasis, Oral; Female; Fluconazole; Humans; Male; Microbial Sensitivity Tests; Middle Aged; Mouth; Neoplasms; Pichia; Prevalence; Risk Factors; Saccharomycetales; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Xerostomia; Young Adult
PubMed: 29310582
DOI: 10.1186/s12879-017-2916-5 -
Journal of Applied Microbiology Feb 2018The purpose of this study was to evaluate the effect of warehouse storage conditions on the composition of the fungal community of green coffee beans (GCB) that were...
AIMS
The purpose of this study was to evaluate the effect of warehouse storage conditions on the composition of the fungal community of green coffee beans (GCB) that were stored in jute sacks for 1 year.
METHODS AND RESULTS
Molecular characterization of the fungal community composition and population dynamics obtained by Q-PCR, CE-SSCP (Simpson's diversity index D) and Illumina MiSeq sequencing indicated that Saccharomycetales dominated during the first 6 months of storage period with species as Meyerozyma guilliermondii and Pichia kluyveri. However, after 6 months of storage, the filamentous genus Wallemia became dominant. Principal components analysis correlated this fungal dynamic with storage conditions and other variables as chromaticity (colour), water activity, moisture content, reducing sugars concentration, fungal infection and ochratoxin A production.
CONCLUSIONS
This study demonstrated that GCB stored in jute sacks after 6 months of storage lead to fungal population dynamics, decreased chromaticity in GCB by bleaching and, then, affected overall quality.
SIGNIFICANCE AND IMPACT OF THE STUDY
Storage plays an important role in the quality evolution during the handling of the GCB. In this context, the composition of the microbial community could be considered a marker to assess the trade value of the coffee beans.
Topics: Biodiversity; Coffea; Food Storage; Fungi; Ochratoxins; Seeds
PubMed: 29215772
DOI: 10.1111/jam.13656 -
Frontiers in Microbiology 2017The increasing level of hazardous residues in the environment and food chains has led the European Union to restrict the use of chemical fungicides. Thus, exploiting new...
The increasing level of hazardous residues in the environment and food chains has led the European Union to restrict the use of chemical fungicides. Thus, exploiting new natural antagonistic microorganisms against fungal diseases could serve the agricultural production to reduce pre- and post-harvest losses, to boost safer practices for workers and to protect the consumers' health. The main aim of this work was to evaluate the antagonistic potential of epiphytic yeasts against , and pathogen species. In particular, yeast isolation was carried out from grape berries of ssp sylvestris populations, of the Eurasian area, and ssp cultivars from three different farming systems (organic, biodynamic, and conventional). Strains able to inhibit or slow the growth of pathogens were selected by and experiments. The most effective antagonist yeast strains were subsequently assayed for their capability to colonize the grape berries. Finally, possible modes of action, such as nutrients and space competition, iron depletion, cell wall degrading enzymes, diffusible and volatile antimicrobial compounds, and biofilm formation, were investigated as well. Two hundred and thirty-one yeast strains belonging to 26 different species were isolated; 20 of them, ascribed to eight species, showed antagonistic action against all molds. Yeasts isolated from ssp sylvestris were more effective (up to 50%) against rather than those isolated from ssp vinifera. Six strains, all isolated from wild vines, belonging to four species (, and ) revealed one or more phenotypical characteristics associated to the analyzed modes of antagonistic action.
PubMed: 29163377
DOI: 10.3389/fmicb.2017.02025 -
Journal of Applied Microbiology Oct 2017To evaluate the impact of coculturing Bifidobacterium animalis subsp. lactis HN019 with yeasts on microbial viability and metabolite production.
AIMS
To evaluate the impact of coculturing Bifidobacterium animalis subsp. lactis HN019 with yeasts on microbial viability and metabolite production.
METHODS AND RESULTS
Monocultures and bacteria-yeast cocultures of B. lactis HN019 and 10 different yeast strains belonging to different species in skim milk media were fermented at 37°C. The presence of yeasts enhanced the growth rate and metabolic activities of B. lactis HN019, which might be attributed to their antioxidative properties. The viability of yeasts, when cocultured with bifidobacteria, was either unaffected or suppressed, depending on the strain. When the B. lactis HN019 monoculture and cocultures with Saccharomyces cerevisiae EC-1118, Pichia kluyveri FrootZen and Kluyveromyces lactis KL71 were fermented to pH 4·7, there were no significant differences in their organic acid composition. On the other hand, cocultures produced significantly higher quantities of alcohols and/or esters than the monoculture. Coculturing B. lactis HN019 with yeasts did not improve the viability of the probiotic during storage at 10°C for 8 weeks, as the bifidobacteria itself demonstrated satisfactory survival in the fermented SMM.
CONCLUSIONS
Coculturing B. lactis HN019 with yeasts accelerated the growth of the bifidobacteria and increased the production aroma-active volatile metabolites.
SIGNIFICANCE AND IMPACT OF THE STUDY
This study demonstrates the potential of utilizing specific yeast species as starter or adjunct cultures to simultaneously improve the growth of fastidious bifidobacteria and modulate the organoleptic properties of fermented food products.
Topics: Animals; Bifidobacterium animalis; Coculture Techniques; Fermentation; Microbial Viability; Milk; Probiotics; Yeasts
PubMed: 28833937
DOI: 10.1111/jam.13571 -
Journal of Food Science and Technology May 2017Ninety-seven non- wine yeast strains belonging to ten different genera and species ( spp. and spp.; , , , , and were screened for 13 enzymes related to wine aroma,...
Ninety-seven non- wine yeast strains belonging to ten different genera and species ( spp. and spp.; , , , , and were screened for 13 enzymes related to wine aroma, color and clarity. Understanding the yeasts' influence in these wine characteristics provides a platform for selecting strains for their development as starter cultures and for the management of alcoholic fermentation. Most of the strains showed the presence of one or more enzymes of biotechnological interest. Our screening demonstrated several intraspecific differences within the yeast species investigated, indicating that strain selection is of great importance for their enological application, and also that some non- that have not been thoroughly explored, may deserve further consideration. This research represents the first stage for selecting non- strains to be used as a starter along with to enhance some particular characteristics of wines.
PubMed: 28559615
DOI: 10.1007/s13197-017-2587-7 -
BMC Microbiology Jan 2017While recent advances in next generation sequencing technologies have enabled researchers to readily identify countless microbial species in soil, rhizosphere, and...
BACKGROUND
While recent advances in next generation sequencing technologies have enabled researchers to readily identify countless microbial species in soil, rhizosphere, and phyllosphere microbiomes, the biological functions of the majority of these species are unknown. Functional studies are therefore urgently needed in order to characterize the plethora of microorganisms that are being identified and to point out species that may be used for biotechnology or plant protection. Here, we used a dual culture assay and growth analyses to characterise yeasts (40 different isolates) and their antagonistic effect on 16 filamentous fungi; comprising plant pathogens, antagonists, and saprophytes.
RESULTS
Overall, this competition screen of 640 pairwise combinations revealed a broad range of outcomes, ranging from small stimulatory effects of some yeasts up to a growth inhibition of more than 80% by individual species. On average, yeasts isolated from soil suppressed filamentous fungi more strongly than phyllosphere yeasts and the antagonistic activity was a species-/isolate-specific property and not dependent on the filamentous fungus a yeast was interacting with. The isolates with the strongest antagonistic activity were Metschnikowia pulcherrima, Hanseniaspora sp., Cyberlindnera sargentensis, Aureobasidium pullulans, Candida subhashii, and Pichia kluyveri. Among these, the soil yeasts (C. sargentensis, A. pullulans, C. subhashii) assimilated and/or oxidized more di-, tri- and tetrasaccharides and organic acids than yeasts from the phyllosphere. Only the two yeasts C. subhashii and M. pulcherrima were able to grow with N-acetyl-glucosamine as carbon source.
CONCLUSIONS
The competition assays and physiological experiments described here identified known antagonists that have been implicated in the biological control of plant pathogenic fungi in the past, but also little characterised species such as C. subhashii. Overall, soil yeasts were more antagonistic and metabolically versatile than yeasts from the phyllosphere. Noteworthy was the strong antagonistic activity of the soil yeast C. subhashii, which had so far only been described from a clinical sample and not been studied with respect to biocontrol. Based on binary competition assays and growth analyses (e.g., on different carbon sources, growth in root exudates), C. subhashii was identified as a competitive and antagonistic soil yeast with potential as a novel biocontrol agent against plant pathogenic fungi.
Topics: Antibiosis; Biological Control Agents; Candida; DNA, Fungal; Fungi; Genome, Fungal; Genome, Mitochondrial; High-Throughput Nucleotide Sequencing; Malus; Plant Roots; Plants; Rhizosphere; Soil; Soil Microbiology
PubMed: 28056814
DOI: 10.1186/s12866-016-0908-z -
Frontiers in Microbiology 2015Saccharomyces cerevisiae is by far the most widely used yeast in oenology. However, during the last decade, several other yeasts species has been purposed for winemaking... (Review)
Review
Saccharomyces cerevisiae is by far the most widely used yeast in oenology. However, during the last decade, several other yeasts species has been purposed for winemaking as they could positively impact wine quality. Some of these non-conventional yeasts (Torulaspora delbrueckii, Metschnikowia pulcherrima, Pichia kluyveri, Lachancea thermotolerans, etc.) are now proposed as starters culture for winemakers in mixed fermentation with S. cerevisiae, and several others are the subject of various studies (Hanseniaspora uvarum, Starmerella bacillaris, etc.). Along with their biotechnological use, the knowledge of these non-conventional yeasts greatly increased these last 10 years. The aim of this review is to describe the last updates and the current state-of-art of the genetics of non-conventional yeasts (including S. uvarum, T. delbrueckii, S. bacillaris, etc.). We describe how genomics and genetics tools provide new data into the population structure and biodiversity of non-conventional yeasts in winemaking environments. Future challenges will lie on the development of selection programs and/or genetic improvement of these non-conventional species. We discuss how genetics, genomics and the advances in next-generation sequencing will help the wine industry to develop the biotechnological use of non-conventional yeasts to improve the quality and differentiation of wines.
PubMed: 26793188
DOI: 10.3389/fmicb.2015.01563