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Sample records for saccharomyces uvarum pt

  1. Microsatellite analysis of Saccharomyces uvarum diversity.

    PubMed

    Masneuf-Pomarede, Isabelle; Salin, Franck; Börlin, Marine; Coton, Emmanuel; Coton, Monika; Jeune, Christine Le; Legras, Jean-Luc

    2016-03-01

    Considered as a sister species of Saccharomyces cerevisiae, S. uvarum is, to a lesser extent, an interesting species for fundamental and applied research studies. Despite its potential interest as a new gene pool for fermenting agents, the intraspecific molecular genetic diversity of this species is still poorly investigated. In this study, we report the use of nine microsatellite markers to describe S. uvarum genetic diversity and population structure among 108 isolates from various geographical and substrate origins (wine, cider and natural sources). Our combined microsatellite markers set allowed differentiating 89 genotypes. In contrast to S. cerevisiae genetic diversity, wild and human origin isolates were intertwined. A total of 75% of strains were proven to be homozygotes and estimated heterozygosity suggests a selfing rate above 0.95 for the different population tested here. From this point of view, the S. uvarum life cycle appears to be more closely related to S. paradoxus or S. cerevisiae of natural resources than S. cerevisiae wine isolates. Population structure could not be correlated to distinct geographic or technological origins, suggesting lower differentiation that may result from a large exchange between human and natural populations mediated by insects or human activities. PMID:26772797

  2. Interaction between Hanseniaspora uvarum and Saccharomyces cerevisiae during alcoholic fermentation.

    PubMed

    Wang, Chunxiao; Mas, Albert; Esteve-Zarzoso, Braulio

    2015-08-01

    During wine fermentation, Saccharomyces clearly dominate over non-Saccharomyces wine yeasts, and several factors could be related to this dominance. However, the main factor causing the reduction of cultivable non-Saccharomyces populations has not yet been fully established. In the present study, various single and mixed fermentations were performed to evaluate some of the factors likely responsible for the interaction between Saccharomyces cerevisiae and Hanseniaspora uvarum. Alcoholic fermentation was performed in compartmented experimental set ups with ratios of 1:1 and 1:9 and the cultivable population of both species was followed. The cultivable H. uvarum population decreased sharply at late stages when S. cerevisiae was present in the other compartment, similarly to alcoholic fermentations in non-compartmented vessels. Thus, cell-to-cell contact did not seem to be the main cause for the lack of cultivability of H. uvarum. Other compounds related to fermentation performance (such as sugar and ethanol) and/or certain metabolites secreted by S. cerevisiae could be related to the sharp decrease in H. uvarum cultivability. When these factors were analyzed, it was confirmed that metabolites from S. cerevisiae induced lack of cultivability in H. uvarum, however ethanol and other possible compounds did not seem to induce this effect but played some role during the process. This study contributes to a new understanding of the lack of cultivability of H. uvarum populations during the late stages of wine fermentation. PMID:25956738

  3. Saccharomyces eubayanus and Saccharomyces uvarum associated with the fermentation of Araucaria araucana seeds in Patagonia.

    PubMed

    Rodríguez, M Eugenia; Pérez-Través, Laura; Sangorrín, Marcela P; Barrio, Eladio; Lopes, Christian A

    2014-09-01

    Mudai is a traditional fermented beverage, made from the seeds of the Araucaria araucana tree by Mapuche communities. The main goal of the present study was to identify and characterize the yeast microbiota responsible of Mudai fermentation as well as from A. araucana seeds and bark from different locations in Northern Patagonia. Only Hanseniaspora uvarum and a commercial bakery strain of Saccharomyces cerevisiae were isolated from Mudai and all Saccharomyces isolates recovered from A. araucana seed and bark samples belonged to the cryotolerant species Saccharomyces eubayanus and Saccharomyces uvarum. These two species were already reported in Nothofagus trees from Patagonia; however, this is the first time that they were isolated from A. araucana, which extends their ecological distribution. The presence of these species in A. araucana seeds and bark samples, led us to postulate a potential role for them as the original yeasts responsible for the elaboration of Mudai before the introduction of commercial S. cerevisiae cultures. The molecular and genetic characterization of the S. uvarum and S. eubayanus isolates and their comparison with European S. uvarum strains and S. eubayanus hybrids (S. bayanus and S. pastorianus), allowed their ecology and evolution us to be examined. PMID:25041507

  4. New family of pectinase genes PGU1b-PGU3b of the pectinolytic yeast Saccharomyces bayanus var. uvarum.

    PubMed

    Naumov, G I; Shalamitskiy, M Yu; Naumova, E S

    2016-03-01

    Using yeast genome databases and literature data, we have conducted a phylogenetic analysis of pectinase PGU genes from Saccharomyces strains assigned to the biological species S. arboricola, S. bayanus (var. uvarum), S. cariocanus, S. cerevisiae, S. kudriavzevii, S. mikatae, S. paradoxus, and hybrid taxon S. pastorianus (syn. S. carlsbergensis). Single PGU genes were observed in all Saccharomyces species, except S. bayanus. The superfamily of divergent PGU genes has been documented in S. bayanus var. uvarum for the first time. Chromosomal localization of new PGU1b, PGU2b, and PGU3b genes in the yeast S. bayanus var. uvarum has been determined by molecular karyotyping and Southern hybridization. PMID:27193705

  5. A Gondwanan imprint on global diversity and domestication of wine and cider yeast Saccharomyces uvarum

    NASA Astrophysics Data System (ADS)

    Almeida, Pedro; Gonçalves, Carla; Teixeira, Sara; Libkind, Diego; Bontrager, Martin; Masneuf-Pomarède, Isabelle; Albertin, Warren; Durrens, Pascal; Sherman, David James; Marullo, Philippe; Todd Hittinger, Chris; Gonçalves, Paula; Sampaio, José Paulo

    2014-06-01

    In addition to Saccharomyces cerevisiae, the cryotolerant yeast species S. uvarum is also used for wine and cider fermentation but nothing is known about its natural history. Here we use a population genomics approach to investigate its global phylogeography and domestication fingerprints using a collection of isolates obtained from fermented beverages and from natural environments on five continents. South American isolates contain more genetic diversity than that found in the Northern Hemisphere. Moreover, coalescence analyses suggest that a Patagonian sub-population gave rise to the Holarctic population through a recent bottleneck. Holarctic strains display multiple introgressions from other Saccharomyces species, those from S. eubayanus being prevalent in European strains associated with human-driven fermentations. These introgressions are absent in the large majority of wild strains and gene ontology analyses indicate that several gene categories relevant for wine fermentation are overrepresented. Such findings constitute a first indication of domestication in S. uvarum.

  6. Biosorption of water-soluble dyes on magnetically modified Saccharomyces cerevisiae subsp. uvarum cells.

    PubMed

    Safaríková, M; Ptácková, L; Kibriková, I; Safarík, I

    2005-05-01

    Brewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water based magnetic fluid stabilized with perchloric acid. Magnetically modified yeast cells efficiently adsorbed various water soluble dyes. The dyes adsorption can be described by the Langmuir adsorption model. The maximum adsorption capacity of the magnetic cells differed substantially for individual dyes; the highest value was found for aniline blue (approx. 220 mg per g of dried magnetic adsorbent). PMID:15811411

  7. Saccharomyces kudriavzevii and Saccharomyces uvarum differ from Saccharomyces cerevisiae during the production of aroma-active higher alcohols and acetate esters using their amino acidic precursors.

    PubMed

    Stribny, Jiri; Gamero, Amparo; Pérez-Torrado, Roberto; Querol, Amparo

    2015-07-16

    Higher alcohols and acetate esters are important flavour and aroma components in the food industry. In alcoholic beverages these compounds are produced by yeast during fermentation. Although Saccharomyces cerevisiae is one of the most extensively used species, other species of the Saccharomyces genus have become common in fermentation processes. This study analyses and compares the production of higher alcohols and acetate esters from their amino acidic precursors in three Saccharomyces species: Saccharomyces kudriavzevii, Saccharomyces uvarum and S. cerevisiae. The global volatile compound analysis revealed that S. kudriavzevii produced large amounts of higher alcohols, whereas S. uvarum excelled in the production of acetate esters. Particularly from phenylalanine, S. uvarum produced the largest amounts of 2-phenylethyl acetate, while S. kudriavzevii obtained the greatest 2-phenylethanol formation from this precursor. The present data indicate differences in the amino acid metabolism and subsequent production of flavour-active higher alcohols and acetate esters among the closely related Saccharomyces species. This knowledge will prove useful for developing new enhanced processes in fragrance, flavour, and food industries. PMID:25886016

  8. Volatile flavour profile of reduced alcohol wines fermented with the non-conventional yeast species Metschnikowia pulcherrima and Saccharomyces uvarum.

    PubMed

    Varela, C; Sengler, F; Solomon, M; Curtin, C

    2016-10-15

    Production of quality wines with decreased alcohol concentration continues to be one of the major challenges facing wine producers. Therefore, there is considerable interest in the isolation or generation of wine yeasts less efficient at transforming grape sugars into ethanol. We recently demonstrated that Metschnikowia pulcherrima AWRI1149 and Saccharomyces uvarum AWRI2846 were both able to produce reduced alcohol wine when used in sequential inoculation with Saccharomyces cerevisiae. This effect is additive when both strains are co-inoculated in grape must. Here we describe the volatile flavour profile of Chardonnay and Shiraz wines produced with these two strains. Wines fermented with M. pulcherrima showed concentrations of ethyl acetate likely to affect negatively wine aroma. Wines fermented with S. uvarum and with a combination of M. pulcherrima and S. uvarum were characterised by increased concentrations of 2-phenyl ethanol and 2-phenylethyl acetate, both associated with positive sensory attributes. PMID:27173534

  9. The Oenological Potential of Hanseniaspora uvarum in Simultaneous and Sequential Co-fermentation with Saccharomyces cerevisiae for Industrial Wine Production.

    PubMed

    Tristezza, Mariana; Tufariello, Maria; Capozzi, Vittorio; Spano, Giuseppe; Mita, Giovanni; Grieco, Francesco

    2016-01-01

    In oenology, the utilization of mixed starter cultures composed by Saccharomyces and non-Saccharomyces yeasts is an approach of growing importance for winemakers in order to enhance sensory quality and complexity of the final product without compromising the general quality and safety of the oenological products. In fact, several non-Saccharomyces yeasts are already commercialized as oenological starter cultures to be used in combination with Saccharomyces cerevisiae, while several others are the subject of various studies to evaluate their application. Our aim, in this study was to assess, for the first time, the oenological potential of H. uvarum in mixed cultures (co-inoculation) and sequential inoculation with S. cerevisiae for industrial wine production. Three previously characterized H. uvarum strains were separately used as multi-starter together with an autochthonous S. cerevisiae starter culture in lab-scale micro-vinification trials. On the basis of microbial development, fermentation kinetics and secondary compounds formation, the strain H. uvarum ITEM8795 was further selected and it was co- and sequentially inoculated, jointly with the S. cerevisiae starter, in a pilot scale wine production. The fermentation course and the quality of final product indicated that the co-inoculation was the better performing modality of inoculum. The above results were finally validated by performing an industrial scale vinification The mixed starter was able to successfully dominate the different stages of the fermentation process and the H. uvarum strain ITEM8795 contributed to increasing the wine organoleptic quality and to simultaneously reduce the volatile acidity. At the best of our knowledge, the present report is the first study regarding the utilization of a selected H. uvarum strain in multi-starter inoculation with S. cerevisiae for the industrial production of a wine. In addition, we demonstrated, at an industrial scale, the importance of non-Saccharomyces in

  10. The Oenological Potential of Hanseniaspora uvarum in Simultaneous and Sequential Co-fermentation with Saccharomyces cerevisiae for Industrial Wine Production

    PubMed Central

    Tristezza, Mariana; Tufariello, Maria; Capozzi, Vittorio; Spano, Giuseppe; Mita, Giovanni; Grieco, Francesco

    2016-01-01

    In oenology, the utilization of mixed starter cultures composed by Saccharomyces and non-Saccharomyces yeasts is an approach of growing importance for winemakers in order to enhance sensory quality and complexity of the final product without compromising the general quality and safety of the oenological products. In fact, several non-Saccharomyces yeasts are already commercialized as oenological starter cultures to be used in combination with Saccharomyces cerevisiae, while several others are the subject of various studies to evaluate their application. Our aim, in this study was to assess, for the first time, the oenological potential of H. uvarum in mixed cultures (co-inoculation) and sequential inoculation with S. cerevisiae for industrial wine production. Three previously characterized H. uvarum strains were separately used as multi-starter together with an autochthonous S. cerevisiae starter culture in lab-scale micro-vinification trials. On the basis of microbial development, fermentation kinetics and secondary compounds formation, the strain H. uvarum ITEM8795 was further selected and it was co- and sequentially inoculated, jointly with the S. cerevisiae starter, in a pilot scale wine production. The fermentation course and the quality of final product indicated that the co-inoculation was the better performing modality of inoculum. The above results were finally validated by performing an industrial scale vinification The mixed starter was able to successfully dominate the different stages of the fermentation process and the H. uvarum strain ITEM8795 contributed to increasing the wine organoleptic quality and to simultaneously reduce the volatile acidity. At the best of our knowledge, the present report is the first study regarding the utilization of a selected H. uvarum strain in multi-starter inoculation with S. cerevisiae for the industrial production of a wine. In addition, we demonstrated, at an industrial scale, the importance of non-Saccharomyces in

  11. Differences in Enzymatic Properties of the Saccharomyces kudriavzevii and Saccharomyces uvarum Alcohol Acetyltransferases and Their Impact on Aroma-Active Compounds Production

    PubMed Central

    Stribny, Jiri; Querol, Amparo; Pérez-Torrado, Roberto

    2016-01-01

    Higher alcohols and acetate esters belong to the most important yeast secondary metabolites that significantly contribute to the overall flavor and aroma profile of fermented products. In Saccharomyces cerevisiae, esterification of higher alcohols is catalyzed mainly by the alcohol acetyltransferases encoded by genes ATF1 and ATF2. Previous investigation has shown other Saccharomyces species, e.g., S. kudriavzevii and S. uvarum, to vary in aroma-active higher alcohols and acetate esters formation when compared to S. cerevisiae. Here, we aimed to analyze the enzymes encoded by the ATF1 and ATF2 genes from S. kudriavzevii (SkATF1, SkATF2) and S. uvarum (SuATF1, SuATF2). The heterologous expression of the individual ATF1 and ATF2 genes in a host S. cerevisiae resulted in the enhanced production of several higher alcohols and acetate esters. Particularly, an increase of 2-phenylethyl acetate production by the strains that harbored ATF1 and ATF2 genes from S. kudriavzevii and S. uvarum was observed. When grown with individual amino acids as the nitrogen source, the strain that harbored SkATF1 showed particularly high 2-phenylethyl acetate production and the strains with introduced SkATF2 or SuATF2 revealed increased production of isobutyl acetate, isoamyl acetate, and 2-phenylethyl acetate compared to the reference strains with endogenous ATF genes. The alcohol acetyltransferase activities of the individual Atf1 and Atf2 enzymes measured in the cell extracts of the S. cerevisiae atf1 atf2 iah1 triple-null strain were detected for all the measured substrates. This indicated that S. kudriavzevii and S. uvarum Atf enzymes had broad range substrate specificity as S. cerevisiae Atf enzymes. Individual Atf1 enzymes exhibited markedly different kinetic properties since SkAtf1p showed c. twofold higher and SuAtf1p c. threefold higher Km for isoamyl alcohol than ScAtf1p. Together these results indicated that the differences found among the three Saccharomyces species during the

  12. Analysis of temperature-mediated changes in the wine yeast Saccharomyces bayanus var uvarum. An oenological study of how the protein content influences wine quality.

    PubMed

    Muñoz-Bernal, Eugenia; Deery, Michael J; Rodríguez, María Esther; Cantoral, Jesús M; Howard, Julie; Feret, Renata; Natera, Ramón; Lilley, Kathryn S; Fernández-Acero, Francisco Javier

    2016-02-01

    Saccharomyces bayanus var. uvarum plays an important role in the fermentation of red wine from the D.O. Ribera del Duero. This is due to the special organoleptic taste that this yeast gives the wines and their ability to ferment at low temperature. To determine the molecular factors involved in the fermentation process at low temperature, a differential proteomic approach was performed by using 2D-DIGE, comparing, qualitatively and quantitatively, the profiles obtained at 13 and 25°C. A total of 152 protein spots were identified. We detected proteins upregulated at 13°C that were shown to be related to temperature stress, the production of aromatic compounds involved in the metabolism of amino acids, and the production of fusel alcohols and their derivatives, each of which is directly related to the quality of the wines. To check the temperature effects, an aromatic analysis by GC-MS was performed. The proteomic and "aromatomic" results are discussed in relation to the oenological properties of S. bayanus var. uvarum. PMID:26621492

  13. Hanseniaspora uvarum from Winemaking Environments Show Spatial and Temporal Genetic Clustering.

    PubMed

    Albertin, Warren; Setati, Mathabatha E; Miot-Sertier, Cécile; Mostert, Talitha T; Colonna-Ceccaldi, Benoit; Coulon, Joana; Girard, Patrick; Moine, Virginie; Pillet, Myriam; Salin, Franck; Bely, Marina; Divol, Benoit; Masneuf-Pomarede, Isabelle

    2015-01-01

    Hanseniaspora uvarum is one of the most abundant yeast species found on grapes and in grape must, at least before the onset of alcoholic fermentation (AF) which is usually performed by Saccharomyces species. The aim of this study was to characterize the genetic and phenotypic variability within the H. uvarum species. One hundred and fifteen strains isolated from winemaking environments in different geographical origins were analyzed using 11 microsatellite markers and a subset of 47 strains were analyzed by AFLP. H. uvarum isolates clustered mainly on the basis of their geographical localization as revealed by microsatellites. In addition, a strong clustering based on year of isolation was evidenced, indicating that the genetic diversity of H. uvarum isolates was related to both spatial and temporal variations. Conversely, clustering analysis based on AFLP data provided a different picture with groups showing no particular characteristics, but provided higher strain discrimination. This result indicated that AFLP approaches are inadequate to establish the genetic relationship between individuals, but allowed good strain discrimination. At the phenotypic level, several extracellular enzymatic activities of enological relevance (pectinase, chitinase, protease, β-glucosidase) were measured but showed low diversity. The impact of environmental factors of enological interest (temperature, anaerobia, and copper addition) on growth was also assessed and showed poor variation. Altogether, this work provided both new analytical tool (microsatellites) and new insights into the genetic and phenotypic diversity of H. uvarum, a yeast species that has previously been identified as a potential candidate for co-inoculation in grape must, but whose intraspecific variability had never been fully assessed. PMID:26834719

  14. Hanseniaspora uvarum from Winemaking Environments Show Spatial and Temporal Genetic Clustering

    PubMed Central

    Albertin, Warren; Setati, Mathabatha E.; Miot-Sertier, Cécile; Mostert, Talitha T.; Colonna-Ceccaldi, Benoit; Coulon, Joana; Girard, Patrick; Moine, Virginie; Pillet, Myriam; Salin, Franck; Bely, Marina; Divol, Benoit; Masneuf-Pomarede, Isabelle

    2016-01-01

    Hanseniaspora uvarum is one of the most abundant yeast species found on grapes and in grape must, at least before the onset of alcoholic fermentation (AF) which is usually performed by Saccharomyces species. The aim of this study was to characterize the genetic and phenotypic variability within the H. uvarum species. One hundred and fifteen strains isolated from winemaking environments in different geographical origins were analyzed using 11 microsatellite markers and a subset of 47 strains were analyzed by AFLP. H. uvarum isolates clustered mainly on the basis of their geographical localization as revealed by microsatellites. In addition, a strong clustering based on year of isolation was evidenced, indicating that the genetic diversity of H. uvarum isolates was related to both spatial and temporal variations. Conversely, clustering analysis based on AFLP data provided a different picture with groups showing no particular characteristics, but provided higher strain discrimination. This result indicated that AFLP approaches are inadequate to establish the genetic relationship between individuals, but allowed good strain discrimination. At the phenotypic level, several extracellular enzymatic activities of enological relevance (pectinase, chitinase, protease, β-glucosidase) were measured but showed low diversity. The impact of environmental factors of enological interest (temperature, anaerobia, and copper addition) on growth was also assessed and showed poor variation. Altogether, this work provided both new analytical tool (microsatellites) and new insights into the genetic and phenotypic diversity of H. uvarum, a yeast species that has previously been identified as a potential candidate for co-inoculation in grape must, but whose intraspecific variability had never been fully assessed. PMID:26834719

  15. Saccharomyces boulardii

    MedlinePlus

    ... believed to be a strain of Saccharomyces cerevisiae (baker's yeast). Saccharomyces boulardii is used as medicine. Saccharomyces boulardii ... Hansen CBS 5926), Probiotic, Probiotique, Saccharomyces, Saccharomyces boulardii, Saccharomyces Cerevisiae, S. Boulardii.

  16. Viability of Hanseniaspora uvarum yeast preserved by lyophilization and cryopreservation.

    PubMed

    de Arruda Moura Pietrowski, Giovana; Grochoski, Mayara; Sartori, Gabriela Felkl; Gomes, Tatiane Aparecida; Wosiacki, Gilvan; Nogueira, Alessandro

    2015-08-01

    Hanseniaspora yeasts are known to produce volatile compounds that give fruity aromas in wine and fermented fruit. This study aimed to verify the feasibility of the Hanseniaspora uvarum strain that had been isolated and identified during a previous study and preserved by lyophilization and freezing at -80 °C (cryopreservation). This strain was assessed in relation to its macroscopic and microscopic morphology and for its ability to ferment apple must. After having been subjected to lyophilization and cryopreservation, viability was assessed in relation to these characteristics during 12 months of storage. The strain showed stable colonial features and its microscopic appearance was unchanged during all recoveries. The plate count results showed consistency in both processes. Regarding the fermentative capacity, the kinetic results showed 100% viability for the strain subjected to lyophilization, as well as for those preserved at -80 °C. These results demonstrate that the preservation methods used are compatible with the maintenance of the relevant characteristics of the strain for the period of evaluation of this study (12 months). PMID:26095929

  17. Pure and mixed genetic lines of Saccharomyces bayanus and Saccharomyces pastorianus and their contribution to the lager brewing strain genome.

    PubMed

    Rainieri, Sandra; Kodama, Yukiko; Kaneko, Yoshinobu; Mikata, Kozaburo; Nakao, Yoshihiro; Ashikari, Toshihiko

    2006-06-01

    The yeast species Saccharomyces bayanus and Saccharomyces pastorianus are of industrial importance since they are involved in the production process of common beverages such as wine and lager beer; however, they contain strains whose variability has been neither fully investigated nor exploited in genetic improvement programs. We evaluated this variability by using PCR-restriction fragment length polymorphism analysis of 48 genes and partial sequences of 16. Within these two species, we identified "pure" strains containing a single type of genome and "hybrid" strains that contained portions of the genomes from the "pure" lines, as well as alleles termed "Lager" that represent a third genome commonly associated with lager brewing strains. The two pure lines represent S. uvarum and S. bayanus, the latter a novel group of strains that may be of use in strain improvement programs. Hybrid lines identified include (i) S. cerevisiae/S. bayanus/Lager, (ii) S. bayanus/S. uvarum/Lager, and (iii) S. cerevisiae/S. bayanus/S. uvarum/Lager. The genome of the lager strains may have resulted from chromosomal loss, replacement, or rearrangement within the hybrid genetic lines. This study identifies brewing strains that could be used as novel genetic sources in strain improvement programs and provides data that can be used to generate a model of how naturally occurring and industrial hybrid strains may have evolved. PMID:16751504

  18. Molecular genetic study of introgression between Saccharomyces bayanus and S. cerevisiae.

    PubMed

    Naumova, Elena S; Naumov, Gennadi I; Masneuf-Pomarède, Isabelle; Aigle, Michel; Dubourdieu, Denis

    2005-10-30

    The genomic constitution of different S. bayanus strains and natural interspecific Saccharomyces hybrids has been studied by genetic and molecular methods. Unlike S. bayanus var. uvarum, some S. bayanus var. bayanus strains (the type culture CBS 380, CBS 378, CBS 425, CBS 1548) harbour a number of S. cerevisiae subtelomeric sequences: Y', pEL50, SUC, RTM and MAL. The two varieties, having 86-100% nDNA-nDNA reassociation, are partly genetically isolated from one another but completely isolated from S. cerevisiae. Genetic and molecular data support the maintaining of var. bayanus and var. uvarum strains in the species S. bayanus. Using Southern hybridization with species-specific molecular markers, RFLP of the MET2 gene and flow cytometry analysis, we showed that the non-S. cerevisiae parents are different in lager brewing yeasts and in wine hybrid strains. Our results suggest that S. pastorianus is a hybrid between S. cerevisiae and S. bayanus var. bayanus, while S. bayanus var. uvarum contributed to the formation of the wine hybrids S6U and CID1. According to the partial sequence of ACT1 gene and flow cytometry analysis, strain CID1 is a triple hybrid between S. cerevisiae, S. kudriavzevii and S. bayanus var. uvarum. PMID:16240458

  19. Hybridization within Saccharomyces Genus Results in Homoeostasis and Phenotypic Novelty in Winemaking Conditions

    PubMed Central

    Dillmann, Christine; Bely, Marina; la Guerche, Stéphane; Giraud, Christophe; Huet, Sylvie; Sicard, Delphine; Masneuf-Pomarede, Isabelle; de Vienne, Dominique; Marullo, Philippe

    2015-01-01

    Despite its biotechnological interest, hybridization, which can result in hybrid vigor, has not commonly been studied or exploited in the yeast genus. From a diallel design including 55 intra- and interspecific hybrids between Saccharomyces cerevisiae and S. uvarum grown at two temperatures in enological conditions, we analyzed as many as 35 fermentation traits with original statistical and modeling tools. We first showed that, depending on the types of trait – kinetics parameters, life-history traits, enological parameters and aromas –, the sources of variation (strain, temperature and strain * temperature effects) differed in a large extent. Then we compared globally three groups of hybrids and their parents at two growth temperatures: intraspecific hybrids S. cerevisiae * S. cerevisiae, intraspecific hybrids S. uvarum * S. uvarum and interspecific hybrids S. cerevisiae * S. uvarum. We found that hybridization could generate multi-trait phenotypes with improved oenological performances and better homeostasis with respect to temperature. These results could explain why interspecific hybridization is so common in natural and domesticated yeast, and open the way to applications for wine-making. PMID:25946464

  20. Hybridization within Saccharomyces Genus Results in Homoeostasis and Phenotypic Novelty in Winemaking Conditions.

    PubMed

    da Silva, Telma; Albertin, Warren; Dillmann, Christine; Bely, Marina; la Guerche, Stéphane; Giraud, Christophe; Huet, Sylvie; Sicard, Delphine; Masneuf-Pomarede, Isabelle; de Vienne, Dominique; Marullo, Philippe

    2015-01-01

    Despite its biotechnological interest, hybridization, which can result in hybrid vigor, has not commonly been studied or exploited in the yeast genus. From a diallel design including 55 intra- and interspecific hybrids between Saccharomyces cerevisiae and S. uvarum grown at two temperatures in enological conditions, we analyzed as many as 35 fermentation traits with original statistical and modeling tools. We first showed that, depending on the types of trait--kinetics parameters, life-history traits, enological parameters and aromas -, the sources of variation (strain, temperature and strain * temperature effects) differed in a large extent. Then we compared globally three groups of hybrids and their parents at two growth temperatures: intraspecific hybrids S. cerevisiae * S. cerevisiae, intraspecific hybrids S. uvarum * S. uvarum and interspecific hybrids S. cerevisiae * S. uvarum. We found that hybridization could generate multi-trait phenotypes with improved oenological performances and better homeostasis with respect to temperature. These results could explain why interspecific hybridization is so common in natural and domesticated yeast, and open the way to applications for wine-making. PMID:25946464

  1. The Interaction between Saccharomyces cerevisiae and Non-Saccharomyces Yeast during Alcoholic Fermentation Is Species and Strain Specific.

    PubMed

    Wang, Chunxiao; Mas, Albert; Esteve-Zarzoso, Braulio

    2016-01-01

    The present study analyzes the lack of culturability of different non-Saccharomyces strains due to interaction with Saccharomyces cerevisiae during alcoholic fermentation. Interaction was followed in mixed fermentations with 1:1 inoculation of S. cerevisiae and ten non-Saccharomyces strains. Starmerella bacillaris, and Torulaspora delbrueckii indicated longer coexistence in mixed fermentations compared with Hanseniaspora uvarum and Metschnikowia pulcherrima. Strain differences in culturability and nutrient consumption (glucose, alanine, ammonium, arginine, or glutamine) were found within each species in mixed fermentation with S. cerevisiae. The interaction was further analyzed using cell-free supernatant from S. cerevisiae and synthetic media mimicking both single fermentations with S. cerevisiae and using mixed fermentations with the corresponding non-Saccharomyces species. Cell-free S. cerevisiae supernatants induced faster culturability loss than synthetic media corresponding to the same fermentation stage. This demonstrated that some metabolites produced by S. cerevisiae played the main role in the decreased culturability of the other non-Saccharomyces yeasts. However, changes in the concentrations of main metabolites had also an effect. Culturability differences were observed among species and strains in culture assays and thus showed distinct tolerance to S. cerevisiae metabolites and fermentation environment. Viability kit and recovery analyses on non-culturable cells verified the existence of viable but not-culturable status. These findings are discussed in the context of interaction between non-Saccharomyces and S. cerevisiae. PMID:27148191

  2. The Interaction between Saccharomyces cerevisiae and Non-Saccharomyces Yeast during Alcoholic Fermentation Is Species and Strain Specific

    PubMed Central

    Wang, Chunxiao; Mas, Albert; Esteve-Zarzoso, Braulio

    2016-01-01

    The present study analyzes the lack of culturability of different non-Saccharomyces strains due to interaction with Saccharomyces cerevisiae during alcoholic fermentation. Interaction was followed in mixed fermentations with 1:1 inoculation of S. cerevisiae and ten non-Saccharomyces strains. Starmerella bacillaris, and Torulaspora delbrueckii indicated longer coexistence in mixed fermentations compared with Hanseniaspora uvarum and Metschnikowia pulcherrima. Strain differences in culturability and nutrient consumption (glucose, alanine, ammonium, arginine, or glutamine) were found within each species in mixed fermentation with S. cerevisiae. The interaction was further analyzed using cell-free supernatant from S. cerevisiae and synthetic media mimicking both single fermentations with S. cerevisiae and using mixed fermentations with the corresponding non-Saccharomyces species. Cell-free S. cerevisiae supernatants induced faster culturability loss than synthetic media corresponding to the same fermentation stage. This demonstrated that some metabolites produced by S. cerevisiae played the main role in the decreased culturability of the other non-Saccharomyces yeasts. However, changes in the concentrations of main metabolites had also an effect. Culturability differences were observed among species and strains in culture assays and thus showed distinct tolerance to S. cerevisiae metabolites and fermentation environment. Viability kit and recovery analyses on non-culturable cells verified the existence of viable but not-culturable status. These findings are discussed in the context of interaction between non-Saccharomyces and S. cerevisiae. PMID:27148191

  3. Efficient engineering of marker-free synthetic allotetraploids of Saccharomyces.

    PubMed

    Alexander, William G; Peris, David; Pfannenstiel, Brandon T; Opulente, Dana A; Kuang, Meihua; Hittinger, Chris Todd

    2016-04-01

    Saccharomyces interspecies hybrids are critical biocatalysts in the fermented beverage industry, including in the production of lager beers, Belgian ales, ciders, and cold-fermented wines. Current methods for making synthetic interspecies hybrids are cumbersome and/or require genome modifications. We have developed a simple, robust, and efficient method for generating allotetraploid strains of prototrophic Saccharomyces without sporulation or nuclear genome manipulation. S. cerevisiae×S. eubayanus, S. cerevisiae×S. kudriavzevii, and S. cerevisiae×S. uvarum designer hybrid strains were created as synthetic lager, Belgian, and cider strains, respectively. The ploidy and hybrid nature of the strains were confirmed using flow cytometry and PCR-RFLP analysis, respectively. This method provides an efficient means for producing novel synthetic hybrids for beverage and biofuel production, as well as for constructing tetraploids to be used for basic research in evolutionary genetics and genome stability. PMID:26555931

  4. Potential of Glycosidase from Non-Saccharomyces Isolates for Enhancement of Wine Aroma.

    PubMed

    Hu, Kai; Qin, Yi; Tao, Yong-Sheng; Zhu, Xiao-Lin; Peng, Chuan-Tao; Ullah, Niamat

    2016-04-01

    The aim of this work was to rapidly screen indigenous yeasts with high levels of β-glucosidase activity and assess the potential of glycosidase extracts for aroma enhancement in winemaking. A semiquantitative colorimetric assay was applied using 96-well plates to screen yeasts from 3 different regions of China. Isolates with high β-glucosidase activity were confirmed by the commonly used pNP assay. Among 493 non-Saccharomyces isolates belonging to 8 generas, 3 isolates were selected for their high levels of β-glucosidase activity and were identified as Hanseniaspora uvarum, Pichia membranifaciens, and Rhodotorula mucilaginosa by sequence analysis of the 26S rDNA D1/D2 domain. β-Glucosidase in the glycosidase extract from H. uvarum strain showed the highest activity in winemaking conditions among the selected isolates. For aroma enhancement in winemaking, the glycosidase extract from H. uvarum strain exhibited catalytic specificity for aromatic glycosides of C13 -norisoprenoids and some terpenes, enhancing fresh floral, sweet, berry, and nutty aroma characteristics in wine. PMID:26954887

  5. Sequential Fermentation with Selected Immobilized Non-Saccharomyces Yeast for Reduction of Ethanol Content in Wine.

    PubMed

    Canonico, Laura; Comitini, Francesca; Oro, Lucia; Ciani, Maurizio

    2016-01-01

    The average ethanol content of wine has increased over the last two decades. This increase was due to consumer preference, and also to climate change that resulted in increased grape maturity at harvest. In the present study, to reduce ethanol content in wine, a microbiological approach was investigated, using immobilized selected strains of non-Saccharomyces yeasts namely Starmerella bombicola, Metschnikowia pulcherrima, Hanseniaspora osmophila, and Hanseniaspora uvarum to start fermentation, followed by inoculation of free Saccharomyces cerevisiae cells. The immobilization procedures, determining high reaction rates, led a feasible sequential inoculation management avoiding possible contamination under actual winemaking. Under these conditions, the immobilized cells metabolized almost 50% of the sugar in 3 days, while S. cerevisiae inoculation completed all of fermentation. The S. bombicola and M. pulcherrima initial fermentations showed the best reductions in the final ethanol content (1.6 and 1.4% v/v, respectively). Resulting wines did not have any negative fermentation products with the exception of H. uvarum sequential fermentation that showed significant amount of ethyl acetate. On the other hand, there were increases in desirable compounds such as glycerol and succinic acid for S. bombicola, geraniol for M. pulcherrima and isoamyl acetate and isoamyl alcohol for H. osmophila sequential fermentations. The overall results indicated that a promising ethanol reduction could be obtained using sequential fermentation of immobilized selected non-Saccharomyces strains. In this way, a suitable timing of second inoculation and an enhancement of analytical profile of wine were obtained. PMID:27014203

  6. Sequential Fermentation with Selected Immobilized Non-Saccharomyces Yeast for Reduction of Ethanol Content in Wine

    PubMed Central

    Canonico, Laura; Comitini, Francesca; Oro, Lucia; Ciani, Maurizio

    2016-01-01

    The average ethanol content of wine has increased over the last two decades. This increase was due to consumer preference, and also to climate change that resulted in increased grape maturity at harvest. In the present study, to reduce ethanol content in wine, a microbiological approach was investigated, using immobilized selected strains of non-Saccharomyces yeasts namely Starmerella bombicola, Metschnikowia pulcherrima, Hanseniaspora osmophila, and Hanseniaspora uvarum to start fermentation, followed by inoculation of free Saccharomyces cerevisiae cells. The immobilization procedures, determining high reaction rates, led a feasible sequential inoculation management avoiding possible contamination under actual winemaking. Under these conditions, the immobilized cells metabolized almost 50% of the sugar in 3 days, while S. cerevisiae inoculation completed all of fermentation. The S. bombicola and M. pulcherrima initial fermentations showed the best reductions in the final ethanol content (1.6 and 1.4% v/v, respectively). Resulting wines did not have any negative fermentation products with the exception of H. uvarum sequential fermentation that showed significant amount of ethyl acetate. On the other hand, there were increases in desirable compounds such as glycerol and succinic acid for S. bombicola, geraniol for M. pulcherrima and isoamyl acetate and isoamyl alcohol for H. osmophila sequential fermentations. The overall results indicated that a promising ethanol reduction could be obtained using sequential fermentation of immobilized selected non-Saccharomyces strains. In this way, a suitable timing of second inoculation and an enhancement of analytical profile of wine were obtained. PMID:27014203

  7. Saccharomyces boulardii

    MedlinePlus

    ... colitis), Lyme disease, a bowel disorder called relapsing Clostridium difficile colitis, and bacterial overgrowth in short bowel syndrome. ... appearance of acne. Diarrhea caused by the bacteria Clostridium difficile. Taking Saccharomyces boulardii by mouth along with the ...

  8. "Hanseniaspora uvarum" the ultrastructural morphology of a rare ascomycete, isolated from oral thrush.

    PubMed

    Emmanouil-Nikoloussi, E; Kanellaki-Kyparissi, M; Papavassiliou, P; Koliakos, K; Dermentzopoulou, M; Foroglou, C

    1994-01-01

    Superficial fungal infections, including oral thrush, often affect aged full denture wearers and many individuals over 65 years old. The aim of this study was to examine the ultrastructural morphology of a very rare yeast, named Hanseniaspora uvarum/guillermondi, member of the Ascomycetes family, whose pathogenesis and behaviour is not widely known. The yeast was isolated from whitish lesions of the buccal mucosa of an 70 years old woman. The specimen was collected with a mouth swab and cultured in Sabourauds-Dextrose agar. The identification of the organism was performed on the Api 20C Aux system. The yeast colonies, after fixation in glutaraldehyde 3% for 1 hour were immersed in OsO4 1% solution for 1 hour and were "in tissue" stained with uranyl acetate. Ultrathin sections, were observed with TEM Jeol C x 100. Our ultrastructural observations showed that this yeast had a thick cell wall in which the outer surface appeared fuzzy. In some yeasts we observed multilayered intracytoplasmic membrane a figure which is not described as far as we know in any yeast. Many vacuoles were frequently observed in the cytoplasm and especially in the center of the oval shaped cells. Bilateral budding which form ascospores is identical for the morphology of this yeast. PMID:7994154

  9. Povalibacter uvarum gen. nov., sp. nov., a polyvinyl-alcohol-degrading bacterium isolated from grapes.

    PubMed

    Nogi, Yuichi; Yoshizumi, Masaki; Hamana, Koei; Miyazaki, Masayuki; Horikoshi, Koki

    2014-08-01

    Polyvinyl-alcohol-degrading bacteria were isolated from the fruit of a grape in Yokosuka, Japan. The isolated strain, Zumi 37(T), was a Gram-stain-negative, rod-shaped, motile, non-spore-forming and strictly aerobic chemo-organotroph, showing optimal growth at pH 7.5, 30 °C and 0.1% (w/v) NaCl. The major respiratory quinone was Q-8. The predominant fatty acids were iso-C(15 : 0), C(16 : 0) and C(16 : 1)ω7c. The major polyamines were homospermidine and putrescine. The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The DNA G+C content of the novel strain was 64.2 mol%. 16S rRNA gene sequence comparison revealed that strain Zumi 37(T) belongs to the family Sinobacteraceae within the class Gammaproteobacteria. Steroidobacter denitrificans DSM 18526(T) was the most closely related species with a validly published name, with 98.0% similarity based on 16S rRNA gene sequence comparison (and showed less than 87.5% sequence similarity to members of the genera Alkanibacter, Fontimonas, Hydrocarboniphaga, Nevskia and Solimonas with known 16S rRNA gene sequences). Phenotypes for growth under aerobic conditions and on complex media and major fatty acid composition, differed greatly from those of with comparatively high 16S rRNA gene sequence similarity. Based on phylogenetic, phenotypic and chemotaxonomic evidence, it is proposed that strain Zumi 37(T) represents a novel species in a new genus for which the name Povalibacter uvarum gen. nov., sp. nov. is proposed. The type strain of the type species is Zumi 37(T) ( = JCM 18749(T) = DSM 26723(T)). PMID:24844263

  10. On the Complexity of the Saccharomyces bayanus Taxon: Hybridization and Potential Hybrid Speciation

    PubMed Central

    Pérez-Través, Laura; Lopes, Christian A.; Querol, Amparo; Barrio, Eladio

    2014-01-01

    Although the genus Saccharomyces has been thoroughly studied, some species in the genus has not yet been accurately resolved; an example is S. bayanus, a taxon that includes genetically diverse lineages of pure and hybrid strains. This diversity makes the assignation and classification of strains belonging to this species unclear and controversial. They have been subdivided by some authors into two varieties (bayanus and uvarum), which have been raised to the species level by others. In this work, we evaluate the complexity of 46 different strains included in the S. bayanus taxon by means of PCR-RFLP analysis and by sequencing of 34 gene regions and one mitochondrial gene. Using the sequence data, and based on the S. bayanus var. bayanus reference strain NBRC 1948, a hypothetical pure S. bayanus was reconstructed for these genes that showed alleles with similarity values lower than 97% with the S. bayanus var. uvarum strain CBS 7001, and of 99–100% with the non S. cerevisiae portion in S. pastorianus Weihenstephan 34/70 and with the new species S. eubayanus. Among the S. bayanus strains under study, different levels of homozygosity, hybridization and introgression were found; however, no pure S. bayanus var. bayanus strain was identified. These S. bayanus hybrids can be classified into two types: homozygous (type I) and heterozygous hybrids (type II), indicating that they have been originated by different hybridization processes. Therefore, a putative evolutionary scenario involving two different hybridization events between a S. bayanus var. uvarum and unknown European S. eubayanus-like strains can be postulated to explain the genomic diversity observed in our S. bayanus var. bayanus strains. PMID:24705561

  11. On the complexity of the Saccharomyces bayanus taxon: hybridization and potential hybrid speciation.

    PubMed

    Pérez-Través, Laura; Lopes, Christian A; Querol, Amparo; Barrio, Eladio

    2014-01-01

    Although the genus Saccharomyces has been thoroughly studied, some species in the genus has not yet been accurately resolved; an example is S. bayanus, a taxon that includes genetically diverse lineages of pure and hybrid strains. This diversity makes the assignation and classification of strains belonging to this species unclear and controversial. They have been subdivided by some authors into two varieties (bayanus and uvarum), which have been raised to the species level by others. In this work, we evaluate the complexity of 46 different strains included in the S. bayanus taxon by means of PCR-RFLP analysis and by sequencing of 34 gene regions and one mitochondrial gene. Using the sequence data, and based on the S. bayanus var. bayanus reference strain NBRC 1948, a hypothetical pure S. bayanus was reconstructed for these genes that showed alleles with similarity values lower than 97% with the S. bayanus var. uvarum strain CBS 7001, and of 99-100% with the non S. cerevisiae portion in S. pastorianus Weihenstephan 34/70 and with the new species S. eubayanus. Among the S. bayanus strains under study, different levels of homozygosity, hybridization and introgression were found; however, no pure S. bayanus var. bayanus strain was identified. These S. bayanus hybrids can be classified into two types: homozygous (type I) and heterozygous hybrids (type II), indicating that they have been originated by different hybridization processes. Therefore, a putative evolutionary scenario involving two different hybridization events between a S. bayanus var. uvarum and unknown European S. eubayanus-like strains can be postulated to explain the genomic diversity observed in our S. bayanus var. bayanus strains. PMID:24705561

  12. Deciphering the Hybridisation History Leading to the Lager Lineage Based on the Mosaic Genomes of Saccharomyces bayanus Strains NBRC1948 and CBS380T

    PubMed Central

    Nguyen, Huu-Vang; Legras, Jean-Luc; Neuvéglise, Cécile; Gaillardin, Claude

    2011-01-01

    Saccharomyces bayanus is a yeast species described as one of the two parents of the hybrid brewing yeast S. pastorianus. Strains CBS380T and NBRC1948 have been retained successively as pure-line representatives of S. bayanus. In the present study, sequence analyses confirmed and upgraded our previous finding: S. bayanus type strain CBS380T harbours a mosaic genome. The genome of strain NBRC1948 was also revealed to be mosaic. Both genomes were characterized by amplification and sequencing of different markers, including genes involved in maltotriose utilization or genes detected by array-CGH mapping. Sequence comparisons with public Saccharomyces spp. nucleotide sequences revealed that the CBS380T and NBRC1948 genomes are composed of: a predominant non-cerevisiae genetic background belonging to S. uvarum, a second unidentified species provisionally named S. lagerae, and several introgressed S. cerevisiae fragments. The largest cerevisiae-introgressed DNA common to both genomes totals 70kb in length and is distributed in three contigs, cA, cB and cC. These vary in terms of length and presence of MAL31 or MTY1 (maltotriose-transporter gene). In NBRC1948, two additional cerevisiae-contigs, cD and cE, totaling 12kb in length, as well as several smaller cerevisiae fragments were identified. All of these contigs were partially detected in the genomes of S. pastorianus lager strains CBS1503 (S. monacensis) and CBS1513 (S. carlsbergensis) explaining the noticeable common ability of S. bayanus and S. pastorianus to metabolize maltotriose. NBRC1948 was shown to be inter-fertile with S. uvarum CBS7001. The cross involving these two strains produced F1 segregants resembling the strains CBS380T or NRRLY-1551. This demonstrates that these S. bayanus strains were the offspring of a cross between S. uvarum and a strain similar to NBRC1948. Phylogenies established with selected cerevisiae and non-cerevisiae genes allowed us to decipher the complex hybridisation events linking S

  13. Deciphering the hybridisation history leading to the Lager lineage based on the mosaic genomes of Saccharomyces bayanus strains NBRC1948 and CBS380.

    PubMed

    Nguyen, Huu-Vang; Legras, Jean-Luc; Neuvéglise, Cécile; Gaillardin, Claude

    2011-01-01

    Saccharomyces bayanus is a yeast species described as one of the two parents of the hybrid brewing yeast S. pastorianus. Strains CBS380(T) and NBRC1948 have been retained successively as pure-line representatives of S. bayanus. In the present study, sequence analyses confirmed and upgraded our previous finding: S. bayanus type strain CBS380(T) harbours a mosaic genome. The genome of strain NBRC1948 was also revealed to be mosaic. Both genomes were characterized by amplification and sequencing of different markers, including genes involved in maltotriose utilization or genes detected by array-CGH mapping. Sequence comparisons with public Saccharomyces spp. nucleotide sequences revealed that the CBS380(T) and NBRC1948 genomes are composed of: a predominant non-cerevisiae genetic background belonging to S. uvarum, a second unidentified species provisionally named S. lagerae, and several introgressed S. cerevisiae fragments. The largest cerevisiae-introgressed DNA common to both genomes totals 70kb in length and is distributed in three contigs, cA, cB and cC. These vary in terms of length and presence of MAL31 or MTY1 (maltotriose-transporter gene). In NBRC1948, two additional cerevisiae-contigs, cD and cE, totaling 12kb in length, as well as several smaller cerevisiae fragments were identified. All of these contigs were partially detected in the genomes of S. pastorianus lager strains CBS1503 (S. monacensis) and CBS1513 (S. carlsbergensis) explaining the noticeable common ability of S. bayanus and S. pastorianus to metabolize maltotriose. NBRC1948 was shown to be inter-fertile with S. uvarum CBS7001. The cross involving these two strains produced F1 segregants resembling the strains CBS380(T) or NRRLY-1551. This demonstrates that these S. bayanus strains were the offspring of a cross between S. uvarum and a strain similar to NBRC1948. Phylogenies established with selected cerevisiae and non-cerevisiae genes allowed us to decipher the complex hybridisation events

  14. Alternative Glycerol Balance Strategies among Saccharomyces Species in Response to Winemaking Stress

    PubMed Central

    Pérez-Torrado, Roberto; Oliveira, Bruno M.; Zemančíková, Jana; Sychrová, Hana; Querol, Amparo

    2016-01-01

    Production and balance of glycerol is essential for the survival of yeast cells in certain stressful conditions as hyperosmotic or cold shock that occur during industrial processes as winemaking. These stress responses are well-known in S. cerevisiae, however, little is known in other phylogenetically close related Saccharomyces species associated with natural or fermentation environments such as S. uvarum, S. paradoxus or S. kudriavzevii. In this work we have investigated the expression of four genes (GPD1, GPD2, STL1, and FPS1) crucial in the glycerol pool balance in the four species with a biotechnological potential (S. cerevisiae; S. paradoxus; S. uvarum; and S. kudriavzevii), and the ability of strains to grow under osmotic and cold stresses. The results show different pattern and level of expression among the different species, especially for STL1. We also studied the function of Stl1 glycerol symporter in the survival to osmotic changes and cell growth capacity in winemaking environments. These experiments also revealed a different functionality of the glycerol transporters among the different species studied. All these data point to different strategies to handle glycerol accumulation in response to winemaking stresses as hyperosmotic or cold-hyperosmotic stress in the different species, with variable emphasis in the production, influx, or efflux of glycerol. PMID:27064588

  15. Persistence of Two Non-Saccharomyces Yeasts (Hanseniaspora and Starmerella) in the Cellar

    PubMed Central

    Grangeteau, Cédric; Gerhards, Daniel; von Wallbrunn, Christian; Alexandre, Hervé; Rousseaux, Sandrine; Guilloux-Benatier, Michèle

    2016-01-01

    Different genera and/or species of yeasts present on grape berries, in musts and wines are widely described. Nevertheless, the community of non-Saccharomyces yeasts present in the cellar is still given little attention. Thus it is not known if the cellar is a real ecological niche for these yeasts or if it is merely a transient habitat for populations brought in by grape berries during the winemaking period. This study focused on three species of non-Saccharomyces yeasts commonly encountered during vinification: Starmerella bacillaris (synonymy with Candida zemplinina), Hanseniaspora guilliermondii and Hanseniaspora uvarum. More than 1200 isolates were identified at the strain level by FT-IR spectroscopy (207 different FTIR strain pattern). Only a small proportion of non-Saccharomyces yeasts present in musts came directly from grape berries for the three species studied. Some strains were found in the must in two consecutive years and some of them were also found in the cellar environment before the arrival of the harvest of second vintage. This study demonstrates for the first time the persistence of non-Saccharomyces yeast strains from year to year in the cellar. Sulfur dioxide can affect yeast populations in the must and therefore their persistence in the cellar environment. PMID:27014199

  16. Enological characterization of Spanish Saccharomyces kudriavzevii strains, one of the closest relatives to parental strains of winemaking and brewing Saccharomyces cerevisiae × S. kudriavzevii hybrids.

    PubMed

    Peris, D; Pérez-Través, L; Belloch, C; Querol, A

    2016-02-01

    Wine fermentation and innovation have focused mostly on Saccharomyces cerevisiae strains. However, recent studies have shown that other Saccharomyces species can also be involved in wine fermentation or are useful for wine bouquet, such as Saccharomyces uvarum and Saccharomyces paradoxus. Many interspecies hybrids have also been isolated from wine fermentation, such as S. cerevisiae × Saccharomyces kudriavzevii hybrids. In this study, we explored the genetic diversity and fermentation performance of Spanish S. kudriavzevii strains, which we compared to other S. kudriavzevii strains. Fermentations of red and white grape musts were performed, and the phenotypic differences between Spanish S. kudriavzevii strains under different temperature conditions were examined. An ANOVA analysis suggested striking similarity between strains for glycerol and ethanol production, although a high diversity of aromatic profiles among fermentations was found. The sources of these phenotypic differences are not well understood and require further investigation. Although the Spanish S. kudriavzevii strains showed desirable properties, particularly must fermentations, the quality of their wines was no better than those produced with a commercial S. cerevisiae. We suggest hybridization or directed evolution as methods to improve and innovate wine. PMID:26678127

  17. Functional toxicity and tolerance patterns of bioavailable Pd(II), Pt(II), and Rh(III) on suspended Saccharomyces cerevisiae cells assayed in tandem by a respirometric biosensor.

    PubMed

    Frazzoli, Chiara; Dragone, Roberto; Mantovani, Alberto; Massimi, Cristiana; Campanella, Luigi

    2007-12-01

    Toxicological implications of exposure to bioavailable platinum group metals, here Pd, Pt, and Rh, are still to be clarified. This study obtained by a biosensor-based method preliminary information on potential effects on cellular metabolism as well as on possible tolerance mechanisms. Aerobic respiration was taken as the toxicological end point to perform tandem tests, namely functional toxicity test and tolerance test. Cells were suspended in the absence of essential constituents for growth. The dose-response curves obtained by exposure (2 h) to the metals (nanogram per gram range) suggested the same mechanisms of action, with Rh showing the greatest curve steepness and the lowest EC50 value. Conservative (95% lower confidence interval) EC10 values were 187, 85 and 51 ng g(-1) for Pt, Pd, and Rh respectively. Tolerance patterns were tested during the same runs. The full tolerance obtained after 12 h of exposure to each metal suggested mitochondrial inhibition of aerobic respiration as a target effect. The hazard rating of the metals in the tolerance test changed in the Rh EC50 range, where Rh showed the lowest toxicity. The observed tolerance might suggest a protective mechanism such as metallothionein induction at concentrations around the EC50 values. The performance of the bioassay was satisfactory, in terms of the limit of detection, repeatability, reproducibility, roboustness, sensibility, and stability; the method's critical uncertainty sources were identified for improvements. PMID:17960368

  18. Fermentative capabilities and volatile compounds produced by Kloeckera/Hanseniaspora and Saccharomyces yeast strains in pure and mixed cultures during Agave tequilana juice fermentation.

    PubMed

    González-Robles, Ivonne Wendolyne; Estarrón-Espinosa, Mirna; Díaz-Montaño, Dulce María

    2015-09-01

    The fermentative and aromatic capabilities of Kloeckera africana/Hanseniaspora vineae K1, K. apiculata/H. uvarum K2, and Saccharomyces cerevisiae S1 and S2 were studied in pure and mixed culture fermentations using Agave tequila juice as the culture medium. In pure and mixed cultures, Kloeckera/Hanseniaspora strains showed limited growth and sugar consumption, as well as low ethanol yield and productivity, compared to S. cerevisiae, which yielded more biomass, ethanol and viable cell concentrations. In pure and mixed cultures, S. cerevisiae presented a similar behaviour reaching high biomass production, completely consuming the sugar, leading to high ethanol production. Furthermore, the presence of S. cerevisiae strains in the mixed cultures promoted the production of higher alcohols, acetaldehyde and ethyl esters, whereas Kloeckera/Hanseniaspora strains stimulated the production of ethyl acetate and 2-phenyl ethyl acetate compounds. PMID:26108494

  19. A New System for Comparative Functional Genomics of Saccharomyces Yeasts

    PubMed Central

    Caudy, Amy A.; Guan, Yuanfang; Jia, Yue; Hansen, Christina; DeSevo, Chris; Hayes, Alicia P.; Agee, Joy; Alvarez-Dominguez, Juan R.; Arellano, Hugo; Barrett, Daniel; Bauerle, Cynthia; Bisaria, Namita; Bradley, Patrick H.; Breunig, J. Scott; Bush, Erin; Cappel, David; Capra, Emily; Chen, Walter; Clore, John; Combs, Peter A.; Doucette, Christopher; Demuren, Olukunle; Fellowes, Peter; Freeman, Sam; Frenkel, Evgeni; Gadala-Maria, Daniel; Gawande, Richa; Glass, David; Grossberg, Samuel; Gupta, Anita; Hammonds-Odie, Latanya; Hoisos, Aaron; Hsi, Jenny; Hsu, Yu-Han Huang; Inukai, Sachi; Karczewski, Konrad J.; Ke, Xiaobo; Kojima, Mina; Leachman, Samuel; Lieber, Danny; Liebowitz, Anna; Liu, Julia; Liu, Yufei; Martin, Trevor; Mena, Jose; Mendoza, Rosa; Myhrvold, Cameron; Millian, Christian; Pfau, Sarah; Raj, Sandeep; Rich, Matt; Rokicki, Joe; Rounds, William; Salazar, Michael; Salesi, Matthew; Sharma, Rajani; Silverman, Sanford; Singer, Cara; Sinha, Sandhya; Staller, Max; Stern, Philip; Tang, Hanlin; Weeks, Sharon; Weidmann, Maxwell; Wolf, Ashley; Young, Carmen; Yuan, Jie; Crutchfield, Christopher; McClean, Megan; Murphy, Coleen T.; Llinás, Manuel; Botstein, David; Troyanskaya, Olga G.; Dunham, Maitreya J.

    2013-01-01

    Whole-genome sequencing, particularly in fungi, has progressed at a tremendous rate. More difficult, however, is experimental testing of the inferences about gene function that can be drawn from comparative sequence analysis alone. We present a genome-wide functional characterization of a sequenced but experimentally understudied budding yeast, Saccharomyces bayanus var. uvarum (henceforth referred to as S. bayanus), allowing us to map changes over the 20 million years that separate this organism from S. cerevisiae. We first created a suite of genetic tools to facilitate work in S. bayanus. Next, we measured the gene-expression response of S. bayanus to a diverse set of perturbations optimized using a computational approach to cover a diverse array of functionally relevant biological responses. The resulting data set reveals that gene-expression patterns are largely conserved, but significant changes may exist in regulatory networks such as carbohydrate utilization and meiosis. In addition to regulatory changes, our approach identified gene functions that have diverged. The functions of genes in core pathways are highly conserved, but we observed many changes in which genes are involved in osmotic stress, peroxisome biogenesis, and autophagy. A surprising number of genes specific to S. bayanus respond to oxidative stress, suggesting the organism may have evolved under different selection pressures than S. cerevisiae. This work expands the scope of genome-scale evolutionary studies from sequence-based analysis to rapid experimental characterization and could be adopted for functional mapping in any lineage of interest. Furthermore, our detailed characterization of S. bayanus provides a valuable resource for comparative functional genomics studies in yeast. PMID:23852385

  20. Aroma Profile of Montepulciano d'Abruzzo Wine Fermented by Single and Co-culture Starters of Autochthonous Saccharomyces and Non-saccharomyces Yeasts.

    PubMed

    Tofalo, Rosanna; Patrignani, Francesca; Lanciotti, Rosalba; Perpetuini, Giorgia; Schirone, Maria; Di Gianvito, Paola; Pizzoni, Daniel; Arfelli, Giuseppe; Suzzi, Giovanna

    2016-01-01

    Montepulciano d'Abruzzo is a native grape variety of Vitis vinifera L., grown in central Italy and used for production of high quality red wines. Limited studies have been carried out to improve its enological characteristics through the use of indigenous strains of Saccharomyces cerevisiae. The main objective of the present work was to test two indigenous strains of S. cerevisiae (SRS1, RT73), a strain of Starmerella bacillaris (STS12), one of Hanseniaspora uvarum (STS45) and a co-culture of S. cerevisiae (SRS1) and S. bacillaris (STS12), in an experimental cellar to evaluate their role in the sensory characteristic of Montepulciano d'Abruzzo wine. A S. cerevisiae commercial strain was used. Fermentations were conducted under routine Montepulciano d'Abruzzo wine production, in which the main variables were the yeast strains used for fermentation. Basic winemaking parameters, some key chemical analysis and aroma compounds were considered. S. cerevisiae strain dynamics during fermentation were determined by molecular methods. The musts inoculated with the co-culture were characterized by a faster fermentation start and a higher content of glycerol after 3 days of fermentation, as well as the musts added with strains S. bacillaris (STS12) and H. uvarum (STS45). At the end of fermentation the parameters studied were quite similar in all the wines. Total biogenic amines (BA) content of all the wines was low. Ethanolamine was the predominant BA, with a concentration ranging from 21 to 24 mg/l. Wines were characterized by esters and alcohols. In particular, 2-phenylethanol, 3-methylbut-1-yl methanoate, and ethyl ethanoate were the major aroma volatile compounds in all wines. Statistical analysis highlighted the different role played by aroma compounds in the differentiation of wines, even if it was impossible to select a single class of compounds as the most important for a specific yeast. The present study represents a further step toward the use of tailored

  1. Aroma Profile of Montepulciano d'Abruzzo Wine Fermented by Single and Co-culture Starters of Autochthonous Saccharomyces and Non-saccharomyces Yeasts

    PubMed Central

    Tofalo, Rosanna; Patrignani, Francesca; Lanciotti, Rosalba; Perpetuini, Giorgia; Schirone, Maria; Di Gianvito, Paola; Pizzoni, Daniel; Arfelli, Giuseppe; Suzzi, Giovanna

    2016-01-01

    Montepulciano d'Abruzzo is a native grape variety of Vitis vinifera L., grown in central Italy and used for production of high quality red wines. Limited studies have been carried out to improve its enological characteristics through the use of indigenous strains of Saccharomyces cerevisiae. The main objective of the present work was to test two indigenous strains of S. cerevisiae (SRS1, RT73), a strain of Starmerella bacillaris (STS12), one of Hanseniaspora uvarum (STS45) and a co-culture of S. cerevisiae (SRS1) and S. bacillaris (STS12), in an experimental cellar to evaluate their role in the sensory characteristic of Montepulciano d'Abruzzo wine. A S. cerevisiae commercial strain was used. Fermentations were conducted under routine Montepulciano d'Abruzzo wine production, in which the main variables were the yeast strains used for fermentation. Basic winemaking parameters, some key chemical analysis and aroma compounds were considered. S. cerevisiae strain dynamics during fermentation were determined by molecular methods. The musts inoculated with the co-culture were characterized by a faster fermentation start and a higher content of glycerol after 3 days of fermentation, as well as the musts added with strains S. bacillaris (STS12) and H. uvarum (STS45). At the end of fermentation the parameters studied were quite similar in all the wines. Total biogenic amines (BA) content of all the wines was low. Ethanolamine was the predominant BA, with a concentration ranging from 21 to 24 mg/l. Wines were characterized by esters and alcohols. In particular, 2-phenylethanol, 3-methylbut-1-yl methanoate, and ethyl ethanoate were the major aroma volatile compounds in all wines. Statistical analysis highlighted the different role played by aroma compounds in the differentiation of wines, even if it was impossible to select a single class of compounds as the most important for a specific yeast. The present study represents a further step toward the use of tailored

  2. Screening of β-Glucosidase and β-Xylosidase Activities in Four Non-Saccharomyces Yeast Isolates.

    PubMed

    López, María Consuelo; Mateo, José Juan; Maicas, Sergi

    2015-08-01

    The finding of new isolates of non-Saccharomyces yeasts, showing beneficial enzymes (such as β-glucosidase and β-xylosidase), can contribute to the production of quality wines. In a selection and characterization program, we have studied 114 isolates of non-Saccharomyces yeasts. Four isolates were selected because of their both high β-glucosidase and β-xylosidase activities. The ribosomal D1/D2 regions were sequenced to identify them as Pichia membranifaciens Pm7, Hanseniaspora vineae Hv3, H. uvarum Hu8, and Wickerhamomyces anomalus Wa1. The induction process was optimized to be carried on YNB-medium supplemented with 4% xylan, inoculated with 106 cfu/mL and incubated 48 h at 28 °C without agitation. Most of the strains had a pH optimum of 5.0 to 6.0 for both the β-glucosidase and β-xylosidase activities. The effect of sugars was different for each isolate and activity. Each isolate showed a characteristic set of inhibition, enhancement or null effect for β-glucosidase and β-xylosidase. The volatile compounds liberated from wine incubated with each of the 4 yeasts were also studied, showing an overall terpene increase (1.1 to 1.3-folds) when wines were treated with non-Saccharomyces isolates. In detail, terpineol, 4-vinyl-phenol and 2-methoxy-4-vinylphenol increased after the addition of Hanseniaspora isolates. Wines treated with Hanseniaspora, Wickerhamomyces, or Pichia produced more 2-phenyl ethanol than those inoculated with other yeasts. PMID:26126488

  3. Enhancing the Bioconversion of Winery and Olive Mill Waste Mixtures into Lignocellulolytic Enzymes and Animal Feed by Aspergillus uvarum Using a Packed-Bed Bioreactor.

    PubMed

    Salgado, José Manuel; Abrunhosa, Luís; Venâncio, Armando; Domínguez, José Manuel; Belo, Isabel

    2015-10-28

    Wineries and olive oil industries are dominant agro-industrial activities in southern European regions. Olive pomace, exhausted grape marc, and vine shoot trimmings are lignocellulosic residues generated by these industries, which could be valued biotechnologically. In the present work these residues were used as substrate to produce cellulases and xylanases through solid-state fermentation using Aspergillus uvarum MUM 08.01. For that, two factorial designs (3(2)) were first planned to optimize substrate composition, temperature, and initial moisture level. Subsequently, the kinectics of cellulolytic enzyme production, fungal growth, and fermented solid were characterized. Finally, the process was performed in a packed-bed bioreactor. The results showed that cellulase activity improved with the optimization processes, reaching 33.56 U/g, and with the packed-bed bioreactor aeration of 0.2 L/min, reaching 38.51 U/g. The composition of fermented solids indicated their potential use for animal feed because cellulose, hemicellulose, lignin, and phenolic compounds were partially degraded 28.08, 10.78, 13.3, and 28.32%, respectively, crude protein was increased from 8.47 to 17.08%, and the mineral contents meet the requirements of main livestock. PMID:26165254

  4. Analysis of the Saccharomyces cerevisiae pan-genome reveals a pool of copy number variants distributed in diverse yeast strains from differing industrial environments

    PubMed Central

    Dunn, Barbara; Richter, Chandra; Kvitek, Daniel J.; Pugh, Tom; Sherlock, Gavin

    2012-01-01

    Although the budding yeast Saccharomyces cerevisiae is arguably one of the most well-studied organisms on earth, the genome-wide variation within this species—i.e., its “pan-genome”—has been less explored. We created a multispecies microarray platform containing probes covering the genomes of several Saccharomyces species: S. cerevisiae, including regions not found in the standard laboratory S288c strain, as well as the mitochondrial and 2-μm circle genomes–plus S. paradoxus, S. mikatae, S. kudriavzevii, S. uvarum, S. kluyveri, and S. castellii. We performed array-Comparative Genomic Hybridization (aCGH) on 83 different S. cerevisiae strains collected across a wide range of habitats; of these, 69 were commercial wine strains, while the remaining 14 were from a diverse set of other industrial and natural environments. We observed interspecific hybridization events, introgression events, and pervasive copy number variation (CNV) in all but a few of the strains. These CNVs were distributed throughout the strains such that they did not produce any clear phylogeny, suggesting extensive mating in both industrial and wild strains. To validate our results and to determine whether apparently similar introgressions and CNVs were identical by descent or recurrent, we also performed whole-genome sequencing on nine of these strains. These data may help pinpoint genomic regions involved in adaptation to different industrial milieus, as well as shed light on the course of domestication of S. cerevisiae. PMID:22369888

  5. Actin from Saccharomyces cerevisiae.

    PubMed Central

    Greer, C; Schekman, R

    1982-01-01

    Inhibition of DNase I activity has been used as an assay to purify actin from Saccharomyces cerevisiae (yeast actin). The final fraction, obtained after a 300-fold purification, is approximately 97% pure as judged by sodium dodecyl sulfate-gel electrophoresis. Like rabbit skeletal muscle actin, yeast actin has a molecular weight of about 43,000, forms 7-nm-diameter filaments when polymerization is induced by KCl or Mg2+, and can be decorated with a proteolytic fragment of muscle myosin (heavy meromyosin). Although heavy meromyosin ATPase activity is stimulated by rabbit muscle and yeast actins to approximately the same Vmax (2 mmol of Pi per min per mumol of heavy meromyosin), half-maximal activation (Kapp) is obtained with 14 micro M muscle actin, but requires approximately 135 micro M yeast actin. This difference suggests a low affinity of yeast actin for muscle myosin. Yeast and muscle filamentous actin respond similarly to cytochalasin and phalloidin, although the drugs have no effect on S. cerevisiae cell growth. Images PMID:6217414

  6. Prothrombin time (PT)

    MedlinePlus

    PT; Pro-time; Anticoagulant-prothrombin time; Clotting time: protime; INR; International normalized ratio ... PT is measured in seconds. Most of the time, results are given as what is called INR ( ...

  7. PT -symmetry Wave Chaos

    NASA Astrophysics Data System (ADS)

    West, Carl T.; Kottos, Tsampikos; Prosen, Tomaz

    2010-03-01

    We study a new class of chaotic systems with dynamical localization, where gain/loss processes break the hermiticity, while allowing for parity-time PT symmetry. For a value γPT of the gain/loss parameter the spectrum undergoes a spontaneous phase transition from real (exact phase) to complex values (broken phase). We develop a one parameter scaling theory for γPT, and show that chaos assists the exact PT-phase. Our results will have applications to the design of optical elements with PT-symmetry.

  8. Peptidase activities in Saccharomyces cerevisiae.

    PubMed Central

    Rose, B; Becker, J M; Naider, F

    1979-01-01

    At least four distinct aminopeptidase activities and a single dipeptidase activity were found in cell extracts of a leucine-lysine auxotroph of Saccharomyces cerevisiae. The assay for peptidase activity involved polyacrylamide gel electrophoresis followed by an enzyme-coupled activity staining procedure. The aminopeptidases had largely overlapping specificities but could be distinguished from one another by their electrophoretic mobilities and activities toward different peptide substrates. Substrates tested included both free and blocked di- and tripeptides and amino acid derivatives. Images PMID:378955

  9. Selected non-Saccharomyces wine yeasts in controlled multistarter fermentations with Saccharomyces cerevisiae.

    PubMed

    Comitini, Francesca; Gobbi, Mirko; Domizio, Paola; Romani, Cristina; Lencioni, Livio; Mannazzu, Ilaria; Ciani, Maurizio

    2011-08-01

    Non-Saccharomyces yeasts are metabolically active during spontaneous and inoculated must fermentations, and by producing a plethora of by-products, they can contribute to the definition of the wine aroma. Thus, use of Saccharomyces and non-Saccharomyces yeasts as mixed starter cultures for inoculation of wine fermentations is of increasing interest for quality enhancement and improved complexity of wines. We initially characterized 34 non-Saccharomyces yeasts of the genera Candida, Lachancea (Kluyveromyces), Metschnikowia and Torulaspora, and evaluated their enological potential. This confirmed that non-Saccharomyces yeasts from wine-related environments represent a rich sink of unexplored biodiversity for the winemaking industry. From these, we selected four non-Saccharomyces yeasts to combine with starter cultures of Saccharomyces cerevisiae in mixed fermentation trials. The kinetics of growth and fermentation, and the analytical profiles of the wines produced indicate that these non-Saccharomyces strains can be used with S. cerevisiae starter cultures to increase polysaccharide, glycerol and volatile compound production, to reduce volatile acidity, and to increase or reduce the total acidity of the final wines, depending on yeast species and inoculum ratio used. The overall effects of the non-Saccharomyces yeasts on fermentation and wine quality were strictly dependent on the Saccharomyces/non-Saccharomyces inoculum ratio that mimicked the differences of fermentation conditions (natural or simultaneous inoculated fermentation). PMID:21569929

  10. Cadmium biosorption by Saccharomyces cerevisiae

    SciTech Connect

    Volesky, B.; May, H.; Holan, Z.R. )

    1993-04-01

    Cadmium uptake by nonliving and resting cells of Saccharomyces cerevisiae obtained from aerobic or anaerobic cultures from pure cadmium-bearing solutions was examined. The highest cadmium uptake exceeding 70 mg Cd/g was observed with aerobic baker's yeast biomass from the exponential growth phase. Nearly linear sorption isotherms featured by higher sorbing resting cells together with metal deposits localized exclusively in vacuoles indicate the possibility of a different metal-sequestering mechanism when compared to dry nonliving yeasts which did not usually accumulate more than 20 mg Cd/g. The uptake of cadmium was relatively fast, 75% of the sorption completed in less than 5 min.

  11. PT-symmetric strings

    SciTech Connect

    Amore, Paolo; Fernández, Francisco M.; Garcia, Javier; Gutierrez, German

    2014-04-15

    We study both analytically and numerically the spectrum of inhomogeneous strings with PT-symmetric density. We discuss an exactly solvable model of PT-symmetric string which is isospectral to the uniform string; for more general strings, we calculate exactly the sum rules Z(p)≡∑{sub n=1}{sup ∞}1/E{sub n}{sup p}, with p=1,2,… and find explicit expressions which can be used to obtain bounds on the lowest eigenvalue. A detailed numerical calculation is carried out for two non-solvable models depending on a parameter, obtaining precise estimates of the critical values where pair of real eigenvalues become complex. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •We study PT-symmetric strings with complex density. •They exhibit regions of unbroken PT symmetry. •We calculate the critical parameters at the boundaries of those regions. •There are exact real sum rules for some particular complex densities.

  12. Metabolic Engineering of Saccharomyces cerevisiae

    PubMed Central

    Ostergaard, Simon; Olsson, Lisbeth; Nielsen, Jens

    2000-01-01

    Comprehensive knowledge regarding Saccharomyces cerevisiae has accumulated over time, and today S. cerevisiae serves as a widley used biotechnological production organism as well as a eukaryotic model system. The high transformation efficiency, in addition to the availability of the complete yeast genome sequence, has facilitated genetic manipulation of this microorganism, and new approaches are constantly being taken to metabolicially engineer this organism in order to suit specific needs. In this paper, strategies and concepts for metabolic engineering are discussed and several examples based upon selected studies involving S. cerevisiae are reviewed. The many different studies of metabolic engineering using this organism illustrate all the categories of this multidisciplinary field: extension of substrate range, improvements of producitivity and yield, elimination of byproduct formation, improvement of process performance, improvements of cellular properties, and extension of product range including heterologous protein production. PMID:10704473

  13. Methionine catabolism in Saccharomyces cerevisiae.

    PubMed

    Perpète, Philippe; Duthoit, Olivier; De Maeyer, Simon; Imray, Louise; Lawton, Andrew I; Stavropoulos, Konstantinos E; Gitonga, Virginia W; Hewlins, Michael J E; Dickinson, J Richard

    2006-01-01

    The catabolism of methionine to methionol and methanethiol in Saccharomyces cerevisiae was studied using (13)C NMR spectroscopy, GC-MS, enzyme assays and a number of mutants. Methionine is first transaminated to alpha-keto-gamma-(methylthio)butyrate. Methionol is formed by a decarboxylation reaction, which yields methional, followed by reduction. The decarboxylation is effected specifically by Ydr380wp. Methanethiol is formed from both methionine and alpha-keto-gamma-(methylthio)butyrate by a demethiolase activity. In all except one strain examined, demethiolase was induced by the presence of methionine in the growth medium. This pathway results in the production of alpha-ketobutyrate, a carbon skeleton, which can be re-utilized. Hence, methionine catabolism is more complex and economical than the other amino acid catabolic pathways in yeast, which use the Ehrlich pathway and result solely in the formation of a fusel alcohol. PMID:16423070

  14. Glucose repression in Saccharomyces cerevisiae.

    PubMed

    Kayikci, Ömur; Nielsen, Jens

    2015-09-01

    Glucose is the primary source of energy for the budding yeast Saccharomyces cerevisiae. Although yeast cells can utilize a wide range of carbon sources, presence of glucose suppresses molecular activities involved in the use of alternate carbon sources as well as it represses respiration and gluconeogenesis. This dominant effect of glucose on yeast carbon metabolism is coordinated by several signaling and metabolic interactions that mainly regulate transcriptional activity but are also effective at post-transcriptional and post-translational levels. This review describes effects of glucose repression on yeast carbon metabolism with a focus on roles of the Snf3/Rgt2 glucose-sensing pathway and Snf1 signal transduction in establishment and relief of glucose repression. PMID:26205245

  15. Postreplication repair in Saccharomyces cerevisiae

    SciTech Connect

    Resnick, M.A.; Boyce, J.; Cox, B.

    1981-04-01

    Postreplication events in logarithmically growing excision-defective mutants of Saccharomyces cerevisiae were examined after low doses of ultraviolet light. Pulse-labeled deoxyribonucleic acid had interruptions, and when the cells were chased, the interruptions were no longer detected. Since the loss of interruptions was not associated with an exchange of pyrimidine dimers at a detection level of 10 to 20% of the induced dimers, it was concluded that postreplication repair in excision-defective mutants does not involve molecular recombination. Pyrimidine dimers were assayed by utilizing the ultraviolet-endonuclease activity in extracts of Micrococcus luteus and newly developed alkaline sucrose gradient techniques, which yielded chromosomal-size deoxyribonucleic acid after treatment of irradiated cells.

  16. Glucose repression in Saccharomyces cerevisiae

    PubMed Central

    Kayikci, Ömur; Nielsen, Jens

    2015-01-01

    Glucose is the primary source of energy for the budding yeast Saccharomyces cerevisiae. Although yeast cells can utilize a wide range of carbon sources, presence of glucose suppresses molecular activities involved in the use of alternate carbon sources as well as it represses respiration and gluconeogenesis. This dominant effect of glucose on yeast carbon metabolism is coordinated by several signaling and metabolic interactions that mainly regulate transcriptional activity but are also effective at post-transcriptional and post-translational levels. This review describes effects of glucose repression on yeast carbon metabolism with a focus on roles of the Snf3/Rgt2 glucose-sensing pathway and Snf1 signal transduction in establishment and relief of glucose repression. PMID:26205245

  17. PT quantum mechanics.

    PubMed

    Bender, Carl M; DeKieviet, Maarten; Klevansky, S P

    2013-04-28

    PT-symmetric quantum mechanics (PTQM) has become a hot area of research and investigation. Since its beginnings in 1998, there have been over 1000 published papers and more than 15 international conferences entirely devoted to this research topic. Originally, PTQM was studied at a highly mathematical level and the techniques of complex variables, asymptotics, differential equations and perturbation theory were used to understand the subtleties associated with the analytic continuation of eigenvalue problems. However, as experiments on PT-symmetric physical systems have been performed, a simple and beautiful physical picture has emerged, and a PT-symmetric system can be understood as one that has a balanced loss and gain. Furthermore, the PT phase transition can now be understood intuitively without resorting to sophisticated mathematics. Research on PTQM is following two different paths: at a fundamental level, physicists are attempting to understand the underlying mathematical structure of these theories with the long-range objective of applying the techniques of PTQM to understanding some of the outstanding problems in physics today, such as the nature of the Higgs particle, the properties of dark matter, the matter-antimatter asymmetry in the universe, neutrino oscillations and the cosmological constant; at an applied level, new kinds of PT-synthetic materials are being developed, and the PT phase transition is being observed in many physical contexts, such as lasers, optical wave guides, microwave cavities, superconducting wires and electronic circuits. The purpose of this Theme Issue is to acquaint the reader with the latest developments in PTQM. The articles in this volume are written in the style of mini-reviews and address diverse areas of the emerging and exciting new area of PT-symmetric quantum mechanics. PMID:23509390

  18. Xe adsorption site distributions on Pt(111), Pt(221) and Pt(531)

    NASA Astrophysics Data System (ADS)

    Gellman, Andrew J.; Baker, L.; Holsclaw, B. S.

    2016-04-01

    The ideal structures of the Pt(111), Pt(221) and Pt(531) surfaces expose adsorption sites that can be qualitatively described as terrace sites on Pt(111), both step and terrace sites on Pt(221), and kink sites on Pt(531). The real surface structures of these surfaces can be complicated by imperfections such as misorientation, reconstruction and thermal roughening, all of which will influence their distributions of adsorption sites. Xe adsorption sites on the Pt(111), Pt(221) and Pt(531) surfaces have been probed using both photoemission of adsorbed Xe (PAX) and temperature programmed desorption (TPD) of Xe. Both PAX and Xe TPD are sensitive to the adsorption sites of the Xe and serve as complementary means of assessing the distributions of adsorption sites on these three Pt surfaces. The adsorption of Xe is sufficiently sensitive to detect the presence of residual steps on the Pt(111) surface at a density of ~ 1.5% step atoms per Pt atom. On the Pt(221) surface, PAX and Xe TPD reveal adsorption at both terrace and step sites simultaneously. Although the ideal structure of the Pt(531) surface has no well-defined steps or terraces, Xe adsorption indicates that its adsorption sites are best described as a distribution of both step and kink sites with roughly twice as many steps sites as kinks.

  19. Proteomics of Saccharomyces cerevisiae Organelles*

    PubMed Central

    Wiederhold, Elena; Veenhoff, Liesbeth M.; Poolman, Bert; Slotboom, Dirk Jan

    2010-01-01

    Knowledge of the subcellular localization of proteins is indispensable to understand their physiological roles. In the past decade, 18 studies have been performed to analyze the protein content of isolated organelles from Saccharomyces cerevisiae. Here, we integrate the data sets and compare them with other large scale studies on protein localization and abundance. We evaluate the completeness and reliability of the organelle proteomics studies. Reliability depends on the purity of the organelle preparations, which unavoidably contain (small) amounts of contaminants from different locations. Quantitative proteomics methods can be used to distinguish between true organellar constituents and contaminants. Completeness is compromised when loosely or dynamically associated proteins are lost during organelle preparation and also depends on the sensitivity of the analytical methods for protein detection. There is a clear trend in the data from the 18 organelle proteomics studies showing that proteins of low abundance frequently escape detection. Proteins with unknown function or cellular abundance are also infrequently detected, indicating that these proteins may not be expressed under the conditions used. We discuss that the yeast organelle proteomics studies provide powerful lead data for further detailed studies and that methodological advances in organelle preparation and in protein detection may help to improve the completeness and reliability of the data. PMID:19955081

  20. PET genes of Saccharomyces cerevisiae.

    PubMed Central

    Tzagoloff, A; Dieckmann, C L

    1990-01-01

    We describe a collection of nuclear respiratory-defective mutants (pet mutants) of Saccharomyces cerevisiae consisting of 215 complementation groups. This set of mutants probably represents a substantial fraction of the total genetic information of the nucleus required for the maintenance of functional mitochondria in S. cerevisiae. The biochemical lesions of mutants in approximately 50 complementation groups have been related to single enzymes or biosynthetic pathways, and the corresponding wild-type genes have been cloned and their structures have been determined. The genes defined by an additional 20 complementation groups were identified by allelism tests with mutants characterized in other laboratories. Mutants representative of the remaining complementation groups have been assigned to one of the following five phenotypic classes: (i) deficiency in cytochrome oxidase, (ii) deficiency in coenzyme QH2-cytochrome c reductase, (iii) deficiency in mitochondrial ATPase, (iv) absence of mitochondrial protein synthesis, and (v) normal composition of respiratory-chain complexes and of oligomycin-sensitive ATPase. In addition to the genes identified through biochemical and genetic analyses of the pet mutants, we have cataloged PET genes not matched to complementation groups in the mutant collection and other genes whose products function in the mitochondria but are not necessary for respiration. Together, this information provides an up-to-date list of the known genes coding for mitochondrial constituents and for proteins whose expression is vital for the respiratory competence of S. cerevisiae. PMID:2215420

  1. PT-symmetric kinks

    SciTech Connect

    Souza Dutra, A. de; Santos, V. G. C. S. dos; Amaro de Faria, A. C. Jr.

    2007-06-15

    Some kinks for non-Hermitian quantum field theories in 1+1 dimensions are constructed. A class of models where the soliton energies are stable and real are found. Although these kinks are not Hermitian, they are symmetric under PT transformations.

  2. Pt, Co-Pt and Fe-Pt alloy nanoclusters encapsulated in virus capsids

    NASA Astrophysics Data System (ADS)

    Okuda, M.; Eloi, J.-C.; Jones, S. E. Ward; Verwegen, M.; Cornelissen, J. J. L. M.; Schwarzacher, W.

    2016-03-01

    Nanostructured Pt-based alloys show great promise, not only for catalysis but also in medical and magnetic applications. To extend the properties of this class of materials, we have developed a means of synthesizing Pt and Pt-based alloy nanoclusters in the capsid of a virus. Pure Pt and Pt-alloy nanoclusters are formed through the chemical reduction of [PtCl4]- by NaBH4 with/without additional metal ions (Co or Fe). The opening and closing of the ion channels in the virus capsid were controlled by changing the pH and ionic strength of the solution. The size of the nanoclusters is limited to 18 nm by the internal diameter of the capsid. Their magnetic properties suggest potential applications in hyperthermia for the Co-Pt and Fe-Pt magnetic alloy nanoclusters. This study introduces a new way to fabricate size-restricted nanoclusters using virus capsid.

  3. PT-Symmetric Wave Chaos

    NASA Astrophysics Data System (ADS)

    West, Carl T.; Kottos, Tsampikos; Prosen, Tomaž

    2010-02-01

    We study a new class of chaotic systems with dynamical localization, where gain or loss mechanisms break the Hermiticity, while allowing for parity-time (PT) symmetry. For a value γPT of the gain or loss parameter the spectrum undergoes a spontaneous phase transition from real (exact phase) to complex values (broken phase). We develop a one parameter scaling theory for γPT, and show that chaos assists the exact PT phase. Our results have applications to the design of optical elements with PT symmetry.

  4. The permanent electric dipole moment of PtO, PtS, PtN, and PtC

    SciTech Connect

    Steimle, T.C.; Jung, K.Y.; Li, B.

    1995-08-01

    The permanent electric dipole moments of the ground, and the low-lying excited electronic states of platinum monocarbide, PtC, platinum monoxide, PtO, and platinum monosulfide, PtS, were measured using a molecular beam optical Stark spectroscopic scheme. The determined values were (in Debye): PtO({ital X} {sup 3}{Sigma}{sup {minus}}) 2.77(2); PtO({ital A} {sup 1}{Sigma}{sup +}) 1.15(4); PtS[{ital X}({Omega}=0)] 1.78(2); PtS[{ital B}({Omega}=0)] 0.54(6); PtC({ital X} {sup 1}{Sigma}{sup +}) 0.99(5); and PtC({ital A} {sup 1}{Pi}) 2.454(3). These results, along with the previous results for PtN({ital X} {sup 2}{Pi}{sub 1/2}) 1.977(9); PtN({ital d} {sup 4}{Pi}{sub 1/2}) 1.05(9) [J. Chem. Phys. {bold 102}, 643 (1995)], are used as a basis for a discussion of the nature of the electronic states. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  5. Enzymatic activities produced by mixed Saccharomyces and non-Saccharomyces cultures: relationship with wine volatile composition.

    PubMed

    Maturano, Yolanda Paola; Assof, Mariela; Fabani, María Paula; Nally, María Cristina; Jofré, Viviana; Rodríguez Assaf, Leticia Anahí; Toro, María Eugenia; Castellanos de Figueroa, Lucía Inés; Vazquez, Fabio

    2015-11-01

    During certain wine fermentation processes, yeasts, and mainly non-Saccharomyces strains, produce and secrete enzymes such as β-glucosidases, proteases, pectinases, xylanases and amylases. The effects of enzyme activity on the aromatic quality of wines during grape juice fermentation, using different co-inoculation strategies of non-Saccharomyces and Saccharomyces cerevisiae yeasts, were assessed in the current study. Three strains with appropriate enological performance and high enzymatic activities, BSc562 (S. cerevisiae), BDv566 (Debaryomyces vanrijiae) and BCs403 (Candida sake), were assayed in pure and mixed Saccharomyces/non-Saccharomyces cultures. β-Glucosidase, pectinase, protease, xylanase and amylase activities were quantified during fermentations. The aromatic profile of pure and mixed cultures was determined at the end of each fermentation. In mixed cultures, non-Saccharomyces species were detected until day 4-5 of the fermentation process, and highest populations were observed in MSD2 (10% S. cerevisiae/90% D. vanrijiae) and MSC1 (1% S. cerevisiae/99% C. sake). According to correlation and multivariate analysis, MSD2 presented the highest concentrations of terpenes and higher alcohols which were associated with pectinase, amylase and xylanase activities. On the other hand, MSC1 high levels of β-glucosidase, proteolytic and xylanolytic activities were correlated to esters and fatty acids. Our study contributes to a better understanding of the effect of enzymatic activities by yeasts on compound transformations that occur during wine fermentation. PMID:26386703

  6. PT symmetry in optics

    NASA Astrophysics Data System (ADS)

    Christodoulides, Demetrios

    2015-03-01

    Interest in complex Hamiltonians has been rekindled after the realization that a wide class of non-Hermitian Hamiltonians can have entirely real spectra as long as they simultaneously respect parity and time reversal operators. In non-relativistic quantum mechanics, governed by the Schrödinger equation, a necessary but not sufficient condition for PT symmetry to hold is that the complex potential should involve real and imaginary parts which are even and odd functions of position respectively. As recently indicated, optics provides a fertile ground to observe and utilize notions of PT symmetry. In optics, the refractive index and gain/loss profiles play the role of the real and imaginary parts of the aforementioned complex potentials. As it has been demonstrated in several studies, PT-symmetric optical structures can exhibit peculiar properties that are otherwise unattainable in traditional Hermitian (conservative) optical settings. Among them, is the possibility for breaking this symmetry through an abrupt phase transition, band merging effects and unidirectional invisibility. Here we review recent developments in the field of -symmetric optics.

  7. Thermodynamic Modeling of the Pt-Te and Pt-Sb-Te Systems

    NASA Astrophysics Data System (ADS)

    Guo, Cuiping; Huang, Liang; Li, Changrong; Shang, Shunli; Du, Zhenmin

    2015-08-01

    The Pt-Te and the Pt-Sb-Te systems are modeled using the calculation of phase diagram (CALPHAD) technique. In the Pt-Te system, the liquid phase is modeled as (Pt, PtTe2, Te) using the associate model, and four intermediates, PtTe2, Pt2Te3, Pt3Te4 and PtTe, are treated as stoichiometric compounds and their enthalpies of formation are obtained by means of first-principles calculations. The solution phases, fcc(Pt) and hex(Te), are described as substitutional solutions. Combined with the thermodynamic models of the liquid phase in the Pt-Sb and Sb-Te systems in the literature, the liquid phase of the Pt-Sb-Te ternary system is modeled as (Pt, Sb, Te, Sb2Te3, PtTe2) also using the associate model. The compounds, PtTe2, Pt2Te3, Pt3Te4 and PtTe in the Pt-Te system and PtSb2, PtSb, Pt3Sb2 and Pt7Sb in the Pt-Sb system are treated as line compounds Pt m (Sb,Te) n in the Pt-Sb-Te system, and the compound Pt5Sb is treated as (Pt,Sb)5(Pt,Sb,Te). A set of self-consistent thermodynamic parameters is obtained. Using these thermodynamic parameters, the experimental Pt-Te phase diagram, the experimental heat capacities of PtTe and PtTe2, the enthalpies of formation from first-principles calculations for PtTe2, Pt2Te3, Pt3Te4, and PtTe, and the ternary isothermal sections at 873 K, 923 K, 1073 K and 1273 K are well reproduced.

  8. Asymmetrical division of Saccharomyces cerevisiae.

    PubMed Central

    Lord, P G; Wheals, A E

    1980-01-01

    The unequal division model proposed for budding yeast (L. H. Hartwell and M. W. Unger, J. Cell Biol. 75:422-435, 1977) was tested by bud scar analyses of steady-state exponential batch cultures of Saccharomyces cerevisiae growing at 30 degrees C at 19 different rates, which were obtained by altering the carbon source. The analyses involved counting the number of bud scars, determining the presence or absence of buds on at least 1,000 cells, and independently measuring the doubling times (gamma) by cell number increase. A number of assumptions in the model were tested and found to be in good agreement with the model. Maximum likelihood estimates of daughter cycle time (D), parent cycle time (P), and the budded phase (B) were obtained, and we concluded that asymmetrical division occurred at all growth rates tested (gamma, 75 to 250 min). D, P, and B are all linearly related to gamma, and D, P, and gamma converge to equality (symmetrical division) at gamma = 65 min. Expressions for the genealogical age distribution for asymmetrically dividing yeast cells were derived. The fraction of daughter cells in steady-state populations is e-alpha P, and the fraction of parent cells of age n (where n is the number of buds that a cell has produced) is (e-alpha P)n-1(1-e-alpha P)2, where alpha = IN2/gamma; thus, the distribution changes with growth rate. The frequency of cells with different numbers of bud scars (i.e., different genealogical ages) was determined for all growth rates, and the observed distribution changed with the growth rate in the manner predicted. In this haploid strain new buds formed adjacent to the previous buds in a regular pattern, but at slower growth rates the pattern was more irregular. The median volume of the cells and the volume at start in the cell cycle both increased at faster growth rates. The implications of these findings for the control of the cell cycle are discussed. PMID:6991494

  9. Fatal Saccharomyces Cerevisiae Aortic Graft Infection

    NASA Technical Reports Server (NTRS)

    Meyer, Michael (Technical Monitor); Smith, Davey; Metzgar, David; Wills, Christopher; Fierer, Joshua

    2002-01-01

    Saccharomyces cerevisiae is a yeast commonly used in baking and a frequent colonizer of human mucosal surfaces. It is considered relatively nonpathogenic in immunocompetent adults. We present a case of S. cerevisiae fungemia and aortic graft infection in an immunocompetent adult. This is the first reported case of S. cerevisiue fungemia where the identity of the pathogen was confirmed by rRNA sequencing.

  10. Mechanisms of Ethanol Tolerance in Saccharomyces cerevisiae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Saccharomyces cerevisiae is a superb ethanol producer, yet is also sensitive to higher ethanol concentrations especially under high gravity or very high gravity fermentation conditions. Ethanol tolerance is associated with interplay of complex networks at the genome level. Although significant eff...

  11. Saccharomyces cerevisiae osteomyelitis in an immunocompetent baker.

    PubMed

    Seng, Piseth; Cerlier, Alexandre; Cassagne, Carole; Coulange, Mathieu; Legré, Regis; Stein, Andreas

    2016-01-01

    Invasive infection caused by Saccharomyces cerevisiae is rare. We report the first case of osteomyelitis caused by S. cerevisiae (baker's yeast) in a post-traumatic patient. The clinical outcome was favorable after surgical debridement, prolonged antifungal treatment and hyperbaric oxygen therapy. PMID:27347482

  12. Tangential Ultrafiltration of Aqueous "Saccharomyces Cerevisiae" Suspensions

    ERIC Educational Resources Information Center

    Silva, Carlos M.; Neves, Patricia S.; Da Silva, Francisco A.; Xavier, Ana M. R. B.; Eusebio, M. F. J.

    2008-01-01

    Experimental work on ultrafiltration is presented to illustrate the practical and theoretical principles of this separation technique. The laboratory exercise comprises experiments with pure water and with aqueous "Saccharomyces cerevisiae" (from commercial Baker's yeast) suspensions. With this work students detect the characteristic phenomena…

  13. MEL gene polymorphism in the genus Saccharomyces.

    PubMed Central

    Turakainen, H; Aho, S; Korhola, M

    1993-01-01

    In Saccharomyces spp. the ability to use melibiose depends on the presence of a MEL gene encoding alpha-galactosidase. We used two cloned MEL genes as probes to characterize the physical structure and chromosomal location of the MEL genes in several industrial and natural Mel+ strains of Saccharomyces cerevisiae, Saccharomyces pastorianus, and Saccharomyces bayanus. Electrokaryotyping showed that all of the S. pastorianus strains and most of the S. bayanus strains studied had one MEL locus. The MEL gene in S. bayanus strains was similar but not identical to the S. pastorianus MEL gene. Mel+ S. cerevisiae strains had one to seven loci containing MEL sequences. The MEL genes of these strains could be divided into two categories on the basis of hybridization to MEL1, one group exhibiting strong hybridization to MEL1 and the other group exhibiting weak hybridization to MEL1. In S. pastorianus and S. bayanus strains, the MEL gene was expressed as a single 1.5-kb transcript, and the expression was galactose inducible. In some S. cerevisiae strains, the MEL genes were expressed even without induction at fairly high levels. Expression was usually further induced by galactose. In two strains, CBS 5378 and CBS 4903, expression of the MEL genes was at the same level without induction as it was in most other strains with induction. In all S. cerevisiae strains, irrespective of the number of MEL genes, mRNA of only one size (1.6 kb) was observed. Images PMID:8396384

  14. Pt and Pt/(Cu) Carbonyl clusters synthesized by radiolysis

    NASA Astrophysics Data System (ADS)

    Le Gratiet, B.; Remita, H.; Picq, G.; Delcourt, M. O.

    1996-02-01

    In the mixed solvent: 50/50% v/v water/2-propanol, [Pt 3(CO) 6] n2- clusters with n = 3-10 have been obtained by irradiating solutions containing K 2PtCl 4 under 1 atm CO. n is deduced from the very typical UV-visible and IR absorption spectra. The reduction occurs by a combined effect of CO and of the radicals produced by radiolysis (radiocatalysis). The synthesis is selective: the nuclearity n can be chosen by adjusting the dose (high doses yield low n values). Increasing the Pt salt concentration leads to CO-stabilized subcolloid particles. Intermetallic cluster compounds are expected from solutions containing two metal salts: bimetallic Pt/Cu carbonyl clusters have been obtained. Two distinct compounds have been characterized by their UV-visible spectra. Attempts with Pt/Ru and Pt/Sn systems were unsuccessful.

  15. Characterization of azo dyes on Pt and Pt/polyaniline/dispersed Pt electrodes

    NASA Astrophysics Data System (ADS)

    Molina, J.; Fernández, J.; del Río, A. I.; Bonastre, J.; Cases, F.

    2012-06-01

    The electrochemical characterization of two organic dyes (amaranth and procion orange MX-2R) has been performed on Pt electrodes and Pt electrodes coated with polyaniline and dispersed Pt. Electrodes with different Pt loads have been synthesized and characterized obtaining that a load of 300 μg cm-2 was the optimum one. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was employed to observe the distribution and morphology of the Pt nanoparticles. The electroactivity of the electrodes has also been characterized by means of scanning electrochemical microscopy (SECM). The chemical characterization of Pt dispersed Pani coated Pt electrodes (Pt-Pani-Pt) was performed by means of X-ray photoelectron spectroscopy (XPS). The electrochemical characterization of the dyes has been performed by means of cyclic voltammetry. Voltammograms have shown that the presence of the dyes diminishes characteristic Pt oxidation and reduction peaks. However, redox processes due to the dyes, appeared in the voltammograms. The different species responsible of these redox processes were generated in the vicinity of the electrode and were not adsorbed on the electrode surface since after stirring, the different redox processes disappeared. Characterization with different scan rates showed that redox processes of both dyes were controlled by diffusion.

  16. Saccharomyces Fungemia Associated with Esophageal Disease Identified by D1/D2 Ribosomal RNA Gene Sequence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Disseminated Saccharomyces infection has been reported in immunosuppressed patients treated with probiotics, but disseminated Saccharomyces cerevisiae infection associated with underlying esophageal disease is not previously described. Saccharomyces cerevisiae (which occasionally colonizes the gast...

  17. Surface-layered ordered alloy (Pt/Pt3Mn) on Pt(111)

    NASA Astrophysics Data System (ADS)

    Gallego, S.; Ocal, C.; Muñoz, M. C.; Soria, F.

    1997-11-01

    A Mn-Pt layered intermetallic compound formed by alternated planes of Pt(111) and Pt3Mn(111) composition has been stabilized in a controlled way by two different mechanisms, which confirm the great stability of the final system. The surface exhibits a 2×2 superstructure due to chemical order underneath a Pt topmost layer. The structural analysis by low-energy electron diffraction gives a Pendry reliability factor (R-factor) of RP=0.17. The hybridization of the Pt and Mn atomic levels leads to atomic magnetic moments of 3.17μB and ~0.10μB at the Mn and Pt sites of the topmost layers, respectively.

  18. Comparison of Properties of Pt/PZT/Pt and Ru/PZT/Pt Ferroelectric Capacitors

    NASA Astrophysics Data System (ADS)

    Jia, Ze; Ren, Tian-Ling; Liu, Tian-Zhi; Hu, Hong; Zhang, Zhi-Gang; Xie, Dan; Liu, Li-Tian

    2006-04-01

    Pb(Zr0.4Ti0.6)O3 film prepared by sol-gel spin coating on a Pt/Ti/SiO2/Si substrate is applied to ferroelectric capacitors with Pt or Ru as the top electrode. For the Pt/PZT/Pt and Ru/PZT/Pt ferroelectric capacitors, although with the same ferroelectric film, different top electrode materials incur different properties of PZT capacitors, such as fatigue, leakage, remanent and saturated polarization, except the similar crystal orientations of the PZT film. After 1010 switch cycles, the remanent polarizations of the Ru/PZT/Pt and Pt/PZT/Pt capacitors decrease to 70% and 84%, respectively. The leakage current density of the latter increases obviously at positive bias after 108 switch cycles, compared with the former. Different materials for the top electrode bring different conditions at the PZT/top electrode interface. The influence of oxygen-vacancy concentration at the PZT/electrode interface and the influence of oxides of the electrode material at the PZT/electrode interface to charge injection can explain the difference of properties of the PZT capacitors with Pt or Ru as the top electrodes.

  19. Genomic Insights into the Saccharomyces sensu stricto Complex

    PubMed Central

    Borneman, Anthony R.; Pretorius, Isak S.

    2015-01-01

    The Saccharomyces sensu stricto group encompasses species ranging from the industrially ubiquitous yeast Saccharomyces cerevisiae to those that are confined to geographically limited environmental niches. The wealth of genomic data that are now available for the Saccharomyces genus is providing unprecedented insights into the genomic processes that can drive speciation and evolution, both in the natural environment and in response to human-driven selective forces during the historical “domestication” of these yeasts for baking, brewing, and winemaking. PMID:25657346

  20. The Saccharomyces Genome Database Variant Viewer.

    PubMed

    Sheppard, Travis K; Hitz, Benjamin C; Engel, Stacia R; Song, Giltae; Balakrishnan, Rama; Binkley, Gail; Costanzo, Maria C; Dalusag, Kyla S; Demeter, Janos; Hellerstedt, Sage T; Karra, Kalpana; Nash, Robert S; Paskov, Kelley M; Skrzypek, Marek S; Weng, Shuai; Wong, Edith D; Cherry, J Michael

    2016-01-01

    The Saccharomyces Genome Database (SGD; http://www.yeastgenome.org) is the authoritative community resource for the Saccharomyces cerevisiae reference genome sequence and its annotation. In recent years, we have moved toward increased representation of sequence variation and allelic differences within S. cerevisiae. The publication of numerous additional genomes has motivated the creation of new tools for their annotation and analysis. Here we present the Variant Viewer: a dynamic open-source web application for the visualization of genomic and proteomic differences. Multiple sequence alignments have been constructed across high quality genome sequences from 11 different S. cerevisiae strains and stored in the SGD. The alignments and summaries are encoded in JSON and used to create a two-tiered dynamic view of the budding yeast pan-genome, available at http://www.yeastgenome.org/variant-viewer. PMID:26578556

  1. Homogeneous Pt-bimetallic Electrocatalysts

    SciTech Connect

    Wang, Chao; Chi, Miaofang; More, Karren Leslie; Markovic, Nenad; Stamenkovic, Vojislav

    2011-01-01

    Alloying has shown enormous potential for tailoring the atomic and electronic structures, and improving the performance of catalytic materials. Systematic studies of alloy catalysts are, however, often compromised by inhomogeneous distribution of alloying components. Here we introduce a general approach for the synthesis of monodispersed and highly homogeneous Pt-bimetallic alloy nanocatalysts. Pt{sub 3}M (where M = Fe, Ni, or Co) nanoparticles were prepared by an organic solvothermal method and then supported on high surface area carbon. These catalysts attained a homogeneous distribution of elements, as demonstrated by atomic-scale elemental analysis using scanning transmission electron microscopy. They also exhibited high catalytic activities for the oxygen reduction reaction (ORR), with improvement factors of 2-3 versus conventional Pt/carbon catalysts. The measured ORR catalytic activities for Pt{sub 3}M nanocatalysts validated the volcano curve established on extended surfaces, with Pt{sub 3}Co being the most active alloy.

  2. The ecology and evolution of non-domesticated Saccharomyces species

    PubMed Central

    Boynton, Primrose J; Greig, Duncan

    2014-01-01

    Yeast researchers need model systems for ecology and evolution, but the model yeast Saccharomyces cerevisiae is not ideal because its evolution has been affected by domestication. Instead, ecologists and evolutionary biologists are focusing on close relatives of S. cerevisiae, the seven species in the genus Saccharomyces. The best-studied Saccharomyces yeast, after S. cerevisiae, is S. paradoxus, an oak tree resident throughout the northern hemisphere. In addition, several more members of the genus Saccharomyces have recently been discovered. Some Saccharomyces species are only found in nature, while others include both wild and domesticated strains. Comparisons between domesticated and wild yeasts have pinpointed hybridization, introgression and high phenotypic diversity as signatures of domestication. But studies of wild Saccharomyces natural history, biogeography and ecology are only beginning. Much remains to be understood about wild yeasts' ecological interactions and life cycles in nature. We encourage researchers to continue to investigate Saccharomyces yeasts in nature, both to place S. cerevisiae biology into its ecological context and to develop the genus Saccharomyces as a model clade for ecology and evolution. © 2014 The Authors. Yeast published by John Wiley & Sons Ltd. PMID:25242436

  3. Saccharomyces eubayanus and Saccharomyces arboricola reside in North Island native New Zealand forests.

    PubMed

    Gayevskiy, Velimir; Goddard, Matthew R

    2016-04-01

    Saccharomyces is one of the best-studied microbial genera, but our understanding of the global distributions and evolutionary histories of its members is relatively poor. Recent studies have altered our view of Saccharomyces' origin, but a lack of sampling from the vast majority of the world precludes a holistic perspective. We evaluate alternate Gondwanan and Far East Asian hypotheses concerning the origin of these yeasts. Being part of Gondwana, and only colonized by humans in the last ∼1000 years, New Zealand represents a unique environment for testing these ideas. Genotyping and ribosomal sequencing of samples from North Island native forest parks identified a widespread population of Saccharomyces. Whole genome sequencing identified the presence of S. arboricola and S. eubayanus in New Zealand, which is the first report of S. arboricola outside Far East Asia, and also expands S. eubayanus' known distribution to include the Oceanic region. Phylogenomic approaches place the S. arboricola population as significantly diverged from the only other sequenced Chinese isolate but indicate that S. eubayanus might be a recent migrant from South America. These data tend to support the Far East Asian origin of the Saccharomyces, but the history of this group is still far from clear. PMID:26522264

  4. Lifetime measurements in 180Pt

    NASA Astrophysics Data System (ADS)

    Chen, Q. M.; Wu, X. G.; Chen, Y. S.; Li, C. B.; Gao, Z. C.; Li, G. S.; Chen, F. Q.; He, C. Y.; Zheng, Y.; Hu, S. P.; Zhong, J.; Wu, Y. H.; Li, H. W.; Luo, P. W.

    2016-04-01

    Lifetimes of the yrast states in 180Pt have been measured from 4+ to 8+ using the recoil distance Doppler-shift technique in the coincidence mode. These states were populated by the reaction 156Gd(28Si,4 n )180Pt at a beam energy of 144 MeV. The differential decay curve method was applied to determine the lifetimes from experimental coincidence data. The B (E 2 ) values extracted from lifetimes increase with increasing spin, implying rotor behavior, but do not show the typical shape coexistence where the B (E 2 ) values present a rapid increase at very low spins. Calculations based on the triaxial projected shell model were performed for the yrast states in 180Pt and the results of both energies and E 2 transition probabilities reproduce the experimental data very well. The result also shows that a better description of the yrast band in 180Pt requires consideration of the γ degree of freedom.

  5. Preparation of Saccharomyces cerevisiae expression plasmids.

    PubMed

    Drew, David; Kim, Hyun

    2012-01-01

    Expression plasmids for Saccharomyces cerevisiae offer a wide choice of vector copy number, promoters of varying strength and selection markers. These expression plasmids are usually shuttle vectors that can be propagated both in yeast and bacteria, making them useful in gene cloning. For heterologous production of membrane proteins, we used the green fluorescent protein (GFP) fusion technology which was previously developed in the Escherichia coli system. We designed an expression plasmid carrying an inducible GAL1 promoter, a gene encoding a membrane protein of interest and the GFP-octa-histidine sequence. Here we describe construction of multi-copy yeast expression plasmids by homologous recombination in S. cerevisiae. PMID:22454112

  6. Fermentation studies using Saccharomyces diastaticus yeast strains

    SciTech Connect

    Erratt, J.A.; Stewart, G.G.

    1981-01-01

    The yeast species, Saccharomyces diastaticus, has the ability to ferment starch and dextrin, because of the extracellular enzyme, glucoamylase, which hydrolyzes the starch/dextrin to glucose. A number of nonallelic genes--DEX 1, DEX 2, and dextrinase B which is allelic to STA 3--have been isolated, which impart to the yeast the ability to ferment dextrin. Various diploid yeast strains were constructed, each being either heterozygous or homozygous for the individual dextrinase genes. Using 12 (sup 0) plato hopped wort (30% corn adjunct) under agitated conditions, the fermentation rates of the various diploid yeast strains were monitored. A gene-dosage effect was exhibited by yeast strains containing DEX 1 or DEX 2, however, not with yeast strains containing dextrinase B (STA 3). The fermentation and growth rates and extents were determined under static conditions at 14.4 C and 21 C. With all yeast strains containing the dextrinase genes, both fermentation and growth were increased at the higher incubation temperature. Using 30-liter fermentors, beer was produced with the various yeast strains containing the dextrinase genes and the physical and organoleptic characteristics of the products were determined. The concentration of glucose in the beer was found to increase during a 3-mo storage period at 21 C, indicating that the glucoamylase from Saccharomyces diastaticus is not inactivated by pasteurization. (Refs. 36).

  7. Biocuration at the Saccharomyces genome database.

    PubMed

    Skrzypek, Marek S; Nash, Robert S

    2015-08-01

    Saccharomyces Genome Database is an online resource dedicated to managing information about the biology and genetics of the model organism, yeast (Saccharomyces cerevisiae). This information is derived primarily from scientific publications through a process of human curation that involves manual extraction of data and their organization into a comprehensive system of knowledge. This system provides a foundation for further analysis of experimental data coming from research on yeast as well as other organisms. In this review we will demonstrate how biocuration and biocurators add a key component, the biological context, to our understanding of how genes, proteins, genomes and cells function and interact. We will explain the role biocurators play in sifting through the wealth of biological data to incorporate and connect key information. We will also discuss the many ways we assist researchers with their various research needs. We hope to convince the reader that manual curation is vital in converting the flood of data into organized and interconnected knowledge, and that biocurators play an essential role in the integration of scientific information into a coherent model of the cell. PMID:25997651

  8. Metabolic Engineering of Probiotic Saccharomyces boulardii.

    PubMed

    Liu, Jing-Jing; Kong, In Iok; Zhang, Guo-Chang; Jayakody, Lahiru N; Kim, Heejin; Xia, Peng-Fei; Kwak, Suryang; Sung, Bong Hyun; Sohn, Jung-Hoon; Walukiewicz, Hanna E; Rao, Christopher V; Jin, Yong-Su

    2016-04-01

    Saccharomyces boulardiiis a probiotic yeast that has been used for promoting gut health as well as preventing diarrheal diseases. This yeast not only exhibits beneficial phenotypes for gut health but also can stay longer in the gut than Saccharomyces cerevisiae Therefore, S. boulardiiis an attractive host for metabolic engineering to produce biomolecules of interest in the gut. However, the lack of auxotrophic strains with defined genetic backgrounds has hampered the use of this strain for metabolic engineering. Here, we report the development of well-defined auxotrophic mutants (leu2,ura3,his3, and trp1) through clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9-based genome editing. The resulting auxotrophic mutants can be used as a host for introducing various genetic perturbations, such as overexpression or deletion of a target gene, using existing genetic tools forS. cerevisiae We demonstrated the overexpression of a heterologous gene (lacZ), the correct localization of a target protein (red fluorescent protein) into mitochondria by using a protein localization signal, and the introduction of a heterologous metabolic pathway (xylose-assimilating pathway) in the genome ofS. boulardii We further demonstrated that human lysozyme, which is beneficial for human gut health, could be secreted by S. boulardii Our results suggest that more sophisticated genetic perturbations to improveS. boulardii can be performed without using a drug resistance marker, which is a prerequisite for in vivo applications using engineeredS. boulardii. PMID:26850302

  9. Biocuration at the Saccharomyces Genome Database

    PubMed Central

    Skrzypek, Marek S.; Nash, Robert S.

    2015-01-01

    Saccharomyces Genome Database is an online resource dedicated to managing information about the biology and genetics of the model organism, yeast (Saccharomyces cerevisiae). This information is derived primarily from scientific publications through a process of human curation that involves manual extraction of data and their organization into a comprehensive system of knowledge. This system provides a foundation for further analysis of experimental data coming from research on yeast as well as other organisms. In this review we will demonstrate how biocuration and biocurators add a key component, the biological context, to our understanding of how genes, proteins, genomes and cells function and interact. We will explain the role biocurators play in sifting through the wealth of biological data to incorporate and connect key information. We will also discuss the many ways we assist researchers with their various research needs. We hope to convince the reader that manual curation is vital in converting the flood of data into organized and interconnected knowledge, and that biocurators play an essential role in the integration of scientific information into a coherent model of the cell. PMID:25997651

  10. PT quantum mechanics - Recent results

    NASA Astrophysics Data System (ADS)

    Bender, Carl M.

    2012-09-01

    Most quantum physicists believe that a quantum-mechanical Hamiltonian must be Dirac Hermitian (invariant under matrix transposition and complex conjugation) to be sure that the energy eigenvalues are real and that time evolution is unitary. However, the non-Dirac-hermitian Hamiltonian H = p2+ix3 has a real positive discrete spectrum and generates unitary time evolution and defines a fully consistent and physical quantum theory. Evidently, Dirac Hermiticity is too restrictive. While H = p2+ix3 is not Dirac Hermitian, it is PT symmetric (invariant under combined space reflection P and time reversal T). Another PT-symmetric Hamiltonian whose energy levels are real, positive and discrete is H = p2-x4, which contains an upside-down potential. The quantum mechanics defined by a PT-symmetric Hamiltonian is a complex generalization of ordinary quantum mechanics. When quantum mechanics and quantum field theory are extended into the complex domain, new kinds of theories having strange and remarkable properties emerge. In the past two years some of these properties have been verified in laboratory experiments. Here, we first discuss PT-symmetric Hamiltonians at a simple intuitive level and explain why the energy levels of such Hamiltonians may be real, positive, and discrete. Second, we describe a recent experiment in which the PT phase transition was observed. Third, we briefly mention that PT-symmetric theories can be useful at a fundamental level. While the double-scaling limit of an O(N)-symmetric gφ4 quantum field theory appears to be inconsistent because the critical value of g is negative, this limit is in fact not inconsistent because the critical theory is PT symmetric.

  11. Segmented Pt/Ru, Pt/Ni, and Pt/RuNi nanorods as model bifunctional catalysts for methanol oxidation.

    PubMed

    Liu, Fang; Lee, Jim Yang; Zhou, Wei Jiang

    2006-01-01

    Five-segment (Pt-Ru-Pt-Ru-Pt, Pt-Ni-Pt-Ni-Pt, and Pt-RuNi-Pt-RuNi-Pt) nanorods with the same overall rod length and the same total Pt segment length were prepared by sequential electrodeposition of the metals into the pores of commercially available anodic aluminum oxide (AAO) membranes. Field-emission scanning electron microscopy (FESEM) showed that the nanorods were about 210 nm in diameter and about 1.5 microm in length. The alternating Pt and oxophilic metal(s) segments could be easily differentiated in backscattered-electron images. X-ray diffraction (XRD) analysis of the nanorods indicated that Pt and Ni were polycrystalline with fcc structures, Ru was hcp, and the co-deposited RuNi adopted the nickel fcc structure with some negative shifts in the Bragg angles. The chemical states of Pt, Ru, and Ni on the nanorod surface were assayed by X-ray photoelectron spectroscopy (XPS), and the presence of Pt(0), Pt(II), Pt(IV), Ru(0), Ru(VI), Ni(0), and Ni(II) was observed. The nanorods were catalytically active for the room-temperature electrooxidation of methanol in acidic solutions. The relative rates of reaction showed the Pt-RuNi pair sites as having the lowest overpotential to dissociate water, the highest catalytic activity in methanol oxidation, and the strongest CO-tolerance in the potential window employed. The use of segmented nanorods with identifiable Pt-oxophilic metal(s) interfaces removes many of the ambiguities in the interpretation of experimental data from conventional alloy catalysts, thereby enabling a direct comparison of the activities of various types of pair sites in methanol oxidation. PMID:17193567

  12. Gains and Losses of Transcription Factor Binding Sites in Saccharomyces cerevisiae and Saccharomyces paradoxus.

    PubMed

    Schaefke, Bernhard; Wang, Tzi-Yuan; Wang, Chuen-Yi; Li, Wen-Hsiung

    2015-08-01

    Gene expression evolution occurs through changes in cis- or trans-regulatory elements or both. Interactions between transcription factors (TFs) and their binding sites (TFBSs) constitute one of the most important points where these two regulatory components intersect. In this study, we investigated the evolution of TFBSs in the promoter regions of different Saccharomyces strains and species. We divided the promoter of a gene into the proximal region and the distal region, which are defined, respectively, as the 200-bp region upstream of the transcription starting site and as the 200-bp region upstream of the proximal region. We found that the predicted TFBSs in the proximal promoter regions tend to be evolutionarily more conserved than those in the distal promoter regions. Additionally, Saccharomyces cerevisiae strains used in the fermentation of alcoholic drinks have experienced more TFBS losses than gains compared with strains from other environments (wild strains, laboratory strains, and clinical strains). We also showed that differences in TFBSs correlate with the cis component of gene expression evolution between species (comparing S. cerevisiae and its sister species Saccharomyces paradoxus) and within species (comparing two closely related S. cerevisiae strains). PMID:26220934

  13. Thermotolerant Kluyveromyces marxianus and Saccharomyces cerevisiae strains representing potentials for bioethanol production from Jerusalem artichoke by consolidated bioprocessing.

    PubMed

    Hu, Nan; Yuan, Bo; Sun, Juan; Wang, Shi-An; Li, Fu-Li

    2012-09-01

    Thermotolerant inulin-utilizing yeast strains are desirable for ethanol production from Jerusalem artichoke tubers by consolidated bioprocessing (CBP). To obtain such strains, 21 naturally occurring yeast strains isolated by using an enrichment method and 65 previously isolated Saccharomyces cerevisiae strains were investigated in inulin utilization, extracellular inulinase activity, and ethanol fermentation from inulin and Jerusalem artichoke tuber flour at 40 °C. The strains Kluyveromyces marxianus PT-1 (CGMCC AS2.4515) and S. cerevisiae JZ1C (CGMCC AS2.3878) presented the highest extracellular inulinase activity and ethanol yield in this study. The highest ethanol concentration in Jerusalem artichoke tuber flour fermentation (200 g L(-1)) at 40 °C achieved by K. marxianus PT-1 and S. cerevisiae JZ1C was 73.6 and 65.2 g L(-1), which corresponded to the theoretical ethanol yield of 90.0 and 79.7 %, respectively. In the range of 30 to 40 °C, temperature did not have a significant effect on ethanol production for both strains. This study displayed the distinctive superiority of K. marxianus PT-1 and S. cerevisiae JZ1C in the thermotolerance and utilization of inulin-type oligosaccharides reserved in Jerusalem artichoke tubers. It is proposed that both K. marxianus and S. cerevisiae have considerable potential in ethanol production from Jerusalem artichoke tubers by a high temperature CBP. PMID:22760784

  14. Transcriptional Regulatory Networks in Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Lee, Tong Ihn; Rinaldi, Nicola J.; Robert, François; Odom, Duncan T.; Bar-Joseph, Ziv; Gerber, Georg K.; Hannett, Nancy M.; Harbison, Christopher T.; Thompson, Craig M.; Simon, Itamar; Zeitlinger, Julia; Jennings, Ezra G.; Murray, Heather L.; Gordon, D. Benjamin; Ren, Bing; Wyrick, John J.; Tagne, Jean-Bosco; Volkert, Thomas L.; Fraenkel, Ernest; Gifford, David K.; Young, Richard A.

    2002-10-01

    We have determined how most of the transcriptional regulators encoded in the eukaryote Saccharomyces cerevisiae associate with genes across the genome in living cells. Just as maps of metabolic networks describe the potential pathways that may be used by a cell to accomplish metabolic processes, this network of regulator-gene interactions describes potential pathways yeast cells can use to regulate global gene expression programs. We use this information to identify network motifs, the simplest units of network architecture, and demonstrate that an automated process can use motifs to assemble a transcriptional regulatory network structure. Our results reveal that eukaryotic cellular functions are highly connected through networks of transcriptional regulators that regulate other transcriptional regulators.

  15. Sporulation in the Budding Yeast Saccharomyces cerevisiae

    PubMed Central

    Neiman, Aaron M.

    2011-01-01

    In response to nitrogen starvation in the presence of a poor carbon source, diploid cells of the yeast Saccharomyces cerevisiae undergo meiosis and package the haploid nuclei produced in meiosis into spores. The formation of spores requires an unusual cell division event in which daughter cells are formed within the cytoplasm of the mother cell. This process involves the de novo generation of two different cellular structures: novel membrane compartments within the cell cytoplasm that give rise to the spore plasma membrane and an extensive spore wall that protects the spore from environmental insults. This article summarizes what is known about the molecular mechanisms controlling spore assembly with particular attention to how constitutive cellular functions are modified to create novel behaviors during this developmental process. Key regulatory points on the sporulation pathway are also discussed as well as the possible role of sporulation in the natural ecology of S. cerevisiae. PMID:22084423

  16. [Urinary infection by Saccharomyces cerevisiae: Emerging yeast?].

    PubMed

    Elkhihal, B; Elhalimi, M; Ghfir, B; Mostachi, A; Lyagoubi, M; Aoufi, S

    2015-12-01

    Saccharomyces cerevisiae is a commensal yeast of the digestive, respiratory and genito-urinary tract. It is widely used as a probiotic for the treatment of post-antibiotic diarrhea. It most often occurs in immunocompromised patients frequently causing fungemia. We report the case of an adult diabetic patient who had a urinary tract infection due to S. cerevisiae. The disease started with urination associated with urinary frequency burns without fever. The diagnosis was established by the presence of yeasts on direct examination and positivity of culture on Sabouraud-chloramphenicol three times. The auxanogramme gallery (Auxacolor BioRad(®)) allowed the identification of S. cerevisiae. The patient was put on fluconazole with good outcome. This observation points out that this is an opportunistic yeast in immunocompromised patients. PMID:26522963

  17. Synchronization of the Budding Yeast Saccharomyces cerevisiae.

    PubMed

    Foltman, Magdalena; Molist, Iago; Sanchez-Diaz, Alberto

    2016-01-01

    A number of model organisms have provided the basis for our understanding of the eukaryotic cell cycle. These model organisms are generally much easier to manipulate than mammalian cells and as such provide amenable tools for extensive genetic and biochemical analysis. One of the most common model organisms used to study the cell cycle is the budding yeast Saccharomyces cerevisiae. This model provides the ability to synchronise cells efficiently at different stages of the cell cycle, which in turn opens up the possibility for extensive and detailed study of mechanisms regulating the eukaryotic cell cycle. Here, we describe methods in which budding yeast cells are arrested at a particular phase of the cell cycle and then released from the block, permitting the study of molecular mechanisms that drive the progression through the cell cycle. PMID:26519319

  18. Social wasps are a Saccharomyces mating nest

    PubMed Central

    Stefanini, Irene; Dapporto, Leonardo; Berná, Luisa; Polsinelli, Mario; Turillazzi, Stefano; Cavalieri, Duccio

    2016-01-01

    The reproductive ecology of Saccharomyces cerevisiae is still largely unknown. Recent evidence of interspecific hybridization, high levels of strain heterozygosity, and prion transmission suggest that outbreeding occurs frequently in yeasts. Nevertheless, the place where yeasts mate and recombine in the wild has not been identified. We found that the intestine of social wasps hosts highly outbred S. cerevisiae strains as well as a rare S. cerevisiae×S. paradoxus hybrid. We show that the intestine of Polistes dominula social wasps favors the mating of S. cerevisiae strains among themselves and with S. paradoxus cells by providing a succession of environmental conditions prompting cell sporulation and spores germination. In addition, we prove that heterospecific mating is the only option for European S. paradoxus strains to survive in the gut. Taken together, these findings unveil the best hidden secret of yeast ecology, introducing the insect gut as an environmental alcove in which crosses occur, maintaining and generating the diversity of the ascomycetes. PMID:26787874

  19. Glycerol production of various strains of saccharomyces

    SciTech Connect

    Radler, F.; Schuetz, H.

    1982-01-01

    The quantity of glycerol as principal by-product of the alcoholic fermentation depends to a large extent on the yeast strain. Different strains of Saccharomyces cerevisiae were found to form amounts of glycerol varying between 4.2 to 10.4 g/L. The formation of glycerol is regarded as a result of the competition between alcohol dehydrogenase and glycerol-3-phosphate dehydrogenase that compete for the reduced coenzyme NADH/sub 2/. High and low glycerol forming yeast strains showed large differences in the activity of glycerol-3-phosphate dehydrogenase and only small variation in the activity of alcohol dehydrogenase. The total amount of glycerol formed was also influenced by amino acids. In thiamine deficient media a decrease in glycerol formation was observed. Experiments indicate a correlation between the formation of acetaldehyde and glycerol and the production of cell mass that may be of practical interest. (Refs. 12).

  20. Social wasps are a Saccharomyces mating nest.

    PubMed

    Stefanini, Irene; Dapporto, Leonardo; Berná, Luisa; Polsinelli, Mario; Turillazzi, Stefano; Cavalieri, Duccio

    2016-02-23

    The reproductive ecology of Saccharomyces cerevisiae is still largely unknown. Recent evidence of interspecific hybridization, high levels of strain heterozygosity, and prion transmission suggest that outbreeding occurs frequently in yeasts. Nevertheless, the place where yeasts mate and recombine in the wild has not been identified. We found that the intestine of social wasps hosts highly outbred S. cerevisiae strains as well as a rare S. cerevisiae×S. paradoxus hybrid. We show that the intestine of Polistes dominula social wasps favors the mating of S. cerevisiae strains among themselves and with S. paradoxus cells by providing a succession of environmental conditions prompting cell sporulation and spores germination. In addition, we prove that heterospecific mating is the only option for European S. paradoxus strains to survive in the gut. Taken together, these findings unveil the best hidden secret of yeast ecology, introducing the insect gut as an environmental alcove in which crosses occur, maintaining and generating the diversity of the ascomycetes. PMID:26787874

  1. Characterization of NiPt, FePt, and NiFePt nanoparticles

    NASA Astrophysics Data System (ADS)

    Sutherland, Greg; Wood, Darren; Jackson, Amy; Warren, Andrew; Coffey, Kevin; Vanfleet, Richard

    2012-10-01

    Many metal alloys can form in chemically ordered structures, often resulting in significant changes in properties. The ordered structures are preferred at low temperatures and will go through an order-disorder phase transition at a critical temperature. The formation and stability of these ordered structures in alloy nanoparticles is not well understood but may give insight into the role size plays in phase transitions. To this end we are studying FePt, NiPt, and FeNiPt alloy nanoparticles. We will focus this presentation on the characterization of these nanoparticles in a Transmission Electron Microscope (TEM) for composition, size, and structure. These nanoparticles are made by co-sputtering the constituents and annealing at different temperatures in various gas mixtures. The nanoparticle samples are prepared for TEM viewing by wedge polishing. We find FePt to be ``well behaved'' meaning this alloy forms particles, retains the as deposited composition, and chemically orders as expected. However, the order-disorder temperature is too high for the desired further studies. NiPt, which has a lower order-disorder temperature, is not ``well behaved'' in that the nanoparticle compositions are not good matches to the as deposited conditions and no chemical ordering has been achieved even under conditions that should be sufficient based on bulk processing. We will discuss these results and possible implications.

  2. Prediction of Saccharomyces cerevisiae replication origins

    PubMed Central

    Breier, Adam M; Chatterji, Sourav; Cozzarelli, Nicholas R

    2004-01-01

    Background Autonomously replicating sequences (ARSs) function as replication origins in Saccharomyces cerevisiae. ARSs contain the 17 bp ARS consensus sequence (ACS), which binds the origin recognition complex. The yeast genome contains more than 10,000 ACS matches, but there are only a few hundred origins, and little flanking sequence similarity has been found. Thus, identification of origins by sequence alone has not been possible. Results We developed an algorithm, Oriscan, to predict yeast origins using similarity to 26 characterized origins. Oriscan used 268 bp of sequence, including the T-rich ACS and a 3' A-rich region. The predictions identified the exact location of the ACS. A total of 84 of the top 100 Oriscan predictions, and 56% of the top 350, matched known ARSs or replication protein binding sites. The true accuracy was even higher because we tested 25 discrepancies, and 15 were in fact ARSs. Thus, 94% of the top 100 predictions and an estimated 70% of the top 350 were correct. We compared the predictions to corresponding sequences in related Saccharomyces species and found that the ACSs of experimentally supported predictions show significant conservation. Conclusions The high accuracy of the predictions indicates that we have defined near-sufficient conditions for ARS activity, the A-rich region is a recognizable feature of ARS elements with a probable role in replication initiation, and nucleotide sequence is a reliable predictor of yeast origins. Oriscan detected most origins in the genome, demonstrating previously unrecognized generality in yeast replication origins and significant discriminatory power in the algorithm. PMID:15059255

  3. The Mitochondrial Genome Impacts Respiration but Not Fermentation in Interspecific Saccharomyces Hybrids

    PubMed Central

    Rigoulet, Michel; Salin, Benedicte; Masneuf-Pomarede, Isabelle; de Vienne, Dominique; Sicard, Delphine; Bely, Marina; Marullo, Philippe

    2013-01-01

    In eukaryotes, mitochondrial DNA (mtDNA) has high rate of nucleotide substitution leading to different mitochondrial haplotypes called mitotypes. However, the impact of mitochondrial genetic variant on phenotypic variation has been poorly considered in microorganisms because mtDNA encodes very few genes compared to nuclear DNA, and also because mitochondrial inheritance is not uniparental. Here we propose original material to unravel mitotype impact on phenotype: we produced interspecific hybrids between S. cerevisiae and S. uvarum species, using fully homozygous diploid parental strains. For two different interspecific crosses involving different parental strains, we recovered 10 independent hybrids per cross, and allowed mtDNA fixation after around 80 generations. We developed PCR-based markers for the rapid discrimination of S. cerevisiae and S. uvarum mitochondrial DNA. For both crosses, we were able to isolate fully isogenic hybrids at the nuclear level, yet possessing either S. cerevisiae mtDNA (Sc-mtDNA) or S. uvarum mtDNA (Su-mtDNA). Under fermentative conditions, the mitotype has no phenotypic impact on fermentation kinetics and products, which was expected since mtDNA are not necessary for fermentative metabolism. Alternatively, under respiratory conditions, hybrids with Sc-mtDNA have higher population growth performance, associated with higher respiratory rate. Indeed, far from the hypothesis that mtDNA variation is neutral, our work shows that mitochondrial polymorphism can have a strong impact on fitness components and hence on the evolutionary fate of the yeast populations. We hypothesize that under fermentative conditions, hybrids may fix stochastically one or the other mt-DNA, while respiratory environments may increase the probability to fix Sc-mtDNA. PMID:24086452

  4. PT-symmetric quantum theory

    NASA Astrophysics Data System (ADS)

    Bender, Carl M.

    2015-07-01

    The average quantum physicist on the street would say that a quantum-mechanical Hamiltonian must be Dirac Hermitian (invariant under combined matrix transposition and complex conjugation) in order to guarantee that the energy eigenvalues are real and that time evolution is unitary. However, the Hamiltonian H = p2 + ix3, which is obviously not Dirac Hermitian, has a positive real discrete spectrum and generates unitary time evolution, and thus it defines a fully consistent and physical quantum theory. Evidently, the axiom of Dirac Hermiticity is too restrictive. While H = p2 + ix3 is not Dirac Hermitian, it is PT symmetric; that is, invariant under combined parity P (space reflection) and time reversal T. The quantum mechanics defined by a PT-symmetric Hamiltonian is a complex generalization of ordinary quantum mechanics. When quantum mechanics is extended into the complex domain, new kinds of theories having strange and remarkable properties emerge. In the past few years, some of these properties have been verified in laboratory experiments. A particularly interesting PT-symmetric Hamiltonian is H = p2 - x4, which contains an upside-down potential. This potential is discussed in detail, and it is explained in intuitive as well as in rigorous terms why the energy levels of this potential are real, positive, and discrete. Applications of PT-symmetry in quantum field theory are also discussed.

  5. Lessons Learned from PT3

    ERIC Educational Resources Information Center

    Duffield, Judith A.; Moore, Julie A.

    2006-01-01

    Technology integration is a three-pronged effort. Not only do teachers, no matter the level, need to know how to use technology, they need to know how to integrate it into their curriculum. These two prongs were a consistent theme throughout the Preparing Tomorrow's Teachers to Use Technology (PT3) projects. Add access to technology to these and…

  6. PT3. [SITE 2002 Section].

    ERIC Educational Resources Information Center

    Thompson, Mary, Ed.; Price, Jerry, Ed.

    This document contains 142 papers on PT3 (Preparing Tomorrow's Teachers to use Technology) from the SITE (Society for Information Technology & Teacher Education) 2002 conference. Topics covered include: a technology in urban education summit; student professional development; meeting NCATE (National Council of Teachers of English) standards;…

  7. Force Sensitivity in Saccharomyces cerevisiae Flocculins

    PubMed Central

    Chan, Cho X. J.; El-Kirat-Chatel, Sofiane; Joseph, Ivor G.; Jackson, Desmond N.; Ramsook, Caleen B.; Dufrêne, Yves F.

    2016-01-01

    ABSTRACT Many fungal adhesins have short, β-aggregation-prone sequences that play important functional roles, and in the Candida albicans adhesin Als5p, these sequences cluster the adhesins after exposure to shear force. Here, we report that Saccharomyces cerevisiae flocculins Flo11p and Flo1p have similar β-aggregation-prone sequences and are similarly stimulated by shear force, despite being nonhomologous. Shear from vortex mixing induced the formation of small flocs in cells expressing either adhesin. After the addition of Ca2+, yeast cells from vortex-sheared populations showed greatly enhanced flocculation and displayed more pronounced thioflavin-bright surface nanodomains. At high concentrations, amyloidophilic dyes inhibited Flo1p- and Flo11p-mediated agar invasion and the shear-induced increase in flocculation. Consistent with these results, atomic force microscopy of Flo11p showed successive force-distance peaks characteristic of sequentially unfolding tandem repeat domains, like Flo1p and Als5p. Flo11p-expressing cells bound together through homophilic interactions with adhesion forces of up to 700 pN and rupture lengths of up to 600 nm. These results are consistent with the potentiation of yeast flocculation by shear-induced formation of high-avidity domains of clustered adhesins at the cell surface, similar to the activation of Candida albicans adhesin Als5p. Thus, yeast adhesins from three independent gene families use similar force-dependent interactions to drive cell adhesion. IMPORTANCE The Saccharomyces cerevisiae flocculins mediate the formation of cellular aggregates and biofilm-like mats, useful in clearing yeast from fermentations. An important property of fungal adhesion proteins, including flocculins, is the ability to form catch bonds, i.e., bonds that strengthen under tension. This strengthening is based, at least in part, on increased avidity of binding due to clustering of adhesins in cell surface nanodomains. This clustering depends

  8. Force Sensitivity in Saccharomyces cerevisiae Flocculins.

    PubMed

    Chan, Cho X J; El-Kirat-Chatel, Sofiane; Joseph, Ivor G; Jackson, Desmond N; Ramsook, Caleen B; Dufrêne, Yves F; Lipke, Peter N

    2016-01-01

    Many fungal adhesins have short, β-aggregation-prone sequences that play important functional roles, and in the Candida albicans adhesin Als5p, these sequences cluster the adhesins after exposure to shear force. Here, we report that Saccharomyces cerevisiae flocculins Flo11p and Flo1p have similar β-aggregation-prone sequences and are similarly stimulated by shear force, despite being nonhomologous. Shear from vortex mixing induced the formation of small flocs in cells expressing either adhesin. After the addition of Ca(2+), yeast cells from vortex-sheared populations showed greatly enhanced flocculation and displayed more pronounced thioflavin-bright surface nanodomains. At high concentrations, amyloidophilic dyes inhibited Flo1p- and Flo11p-mediated agar invasion and the shear-induced increase in flocculation. Consistent with these results, atomic force microscopy of Flo11p showed successive force-distance peaks characteristic of sequentially unfolding tandem repeat domains, like Flo1p and Als5p. Flo11p-expressing cells bound together through homophilic interactions with adhesion forces of up to 700 pN and rupture lengths of up to 600 nm. These results are consistent with the potentiation of yeast flocculation by shear-induced formation of high-avidity domains of clustered adhesins at the cell surface, similar to the activation of Candida albicans adhesin Als5p. Thus, yeast adhesins from three independent gene families use similar force-dependent interactions to drive cell adhesion. IMPORTANCE The Saccharomyces cerevisiae flocculins mediate the formation of cellular aggregates and biofilm-like mats, useful in clearing yeast from fermentations. An important property of fungal adhesion proteins, including flocculins, is the ability to form catch bonds, i.e., bonds that strengthen under tension. This strengthening is based, at least in part, on increased avidity of binding due to clustering of adhesins in cell surface nanodomains. This clustering depends on

  9. Effect of Pt layers on chemical ordering in FePt thin films

    NASA Astrophysics Data System (ADS)

    Gupta, R.; Medwal, R.; Sharma, P.; Mahapatro, A. K.; Annapoorni, S.

    2013-12-01

    The tunability in the structural and magnetic phases present in RF-sputtered Fe3Pt thin films over Si (1 0 0) substrates have been studied by introducing thin films of platinum (Pt) as an underlayer and/or overlayers. Annealing of the Fe3Pt thin films with Pt underlayers (Pt/Fe3Pt) structures at 600 °C for 1 h, indicates well organized nanostructured grains as imaged through an atomic force microscope (AFM). The evolution of superstructure peaks as well as the preferred orientation along (0 0 1) plane observed in the X-ray diffraction (XRD) study is well supported by the magnetic measurements. These annealed Pt/Fe3Pt structures show high magnetocrystalline anisotropy and the presence of hard phase with a coercivity of 8.5 kOe. Here, the annealing process allows the adjacent Pt atoms to diffuse into the Fe3Pt unit cells and triggers the structural transformation to chemically ordered L10 phase. An additional L12 phase is observed in the annealed Fe3Pt thin films with Pt overlayer and underlayer (Pt/Fe3Pt/Pt) tri-layered structures.

  10. Filamentation of Metabolic Enzymes in Saccharomyces cerevisiae.

    PubMed

    Shen, Qing-Ji; Kassim, Hakimi; Huang, Yong; Li, Hui; Zhang, Jing; Li, Guang; Wang, Peng-Ye; Yan, Jun; Ye, Fangfu; Liu, Ji-Long

    2016-06-20

    Compartmentation via filamentation has recently emerged as a novel mechanism for metabolic regulation. In order to identify filament-forming metabolic enzymes systematically, we performed a genome-wide screening of all strains available from an open reading frame-GFP collection in Saccharomyces cerevisiae. We discovered nine novel filament-forming proteins and also confirmed those identified previously. From the 4159 strains, we found 23 proteins, mostly metabolic enzymes, which are capable of forming filaments in vivo. In silico protein-protein interaction analysis suggests that these filament-forming proteins can be clustered into several groups, including translational initiation machinery and glucose and nitrogen metabolic pathways. Using glutamine-utilising enzymes as examples, we found that the culture conditions affect the occurrence and length of the metabolic filaments. Furthermore, we found that two CTP synthases (Ura7p and Ura8p) and two asparagine synthetases (Asn1p and Asn2p) form filaments both in the cytoplasm and in the nucleus. Live imaging analyses suggest that metabolic filaments undergo sub-diffusion. Taken together, our genome-wide screening identifies additional filament-forming proteins in S. cerevisiae and suggests that filamentation of metabolic enzymes is more general than currently appreciated. PMID:27312010

  11. Progress in Metabolic Engineering of Saccharomyces cerevisiae

    PubMed Central

    Nevoigt, Elke

    2008-01-01

    Summary: The traditional use of the yeast Saccharomyces cerevisiae in alcoholic fermentation has, over time, resulted in substantial accumulated knowledge concerning genetics, physiology, and biochemistry as well as genetic engineering and fermentation technologies. S. cerevisiae has become a platform organism for developing metabolic engineering strategies, methods, and tools. The current review discusses the relevance of several engineering strategies, such as rational and inverse metabolic engineering, evolutionary engineering, and global transcription machinery engineering, in yeast strain improvement. It also summarizes existing tools for fine-tuning and regulating enzyme activities and thus metabolic pathways. Recent examples of yeast metabolic engineering for food, beverage, and industrial biotechnology (bioethanol and bulk and fine chemicals) follow. S. cerevisiae currently enjoys increasing popularity as a production organism in industrial (“white”) biotechnology due to its inherent tolerance of low pH values and high ethanol and inhibitor concentrations and its ability to grow anaerobically. Attention is paid to utilizing lignocellulosic biomass as a potential substrate. PMID:18772282

  12. Biosorption of heavy metals by Saccharomyces cerevisiae.

    PubMed

    Volesky, B; May-Phillips, H A

    1995-01-01

    Abundant and common yeast biomass has been examined for its capacity to sequester heavy metals from dilute aqueous solutions. Live and non-living biomass of Saccharomyces cerevisiae differs in the uptake of uranium, zinc and copper at the optimum pH 4-5. Culture growth conditions can influence the biosorbent metal uptake capacity which normally was: living and non-living brewer's yeast: U > Zn > Cd > Cu; non-living baker's yeast: Zn > (Cd) > U > Cu; living baker's yeast: Zn > Cu approximately (Cd) > U. Non-living brewer's yeast biomass accumulated 0.58 mmol U/g. The best biosorbent of zinc was non-living baker's yeast (approximately 0.56 mmol Zn/g). Dead cells of S. cerevisiae removed approximately 40% more uranium or zinc than the corresponding live cultures. Biosorption of uranium by S. cerevisiae was a rapid process reaching 60% of the final uptake value within the first 15 min of contact. Its deposition differing from that of other heavy metals more associated with the cell wall, uranium was deposited as fine needle-like crystals both on the inside and outside of the S. cerevisiae cells. PMID:7765919

  13. Stationary phase in the yeast Saccharomyces cerevisiae.

    PubMed Central

    Werner-Washburne, M; Braun, E; Johnston, G C; Singer, R A

    1993-01-01

    Growth and proliferation of microorganisms such as the yeast Saccharomyces cerevisiae are controlled in part by the availability of nutrients. When proliferating yeast cells exhaust available nutrients, they enter a stationary phase characterized by cell cycle arrest and specific physiological, biochemical, and morphological changes. These changes include thickening of the cell wall, accumulation of reserve carbohydrates, and acquisition of thermotolerance. Recent characterization of mutant cells that are conditionally defective only for the resumption of proliferation from stationary phase provides evidence that stationary phase is a unique developmental state. Strains with mutations affecting entry into and survival during stationary phase have also been isolated, and the mutations have been shown to affect at least seven different cellular processes: (i) signal transduction, (ii) protein synthesis, (iii) protein N-terminal acetylation, (iv) protein turnover, (v) protein secretion, (vi) membrane biosynthesis, and (vii) cell polarity. The exact nature of the relationship between these processes and survival during stationary phase remains to be elucidated. We propose that cell cycle arrest coordinated with the ability to remain viable in the absence of additional nutrients provides a good operational definition of starvation-induced stationary phase. PMID:8393130

  14. Calcium control of Saccharomyces cerevisiae actin assembly.

    PubMed Central

    Greer, C; Schekman, R

    1982-01-01

    Low levels of Ca2+ dramatically influence the polymerization of Saccharomyces cerevisiae actin in KCl. The apparent critical concentration for polymerization (C infinity) increases eightfold in the presence of 0.1 mM Ca2+. This effect is rapidly reversed by the addition of ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid or of 0.1 mM Mg2+. Furthermore, the addition of Ca2+ to polymerized actin causes a reversible increase in the apparent C infinity. In the presence of Ca2+, at actin concentrations below the apparent C infinity, particles of 15 to 50 nm in diameter are seen instead of filaments. These particles are separated from soluble actin when Ca2+-treated filamentous actin is sedimented at high speed; both the soluble and particulate fractions retain Ca2+-sensitive polymerization. The Ca2+ effect is S. cerevisiae actin-specific: the C infinity for rabbit muscle actin is not affected by the presence of Ca2+ and S. cerevisiae actin. Ca2+ may act directly on S. cerevisiae actin to control the assembly state in vivo. Images PMID:6757718

  15. Killer systems of the yeast Saccharomyces cerevisiae

    SciTech Connect

    Nesterova, G.F.

    1989-01-01

    The killer systems of Saccharomyces cerevisiae are an unusual class of cytoplasmic symbionts of primitive eukaryotes. The genetic material of these symbionts is double-stranded RNA. They are characterized by the linearity of the genome, its fragmentation into a major and a minor fraction, which replicate separately, and their ability to control the synthesis of secretory mycocin proteins possessing a toxic action on closely related strains. The secretion of mycocins at the same time ensures acquiring of resistance to them. Strains containing killer symbionts are toxigenic and resistant to the action of their own toxin, but strains that are free of killer double-stranded RNAs are sensitive to the action of mycocins. The killer systems of S. cerevisiae have retained features relating them to viruses and are apparently the result of evolution of infectious viruses. The occurrences of such systems among monocellular eukaryotic organisms is an example of complication of the genome by means of its assembly from virus-like components. We discuss the unusual features of replication and the expression of killer systems and their utilization in the construction of vector molecules.

  16. Regulation of Phosphatidylcholine Biosynthesis in Saccharomyces cerevisiae

    PubMed Central

    Waechter, Charles J.; Lester, Robert L.

    1971-01-01

    Evidence is presented which indicates that the biosynthesis of phosphatidylcholine by the methylation pathway in growing cultures of Saccharomyces cerevisiae is repressed by the presence of choline in the growth medium. This result, obtained previously for glucose-grown cells, was also observed for lactate-grown cells, of which half of the phosphatidylcholine is mitochondrial. A respiration-deficient mutant of the parent wild-type strain has been studied, and its inability to form functional mitochondria cannot be due to an impaired methylation pathway, as it has been shown to incorporate 14C-CH3-methionine into all of the methylated glycerophosphatides. The incorporation rate is depressed by the inclusion of 1 mm choline in the growth medium, suggesting a regulatory effect similar to that demonstrated for the wild-type strain. The effects of choline on the glycerophospholipid composition of lactate and glucose-grown cells is presented. The repressive effects of the two related bases, mono- and dimethylethanolamine, were examined, and reduced levels of 14C-CH3-methionine incorporation were found for cells grown in the presence of these bases. The effect of choline on the methylation rates is reversible and glucosegrown cells regain the nonrepressed level of methylation activity in 60 to 80 min after removal of choline from the growth medium. Images PMID:5547992

  17. Inositol-Requiring Mutants of SACCHAROMYCES CEREVISIAE

    PubMed Central

    Culbertson, Michael R.; Henry, Susan A.

    1975-01-01

    Fifty-two inositol-requiring mutants of Saccharomyces cerevisiae were isolated following mutagenesis with ethyl methanesulfonate. Complementation and tetrad analysis revealed ten major complementation classes, representing ten independently segregating loci (designated ino1 through ino10) which recombined freely with their respective centromeres. Members of any given complementation class segregated as alleles of a single locus. Thirteen complementation subclasses were identified among thirty-six mutants which behaved as alleles of the ino1 locus. The complementation map for these mutants was circular.—Dramatic cell viability losses indicative of unbalanced growth were observed in liquid cultures of representative mutants under conditions of inositol starvation. Investigation of the timing, kinetics, and extent of cell death revealed that losses in cell viability in the range of 2-4 log orders could be prevented by the addition of inositol to the medium or by disruption of protein synthesis with cycloheximide. Mutants defective in nine of the ten loci identified in this study displayed these unusual characteristics. The results suggest an important physiological role for inositol that may be related to its cellular localization and function in membrane phospholipids. The possibility is discussed that inositol deficiency initiates the process of unbalanced growth leading to cell death through the loss of normal assembly, function, or integrity of biomembranes.—Part of this work has been reported in preliminary form (Culbertson and Henry 1974). PMID:1093935

  18. Synthesis of Morphinan Alkaloids in Saccharomyces cerevisiae.

    PubMed

    Fossati, Elena; Narcross, Lauren; Ekins, Andrew; Falgueyret, Jean-Pierre; Martin, Vincent J J

    2015-01-01

    Morphinan alkaloids are the most powerful narcotic analgesics currently used to treat moderate to severe and chronic pain. The feasibility of morphinan synthesis in recombinant Saccharomyces cerevisiae starting from the precursor (R,S)-norlaudanosoline was investigated. Chiral analysis of the reticuline produced by the expression of opium poppy methyltransferases showed strict enantioselectivity for (S)-reticuline starting from (R,S)-norlaudanosoline. In addition, the P. somniferum enzymes salutaridine synthase (PsSAS), salutaridine reductase (PsSAR) and salutaridinol acetyltransferase (PsSAT) were functionally co-expressed in S. cerevisiae and optimization of the pH conditions allowed for productive spontaneous rearrangement of salutaridinol-7-O-acetate and synthesis of thebaine from (R)-reticuline. Finally, we reconstituted a 7-gene pathway for the production of codeine and morphine from (R)-reticuline. Yeast cell feeding assays using (R)-reticuline, salutaridine or codeine as substrates showed that all enzymes were functionally co-expressed in yeast and that activity of salutaridine reductase and codeine-O-demethylase likely limit flux to morphine synthesis. The results of this study describe a significant advance for the synthesis of morphinans in S. cerevisiae and pave the way for their complete synthesis in recombinant microbes. PMID:25905794

  19. Synthesis of Morphinan Alkaloids in Saccharomyces cerevisiae

    PubMed Central

    Fossati, Elena; Narcross, Lauren; Ekins, Andrew; Falgueyret, Jean-Pierre; Martin, Vincent J. J.

    2015-01-01

    Morphinan alkaloids are the most powerful narcotic analgesics currently used to treat moderate to severe and chronic pain. The feasibility of morphinan synthesis in recombinant Saccharomyces cerevisiae starting from the precursor (R,S)-norlaudanosoline was investigated. Chiral analysis of the reticuline produced by the expression of opium poppy methyltransferases showed strict enantioselectivity for (S)-reticuline starting from (R,S)-norlaudanosoline. In addition, the P. somniferum enzymes salutaridine synthase (PsSAS), salutaridine reductase (PsSAR) and salutaridinol acetyltransferase (PsSAT) were functionally co-expressed in S. cerevisiae and optimization of the pH conditions allowed for productive spontaneous rearrangement of salutaridinol-7-O-acetate and synthesis of thebaine from (R)-reticuline. Finally, we reconstituted a 7-gene pathway for the production of codeine and morphine from (R)-reticuline. Yeast cell feeding assays using (R)-reticuline, salutaridine or codeine as substrates showed that all enzymes were functionally co-expressed in yeast and that activity of salutaridine reductase and codeine-O-demethylase likely limit flux to morphine synthesis. The results of this study describe a significant advance for the synthesis of morphinans in S. cerevisiae and pave the way for their complete synthesis in recombinant microbes. PMID:25905794

  20. Myo-inositol transport in Saccharomyces cerevisiae.

    PubMed

    Nikawa, J; Nagumo, T; Yamashita, S

    1982-05-01

    myo-Inositol uptake in Saccharomyces cerevisiae was dependent on temperature, time, and substrate concentration. The transport obeyed saturation kinetics with an apparent Km for myo-inositol of 0.1 mM, myo-Inositol analogs, such as scyllo-inositol, 2-inosose, mannitol, and 1,2-cyclohexanediol, had no effect on myo-inositol uptake, myo-Inositol uptake required metabolic energy. Removal of D-glucose resulted in a loss of activity, and azide and cyanide ions were inhibitory. In the presence of D-glucose, myo-inositol was accumulated in the cells against a concentration gradient. A myo-inositol transport mutant was isolated from UV-mutagenized S. cerevisiae cells using the replica-printing technique. The defect in myo-inositol uptake was due to a single nuclear gene mutation. The activities of L-serine and D-glucose transport were not affected by the mutation. Thus it was shown that S. cerevisiae grown under the present culture conditions possessed a single and specific myo-inositol transport system. myo-Inositol transport activity was reduced by the addition of myo-inositol to the culture medium. The activity was reversibly restored by the removal of myo-inositol from the medium. This restoration of activity was completely abolished by cycloheximide. PMID:7040334

  1. Genetic variation of the repeated MAL loci in natural populations of Saccharomyces cerevisiae and Saccharomyces paradoxus.

    PubMed

    Naumov, G I; Naumova, E S; Michels, C A

    1994-03-01

    In Saccharomyces cerevisiae, the gene functions required to ferment the disaccharide maltose are encoded by the MAL loci. Any one of five highly sequence homologous MAL loci identified in various S. cerevisiae strains (called MAL1, 2, 3, 4 and 6) is sufficient to ferment maltose. Each is a complex of three genes encoding maltose permease, maltase and a transcription activator. This family of loci maps to telomere-linked positions on different chromosomes and most natural strains contain more than one MAL locus. A number of naturally occurring, mutant alleles of MAL1 and MAL3 have been characterized which lack one or more of the gene functions encoded by the fully functional MAL loci. Loss of these gene functions appears to have resulted from mutation and/or rearrangement within the locus. Studies to date concentrated on the standard maltose fermenting strains of S. cerevisiae available from the Berkeley Yeast Stock Center collection. In this report we extend our genetic analysis of the MAL loci to a number of maltose fermenting and nonfermenting natural strains of S. cerevisiae and Saccharomyces paradoxus. No new MAL loci were discovered but several new mutant alleles of MAL1 were identified. The evolution of this gene family is discussed. PMID:8005435

  2. PT AND PT/NI "NEEDLE" ELETROCATALYSTS ON CARBON NANOTUBES WITH HIGH ACTIVITY FOR THE ORR

    SciTech Connect

    Colon-Mercado, H.

    2011-11-10

    Platinum and platinum/nickel alloy electrocatalysts supported on graphitized (gCNT) or nitrogen doped carbon nanotubes (nCNT) are prepared and characterized. Pt deposition onto carbon nanotubes results in Pt 'needle' formations that are 3.5 nm in diameter and {approx}100 nm in length. Subsequent Ni deposition and heat treatment results in PtNi 'needles' with an increased diameter. All Pt and Pt/Ni materials were tested as electrocatalysts for the oxygen reduction reaction (ORR). The Pt and Pt/Ni catalysts showed excellent performance for the ORR, with the heat treated PtNi/gCNT (1.06 mA/cm{sup 2}) and PtNi/nCNT (0.664 mA/cm{sup 2}) showing the highest activity.

  3. The Role of Pt Complex on the Synthesis of FePt by Polyol Process

    SciTech Connect

    Aizawa, S.; Tohji, K.; Jeyadevan, B.

    2008-02-25

    Target materials in this experiment were FePt alloy nanoparticles with face-centered tetragonal structure, narrow size distribution, and the size of 6-8 nm. This type of materials was expected to have high recording-density of 1 Tbit/inch{sup 2} with high magnetic anisotropy. In this study, a detailed investigation was carried out to understand the reduction characteristics of Pt complexes, and FePt alloy nanoparticles with diameters larger than 6 nm was try to synthesize. For the synthesis of Pt nanoparticles by using polyol process, three kinds of Pt complexes, namely, H{sub 2}PtCl{sub 6}, Pt(EDTA), and Pt(acac){sub 2} was used. The size of Pt metal nanoparticles was only few nm in the case of single Pt complex, while it was increased to 7-10 nm in the case of mixed Pt complex and adjusting the reaction temperature increasing ratio. FePt alloy nanoparticles with the diameter of 7-8 nm, distorted shape, and narrow size distribution were successfully synthesized. However, composition ratio of the particle was Fe{sub 12-21}Pt{sub 79-88}, nevertheless the ratio of a Fe:Pt in the original solution was 2:1.

  4. Low Pt content direct methanol fuel cell anode catalyst: nanophase PtRuNiZr

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram R. (Inventor); Whitacre, Jay F. (Inventor)

    2010-01-01

    A method for the preparation of a metallic material having catalytic activity that includes synthesizing a material composition comprising a metal content with a lower Pt content than a binary alloy containing Pt but that displays at least a comparable catalytic activity on a per mole Pt basis as the binary alloy containing Pt; and evaluating a representative sample of the material composition to ensure that the material composition displays a property of at least a comparable catalytic activity on a per mole Pt basis as a representative binary alloy containing Pt. Furthermore, metallic compositions are disclosed that possess substantial resistance to corrosive acids.

  5. Organization of the SUC gene family in Saccharomyces.

    PubMed Central

    Carlson, M; Botstein, D

    1983-01-01

    The SUC gene family of yeast (Saccharomyces) includes six structural genes for invertase (SUC1 through SUC5 and SUC7) found at unlinked chromosomal loci. A given yeast strain does not usually carry SUC+ alleles at all six loci; the natural negative alleles are called suc0 alleles. Cloned SUC2 DNA probes were used to investigate the physical structure of the SUC gene family in laboratory strains, commercial wine strains, and different Saccharomyces species. The active SUC+ genes are homologous. The suc0 allele at the SUC2 locus (suc2(0) in some strains is a silent gene or pseudogene. Other SUC loci carrying suc0 alleles appear to lack SUC DNA sequences. These findings imply that SUC genes have transposed to different chromosomal locations in closely related Saccharomyces strains. Images PMID:6843548

  6. Direct Determination of the Ionization Energies of PtC, PtO, and PtO2 with VUVRadiation

    SciTech Connect

    Citir, Murat; Metz, Ricardo B.; Belau, Leonid; Ahmed, Musahid

    2008-07-21

    Photoionization efficiency curves were measured for gas-phase PtC, PtO, and PtO2 using tunable vacuum ultraviolet (VUV) radiation at the Advanced Light Source. The molecules were prepared by laser ablation of a platinum tube, followed by reaction with CH4 or N2O and supersonic expansion. These measurements providethe first directly measured ionization energy for PtC, IE(PtC) = 9.45 +- 0.05 eV. The direct measurement also gives greatly improved ionization energies for the platinum oxides, IE(PtO) = 10.0 +- 0.1 eV and IE(PtO2) = 11.35 +- 0.05 eV. The ionization energy connects the dissociation energies of the neutral and cation, leading to greatly improved 0 K bond dissociation energies for the neutrals: D0(Pt-C) = 5.95 +- 0.07 eV, D0(Pt-O)= 4.30 +- 0.12 eV, and D0(OPt-O) = 4.41 +- 0.13 eV, as well as enthalpies of formation for the gas-phase molecules Delta H0 f,0(PtC(g)) = 701 +- 7 kJ/mol, Delta H0f,0(PtO(g)) = 396 +- 12 kJ/mol, and Delta H0f,0(PtO2(g)) = 218 +- 11 kJ/mol. Much of the error in previous Knudsen cell measurements of platinum oxide bond dissociation energies is due to the use of thermodynamic second law extrapolations. Third law values calculated using statistical mechanical thermodynamic functions are in much better agreement with values obtained from ionization energies and ion energetics. These experiments demonstrate that laser ablation production with direct VUV ionization measurements is a versatile tool to measure ionization energies and bond dissociation energies for catalytically interesting species such as metal oxides and carbides.

  7. Combinatorial Cis-regulation in Saccharomyces Species

    PubMed Central

    Spivak, Aaron T.; Stormo, Gary D.

    2016-01-01

    Transcriptional control of gene expression requires interactions between the cis-regulatory elements (CREs) controlling gene promoters. We developed a sensitive computational method to identify CRE combinations with conserved spacing that does not require genome alignments. When applied to seven sensu stricto and sensu lato Saccharomyces species, 80% of the predicted interactions displayed some evidence of combinatorial transcriptional behavior in several existing datasets including: (1) chromatin immunoprecipitation data for colocalization of transcription factors, (2) gene expression data for coexpression of predicted regulatory targets, and (3) gene ontology databases for common pathway membership of predicted regulatory targets. We tested several predicted CRE interactions with chromatin immunoprecipitation experiments in a wild-type strain and strains in which a predicted cofactor was deleted. Our experiments confirmed that transcription factor (TF) occupancy at the promoters of the CRE combination target genes depends on the predicted cofactor while occupancy of other promoters is independent of the predicted cofactor. Our method has the additional advantage of identifying regulatory differences between species. By analyzing the S. cerevisiae and S. bayanus genomes, we identified differences in combinatorial cis-regulation between the species and showed that the predicted changes in gene regulation explain several of the species-specific differences seen in gene expression datasets. In some instances, the same CRE combinations appear to regulate genes involved in distinct biological processes in the two different species. The results of this research demonstrate that (1) combinatorial cis-regulation can be inferred by multi-genome analysis and (2) combinatorial cis-regulation can explain differences in gene expression between species. PMID:26772747

  8. Combinatorial Cis-regulation in Saccharomyces Species.

    PubMed

    Spivak, Aaron T; Stormo, Gary D

    2016-01-01

    Transcriptional control of gene expression requires interactions between the cis-regulatory elements (CREs) controlling gene promoters. We developed a sensitive computational method to identify CRE combinations with conserved spacing that does not require genome alignments. When applied to seven sensu stricto and sensu lato Saccharomyces species, 80% of the predicted interactions displayed some evidence of combinatorial transcriptional behavior in several existing datasets including: (1) chromatin immunoprecipitation data for colocalization of transcription factors, (2) gene expression data for coexpression of predicted regulatory targets, and (3) gene ontology databases for common pathway membership of predicted regulatory targets. We tested several predicted CRE interactions with chromatin immunoprecipitation experiments in a wild-type strain and strains in which a predicted cofactor was deleted. Our experiments confirmed that transcription factor (TF) occupancy at the promoters of the CRE combination target genes depends on the predicted cofactor while occupancy of other promoters is independent of the predicted cofactor. Our method has the additional advantage of identifying regulatory differences between species. By analyzing the S. cerevisiae and S. bayanus genomes, we identified differences in combinatorial cis-regulation between the species and showed that the predicted changes in gene regulation explain several of the species-specific differences seen in gene expression datasets. In some instances, the same CRE combinations appear to regulate genes involved in distinct biological processes in the two different species. The results of this research demonstrate that (1) combinatorial cis-regulation can be inferred by multi-genome analysis and (2) combinatorial cis-regulation can explain differences in gene expression between species. PMID:26772747

  9. Regulation of Cation Balance in Saccharomyces cerevisiae

    PubMed Central

    Cyert, Martha S.; Philpott, Caroline C.

    2013-01-01

    All living organisms require nutrient minerals for growth and have developed mechanisms to acquire, utilize, and store nutrient minerals effectively. In the aqueous cellular environment, these elements exist as charged ions that, together with protons and hydroxide ions, facilitate biochemical reactions and establish the electrochemical gradients across membranes that drive cellular processes such as transport and ATP synthesis. Metal ions serve as essential enzyme cofactors and perform both structural and signaling roles within cells. However, because these ions can also be toxic, cells have developed sophisticated homeostatic mechanisms to regulate their levels and avoid toxicity. Studies in Saccharomyces cerevisiae have characterized many of the gene products and processes responsible for acquiring, utilizing, storing, and regulating levels of these ions. Findings in this model organism have often allowed the corresponding machinery in humans to be identified and have provided insights into diseases that result from defects in ion homeostasis. This review summarizes our current understanding of how cation balance is achieved and modulated in baker’s yeast. Control of intracellular pH is discussed, as well as uptake, storage, and efflux mechanisms for the alkali metal cations, Na+ and K+, the divalent cations, Ca2+ and Mg2+, and the trace metal ions, Fe2+, Zn2+, Cu2+, and Mn2+. Signal transduction pathways that are regulated by pH and Ca2+ are reviewed, as well as the mechanisms that allow cells to maintain appropriate intracellular cation concentrations when challenged by extreme conditions, i.e., either limited availability or toxic levels in the environment. PMID:23463800

  10. Spin-flipping in Pt and at Co/Pt interfaces

    NASA Astrophysics Data System (ADS)

    Nguyen, H. Y. T.; Pratt, W. P.; Bass, J.

    2014-06-01

    There has been recent controversy about the magnitude of spin-flipping in the heavy metal Pt, characterized by the spin-diffusion length lsfPt. We propose a resolution of this controversy, and also present evidence for the importance of a phenomenon neglected in prior studies of transport across sputtered Ferromagnet/Pt (F/Pt) interfaces, spin-flipping at the interface. The latter is characterized by an interface spin-flipping parameter, δCo/Pt, that specifies the probability P=[1-exp(-δ)] of a conduction electron flipping its spin direction as it traverses a Co/Pt interface. From studies of the Current-Perpendicular-to-Plane (CPP) Resistances and Magnetoresistances of sputtered ferromagnetically coupled Co/Pt multilayers by themselves, and embedded within Py-based Double Exchange-biased Spin-Valves, we derive values at 4.2 K of δCo/Pt=0.9-0.2+0.5, interface specific resistance, ARCo/Pt*=0.74±0.15 fΩ m2, and interface spin-scattering asymmetry, γCo/Pt=0.53±0.12. This value of δCo/Pt is much larger than ones previously found for five other interfaces involving Co but not Pt. To derive δ requires knowledge of lsfPt for our sputtered Pt, which we obtain from separate measurements. Combining our results with those from others, we find that lsfPt for Pt is approximately proportional to the inverse resistivity, 1/ρPt.

  11. Analysis of the Saccharomyces cerevisiae proteome with PeptideAtlas

    PubMed Central

    King, Nichole L; Deutsch, Eric W; Ranish, Jeffrey A; Nesvizhskii, Alexey I; Eddes, James S; Mallick, Parag; Eng, Jimmy; Desiere, Frank; Flory, Mark; Martin, Daniel B; Kim, Bong; Lee, Hookeun; Raught, Brian; Aebersold, Ruedi

    2006-01-01

    We present the Saccharomyces cerevisiae PeptideAtlas composed from 47 diverse experiments and 4.9 million tandem mass spectra. The observed peptides align to 61% of Saccharomyces Genome Database (SGD) open reading frames (ORFs), 49% of the uncharacterized SGD ORFs, 54% of S. cerevisiae ORFs with a Gene Ontology annotation of 'molecular function unknown', and 76% of ORFs with Gene names. We highlight the use of this resource for data mining, construction of high quality lists for targeted proteomics, validation of proteins, and software development. PMID:17101051

  12. Guiding SPPs with PT-symmetry

    PubMed Central

    Yang, Fan; Lei Mei, Zhong

    2015-01-01

    The concept of parity-time (PT) symmetry in SPPs is proposed and confirmed for the first time in this work. By introducing periodic modulation of the effective refractive index in SPP system, the asymmetric propagation is theoretically predicted and numerically demonstrated. After validation of this concept, we apply it in two applications: PT-waveguide and PT-cloak. Both two applications further illustrate the wide applicability of this concept in SPP system. PMID:26446520

  13. Pt{sub 3}Au and PtAu clusters: Electronic states and potential energy surfaces

    SciTech Connect

    Dai, D.; Balasubramanian, K.

    1994-03-15

    We carried out complete active space multiconfiguration self-consistent-field calculations followed by multireference singles+doubles configuration interaction with the Davidson correction which included up to 3.55 million configurations employing relativistic effective core potentials on Pt{sub 3}+Au and PtAu clusters. Four low-lying electronic states were identified for Pt{sub 3}+Au. The {sup 2}{ital A}{sub 2} electronic state ({ital C}{sub 3{ital v}}) was found to be the ground state of Pt{sub 3}Au. Spin--orbit effects were found to be significant. We also computed six low-lying electronic states of PtAu and four low-lying electronic states of PtAu{sup +}. The 5/2 ({sup 2}{Delta}) and 0{sup +}({sup 1}{Sigma}{sup +}) states were found to be the ground states of PtAu and PtAu{sup +}, respectively.

  14. Physics of YbBiPt

    SciTech Connect

    Thompson, J.D.; Canfield, P.C.; Lacerda, A.; Hundley, M.F.; Fisk, Z. ); Ott, H.R.; Felder, E.; Chernikov, M. ); Maple, M.B.; Visani, P.; Seaman, C.L.; Lopez de la Torre, M.A. ); Aeppli, G. )

    1992-09-15

    YbBiPt has a low temperature linear specific heat coefficient of 8J/mole-Yb K{sup 2} and a small specific-heat anomaly at 0.4K. We discuss new experiments on specific-heat of diluted YbBiPt, and magnetic field dependent effects and electrical resistivity in pure YbBiPt. We argue that in this material the Kondo and crystal-field energy scales are small and of comparable magnitude, placing YbBiPt in the same class as many Uranium heavy-electron compounds.

  15. Magnetic properties and microstructure of FePtB, FePt(B-Ag) granular films

    NASA Astrophysics Data System (ADS)

    Tsai, Jai-Lin; Huang, Jian-Chiang; Tai, Hsueh-Wei; Tsai, Wen-Chieh; Lin, Yi-Cheng

    2013-03-01

    Multilayers [FePt(1 nm)/B(t nm)]10 (t=0.05-0.6) were alternately deposited on a glass substrate and subsequently annealed by the rapid thermal process (RTP) at 800 °C for 3 min. After RTP, FePt and B layers intermix to form the FePtB film with (0 0 1) texture. The ordering degree of FePt was slightly increased with doped B. The (Fe-Pt)100-xBx (x=0, 5, 10) films show perpendicular magnetization and the minor FeB phase was indexed in isotropic (Fe-Pt)100-xBx (x=30, 40, 60) films. By adding Ag into (Fe-Pt)95B5 film, the ordering degree was slightly increased in (Fe-Pt)95(B0.9Ag0.1)5 film. In (Fe-Pt)100-xBx (x=5, 10) and (Fe-Pt)95(B0.9Ag0.1)5 granular films, the intermixed B or Ag atoms were diffused among FePt grain boundaries to isolate and refine FePt grains uniformly with average grain sizes of 20, 15, and 6.7 nm, respectively.

  16. Bulk structures of PtO and PtO2 from density functional calculations

    NASA Astrophysics Data System (ADS)

    Nomiyama, Ricardo K.; Piotrowski, Maurício J.; da Silva, Juarez L. F.

    2011-09-01

    Platinum plays an important role in catalysis and electrochemistry, and it is known that the direct interaction of oxygen with Pt surfaces can lead to the formation of platinum oxides (PtOx), which can affect the reactivity. To contribute to the atomistic understanding of the atomic structure of PtOx, we report a density functional theory study of the atomic structure of bulk PtOx (1≤x≤2). From our calculations, we identified a lowest-energy structure (GeS type, space group Pnma) for PtO, which is 0.181 eV lower in energy than the structure suggested by W. J. Moore and L. Pauling [J. Am. Chem. Soc. 10.1021/ja01850a07463, 1392 (1941)] (PtS type). Furthermore, two atomic structures were identified for PtO2, which are almost degenerate in energy with the lowest-energy structure reported so far for PtO2 (CaCl2 type). Based on our results and analysis, we suggest that Pt and O atoms tend to form octahedron motifs in PtOx even at lower O composition by the formation of Pt-Pt bonds.

  17. Synthesis of ribosomes in Saccharomyces cerevisiae.

    PubMed Central

    Warner, J R

    1989-01-01

    The assembly of a eucaryotic ribosome requires the synthesis of four ribosomal ribonucleic acid (RNA) molecules and more than 75 ribosomal proteins. It utilizes all three RNA polymerases; it requires the cooperation of the nucleus and the cytoplasm, the processing of RNA, and the specific interaction of RNA and protein molecules. It is carried out efficiently and is exquisitely sensitive to the needs of the cell. Our current understanding of this process in the genetically tractable yeast Saccharomyces cerevisiae is reviewed. The ribosomal RNA genes are arranged in a tandem array of 100 to 200 copies. This tandem array has led to unique ways of carrying out a number of functions. Replication is asymmetric and does not initiate from every autonomously replicating sequence. Recombination is suppressed. Transcription of the major ribosomal RNA appears to involve coupling between adjacent transcription units, which are separated by the 5S RNA transcription unit. Genes for many ribosomal proteins have been cloned and sequenced. Few are linked; most are duplicated; most have an intron. There is extensive homology between yeast ribosomal proteins and those of other species. Most, but not all, of the ribosomal protein genes have one or two sites that are essential for their transcription and that bind a common transcription factor. This factor binds also to many other places in the genome, including the telomeres. There is coordinated transcription of the ribosomal protein genes under a variety of conditions. However, the cell seems to possess no mechanism for regulating the transcription of individual ribosomal protein genes in response either to a deficiency or an excess of a particular ribosomal protein. A deficiency causes slow growth. Any excess ribosomal protein is degraded very rapidly, with a half-life of 1 to 5 min. Unlike most types of cells, yeast cells appear not to regulate the translation of ribosomal proteins. However, in the case of ribosomal protein L32

  18. Social wasps promote social behavior in Saccharomyces spp.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This commentary provides background and an evaluation of a paper to be published in the Proceedings of the National Academy of Sciences in which social wasps were found to harbor significant populations of two species of the yeast genus Saccharomyces. Apparently, the yeasts were acquired during feed...

  19. Saccharomyces cerevisiae boulardii transient fungemia after intravenous self-inoculation.

    PubMed

    Cohen, Lola; Ranque, Stéphane; Raoult, Didier

    2013-02-14

    We report the case of a young psychotic intravenous drug user injecting herself with Saccharomyces cervisiae (boulardii). She experienced a 24 h fever, resolving spontaneously confirming, quasi experimentally, the inocuity of this yeast in a non-immunocompromised host. PMID:24432219

  20. Improving biomass sugar utilization by engineered Saccharomyces cerevisiae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The efficient utilization of all available sugars in lignocellulosic biomass, which is more abundant than available commodity crops and starch, represents one of the most difficult technological challenges for the production of bioethanol. The well-studied yeast Saccharomyces cerevisiae has played a...

  1. Analysis of the RNA Content of the Yeast "Saccharomyces Cerevisiae"

    ERIC Educational Resources Information Center

    Deutch, Charles E.; Marshall, Pamela A.

    2008-01-01

    In this article, the authors describe an interconnected set of relatively simple laboratory experiments in which students determine the RNA content of yeast cells and use agarose gel electrophoresis to separate and analyze the major species of cellular RNA. This set of experiments focuses on RNAs from the yeast "Saccharomyces cerevisiae", a…

  2. Thermal resistance of Saccharomyces yeast ascospores in beers.

    PubMed

    Milani, Elham A; Gardner, Richard C; Silva, Filipa V M

    2015-08-01

    The industrial production of beer ends with a process of thermal pasteurization. Saccharomyces cerevisiae and Saccharomyces pastorianus are yeasts used to produce top and bottom fermenting beers, respectively. In this research, first the sporulation rate of 12 Saccharomyces strains was studied. Then, the thermal resistance of ascospores of three S. cerevisiae strains (DSMZ 1848, DSMZ 70487, Ethanol Red(®)) and one strain of S. pastorianus (ATCC 9080) was determined in 4% (v/v) ethanol lager beer. D60 °C-values of 11.2, 7.5, 4.6, and 6.0 min and z-values of 11.7, 14.3, 12.4, and 12.7 °C were determined for DSMZ 1848, DSMZ 70487, ATCC 9080, and Ethanol Red(®), respectively. Lastly, experiments with 0 and 7% (v/v) beers were carried out to investigate the effect of ethanol content on the thermal resistance of S. cerevisiae (DSMZ 1848). D55 °C-values of 34.2 and 15.3 min were obtained for 0 and 7% beers, respectively, indicating lower thermal resistance in the more alcoholic beer. These results demonstrate similar spore thermal resistance for different Saccharomyces strains and will assist in the design of appropriate thermal pasteurization conditions for preserving beers with different alcohol contents. PMID:25996521

  3. Molecular mechanisms of ethanol tolerance in Saccharomyces cerevisiae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The yeast Saccharomyces cerevisiae is a superb ethanol producer, yet sensitive to ethanol at higher concentrations especially under high gravity or very high gravity fermentation conditions. Although significant efforts have been made to study ethanol-stress response in past decades, molecular mecha...

  4. Shape-Controlled Synthesis of Pt Nanopeanuts.

    PubMed

    Zhang, Xuemei; Xia, Zengzilu; Huang, Yingzhou; Jia, Yunpeng; Sun, Xiaonan; Li, Yu; Li, Xueming; Wu, Rui; Liu, Anping; Qi, Xueqiang; Wang, Shuxia; Wen, Weijia

    2016-01-01

    Exploring the novel shape of Pt nanoparticles is one of the most useful ways to improve the electrocatalytic performance of Pt in fuel cells. In this work, the Pt nanopeanuts consisting of two nanospheres grown together have been fabricated through a two-step polyol method. The high resolution scanning electron microscope (SEM) images and energy dispersive x-ray (EDX) spectrum collected at adjacent part point out the Pt nanopeanut is apparently different from the two physical attached nanospheres. To understand the growth mechanism of this nanopeanut, the final products in different synthesis situations are studied. The results indicate the interesting morphology of Pt nanopeanuts mainly benefit from the chemical reagent (FeCl3) while the size and homogeneity are greatly affected by the temperature. Furthermore, the electrocatalytic activity of the Pt nanopeanuts has also been demonstrated here. Our two-step synthesis of Pt nanopeanuts not only enlarges the group of Pt nanoparticles, but also provides a beneficial strategy for the synthesis of novel metal nanoparticles. PMID:27528078

  5. AN ANIMAL MODEL OF PLATINUM (PT) HYPERSENSITIVITY

    EPA Science Inventory

    Exposure to Pt salts has been associated with occupational asthma. Pt, the most active component and widely used metal in catalytic converters, is released in automobile exhaust and is a proposed diesel fuel additive. Thus, with the potential for widespread environmental distrib...

  6. Shape-Controlled Synthesis of Pt Nanopeanuts

    PubMed Central

    Zhang, Xuemei; Xia, Zengzilu; Huang, Yingzhou; Jia, Yunpeng; Sun, Xiaonan; Li, Yu; Li, Xueming; Wu, Rui; Liu, Anping; Qi, Xueqiang; Wang, Shuxia; Wen, Weijia

    2016-01-01

    Exploring the novel shape of Pt nanoparticles is one of the most useful ways to improve the electrocatalytic performance of Pt in fuel cells. In this work, the Pt nanopeanuts consisting of two nanospheres grown together have been fabricated through a two-step polyol method. The high resolution scanning electron microscope (SEM) images and energy dispersive x-ray (EDX) spectrum collected at adjacent part point out the Pt nanopeanut is apparently different from the two physical attached nanospheres. To understand the growth mechanism of this nanopeanut, the final products in different synthesis situations are studied. The results indicate the interesting morphology of Pt nanopeanuts mainly benefit from the chemical reagent (FeCl3) while the size and homogeneity are greatly affected by the temperature. Furthermore, the electrocatalytic activity of the Pt nanopeanuts has also been demonstrated here. Our two-step synthesis of Pt nanopeanuts not only enlarges the group of Pt nanoparticles, but also provides a beneficial strategy for the synthesis of novel metal nanoparticles. PMID:27528078

  7. Linearization of Pt resistance temperature measurement circuit

    NASA Astrophysics Data System (ADS)

    Li, Chuan-xiang

    2001-09-01

    A correction method for non-linear Pt resistance temperature measurement based on the principle of A/D conversion is introduced. The design principle of Pt resistance linear temperature measurement is analyzed and a new method for interfacing A/D converter with single chip computer 89c52 is provided together with the experimental data.

  8. Nonlinear waves in PT -symmetric systems

    NASA Astrophysics Data System (ADS)

    Konotop, Vladimir V.; Yang, Jianke; Zezyulin, Dmitry A.

    2016-07-01

    Recent progress on nonlinear properties of parity-time (PT )-symmetric systems is comprehensively reviewed in this article. PT symmetry started out in non-Hermitian quantum mechanics, where complex potentials obeying PT symmetry could exhibit all-real spectra. This concept later spread out to optics, Bose-Einstein condensates, electronic circuits, and many other physical fields, where a judicious balancing of gain and loss constitutes a PT -symmetric system. The natural inclusion of nonlinearity into these PT systems then gave rise to a wide array of new phenomena which have no counterparts in traditional dissipative systems. Examples include the existence of continuous families of nonlinear modes and integrals of motion, stabilization of nonlinear modes above PT -symmetry phase transition, symmetry breaking of nonlinear modes, distinctive soliton dynamics, and many others. In this article, nonlinear PT -symmetric systems arising from various physical disciplines are presented, nonlinear properties of these systems are thoroughly elucidated, and relevant experimental results are described. In addition, emerging applications of PT symmetry are pointed out.

  9. Introducing a New Breed of Wine Yeast: Interspecific Hybridisation between a Commercial Saccharomyces cerevisiae Wine Yeast and Saccharomyces mikatae

    PubMed Central

    Bellon, Jennifer R.; Schmid, Frank; Capone, Dimitra L.; Dunn, Barbara L.; Chambers, Paul J.

    2013-01-01

    Interspecific hybrids are commonplace in agriculture and horticulture; bread wheat and grapefruit are but two examples. The benefits derived from interspecific hybridisation include the potential of generating advantageous transgressive phenotypes. This paper describes the generation of a new breed of wine yeast by interspecific hybridisation between a commercial Saccharomyces cerevisiae wine yeast strain and Saccharomyces mikatae, a species hitherto not associated with industrial fermentation environs. While commercially available wine yeast strains provide consistent and reliable fermentations, wines produced using single inocula are thought to lack the sensory complexity and rounded palate structure obtained from spontaneous fermentations. In contrast, interspecific yeast hybrids have the potential to deliver increased complexity to wine sensory properties and alternative wine styles through the formation of novel, and wider ranging, yeast volatile fermentation metabolite profiles, whilst maintaining the robustness of the wine yeast parent. Screening of newly generated hybrids from a cross between a S. cerevisiae wine yeast and S. mikatae (closely-related but ecologically distant members of the Saccharomyces sensu stricto clade), has identified progeny with robust fermentation properties and winemaking potential. Chemical analysis showed that, relative to the S. cerevisiae wine yeast parent, hybrids produced wines with different concentrations of volatile metabolites that are known to contribute to wine flavour and aroma, including flavour compounds associated with non-Saccharomyces species. The new S. cerevisiae x S. mikatae hybrids have the potential to produce complex wines akin to products of spontaneous fermentation while giving winemakers the safeguard of an inoculated ferment. PMID:23614011

  10. PT-Symmetric Quantum Field Theory

    NASA Astrophysics Data System (ADS)

    Bender, Carl M.

    2011-09-01

    In 1998 it was discovered that the requirement that a Hamiltonian be Dirac Hermitian (H = H†) can be weakened and generalized to the requirement that a Hamiltonian be PT symmetric ([H,PT] = 0); that is, invariant under combined space reflection and time reversal. Weakening the constraint of Hermiticity allows one to consider new kinds of physically acceptable Hamiltonians and, in effect, it amounts to extending quantum mechanics from the real (Hermitian) domain into the complex domain. Much work has been done on the analysis of various PT-symmetric quantum-mechanical models. However, only very little analysis has been done on PT-symmetric quantum-field-theoretic models. Here, we describe some of what has been done in the context of PT-symmetric quantum field theory and describe some possible fundamental applications.

  11. Reduction of Pt2+ species in model Pt-CeO2 fuel cell catalysts upon reaction with methanol

    NASA Astrophysics Data System (ADS)

    Neitzel, Armin; Johánek, Viktor; Lykhach, Yaroslava; Skála, Tomáš; Tsud, Nataliya; Vorokhta, Mykhailo; Matolín, Vladimír; Libuda, Jörg

    2016-11-01

    The stability of atomically dispersed Pt2+ species on the surface of nanostructured CeO2 films during the reaction with methanol has been investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy. The isolated Pt2+ species were prepared at low Pt concentration in Pt-CeO2 film. Additionally, Pt2+ species coexisting with metallic Pt particles were prepared at high Pt concentration. We found that adsorption of methanol yields similar decomposition products regardless of Pt concentration in Pt-CeO2 films. A small number of oxygen vacancies formed during the methanol decomposition can be replenished in the Pt-CeO2 film with low Pt concentration by diffusion of oxygen from the bulk. In the presence of supported Pt particles, a higher number of oxygen vacancies leads to a partial reduction of the Pt2+ species. The isolated Pt2+ species are reduced under rather strongly reducing conditions only, i.e. during annealing under continuous exposure to methanol. Reduction of isolated Pt2+ species results in the formation of ultra-small Pt particles containing around 25 atoms per particle or less. Such ultra-small Pt particles demonstrate excellent stability against sintering during annealing of Pt-CeO2 film with low Pt concentration under reducing conditions.

  12. Architecturally designed Pt-MoS2 and Pt-graphene composites for electrocatalytic methanol oxidation.

    PubMed

    Patil, Sagar H; Anothumakkool, Bihag; Sathaye, Shivaram D; Patil, Kashinath R

    2015-10-21

    Thin films consisting of platinum nanoparticles (Pt NPs) with uniform size and distribution have been successfully prepared at a liquid-liquid interface. Apart from the usual substrates like glass, Si etc. the films were also deposited on the surfaces of MoS2 thin films and graphene nanosheets (GNS) respectively, by using a layer-by-layer (LbL) deposition technique to form Pt-MoS2 and Pt-GNS composites. The loading concentration of Pt NPs on MoS2 and GNS can be adjusted by selecting the number and sequence of the component layers during LbL deposition. The Pt thin films, Pt-MoS2 and Pt-GNS nanocomposite thin films are characterized using transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). TEM results of the composites show that Pt NPs with sizes in the range of 1 to 3 nm are uniformly dispersed on the MoS2/GNS surface. The catalytic activities of Pt and Pt-composites for the reaction of methanol oxidation are studied using cyclic voltammetry and chronoamperometry. Electrochemical studies reveal that both the Pt-MoS2 and Pt-GNS nanocomposites show excellent electrocatalytic activity towards methanol oxidation. Pt-MoS2 and Pt-GNS nanocomposite electrodes show excellent stability for reuse of the catalyst. A probable mechanism of catalysis has been discussed. We propose that the similar architecture reported here would be promising for the synthesis of high performance catalysts for fuel cells, gas phase reactions, and other applications such as sensors. PMID:26377752

  13. Highly Active Pt(3)Pb and Core-Shell Pt(3)Pb-Pt Electrocatalysts for Formic Acid Oxidation

    SciTech Connect

    Kang Y.; Stach E.; Qi L.; Li M.; Diaz R.E.; Su D.; Adzic R.R.; Li J.; Murray C.B.

    2012-03-27

    Formic acid is a promising chemical fuel for fuel cell applications. However, due to the dominance of the indirect reaction pathway and strong poisoning effects, the development of direct formic acid fuel cells has been impeded by the low activity of existing electrocatalysts at desirable operating voltage. We report the first synthesis of Pt{sub 3}Pb nanocrystals through solution phase synthesis and show they are highly efficient formic acid oxidation electrocatalysts. The activity can be further improved by manipulating the Pt{sub 3}Pb-Pt core-shell structure. Combined experimental and theoretical studies suggest that the high activity from Pt{sub 3}Pb and the Pt-Pb core-shell nanocrystals results from the elimination of CO poisoning and decreased barriers for the dehydrogenation steps. Therefore, the Pt{sub 3}Pb and Pt-Pb core-shell nanocrystals can improve the performance of direct formic acid fuel cells at desired operating voltage to enable their practical application.

  14. Outlining a future for non-Saccharomyces yeasts: selection of putative spoilage wine strains to be used in association with Saccharomyces cerevisiae for grape juice fermentation.

    PubMed

    Domizio, Paola; Romani, Cristina; Lencioni, Livio; Comitini, Francesca; Gobbi, Mirko; Mannazzu, Ilaria; Ciani, Maurizio

    2011-06-30

    The use of non-Saccharomyces yeasts that are generally considered as spoilage yeasts, in association with Saccharomyces cerevisiae for grape must fermentation was here evaluated. Analysis of the main oenological characteristics of pure cultures of 55 yeasts belonging to the genera Hanseniaspora, Pichia, Saccharomycodes and Zygosaccharomyces revealed wide biodiversity within each genus. Moreover, many of these non-Saccharomyces strains had interesting oenological properties in terms of fermentation purity, and ethanol and secondary metabolite production. The use of four non-Saccharomyces yeasts (one per genus) in mixed cultures with a commercial S. cerevisiae strain at different S. cerevisiae/non-Saccharomyces inoculum ratios was investigated. This revealed that most of the compounds normally produced at high concentrations by pure cultures of non-Saccharomyces, and which are considered detrimental to wine quality, do not reach threshold taste levels in these mixed fermentations. On the other hand, the analytical profiles of the wines produced by these mixed cultures indicated that depending on the yeast species and the S. cerevisiae/non-Saccharomyces inoculum ratio, these non-Saccharomyces yeasts can be used to increase production of polysaccharides and to modulate the final concentrations of acetic acid and volatile compounds, such as ethyl acetate, phenyl-ethyl acetate, 2-phenyl ethanol, and 2-methyl 1-butanol. PMID:21531033

  15. Experimental and theoretical studies of ammonia decomposition activity on Fe-Pt, Co-Pt, and Cu-Pt bimetallic surfaces

    NASA Astrophysics Data System (ADS)

    Hansgen, Danielle A.; Thomanek, Lisa M.; Chen, Jingguang G.; Vlachos, Dionisios G.

    2011-05-01

    We investigate the decomposition of ammonia on bimetallic surfaces prepared by the deposition of a monolayer of Fe, Co, or Cu on a Pt(111) surface computationally and experimentally. We explore the correlation between predicted activities based on the nitrogen binding energies with experimental decomposition activity on these bimetallic and corresponding monometallic surfaces. Through density functional theory calculations and microkinetic modeling, it is predicted that the Fe-Pt-Pt(111) and Co-Pt-Pt(111) surfaces, with a monolayer of Fe or Co on top of Pt(111), are active toward decomposing ammonia. In contrast, the corresponding subsurface configurations, Pt-Fe-Pt(111) and Pt-Co-Pt(111) are inactive. These predictions were confirmed experimentally through temperature programmed desorption experiments. Decomposition was seen at temperatures below 350 K for the Fe-Pt-Pt(111) and Co-Pt-Pt(111) surfaces. For the Cu/Pt(111) system, the surface, subsurface and parent metals were each predicted to be inactive, consistent with experiments, further validating the model predictions. The stability of these bimetallic surfaces in the presence of adsorbed nitrogen is also discussed.

  16. Microstructure and electronic behavior of PtPd@Pt core-shell nanowires

    SciTech Connect

    Han, Wei-Qiang; Su, Dong; Murphy, Michael; Ward, Matthew; Sham, Tsun-Kong; Wu, Lijun; Zhu, Yimei; Hu, Yongfeng; Aoki, Toshihiro

    2010-07-19

    PtPd{at}Pt core-shell ultrathin nanowires were prepared using a one-step phase-transfer approach. The diameters of the nanowires range from 2 to 3 nm, and their lengths are up to hundreds of nanometers. Line scanning electron energy loss spectra showed that PtPd bimetallic nanowires have a core-shell structure, with a PtPd alloy core and a Pt monolayer shell. X-ray absorption near edge structure (XANES) spectra reveal that a strong Pt-Pd interaction exists in this nanowire system in that there is PtPd alloying and/or interfacial interaction. Extended x-ray absorption fine structures (EXAFS) further confirms the PtPd@Pt core-shell structure. The bimetallic nanowires were determined to be face-centered cubic structures. The long-chain organic molecules of n-dodecyl trimethylammonium bromide and octadecylamine, used as surfactants during synthesis, were clearly observed using aberration-corrected TEM operated at 80 KV. The interaction of Pt and surfactants was also revealed by EXAFS.

  17. \\cal{PT} -symmetry in Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Ziauddin; Chuang, You-Lin; Lee, Ray-Kuang

    2016-07-01

    We propose a scheme to realize parity-time ( {PT} )-symmetry in an ensemble of strongly interacting Rydberg atoms, which act as superatoms due to the dipole blockade mechanism. We show that Rydberg-dressed 87Rb atoms in a four-level inverted Y-type configuration is highly efficient to generate the refractive index for a probe field, with a symmetric (antisymmetric) profile spatially in the corresponding real (imaginary) part. Comparing with earlier investigations, the present scheme provides a versatile platform to control the system from {PT} -symmetry to non-PT -symmetry via different external parameters, i.e., coupling field detuning, probe field intensity and control field intensity.

  18. The reference genome sequence of Saccharomyces cerevisiae: then and now.

    PubMed

    Engel, Stacia R; Dietrich, Fred S; Fisk, Dianna G; Binkley, Gail; Balakrishnan, Rama; Costanzo, Maria C; Dwight, Selina S; Hitz, Benjamin C; Karra, Kalpana; Nash, Robert S; Weng, Shuai; Wong, Edith D; Lloyd, Paul; Skrzypek, Marek S; Miyasato, Stuart R; Simison, Matt; Cherry, J Michael

    2014-03-01

    The genome of the budding yeast Saccharomyces cerevisiae was the first completely sequenced from a eukaryote. It was released in 1996 as the work of a worldwide effort of hundreds of researchers. In the time since, the yeast genome has been intensively studied by geneticists, molecular biologists, and computational scientists all over the world. Maintenance and annotation of the genome sequence have long been provided by the Saccharomyces Genome Database, one of the original model organism databases. To deepen our understanding of the eukaryotic genome, the S. cerevisiae strain S288C reference genome sequence was updated recently in its first major update since 1996. The new version, called "S288C 2010," was determined from a single yeast colony using modern sequencing technologies and serves as the anchor for further innovations in yeast genomic science. PMID:24374639

  19. Saccharomyces cerevisiae: a sexy yeast with a prion problem.

    PubMed

    Kelly, Amy C; Wickner, Reed B

    2013-01-01

    Yeast prions are infectious proteins that spread exclusively by mating. The frequency of prions in the wild therefore largely reflects the rate of spread by mating counterbalanced by prion growth slowing effects in the host. We recently showed that the frequency of outcross mating is about 1% of mitotic doublings with 23-46% of total matings being outcrosses. These findings imply that even the mildest forms of the [PSI+], [URE3] and [PIN+] prions impart > 1% growth/survival detriment on their hosts. Our estimate of outcrossing suggests that Saccharomyces cerevisiae is far more sexual than previously thought and would therefore be more responsive to the adaptive effects of natural selection compared with a strictly asexual yeast. Further, given its large effective population size, a growth/survival detriment of > 1% for yeast prions should strongly select against prion-infected strains in wild populations of Saccharomyces cerevisiae. PMID:23764836

  20. Bioethanol production from sweet potato using Saccharomyces diastaticus

    NASA Astrophysics Data System (ADS)

    Abdullah, Suryani, Irma; Pradia Paundradewa, J.

    2015-12-01

    Sweet potato contains about 16 to 40% dry matter and about 70-90% of the dry matter is a carbohydrate made up of starch, sugar, cellulose, hemicellulose and pectin so suitable for used as raw material for bioethanol. In this study focused on the manufacture of bioethanol with changes in temperature and concentration variations of yeast with sweet potato raw materials used yeast Saccharomyces diastaticus. Operating variables used are at a temperature of 30°C; 31,475°C; 35°C; 38,525°C; and 40°C with a yeast concentration of 25.9%; 30%; 40%; 50% and 54.1%. The experimental results obtained, the optimum conditions of ethanol fermentation with yeast Saccharomyces diastaticus on 36,67 °C temperature and yeast concentration of 43,43 % v / v.

  1. A Saccharomyces cerevisiae Internet protein resource now available.

    PubMed

    Latter, G I; Boutell, T; Monardo, P J; Kobayashi, R; Futcher, B; Mclaughlin, C S; Garrels, J I

    1995-07-01

    The QUEST Protein Database Center is now making available two Saccharomyces cerevisiae protein databases via the Internet. The yeast electrophoretic protein database (YEPD) is a database of approximately one hundred protein identifications on two-dimensional gels. The yeast protein database (YPD) is a database of gene names and properties of over 3500 yeast proteins of known sequence. These databases can be accessed via a World-Wide Web (WWW) server (URL http:@siva.cshl.org). YPD is available via public ftp (isis.cshl.org) as well, in a spreadsheet format, and in ASCII format. When accessed via WWW, both of these databases have hypertext links to other biological data, such as the SWISS-PROT protein sequence database and the Saccharomyces Genome Database (SacchDB), and to each other. PMID:7498160

  2. The Reference Genome Sequence of Saccharomyces cerevisiae: Then and Now

    PubMed Central

    Engel, Stacia R.; Dietrich, Fred S.; Fisk, Dianna G.; Binkley, Gail; Balakrishnan, Rama; Costanzo, Maria C.; Dwight, Selina S.; Hitz, Benjamin C.; Karra, Kalpana; Nash, Robert S.; Weng, Shuai; Wong, Edith D.; Lloyd, Paul; Skrzypek, Marek S.; Miyasato, Stuart R.; Simison, Matt; Cherry, J. Michael

    2014-01-01

    The genome of the budding yeast Saccharomyces cerevisiae was the first completely sequenced from a eukaryote. It was released in 1996 as the work of a worldwide effort of hundreds of researchers. In the time since, the yeast genome has been intensively studied by geneticists, molecular biologists, and computational scientists all over the world. Maintenance and annotation of the genome sequence have long been provided by the Saccharomyces Genome Database, one of the original model organism databases. To deepen our understanding of the eukaryotic genome, the S. cerevisiae strain S288C reference genome sequence was updated recently in its first major update since 1996. The new version, called “S288C 2010,” was determined from a single yeast colony using modern sequencing technologies and serves as the anchor for further innovations in yeast genomic science. PMID:24374639

  3. Genome annotation of a Saccharomyces sp. lager brewer's yeast.

    PubMed

    De León-Medina, Patricia Marcela; Elizondo-González, Ramiro; Damas-Buenrostro, Luis Cástulo; Geertman, Jan-Maarten; Van den Broek, Marcel; Galán-Wong, Luis Jesús; Ortiz-López, Rocío; Pereyra-Alférez, Benito

    2016-09-01

    The genome of lager brewer's yeast is a hybrid, with Saccharomyces eubayanus and Saccharomyces cerevisiae as sub-genomes. Due to their specific use in the beer industry, relatively little information is available. The genome of brewing yeast was sequenced and annotated in this study. We obtained a genome size of 22.7 Mbp that consisted of 133 scaffolds, with 65 scaffolds larger than 10 kbp. With respect to the annotation, 9939 genes were obtained, and when they were submitted to a local alignment, we found that 53.93% of these genes corresponded to S. cerevisiae, while another 42.86% originated from S. eubayanus. Our results confirm that our strain is a hybrid of at least two different genomes. PMID:27330999

  4. Expression of bacterial mercuric ion reductase in Saccharomyces cerevisiae.

    PubMed Central

    Rensing, C; Kües, U; Stahl, U; Nies, D H; Friedrich, B

    1992-01-01

    The gene merA coding for bacterial mercuric ion reductase was cloned under the control of the yeast promoter for alcohol dehydrogenase I in the yeast-Escherichia coli shuttle plasmid pADH040-2 and transformed into Saccharomyces cerevisiae AH22. The resulting transformant harbored stable copies of the merA-containing hybrid plasmid, displayed a fivefold increase in the MIC of mercuric chloride, and synthesized mercuric ion reductase activity. Images PMID:1735719

  5. Invasive Saccharomyces cerevisiae infection: a friend turning foe?

    PubMed

    Pillai, Unnikrishnan; Devasahayam, Joe; Kurup, Aparna Narayana; Lacasse, Alexandre

    2014-11-01

    We report a very rare case of acute pyelonephritis in a 51-year-old female with a history of chronic kidney disease (CKD) and diabetes caused by a normally benign and a well-known human commensal organism, Saccharomyces cerevisiae that is very often prescribed as a probiotic in modern medical practice. The causal role of S. cerevisiae was confirmed by its isolation in blood, urine, stool as well as vaginal swabs thus proving its virulent nature in suitable situations. PMID:25394448

  6. A global topology map of the Saccharomyces cerevisiae membrane proteome

    NASA Astrophysics Data System (ADS)

    Kim, Hyun; Melén, Karin; Österberg, Marie; von Heijne, Gunnar

    2006-07-01

    The yeast Saccharomyces cerevisiae is, arguably, the best understood eukaryotic model organism, yet comparatively little is known about its membrane proteome. Here, we report the cloning and expression of 617 S. cerevisiae membrane proteins as fusions to a C-terminal topology reporter and present experimentally constrained topology models for 546 proteins. By homology, the experimental topology information can be extended to 15,000 membrane proteins from 38 fully sequenced eukaryotic genomes. membrane proteins | membrane proteomics | yeast

  7. Horizontal Transfer of Genetic Material among Saccharomyces Yeasts

    PubMed Central

    Marinoni, Gaelle; Manuel, Martine; Petersen, Randi Føns; Hvidtfeldt, Jeanne; Sulo, Pavol; Piškur, Jure

    1999-01-01

    The genus Saccharomyces consists of several species divided into the sensu stricto and the sensu lato groups. The genomes of these species differ in the number and organization of nuclear chromosomes and in the size and organization of mitochondrial DNA (mtDNA). In the present experiments we examined whether these yeasts can exchange DNA and thereby create novel combinations of genetic material. Several putative haploid, heterothallic yeast strains were isolated from different Saccharomyces species. All of these strains secreted an a- or α-like pheromone recognized by S. cerevisiae tester strains. When interspecific crosses were performed by mass mating between these strains, hybrid zygotes were often detected. In general, the less related the two parental species were, the fewer hybrids they gave. For some crosses, viable hybrids could be obtained by selection on minimal medium and their nuclear chromosomes and mtDNA were examined. Often the frequency of viable hybrids was very low. Sometimes putative hybrids could not be propagated at all. In the case of sensu stricto yeasts, stable viable hybrids were obtained. These contained both parental sets of chromosomes but mtDNA from only one parent. In the case of sensu lato hybrids, during genetic stabilization one set of the parental chromosomes was partially or completely lost and the stable mtDNA originated from the same parent as the majority of the nuclear chromosomes. Apparently, the interspecific hybrid genome was genetically more or less stable when the genetic material originated from phylogenetically relatively closely related parents; both sets of nuclear genetic material could be transmitted and preserved in the progeny. In the case of more distantly related parents, only one parental set, and perhaps some fragments of the other one, could be found in genetically stabilized hybrid lines. The results obtained indicate that Saccharomyces yeasts have a potential to exchange genetic material. If Saccharomyces

  8. [Lyophilized Saccharomyces boulardii: example of a probiotic medicine].

    PubMed

    Buts, Jean-Paul

    2005-01-01

    Saccharomyces boulardii is a natural yeast without genetic modification isolated from the bark of the litchi tree in Indochina. In its lyophilized form is an example of the called probiotic medicine. The probiotic denomination is in relation to that itself assets in the gastrointestinal tract in interrelation to that biologic environment. And is labelled as medicine because the lyophilized form has a clinical and pharmaceutical expedient included in the regulation of medicinal products in almost 100 countries. PMID:16021204

  9. Integrated X-ray photoelectron spectroscopy and DFT characterization of benzene adsorption on Pt(111), Pt(355) and Pt(322) surfaces.

    PubMed

    Zhang, Renqin; Hensley, Alyssa J; McEwen, Jean-Sabin; Wickert, Sandra; Darlatt, Erik; Fischer, Kristina; Schöppke, Matthias; Denecke, Reinhard; Streber, Regine; Lorenz, Michael; Papp, Christian; Steinrück, Hans-Peter

    2013-12-21

    We systematically investigate the adsorption of benzene on Pt(111), Pt(355) and Pt(322) surfaces by high-resolution X-ray photoelectron spectroscopy (XPS) and first-principle calculations based on density functional theory (DFT), including van der Waals corrections. By comparing the adsorption energies at 1/9, 1/16 and 1/25 ML on Pt(111), we find significant lateral interactions exist between the benzene molecules at 1/9 ML. The adsorption behavior on Pt(355) and Pt(322) is very different. While on Pt(355) a step species is clearly identified in the C 1s spectra at low coverages followed by occupation of a terrace species at high coverages, no evidence for a step species is found on Pt(322). These different adsorption sites are confirmed by extensive DFT calculations, where the most favorable adsorption configurations on Pt(355) and Pt(322) are also found to vary: a highly distorted across the step molecule is found on Pt(355) while a less distorted configuration adjacent to the step molecule is deduced for Pt(322). The theoretically proposed C 1s core level binding energy shifts between these most favorable configurations and the terrace species are found to correlate well with experiment: for Pt(355), two adsorbate states are found, separated by ~0.4 eV in XPS and 0.3 eV in the calculations, in contrast to only one state on Pt(322). PMID:24189500

  10. Stress Evolution Behavior in CoCrPt Alloy Thin Films with varying Pt Concentration

    SciTech Connect

    Im, M.-Y.; Jeong, J.-R.; Shin, S.-C.

    2007-11-01

    CoCrPt alloy thin film is one of the most promising candidates for ultrahigh density magnetic recording media. One of interesting issues for an application of ferromagnetic thin film to high density magnetic recording media is to investigate growth stress, since stress inevitably generated during thin film fabrication drastically alters magnetic properties as well as mechanical properties due to film fracture and buckling [1]. However, sufficient studies have not been addressed on in situ experimental investigation on stress evolution during film growth of magnetic thin film and its correlation with directly observed film growth structure. We have investigated in situ stress evolution of 400-{angstrom} (Co{sub 82}Cr{sub 18}){sub 100-x}Pt{sub x}/1100-{angstrom} Ti alloy films with varying Pt concentration by means of an ultrahigh vacuum (UHV) chamber equipped with a highly sensitive optical deflection-detecting system [2]. Interestingly enough, the stress evolution patterns during the film deposition are remarkably changed with varying the Pt concentration. CoCrPt alloy films with lower Pt concentration (6 {le} x {le} 13) grow through compressive, tensile, and again compressive stress during film deposition, while CoCrPt alloy films with higher Pt concentration (21 {le} x {le} 28) develop with compressive and relaxed compressive stress without tensile stress generation. In situ stress-evolution behavior for 400-{angstrom} (Co{sub 82}Cr{sub 18}){sub 100-x}Pt{sub x}/1100-{angstrom} Ti alloy films with the Pt concentrations of (a) 6, (b) 13, (c) 21, and (d) 28 at.% are demonstrated in Fig.1. Here, the positive slope corresponds to tensile stress, while the negative slope implies compressive stress. The microstructural studies at the stress transition region reveal that film growth structure plays a major role in considerable change of stress evolution pattern in CoCrPt alloy films with the increase of Pt concentration.

  11. Synthesis and optical property characterization of elongated AuPt and Pt@Au metal nanoframes

    NASA Astrophysics Data System (ADS)

    Lee, Sangji; Jang, Hee-Jeong; Jang, Ho Young; Hong, Soonchang; Moh, Sang Hyun; Park, Sungho

    2016-02-01

    We report a facile method to synthesize elongated nanoframes consisting of Pt and Au in solution. Pentagonal Au nanorods served as templates and successfully led to an elongated AuPt nanoframe after etching the core Au. Subsequently, the coating of Au around Pt ridges resulted in Pt@Au metal nanoframes. The resulting elongated nanostructure exhibited 5 well-defined ridges continuously connected along the long axis. During the shape evolution from pure Au nanorods to elongated Pt@Au metal nanoframes, their corresponding localized surface plasmon resonance bands were monitored. Especially, unique surface plasmon features were observed for elongated Pt@Au nanoframes where the short-axis oscillation of surface free electrons is strongly coupled but the long-axis oscillation is not coupled among the ridges.We report a facile method to synthesize elongated nanoframes consisting of Pt and Au in solution. Pentagonal Au nanorods served as templates and successfully led to an elongated AuPt nanoframe after etching the core Au. Subsequently, the coating of Au around Pt ridges resulted in Pt@Au metal nanoframes. The resulting elongated nanostructure exhibited 5 well-defined ridges continuously connected along the long axis. During the shape evolution from pure Au nanorods to elongated Pt@Au metal nanoframes, their corresponding localized surface plasmon resonance bands were monitored. Especially, unique surface plasmon features were observed for elongated Pt@Au nanoframes where the short-axis oscillation of surface free electrons is strongly coupled but the long-axis oscillation is not coupled among the ridges. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08200e

  12. Nanosecond Dynamics in Pt Nanoparticles

    NASA Astrophysics Data System (ADS)

    Vila, F. D.; Moore, J. M.; Rehr, J. J.

    2014-03-01

    Understanding the physical and chemical behavior of supported catalysts is of fundamental and technological importance. However, due to the complex nature of their structure and dynamics at operando temperatures, their nanoscale behavior remains poorly understood. We have shown that DFT/MD calculations provide fundamental insight into the few ps dynamic structure of the nanoparticles, but such methods can be very computationally intensive.[2,3] In order to examine relaxation dynamics in the ns regime here we present finite temperature MD simulations based on a modified Sutton-Chen (SC) model potential, supplemented with Lennard-Jones potentials for the interaction with the support. We find that bulk SC parameters tend to produce nanoparticles with less fluxional dynamics than those in ab initio simulations. To address this issue, we have determined modified SC parameters that capture the DFT dynamics. Nanosecond simulations reveal regimes controlled by internal particle melting and activation of surface mobility. The approach is illustrated for nano-catalysts of Pt/ γ-alumina and compared with ab initio DFT/MD results. Supported in part by DOE grant DE-FG02-03ER15476 (F.D.V and J.J.R) and by NSF grant PHY-1262811, REU Site: University of Washington Physics (J.M.M.), with computer support from DOE - NERSC.

  13. Heavy Lift & Propulsion Technology (HL&PT)

    NASA Video Gallery

    Cris Guidi delivers a presentation from the Heavy Lift & Propulsion Technology (HL&PT) study team on May 25, 2010, at the NASA Exploration Enterprise Workshop held in Galveston, TX. The purpose of ...

  14. Consistency of PT-symmetric quantum mechanics

    NASA Astrophysics Data System (ADS)

    Brody, Dorje C.

    2016-03-01

    In recent reports, suggestions have been put forward to the effect that parity and time-reversal (PT) symmetry in quantum mechanics is incompatible with causality. It is shown here, in contrast, that PT-symmetric quantum mechanics is fully consistent with standard quantum mechanics. This follows from the surprising fact that the much-discussed metric operator on Hilbert space is not physically observable. In particular, for closed quantum systems in finite dimensions there is no statistical test that one can perform on the outcomes of measurements to determine whether the Hamiltonian is Hermitian in the conventional sense, or PT-symmetric—the two theories are indistinguishable. Nontrivial physical effects arising as a consequence of PT symmetry are expected to be observed, nevertheless, for open quantum systems with balanced gain and loss.

  15. Exchange coupled L10-FePt/fcc-FePt nanomagnets: Synthesis, characterization and magnetic properties

    NASA Astrophysics Data System (ADS)

    Srivastava, Sachchidanand; Gajbhiye, Namdeo S.

    2016-03-01

    We report synthesis, characterization and magnetic properties of exchange-coupled L10-FePt/fcc-FePt nanomagnets. Structural and morphological characterization of exchange-coupled L10-FePt/fcc-FePt was carried out by powder X-ray diffraction, Mössbauer spectroscopy and transmission electron microscopy. Rietveld refinement of powder X-ray diffraction pattern has been used to quantify L10-FePt and fcc-FePt phases present in samples. Room temperature Mössbauer spectroscopy showed sextets of both L10-FePt and fcc-FePt phases with their respective hyperfine interaction parameters. Transmission electron microscopic (TEM and HRTEM) images confirmed nanocrystalline nature of exchange-coupled nanomagnets with particle size ranges from 15 nm to 50 nm after annealing for different time at 700 °C. Room temperature magnetic studies showed ferromagnetic nature of nanomagnets and maximum energy product (BH)max~10.92 MGOe was obtained for sample containing 89.0% volume fraction of L10-FePt phase.

  16. Suspended core-shell Pt-PtOx nanostructure for ultrasensitive hydrogen gas sensor

    NASA Astrophysics Data System (ADS)

    Basu, Palash Kr.; Kallatt, Sangeeth; Anumol, Erumpukuthickal A.; Bhat, Navakanta

    2015-06-01

    High sensitivity gas sensors are typically realized using metal catalysts and nanostructured materials, utilizing non-conventional synthesis and processing techniques, incompatible with on-chip integration of sensor arrays. In this work, we report a new device architecture, suspended core-shell Pt-PtOx nanostructure that is fully CMOS-compatible. The device consists of a metal gate core, embedded within a partially suspended semiconductor shell with source and drain contacts in the anchored region. The reduced work function in suspended region, coupled with built-in electric field of metal-semiconductor junction, enables the modulation of drain current, due to room temperature Redox reactions on exposure to gas. The device architecture is validated using Pt-PtO2 suspended nanostructure for sensing H2 down to 200 ppb under room temperature. By exploiting catalytic activity of PtO2, in conjunction with its p-type semiconducting behavior, we demonstrate about two orders of magnitude improvement in sensitivity and limit of detection, compared to the sensors reported in recent literature. Pt thin film, deposited on SiO2, is lithographically patterned and converted into suspended Pt-PtO2 sensor, in a single step isotropic SiO2 etching. An optimum design space for the sensor is elucidated with the initial Pt film thickness ranging between 10 nm and 30 nm, for low power (<5 μW), room temperature operation.

  17. Scattering properties of PT-symmetric objects

    NASA Astrophysics Data System (ADS)

    Miri, Mohammad-Ali; Eftekhar, Mohammad Amin; Facao, Margarida; Abouraddy, Ayman F.; Bakry, Ahmed; Razvi, Mir A. N.; Alshahrie, Ahmed; Alù, Andrea; Christodoulides, Demetrios N.

    2016-07-01

    We investigate the scattering response of parity-time (PT) symmetric structures. We show that, due to the local flow of energy between gain and loss regions, such systems can deflect light in unusual ways, as a function of the gain/loss contrast. Such structures are highly anisotropic and their scattering patterns can drastically change as a function of the angle of incidence. In addition, we derive a modified optical theorem for PT-symmetric scattering systems, and discuss its ramifications.

  18. The CO/Pt(111) Puzzle

    SciTech Connect

    FEIBELMAN,PETER J.; HAMMER,B.; NORSHOV,J.K.; WAGNER,F.; SCHEFFLER,M.; STUMPF,R.; DUMESIC,J.; WATWE,R.

    2000-07-12

    Notwithstanding half a dozen theoretical publications, well-converged density-functional calculations, whether based on a local or generalized-gradient exchange-correlation potential, whether all-electron or employing pseudopotentials underestimate CO's preference for low-coordination binding sites on Pt(111) and vicinals to it. For example, they imply that CO should prefer hollow- to atop-site adsorption on Pt(111), in apparent contradiction to a host of low temperature experimental studies.

  19. Saccharomyces cerevisiae and non-Saccharomyces yeasts in grape varieties of the São Francisco Valley.

    PubMed

    de Ponzzes-Gomes, Camila M P B S; de Mélo, Dângelly L F M; Santana, Caroline A; Pereira, Giuliano E; Mendonça, Michelle O C; Gomes, Fátima C O; Oliveira, Evelyn S; Barbosa, Antonio M; Trindade, Rita C; Rosa, Carlos A

    2014-01-01

    The aims of this work was to characterise indigenous Saccharomyces cerevisiae strains in the naturally fermented juice of grape varieties Cabernet Sauvignon, Grenache, Tempranillo, Sauvignon Blanc and Verdejo used in the São Francisco River Valley, northeastern Brazil. In this study, 155 S. cerevisiae and 60 non-Saccharomyces yeasts were isolated and identified using physiological tests and sequencing of the D1/D2 domains of the large subunit of the rRNA gene. Among the non-Saccharomyces species, Rhodotorula mucilaginosa was the most common species, followed by Pichia kudriavzevii, Candida parapsilosis, Meyerozyma guilliermondii, Wickerhamomyces anomalus, Kloeckera apis, P. manshurica, C. orthopsilosis and C. zemplinina. The population counts of these yeasts ranged among 1.0 to 19 × 10(5) cfu/mL. A total of 155 isolates of S. cerevisiae were compared by mitochondrial DNA restriction analysis, and five molecular mitochondrial DNA restriction profiles were detected. Indigenous strains of S. cerevisiae isolated from grapes of the São Francisco Valley can be further tested as potential starters for wine production. PMID:25242923

  20. Coating Pt-Ni Octahedra with Ultrathin Pt Shells to Enhance the Durability without Compromising the Activity toward Oxygen Reduction.

    PubMed

    Park, Jinho; Liu, Jingyue; Peng, Hsin-Chieh; Figueroa-Cosme, Legna; Miao, Shu; Choi, Sang-Il; Bao, Shixiong; Yang, Xuan; Xia, Younan

    2016-08-23

    We describe a new strategy to enhance the catalytic durability of Pt-Ni octahedral nanocrystals in the oxygen reduction reaction (ORR) by conformally depositing an ultrathin Pt shell on the surface. The Pt-Ni octahedra were synthesized according to a protocol reported previously and then employed directly as seeds for the conformal deposition of ultrathin Pt shells by introducing a Pt precursor dropwise at 200 °C. The amount of Pt precursor was adjusted relative to the number of Pt-Ni octahedra involved to obtain Pt-Ni@Pt1.5L octahedra of 12 nm in edge length for the systematic evaluation of their chemical stability and catalytic durability compared to Pt-Ni octahedra. Specifically, we compared the elemental compositions of the octahedra before and after treatment with acetic and sulfuric acids. We also examined their electrocatalytic stability toward the ORR through an accelerated durability test by using a rotating disk electrode method. Even after treatment with sulfuric acid for 24 h, the Pt-Ni@Pt1.5L octahedra maintained their original Ni content, whereas 11 % of the Ni was lost from the Pt-Ni octahedra. After 10 000 cycles of ORR, the mass activity of the Pt-Ni octahedra decreased by 75 %, whereas the Pt-Ni@Pt1.5L octahedra only showed a 25 % reduction. PMID:27460459

  1. Interface structures in FePt/Fe3Pt hard-soft exchange-coupled magnetic nanocomposites

    NASA Astrophysics Data System (ADS)

    Li, Jing; Wang, Zhong Lin; Zeng, Hao; Sun, Shouheng; Ping Liu, J.

    2003-05-01

    Self-assembly of FePt and Fe3O4 nanoparticles of different sizes led to various FePt-Fe3O4 nanocomposites. Annealing the composite under reducing atmosphere at 650 and 700 °C induced magnetically hard FePt phase and magnetically soft Fe3Pt phase. The FePt and Fe3Pt phases were either linked by a common interface or coexisted within one grain as domains with sizes <10 nm. This ensures the effective exchange coupling of magnetically hard and soft phases. High-resolution transmission electron microscopy studies provide detailed structural characterization for the FePt based nanocomposites.

  2. Unipolar resistance switching and abnormal reset behaviors in Pt/CuO/Pt and Cu/CuO/Pt structures

    NASA Astrophysics Data System (ADS)

    Wu, Liang; Li, Xiaomin; Gao, Xiangdong; Zheng, Renkui; Zhang, Feng; Liu, Xinjun; Wang, Qun

    2012-07-01

    The effects of Pt and Cu top electrodes on resistance switching properties were investigated for CuO thin films with Pt/CuO/Pt and Cu/CuO/Pt sandwich structures. Typical unipolar resistance switching (URS) behaviors and two different kinds of resistance changes in the reset process were observed in both structures. When voltages were applied to the film, the low-resistance state (LRS) with relatively low resistance value (<30 Ω) was switched to the high-resistance state (HRS), exhibiting normal reset behavior. For LRS with relatively high resistance value (>50 Ω), the resistance first decreased then increased to HRS, showing abnormal reset behavior. The former variation of LRS could be ascribed to the decrease in filament size induced by Joule heating, while the latter one could be ascribed to the growth of disconnected filaments induced by high electric fields. This study indicates that the switching modes and the abnormal reset behaviors in CuO thin films are not due to Pt and Cu top electrodes, but the intrinsic properties of CuO film.

  3. Copper dusting effects on perpendicular magnetic anisotropy in Pt/Co/Pt tri-layers

    NASA Astrophysics Data System (ADS)

    Parakkat, Vineeth Mohanan; Ganesh, K. R.; Anil Kumar, P. S.

    2016-05-01

    The effect of Cu dusting on perpendicular magnetic anisotropy of sputter grown Pt/Co/Pt stack in which the Cu layer is in proximity with that of Co is investigated in this work. We used magneto optic Kerr effect microscopy measurements to study the variation in the reversal mechanisms in films with Co thicknesses below 0.8nm by systematically varying their perpendicular magnetic anisotropy using controlled Cu dusting. Cu dusting was done separately above and below the cobalt layer in order to understand the role of bottom and top Pt layers in magnetization reversal mechanisms of sputtered Pt/Co/Pt stack. The introduction of even 0.3nm thick Cu layer below the cobalt layer drastically affected the perpendicular magnetic anisotropy as evident from the nucleation behavior. On the contrary, even a 4nm thick top Cu layer had little effect on the reversal mechanism. These observations along with magnetization data was used to estimate the role of top and bottom Pt in the origin of perpendicular magnetic anisotropy as well as magnetization switching mechanism in Pt/Co/Pt thin films. Also, with an increase in the bottom Cu dusting from 0.2 to 0.4nm there was an increase in the number of nucleation sites resulting in the transformation of domain wall patterns from a smooth interface type to a finger like one and finally to maze type.

  4. 21 CFR 866.5785 - Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test systems.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... techniques, antibodies to S. cerevisiae (baker's or brewer's yeast) in human serum or plasma. Detection of S... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Anti-Saccharomyces cerevisiae (S. cerevisiae... Immunological Test Systems § 866.5785 Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test...

  5. 21 CFR 866.5785 - Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test systems.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... techniques, antibodies to S. cerevisiae (baker's or brewer's yeast) in human serum or plasma. Detection of S... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Anti-Saccharomyces cerevisiae (S. cerevisiae... Immunological Test Systems § 866.5785 Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test...

  6. 21 CFR 866.5785 - Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test systems.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... techniques, antibodies to S. cerevisiae (baker's or brewer's yeast) in human serum or plasma. Detection of S... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Anti-Saccharomyces cerevisiae (S. cerevisiae... Immunological Test Systems § 866.5785 Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test...

  7. 21 CFR 866.5785 - Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test systems.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... techniques, antibodies to S. cerevisiae (baker's or brewer's yeast) in human serum or plasma. Detection of S... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Anti-Saccharomyces cerevisiae (S. cerevisiae... Immunological Test Systems § 866.5785 Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test...

  8. Mutants of the Formyltetrahydrofolate Interconversion Pathway of SACCHAROMYCES CEREVISIAE

    PubMed Central

    McKenzie, K. Q.; Jones, Elizabeth W.

    1977-01-01

    Thirteen mutants of Saccharomyces cerevisiae that lack one or more of the three enzyme activities of the pathway for interconversion of tetrahydrofolate coenzymes at the formate level of oxidation have been isolated. They do not require adenine. All fail to complement mutations in the ade3 locus. Mutations that greatly reduce activity for one enzyme also reduce activity for the other two interconversion enzymes. The three enzyme activities cochromatograph on TEAE-cellulose columns. A mutation that eliminates synthetase activity also alters the chromatographic behavior of the remaining cyclohydrolase and dehydrogenase activities. It is suggested that the three activities reside in an enzyme complex encoded by the ade3 locus. PMID:328341

  9. Immobilized cell cross-flow reactor. [Saccharomyces cerevisiae

    SciTech Connect

    Chotani, G.K.; Constantinides, A.

    1984-01-01

    A cross-current flow reactor was operated using sodium alginate gel entrapped yeast cells (Saccharomyces cerevisiae) under growth conditions. Micron-sized silica, incorporated into the biocatalyst particles (1 mm mean diameter) improved mechanical strength and internal surface adhesion. The process showed decreased productivity and stability at 35/sup 0/C compared to the normal study done at 30/sup 0/C. The increased number of cross flows diminish the product inhibition effect. The residence time distribution shows that the cross-flow bioreactor system can be approximated to either a train of backmixed fermentors in series or a plug flow fermentor with moderate axial dispersion.

  10. Transfer RNA splicing in Saccharomyces cerevisiae: defining the substrates.

    PubMed Central

    Ogden, R C; Lee, M C; Knapp, G

    1984-01-01

    The primary sequences of all the tRNA precursors which contain intervening sequences and which accumulate in the Saccharomyces cerevisiae rnal mutant are presented. A combination of DNA and RNA sequence analysis has led to elucidation of the primary sequence of four hitherto uncharacterized precursors. The location of the intervening sequence has in all cases been unambiguously determined by analysis of the intermediates in the splicing reaction. Secondary structures based upon the tRNA cloverleaf are shown for all the tRNA precursors and discussed with respect to common recognition by the yeast splicing endonuclease. Images PMID:6096826

  11. SACCHAROMYCES CEREVISIAE Recessive Suppressor That Circumvents Phosphatidylserine Deficiency

    PubMed Central

    Atkinson, Katharine D.

    1984-01-01

    Phenotypic reversion of six independent Saccharomyces cerevisiae cho1 mutants was shown to be due predominantly to mutation of an unlinked gene, eam1. The eam1 gene was located very close to ino1 on chromosome X by meiotic tetrad analysis. Recessive eam1 mutations did not correct the primary cho1 defect in phosphatidylserine synthesis but made endogenous ethanolamine available for sustained nitrogenous phospholipid synthesis. A novel biochemical contribution to nitrogenous lipid synthesis is indicated by the eam1 mutants. PMID:17246236

  12. Serotypes in Saccharomyces telluris: Their relation to source of isolation

    USGS Publications Warehouse

    Hasenclever, H.F.; Kocan, R.M.

    1973-01-01

    Three serotypes have been characterized with three reference strains of Saccharomyces telluris and designated as A, B, and C. One reference strain of Torpulopsis bovina, the imperfect form of S. telluris, belonged to serotype B. Strains of S. telluris isolated from four columbid species were serotyped. All 98 strains of this yeast isolated from Columba livia belonged to serotype B. Three other columbid species, C. leucocephala, C. fasciata, and Zenaidura macroura harbored strains of serotype C only. Serotype A was not isolated from any of the avian species.

  13. RNAi-Assisted Genome Evolution (RAGE) in Saccharomyces cerevisiae.

    PubMed

    Si, Tong; Zhao, Huimin

    2016-01-01

    RNA interference (RNAi)-assisted genome evolution (RAGE) applies directed evolution principles to engineer Saccharomyces cerevisiae genomes. Here, we use acetic acid tolerance as a target trait to describe the key steps of RAGE. Briefly, iterative cycles of RNAi screening are performed to accumulate multiplex knockdown modifications, enabling directed evolution of the yeast genome and continuous improvement of a target phenotype. Detailed protocols are provided on the reconstitution of RNAi machinery, creation of genome-wide RNAi libraries, identification and integration of beneficial knockdown cassettes, and repeated RAGE cycles. PMID:27581294

  14. Isobutanol production from D-xylose by recombinant Saccharomyces cerevisiae.

    PubMed

    Brat, Dawid; Boles, Eckhard

    2013-03-01

    Simultaneous overexpression of an optimized, cytosolically localized valine biosynthesis pathway together with overexpression of xylose isomerase XylA from Clostridium phytofermentans, transaldolase Tal1 and xylulokinase Xks1 enabled recombinant Saccharomyces cerevisiae cells to complement the valine auxotrophy of ilv2,3,5 triple deletion mutants for growth on D-xylose as the sole carbon source. Moreover, after additional overexpression of ketoacid decarboxylase Aro10 and alcohol dehydrogenase Adh2, the cells were able to ferment D-xylose directly to isobutanol. PMID:23279585

  15. Differential repair of UV damage in Saccharomyces cerevisiae.

    PubMed Central

    Terleth, C; van Sluis, C A; van de Putte, P

    1989-01-01

    Preferential repair of UV-induced damage is a phenomenon by which mammalian cells might enhance their survival. This paper presents the first evidence that preferential repair occurs in the lower eukaryote Saccharomyces cerevisiae. Moreover an unique approach is reported to compare identical sequences present on the same chromosome and only differing in expression. We determined the removal of pyrimidine dimers from two identical alpha-mating type loci and we were able to show that the active MAT alpha locus is repaired preferentially to the inactive HML alpha locus. In a sir-3 mutant, in which both loci are active this preference is not observed. Images PMID:2664708

  16. Use of bimolecular fluorescence complementation in yeast Saccharomyces cerevisiae.

    PubMed

    Skarp, Kari-Pekka; Zhao, Xueqiang; Weber, Marion; Jantti, Jussi

    2008-01-01

    Visualization of protein-protein interactions in vivo offers a powerful tool to resolve spatial and temporal aspects of cellular functions. Bimolecular fluorescence complementation (BiFC) makes use of nonfluorescent fragments of green fluorescent protein or its variants that are added as "tags" to target proteins under study. Only upon target protein interaction is a fluorescent protein complex assembled and the site of interaction can be monitored by microscopy. In this chapter, we describe the method and tools for use of BiFC in the yeast Saccharomyces cerevisiae. PMID:19066026

  17. Expression of acylphosphatase in Saccharomyces cerevisiae enhances ethanol fermentation rate

    SciTech Connect

    Raugei, G.; Modesti, A.; Magherini, F.

    1996-06-01

    Previous experiments in vitro have demonstrated the ability of acylphosphatase to increase the rate of glucose fermentation in yeast. To evaluate the possibility of increasing fermentation in vivo also, a chemically synthesized DNA sequence coding for human muscle acylphosphatase was expressed at high level in Saccharomyces cerevisiae. Ethanol production was measured in these engineered strains in comparison with a control. Acylphosphatase expression strongly increased the rate of ethanol production both in aerobic and anaerobic culture. This finding may be potentially important for the development of more efficient industrial fermentation processes. 20 refs., 5 figs.

  18. Mutagenesis protocols in Saccharomyces cerevisiae by in vivo overlap extension.

    PubMed

    Alcalde, Miguel

    2010-01-01

    A high recombination frequency and its ease of manipulation has made Saccharomyces cerevisiae a unique model eukaryotic organism to study homologous recombination. Indeed, the well-developed recombination machinery in S. cerevisiae facilitates the construction of mutant libraries for directed evolution experiments. In this context, in vivo overlap extension (IVOE) is a particularly attractive protocol that takes advantage of the eukaryotic apparatus to carry out combinatorial saturation mutagenesis, site-directed recombination or site-directed mutagenesis, avoiding ligation steps and additional PCR reactions that are common to standard in vitro protocols. PMID:20676972

  19. Resistive random access memory utilizing ferritin protein with Pt nanoparticles

    NASA Astrophysics Data System (ADS)

    Uenuma, Mutsunori; Kawano, Kentaro; Zheng, Bin; Okamoto, Naofumi; Horita, Masahiro; Yoshii, Shigeo; Yamashita, Ichiro; Uraoka, Yukiharu

    2011-05-01

    This study reports controlled single conductive paths found in resistive random access memory (ReRAM) formed by embedding Pt nanoparticles (Pt NPs) in NiO film. Homogeneous Pt NPs produced and placed by ferritin protein produce electric field convergence which leads to controlled conductive path formation. The ReRAM with Pt NPs shows stable switching behavior. A Pt NP density decrease results in an increase of OFF state resistance and decrease of forming voltage, whereas ON resistance was independent of the Pt NP density, which indicates that a single metal NP in a memory cell will achieve low power and stable operation.

  20. Dehydrogenation of benzene on Pt(111) surface

    NASA Astrophysics Data System (ADS)

    Gao, W.; Zheng, W. T.; Jiang, Q.

    2008-10-01

    The dehydrogenation of benzene on Pt(111) surface is studied by ab initio density functional theory. The minimum energy pathways for benzene dehydrogenation are found with the nudge elastic band method including several factors of the associated barriers, reactive energies, intermediates, and transient states. The results show that there are two possible parallel minimum energy pathways on the Pt(111) surface. Moreover, the tilting angle of the H atom in benzene can be taken as an index for the actual barrier of dehydrogenation. In addition, the properties of dehydrogenation radicals on the Pt(111) surface are explored through their adsorption energy, adsorption geometry, and electronic structure on the surface. The vibrational frequencies of the dehydrogenation radicals derived from the calculations are in agreement with literature data.

  1. Preparation of onion-like Pt-terminated Pt-Cu bimetallic nano-sized electrocatalysts for oxygen reduction reaction in fuel cells

    NASA Astrophysics Data System (ADS)

    Lim, Taeho; Kim, Ok-Hee; Sung, Yung-Eun; Kim, Hyun-Jong; Lee, Ho-Nyun; Cho, Yong-Hun; Kwon, Oh Joong

    2016-06-01

    Onion-like Pt-terminated Pt-Cu bimetallic nano-sized electrocatalysts (Pt/Cu/Pt/C) were synthesized by using an electroless deposition method. The synthesized Pt/Cu/Pt/C consisted of a Pt-enriched shell, a sandwiched Pt-Cu alloy layer, and a Pt core. The Pt/Cu/Pt/C showed higher electrocatalytic activity toward oxygen reduction reaction in half-cell test than that of commercial Pt/C due to an electronic structure change in the Pt-enriched shell, resulting from the sandwiched Pt-Cu alloy layer underneath. The stability of the Pt/Cu/Pt/C was examined by using both half-cell and single-cell degradation tests. In both tests, the Pt/Cu/Pt/C exhibited stronger resistance to catalyst degradation than that of the commercial Pt/C. It is notable that cell performance with the Pt/Cu/Pt/C was fully recovered by N2 purging after single-cell degradation testing, indicating there was no permanent damage to the electrocatalyst during the test. It is suggested that thermodynamically-stable structure of the Pt/Cu/Pt/C contributed to the improved stability.

  2. Synthesis and Characterization of Pt(IV) Fluorescein Conjugates to Investigate Pt(IV) Intracellular Transformations

    PubMed Central

    Song, Ying; Suntharalingam, Kogularamanan; Yeung, Jessica S.; Royzen, Maksim; Lippard, Stephen J.

    2013-01-01

    Pt(IV) anticancer compounds typically operate as prodrugs that are reduced in the hypoxic environment of cancer cells, losing two axial ligands in the process to generate active Pt(II) species. Here we report the synthesis of two fluorescent Pt(IV) prodrugs of cisplatin in order to image and evaluate the Pt(IV) reduction process in simulated and real biological environments. Treatment of the complexes dissolved in PBS buffer with reducing agents typically encountered in cells, glutathione or ascorbate, afforded a 3- to 5-fold fluorescence turn-on owing to reduction and loss of their fluorescein-based axial ligands, which are quenched when bound to platinum. Both Pt(IV) conjugates displayed moderate cytotoxicity against human cancer cell lines, with IC50 values higher than that of cisplatin. Immunoblotting and DNA flow cytometry analyses of one of the complexes, Pt(IV)FL2, revealed that it damages DNA, causing cell cycle arrest in S or G2/M depending on exposure time, with ultimately triggering of apoptotic cell death. Fluorescence microscopic studies prove that Pt(IV)FL2 enters cells intact and undergoes reduction intracellularly. The results are best interpreted in terms of a model in which the axial fluorescein ligands are expelled through lysosomes, with the platinum(II) moiety generated in the process binding to genomic DNA, which results in cell death. PMID:23957697

  3. Discovery of the Pt-Based Superconductor LaPt5As.

    PubMed

    Fujioka, Masaya; Ishimaru, Manabu; Shibuya, Taizo; Kamihara, Yoichi; Tabata, Chihiro; Amitsuka, Hiroshi; Miura, Akira; Tanaka, Masashi; Takano, Yoshihiko; Kaiju, Hideo; Nishii, Junji

    2016-08-10

    A novel superconductor, LaPt5As, which exhibits a new crystal structure was discovered by high-pressure synthesis using a Kawai-type apparatus. A superconducting transition temperature was observed at 2.6 K. Depending on the sintering pressure, LaPt5As has superconducting and non-superconducting phases with different crystal structures. A sintering pressure of around 10 GPa is effective to form single-phase superconducting LaPt5As. This material has a very unique crystal structure with an extremely long c lattice parameter of over 60 Å and corner-sharing tetrahedrons composed of network-like Pt layers. Density functional theory calculations have suggested that the superconducting current flows through these Pt layers. Also, this unique layered structure characteristic of LaPt5As is thought to play a key role in the emergence of superconductivity. Furthermore, due to a stacking structure which makes up layers, various structural modifications for the LaPt5As family are conceivable. Since such a high-pressure synthesis using a Kawai-type apparatus is not common in the field of materials science, there is large room for further exploration of unknown phases which are induced by high pressure in various materials. PMID:27461965

  4. Tailoring Curie temperature and magnetic anisotropy in ultrathin Pt/Co/Pt films

    NASA Astrophysics Data System (ADS)

    Parakkat, Vineeth Mohanan; Ganesh, K. R.; Anil Kumar, P. S.

    2016-05-01

    The dependence of perpendicular magnetization and Curie temperature (Tc) of Pt/Co/Pt thin films on the thicknesses of Pt seed (Pts) and presence of Ta buffer layer has been investigated in this work. Pt and Co thicknesses were varied between 2 to 8 nm and 0.35 to 1.31 nm (across the spin reorientation transition thickness) respectively and the Tc was measured using SQUID magnetometer. We have observed a systematic dependence of Tc on the thickness of Pts. For 8nm thickness of Pts the Co layer of 0.35nm showed ferromagnetism with perpendicular anisotropy at room temperature. As the thickness of the Pts was decreased to 2nm, the Tc went down below 250K. XRD data indicated polycrystalline growth of Pts on SiO2. On the contrary Ta buffer layer promoted the growth of Pt(111). As a consequence Ta(5nm)/Pt(3nm)/Co(0.35nm)/Pt(2nm) had much higher Tc (above 300K) with perpendicular anisotropy when compared to the same stack without the Ta layer. Thus we could tune the ferromagnetic Tc and anisotropy by varying the Pts thickness and also by introducing Ta buffer layer. We attribute these observations to the micro-structural evolution of Pts layer which hosts the Co layer.

  5. Synthesis and magnetic properties of Fe-Pt-B nanocomposite permanent magnets with low Pt concentrations

    SciTech Connect

    Zhang Wei; Louzguine, Dmitri V.; Inoue, Akihisa

    2004-11-22

    Microstructure and magnetic properties of melt-spun Fe{sub 80-x}Pt{sub x}B{sub 20} (x=20,22,24) alloy ribbons have been investigated. A homogeneous nanoscale mixed structure with amorphous and fcc {gamma}-FePt phases was formed in the melt-spun ribbons. The average sizes of the amorphous and fcc {gamma}-FePt phases are about 5 nm, and the enrichment phenomenon of B is recognized in the coexistent amorphous phase. The melt-spun ribbons exhibit soft magnetic properties. The nanocomposite structure consisting of fct {gamma}{sub 1}-FePt, fcc {gamma}-FePt, and Fe{sub 2}B phases was obtained in the melt-spun ribbons annealed at 798 K for 900 s, and their average grain sizes are about 20 nm. The remanence (B{sub r}), reduced remanence (M{sub r}/M{sub s}), coercivity ({sub i}H{sub c}), and maximum energy product (BH){sub max} of the nanocomposite alloys are in the range of 0.93-1.05 T, 0.79-0.82, 375-487 kA/m, and 118-127 kJ/m{sup 3}, respectively. The good hard magnetic properties are interpreted as resulting from exchange magnetic coupling between nanoscale hard fct {gamma}{sub 1}-FePt and soft magnetic fcc {gamma}-FePt or Fe{sub 2}B phases.

  6. Nuclear Data Sheets for {sup 170}Pt

    SciTech Connect

    Baglin, Coral M.

    1999-02-22

    Nuclear structure data pertaining to 170Pt have been compiled and evaluated, and incorporated into the ENSDF data file. This evaluation of170Pt supersedes the previous publication (Coral M. Baglin,Nuclear Data Sheets 77,125 (1996) (literature cutoff date October 1995)), and includes literature available by 17 February 1999. The newly incorporated references are: 98Se20, 98Ki20, 97Ju04, 96Bi07 and 95Au04. Three new data sets have been added, as follows:174Hg ? decay,171Au p decay (1.02 ms), (HI,xn?).

  7. Sintering Behavior of Spin-coated FePt and FePtAu Nanoparticles

    SciTech Connect

    Kang, Shishou; Jia, Zhiyong; Zoto, Ilir; Reed, R. C.; Nikles, David E.; Harrell, J. W.; Vemuru, Krishnamurthy V; Porcar, L.

    2006-01-01

    FePt and [FePt]{sub 95}Au{sub 5} nanoparticles with an average size of about 4 nm were chemically synthesized and spin coated onto silicon substrates. Samples were subsequently thermally annealed at temperatures ranging from 250 to 500 C for 30 min. Three-dimensional structural characterization was carried out with small-angle neutron scattering (SANS) and small-angle x-ray diffraction (SAXRD) measurements. For both FePt and [FePt]{sub 95}Au{sub 5} particles before annealing, SANS measurements gave an in-plane coherence length parameter a = 7.3 nm, while SAXRD measurements gave a perpendicular coherence length parameter c = 12.0 nm. The ratio of c/a is about 1.64, indicating the as-made particle array has a hexagonal close-packed superstructure. For both FePt and FePtAu nanoparticles, the diffraction peaks shifted to higher angles and broadened with increasing annealing temperature. This effect corresponds to a shrinking of the nanoparticle array, followed by agglomeration and sintering of the nanoparticles, resulting in the eventual loss of positional order with increasing annealing temperature. The effect is more pronounced for FePtAu than for FePt. Dynamic coercivity measurements show that the FePtAu nanoparticles have both higher intrinsic coercivity and higher switching volume at the same annealing temperature. These results are consistent with previous studies that show that additive Au both lowers the chemical ordering temperature and promotes sintering.

  8. Pt-Ni and Pt-Co Catalyst Synthesis Route for Fuel Cell Applications

    NASA Technical Reports Server (NTRS)

    Firdosy, Samad A.; Ravi, Vilupanur A.; Valdez, Thomas I.; Kisor, Adam; Narayan, Sri R.

    2013-01-01

    Oxygen reduction reactions (ORRs) at the cathode are the rate-limiting step in fuel cell performance. The ORR is 100 times slower than the corresponding hydrogen oxidation at the anode. Speeding up the reaction at the cathode will improve fuel cell efficiency. The cathode material is generally Pt powder painted onto a substrate (e.g., graphite paper). Recent efforts in the fuel cell area have focused on replacing Pt with Pt-X alloys (where X = Co, Ni, Zr, etc.) in order to (a) reduce cost, and (b) increase ORR rates. One of these strategies is to increase ORR rates by reducing the powder size, which would result in an increase in the surface area, thereby facilitating faster reaction rates. In this work, a process has been developed that creates Pt-Ni or Pt-Co alloys that are finely divided (on the nano scale) and provide equivalent performance at lower Pt loadings. Lower Pt loadings will translate to lower cost. Precursor salts of the metals are dissolved in water and mixed. Next, the salt mixtures are dried on a hot plate. Finally, the dried salt mixture is heattreated in a furnace under flowing reducing gas. The catalyst powder is then used to fabricate a membrane electrode assembly (MEA) for electrochemical performance testing. The Pt- Co catalyst-based MEA showed comparable performance to an MEA fabri cated using a standard Pt black fuel cell catalyst. The main objective of this program has been to increase the overall efficiencies of fuel cell systems to support power for manned lunar bases. This work may also have an impact on terrestrial programs, possibly to support the effort to develop a carbon-free energy source. This catalyst can be used to fabricate high-efficiency fuel cell units that can be used in space as regenerative fuel cell systems, and terrestrially as primary fuel cells. Terrestrially, this technology will become increasingly important when transition to a hydrogen economy occurs.

  9. Efficient Pt catalysts for polymer electrolyte fuel cells

    SciTech Connect

    Fournier, J.; Gaubert, G.; Tilquin, J.Y.

    1996-12-31

    Commercialization of polymer electrolyte fuel cells (PEFCs) requires an important decrease in their production cost. Cost reduction for the electrodes principally concerns the decrease in the amount of Pt catalyst necessary for the functioning of the PEFC without affecting cell performance. The first PEFCs used in the Gemini Space Program had a loading of 4-10 mg pt/cm{sup 2}. The cost of the electrodes was drastically reduced when pure colloidal Pt was replaced by Pt supported on carbon (Pt/C) with a Pt content of 0.4 Mg/cm{sup 2}. Since the occurrence of that breakthrough, many studies have been aimed at further lowering the Pt loading. Today, the lowest loadings reported for oxygen reduction are of the order of 0.05 mg pt/cm{sup 2}. The carbon support of commercial catalysts is Vulcan XC-72 from Cabot, a carbon black with a specific area of 254 m{sup 2}/g. Graphites with specific areas ranging from 20 to 305 m{sup 2}/g are now available from Lonza. The first aim of the present study was to determine the catalytic properties for 02 reduction of Pt supported on these high specific area graphites. The second aim was to use Pt inclusion synthesis on these high area graphites, and to measure the catalytic performances of these materials. Lastly, this same Pt-inclusion synthesis was extended even for use with Vulcan and Black Pearls as substrates (two carbon blacks from Cabot). All these catalysts have been labelled Pt-included materials to distinguish them from the Pt-supported ones. It will be shown that the reduced Pt content Pt-included materials obtained with high specific area substrates a are excellent catalysts for oxygen reduction, especially at high currents. Therefore, Pt inclusion synthesis appears to be a new method to decrease the cathodic Pt loading.

  10. A multiplex set of species-specific primers for rapid identification of members of the genus Saccharomyces.

    PubMed

    Muir, Alastair; Harrison, Elizabeth; Wheals, Alan

    2011-11-01

    The Saccharomyces genus (previously Saccharomyces sensu stricto) formally comprises Saccharomyces arboricola, Saccharomyces bayanus, Saccharomyces cariocanus, Saccharomyces cerevisiae, Saccharomyces kudriavzevii, Saccharomyces mikatae, Saccharomyces paradoxus and Saccharomyces pastorianus. Species-specific primer pairs that produce a single band of known and different product size have been developed for each member of the clade with the exception of S. pastorianus, which is a polyphyletic allopolyploid hybrid only found in lager breweries, and for which signature sequences could not be reliably created. Saccharomyces cariocanus is now regarded as an American variant of S. paradoxus, and accordingly a single primer pair that recognizes both species was developed. A different orthologous and essential housekeeping gene was used to detect each species, potentially avoiding competition between PCR primers and overlap between amplicons. In multiplex format, two or more different species could be identified in a single reaction; double and triple hybrids could not always be correctly identified. Forty-two unidentified yeasts from sugar cane juice fermentations were correctly identified as S. cerevisiae. A colony PCR method was developed that is rapid, robust, inexpensive and capable of automation, requires no mycological expertise on the part of the user and is thus useful for large-scale preliminary screens. PMID:22093682

  11. Asymmetry in effective fields of spin-orbit torques in Pt/Co/Pt stacks

    SciTech Connect

    Hin Sim, Cheow Cheng Huang, Jian; Tran, Michael; Eason, Kwaku

    2014-01-06

    Measurements of switching via spin-orbit coupling mechanisms are discussed for a pair of inverted Pt/Co/Pt stacks with asymmetrical Pt thicknesses. Taking into account the planar Hall effect contribution, effective fields of spin-orbit torques (SOT) are evaluated using lock-in measurements of the first and second harmonics of the Hall voltage. Reversing the stack structure leads to significant asymmetries in the switching behavior, including clear evidence of a nonlinear current dependence of the transverse effective field. Our results demonstrate potentially complex interplay in devices with all-metallic interfaces utilizing SOT.

  12. Sequence Diversity, Reproductive Isolation and Species Concepts in Saccharomyces

    PubMed Central

    Liti, Gianni; Barton, David B. H.; Louis, Edward J.

    2006-01-01

    Using the biological species definition, yeasts of the genus Saccharomyces sensu stricto comprise six species and one natural hybrid. Previous work has shown that reproductive isolation between the species is due primarily to sequence divergence acted upon by the mismatch repair system and not due to major gene differences or chromosomal rearrangements. Sequence divergence through mismatch repair has also been shown to cause partial reproductive isolation among populations within a species. We have surveyed sequence variation in populations of Saccharomyces sensu stricto yeasts and measured meiotic sterility in hybrids. This allows us to determine the divergence necessary to produce the reproductive isolation seen among species. Rather than a sharp transition from fertility to sterility, which may have been expected, we find a smooth monotonic relationship between diversity and reproductive isolation, even as far as the well-accepted designations of S. paradoxus and S. cerevisiae as distinct species. Furthermore, we show that one species of Saccharomyces—S. cariocanus—differs from a population of S. paradoxus by four translocations, but not by sequence. There is molecular evidence of recent introgression from S. cerevisiae into the European population of S. paradoxus, supporting the idea that in nature the boundary between these species is fuzzy. PMID:16951060

  13. 'Yeast mail': a novel Saccharomyces application (NSA) to encrypt messages.

    PubMed

    Rosemeyer, Helmut; Paululat, Achim; Heinisch, Jürgen J

    2014-09-01

    The universal genetic code is used by all life forms to encode biological information. It can also be used to encrypt semantic messages and convey them within organisms without anyone but the sender and recipient knowing, i.e., as a means of steganography. Several theoretical, but comparatively few experimental, approaches have been dedicated to this subject, so far. Here, we describe an experimental system to stably integrate encrypted messages within the yeast genome using a polymerase chain reaction (PCR)-based, one-step homologous recombination system. Thus, DNA sequences encoding alphabetical and/or numerical information will be inherited by yeast propagation and can be sent in the form of dried yeast. Moreover, due to the availability of triple shuttle vectors, Saccharomyces cerevisiae can also be used as an intermediate construction device for transfer of information to either Drosophila or mammalian cells as steganographic containers. Besides its classical use in alcoholic fermentation and its modern use for heterologous gene expression, we here show that baker's yeast can thus be employed in a novel Saccharomyces application (NSA) as a simple steganographic container to hide and convey messages. PMID:25238077

  14. The Saccharomyces Genome Database: Exploring Biochemical Pathways and Mutant Phenotypes.

    PubMed

    Cherry, J Michael

    2015-12-01

    Many biochemical processes, and the proteins and cofactors involved, have been defined for the eukaryote Saccharomyces cerevisiae. This understanding has been largely derived through the awesome power of yeast genetics. The proteins responsible for the reactions that build complex molecules and generate energy for the cell have been integrated into web-based tools that provide classical views of pathways. The Yeast Pathways in the Saccharomyces Genome Database (SGD) is, however, the only database created from manually curated literature annotations. In this protocol, gene function is explored using phenotype annotations to enable hypotheses to be formulated about a gene's action. A common use of the SGD is to understand more about a gene that was identified via a phenotypic screen or found to interact with a gene/protein of interest. There are still many genes that do not yet have an experimentally defined function and so the information currently available can be used to speculate about their potential function. Typically, computational annotations based on sequence similarity are used to predict gene function. In addition, annotations are sometimes available for phenotypes of mutations in the gene of interest. Integrated results for a few example genes will be explored in this protocol. This will be instructive for the exploration of details that aid the analysis of experimental results and the establishment of connections within the yeast literature. PMID:26631123

  15. Evolutionary engineering of Saccharomyces cerevisiae for efficient aerobic xylose consumption.

    PubMed

    Scalcinati, Gionata; Otero, José Manuel; Van Vleet, Jennifer R H; Jeffries, Thomas W; Olsson, Lisbeth; Nielsen, Jens

    2012-08-01

    Industrial biotechnology aims to develop robust microbial cell factories, such as Saccharomyces cerevisiae, to produce an array of added value chemicals presently dominated by petrochemical processes. Xylose is the second most abundant monosaccharide after glucose and the most prevalent pentose sugar found in lignocelluloses. Significant research efforts have focused on the metabolic engineering of S. cerevisiae for fast and efficient xylose utilization. This study aims to metabolically engineer S. cerevisiae, such that it can consume xylose as the exclusive substrate while maximizing carbon flux to biomass production. Such a platform may then be enhanced with complementary metabolic engineering strategies that couple biomass production with high value-added chemical. Saccharomyces cerevisiae, expressing xylose reductase, xylitol dehydrogenase and xylulose kinase, from the native xylose-metabolizing yeast Pichia stipitis, was constructed, followed by a directed evolution strategy to improve xylose utilization rates. The resulting S. cerevisiae strain was capable of rapid growth and fast xylose consumption producing only biomass and negligible amount of byproducts. Transcriptional profiling of this strain was employed to further elucidate the observed physiology confirms a strongly up-regulated glyoxylate pathway enabling respiratory metabolism. The resulting strain is a desirable platform for the industrial production of biomass-related products using xylose as a sole carbon source. PMID:22487265

  16. Functional Genomics Using the Saccharomyces cerevisiae Yeast Deletion Collections.

    PubMed

    Nislow, Corey; Wong, Lai Hong; Lee, Amy Huei-Yi; Giaever, Guri

    2016-01-01

    Constructed by a consortium of 16 laboratories, the Saccharomyces genome-wide deletion collections have, for the past decade, provided a powerful, rapid, and inexpensive approach for functional profiling of the yeast genome. Loss-of-function deletion mutants were systematically created using a polymerase chain reaction (PCR)-based gene deletion strategy to generate a start-to-stop codon replacement of each open reading frame by homologous recombination. Each strain carries two molecular barcodes that serve as unique strain identifiers, enabling their growth to be analyzed in parallel and the fitness contribution of each gene to be quantitatively assessed by hybridization to high-density oligonucleotide arrays or through the use of next-generation sequencing technologies. Functional profiling of the deletion collections, using either strain-by-strain or parallel assays, provides an unbiased approach to systematically survey the yeast genome. The Saccharomyces yeast deletion collections have proved immensely powerful in contributing to the understanding of gene function, including functional relationships between genes and genetic pathways in response to diverse genetic and environmental perturbations. PMID:27587784

  17. The mannoprotein of Saccharomyces cerevisiae is an effective bioemulsifier.

    PubMed Central

    Cameron, D R; Cooper, D G; Neufeld, R J

    1988-01-01

    The mannoprotein which is a major component of the cell wall of Saccharomyces cerevisiae is an effective bioemulsifier. Mannoprotein emulsifier was extracted in a high yield from whole cells of fresh bakers' yeast by two methods, by autoclaving in neutral citrate buffer and by digestion with Zymolase (Miles Laboratories; Toronto, Ontario, Canada), a beta-1,3-glucanase. Heat-extracted emulsifier was purified by ultrafiltration and contained approximately 44% carbohydrate (mannose) and 17% protein. Treatment of the emulsifier with protease eliminated emulsification. Kerosene-in-water emulsions were stabilized over a broad range of conditions, from pH 2 to 11, with up to 5% sodium chloride or up to 50% ethanol in the aqueous phase. In the presence of a low concentration of various solutes, emulsions were stable to three cycles of freezing and thawing. An emulsifying agent was extracted from each species or strain of yeast tested, including 13 species of genera other than Saccharomyces. Spent yeast from the manufacture of beer and wine was demonstrated to be a possible source for the large-scale production of this bioemulsifier. PMID:3046488

  18. Temperature dependence of oxygen reduction activity at Nafion-coated bulk Pt and Pt/carbon black catalysts.

    PubMed

    Yano, Hiroshi; Higuchi, Eiji; Uchida, Hiroyuki; Watanabe, Masahiro

    2006-08-24

    Oxygen reduction reaction (ORR) activity and H(2)O(2) formation at Nafion-coated film electrodes of bulk-Pt and Pt nanoparticles dispersed on carbon black (Pt/CB) were investigated in 0.1 M HClO(4) solution at 30 to 110 degrees C by using a channel flow double electrode method. We have found that the apparent rate constants k(app) (per real Pt active surface area) for the ORR at bulk-Pt (with and without Nafion-coating) and Nafion-coated Pt/CB (19.3 and 46.7 wt % Pt, d(Pt) = 2.6 to 2.7 nm) thin-film electrodes were in beautiful agreement with each other in the operation conditions of polymer electrolyte fuel cells (PEFCs), i.e., 30-110 degrees C and ca. 0.7 to 0.8 V vs RHE. The H(2)O(2) yield was 0.6-1.0% at 0.7-0.8 V on all Nafion-coated Pt/CB and bulk-Pt and irrespective of Pt-loading level and temperature. Nafion coating was pointed out to be a major factor for the H(2)O(2) formation on Pt catalysts modifying the surface property, because H(2)O(2) production was not detected at the bulk-Pt electrode without Nafion coating. PMID:16913788

  19. Surface structure and chemistry of Pt/Cu/Pt(1 1 1) near surface alloy model catalyst in CO

    NASA Astrophysics Data System (ADS)

    Zeng, Shibi; Nguyen, Luan; Cheng, Fang; Liu, Lacheng; Yu, Ying; Tao, Franklin (Feng)

    2014-11-01

    Near surface alloy (NSA) model catalyst Pt/Cu/Pt(1 1 1) was prepared on Pt(1 1 1) through a controlled vapor deposition of Cu atoms. Different coordination environments of Pt atoms of the topmost Pt layer with the underneath Cu atoms in the subsurface result in different local electronic structures of surface Pt atoms. Surface structure and chemistry of the NAS model catalyst in Torr pressure of CO were studied with high pressure scanning tunneling microscopy (HP-STM) and ambient pressure X-ray photoelectron spectroscopy (AP-XPS). In Torr pressure of CO, the topmost Pt layer of Pt/Cu/Pt(1 1 1) is restructured to thin nanoclusters with size of about 1 nm. Photoemission feature of O 1s of CO on Pt/Cu/Pt(1 1 1) suggests CO adsorbed on both edge and surface of these formed nanoclusters. This surface is active for CO oxidation. Atomic layers of carbon are formed on Pt/Cu/Pt(1 1 1) at 573 K in 2 Torr of CO.

  20. PT3 Papers. [SITE 2001 Section].

    ERIC Educational Resources Information Center

    Pierson, Melissa, Ed.; Thompson, Mary, Ed.; Adams, Angelle, Ed.; Beyer, Evelyn, Ed.; Cheriyan, Saru, Ed.; Starke, Leslie, Ed.

    This document contains the papers on the PT3 (Preparing Tomorrow's Teachers to use Technology) program from the SITE (Society for Information Technology & Teacher Education) 2001 conference. Topics covered include: modeling instruction with modern information and communications technology; transforming computer coursework for preservice teachers;…

  1. Structural and magnetic properties of the ordered FePt{sub 3}, FePt and Fe{sub 3}Pt nanoparticles

    SciTech Connect

    Liu, Yang; Jiang, Yuhong; Zhang, Xiaolong; Wang, Yaxin; Zhang, Yongjun; Liu, Huilian; Zhai, Hongju; Liu, Yanqing; Yang, Jinghai; Yan, Yongsheng

    2014-01-15

    The Fe{sub x}Pt{sub 100−x} nanoparticles (NPs) with different nominal atomic rations (30≤x≤80) were synthesized at 700 °C by the sol–gel method. The structure, morphology and magnetic properties of the samples were investigated. When the Fe content in the Fe–Pt alloy NPs was 30 at%, FePt{sub 3} NPs were successfully synthesized. With the increase in Fe content up to 50 at%, it was found that the superlattice reflections (0 0 1) and (1 1 0) appeared, which indicated the formation of the L1{sub 0}-FePt phase. Meanwhile, the FePt{sub 3} fraction was reduced. When the Fe content increased to 60 at%, single-phase L1{sub 0}-FePt NPs were synthesized. The coercivity (Hc), saturation magnetization (Ms) and chemical order parameter S for Fe{sub 60}Pt{sub 40} NPs were as high as 10,200 Oe, 17.567 emu/g and 0.928, respectively. With the further increase of the Fe content to 80 at%, only Fe{sub 3}Pt phase existed and the Hc of the Fe{sub 3}Pt NPs decreased drastically to 360 Oe. - Graphical abstract: Fe{sub 3}Pt, FePt and FePt{sub 3} nanoparticles was obtained by sol–gel method. The effect of iron and platinum content on structural and magnetic properties of the FePt nanoparticles was investigated. Display Omitted - Highlights: • L1{sub 2}-FePt{sub 3}, L1{sub 0}-FePt and L1{sub 2}-Fe{sub 3}Pt NPs were synthesized by sol–gel method. • The chemical order parameter S affects the magnetic properties of the Fe–Pt alloy. • Structural and magnetic properties of the Fe–Pt alloy NPs were studied. • The synthetic route in this study will open up the possibilities of practical use.

  2. Irreversible modification of magnetic properties of Pt/Co/Pt ultrathin films by femtosecond laser pulses

    SciTech Connect

    Kisielewski, J.; Dobrogowski, W.; Kurant, Z.; Stupakiewicz, A.; Tekielak, M.; Maziewski, A.; Kirilyuk, A.; Kimel, A.; Rasing, Th.; Baczewski, L. T.; Wawro, A.

    2014-02-07

    Annealing ultrathin Pt/Co/Pt films with single femtosecond laser pulses leads to irreversible spin-reorientation transitions and an amplification of the magneto-optical Kerr rotation. The effect was studied as a function of the Co thickness and the pulse fluence, revealing two-dimensional diagrams of magnetic properties. While increasing the fluence, the creation of two branches of the out-of-plane magnetization state was found.

  3. Simulation of electroforming of the Pt/NiO/Pt switching memory structure

    NASA Astrophysics Data System (ADS)

    Sysun, V. I.; Sysun, I. V.; Boriskov, P. P.

    2016-05-01

    We analyze experimental data on a transient thermal electroforming of a Pt/NiO/Pt unipolar memory switching structure. Numerical simulation of this process shows that the channel can be identified with the melting region of nickel oxide, in which its cross section is determined by the maximal breakdown current, a considerable contribution to which can come from a parasitic capacitance. Rough analytic approximations are given for estimating the channel formation parameters.

  4. Unusual cluster shapes and directional bonding of an fcc metal: Pt/Pt(111).

    PubMed

    Schmid, Michael; Garhofer, Andreas; Redinger, Josef; Wimmer, Florian; Scheiber, Philipp; Varga, Peter

    2011-07-01

    Small clusters of Pt adatoms grown on Pt(111) exhibit a preference for the formation of linear chains, which cannot be explained by simple diffusion-limited aggregation. Density functional theory calculations show that short chains are energetically favorable to more compact configurations due to strong directional bonding by d(z)(2)-like orbitals, explaining the stability of the chains. The formation of the chains is governed by substrate distortions, leading to funneling towards the chain ends. PMID:21797553

  5. Reactivity of atomically dispersed Pt(2+) species towards H2: model Pt-CeO2 fuel cell catalyst.

    PubMed

    Lykhach, Yaroslava; Figueroba, Alberto; Camellone, Matteo Farnesi; Neitzel, Armin; Skála, Tomáš; Negreiros, Fabio R; Vorokhta, Mykhailo; Tsud, Nataliya; Prince, Kevin C; Fabris, Stefano; Neyman, Konstantin M; Matolín, Vladimír; Libuda, Jörg

    2016-03-01

    The reactivity of atomically dispersed Pt(2+) species on the surface of nanostructured CeO2 films and the mechanism of H2 activation on these sites have been investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy in combination with density functional calculations. Isolated Pt(2+) sites are found to be inactive towards H2 dissociation due to high activation energy required for H-H bond scission. Trace amounts of metallic Pt are necessary to initiate H2 dissociation on Pt-CeO2 films. H2 dissociation triggers the reduction of Ce(4+) cations which, in turn, is coupled with the reduction of Pt(2+) species. The mechanism of Pt(2+) reduction involves reverse oxygen spillover and formation of oxygen vacancies on Pt-CeO2 films. Our calculations suggest the existence of a threshold concentration of oxygen vacancies associated with the onset of Pt(2+) reduction. PMID:26908194

  6. Alloy Cu3Pt nanoframes through the structure evolution in Cu-Pt nanoparticles with a core-shell construction

    PubMed Central

    Han, Lin; Liu, Hui; Cui, Penglei; Peng, Zhijian; Zhang, Suojiang; Yang, Jun

    2014-01-01

    Noble metal nanoparticles with hollow interiors and customizable shell compositions have immense potential for catalysis. Herein, we present an unique structure transformation phenomenon for the fabrication of alloy Cu3Pt nanoframes with polyhedral morphology. This strategy starts with the preparation of polyhedral Cu-Pt nanoparticles with a core-shell construction upon the anisotropic growth of Pt on multiply twinned Cu seed particles, which are subsequently transformed into alloy Cu3Pt nanoframes due to the Kirkendall effect between the Cu core and Pt shell. The as-prepared alloy Cu3Pt nanoframes possess the rhombic dodecahedral morphology of their core-shell parents after the structural evolution. In particular, the resulting alloy Cu3Pt nanoframes are more effective for oxygen reduction reaction but ineffective for methanol oxidation reaction in comparison with their original Cu-Pt core-shell precursors. PMID:25231376

  7. Microstructure and magnetization reversal of L10-FePt/[Co/Pt]N exchange coupled composite films

    NASA Astrophysics Data System (ADS)

    Guo, H. H.; Liao, J. L.; Ma, B.; Zhang, Z. Z.; Jin, Q. Y.; Wang, H.; Wang, J. P.

    2012-04-01

    Two series of perpendicular exchange coupled composites (ECC) films are prepared by dc magnetron sputtering, FePt(5)/[Co(0.2)/Pt(0.3)]N (ECC-I-N) and FePt(5)/[Co(0.2)/Pt(0.6)]N (ECC-II-N), respectively. Structure analyses reveal the epitaxial growth on (001) oriented L10 FePt island-like grains of [Co/Pt]N with (200) orientation. Coercivity HC and remanent coercivity HCR of both series samples decrease sharply compared to FePt, with the increase of the thickness of [Co/Pt]N. The angular dependence of HCR shows excellent angular tolerance.

  8. Alloy Cu3Pt nanoframes through the structure evolution in Cu-Pt nanoparticles with a core-shell construction

    NASA Astrophysics Data System (ADS)

    Han, Lin; Liu, Hui; Cui, Penglei; Peng, Zhijian; Zhang, Suojiang; Yang, Jun

    2014-09-01

    Noble metal nanoparticles with hollow interiors and customizable shell compositions have immense potential for catalysis. Herein, we present an unique structure transformation phenomenon for the fabrication of alloy Cu3Pt nanoframes with polyhedral morphology. This strategy starts with the preparation of polyhedral Cu-Pt nanoparticles with a core-shell construction upon the anisotropic growth of Pt on multiply twinned Cu seed particles, which are subsequently transformed into alloy Cu3Pt nanoframes due to the Kirkendall effect between the Cu core and Pt shell. The as-prepared alloy Cu3Pt nanoframes possess the rhombic dodecahedral morphology of their core-shell parents after the structural evolution. In particular, the resulting alloy Cu3Pt nanoframes are more effective for oxygen reduction reaction but ineffective for methanol oxidation reaction in comparison with their original Cu-Pt core-shell precursors.

  9. Preparation of Pt Nanocatalyst on Carbon Materials via a Reduction Reaction of a Pt Precursor in a Drying Process.

    PubMed

    Lee, Jae-Young; Lee, Woo-Kum; Rim, Hyung-Ryul; Joung, Gyu-Bum; Weidner, John W; Lee, Hong-Ki

    2016-06-01

    Platinum (Pt) nanocatalyst for a proton-exchange membrane fuel cell (PEMFC) was prepared on a carbon black particle or a graphite particle coated with a nafion polymer via a reduction of platinum(II) bis(acetylacetonate) denoted as Pt(acac)2 as a Pt precursor in a drying process. Sublimed Pt(acac)2 adsorbed on the nafion-coated carbon materials was reduced to Pt nanoparticles in a glass reactor at 180 degrees C of N2 atmosphere. The morphology of Pt nanoparticles on carbon materials was observed by scanning electron microscopy (SEM) and the distribution of Pt nanoparticles was done by transmission electron microscopy (TEM). The particle size was estimated by analyzing the TEM image using an image analyzer. It was found that nano-sized Pt particles were deposited on the surface of carbon materials, and the number density and the average particle size increased with increasing reduction time. PMID:27427723

  10. Synthesis And Characterization of Gamma-Al2O3-Supported Pt Catalysts From Pt(4) And Pt(6) Clusters Formed in Aqueous Solutions

    SciTech Connect

    Siani, A.; Wigal, K.R.; Alexeev, A.S.; Amiridis, M.D.

    2009-05-26

    Highly dispersed Pt catalysts were prepared by deposition of Pt{sub 4} and Pt{sub 6} clusters, initially formed in unprotected and poly(vinyl alcohol) (PVA)-protected colloidal Pt suspensions, onto a {gamma}-Al{sub 2}O{sub 3} surface. These catalysts were characterized by extended X-ray absorption fine structure (EXAFS) and Fourier transform infrared (FTIR) spectroscopies. The EXAFS results indicate that the supported Pt species formed were very similar in structure to those of the original clusters in the corresponding colloidal suspensions. The FTIR results further indicate that the {gamma}-Al{sub 2}O{sub 3}-supported Pt{sub 4} clusters have significantly lower chemisorptive properties compared with larger supported Pt nanoparticles; nevertheless, the Pt{sub 4}/{gamma}-Al{sub 2}O{sub 3} sample was active for the oxidation of CO with no need for additional activation treatment. In fact, treatment of this sample with H{sub 2} at 150--200 {sup o}C led to the formation of Pt aggregates with sizes of 1.0--1.6 nm, demonstrating that the surface Pt4 species readily sintered in this temperature range under reducing conditions.

  11. Adsorption of ethene on Pt(1 1 1) and ordered Pt xSn/Pt(1 1 1) surface alloys: A comparative HREELS and DFT investigation

    NASA Astrophysics Data System (ADS)

    Essen, J. M.; Haubrich, J.; Becker, C.; Wandelt, K.

    2007-08-01

    The adsorption of ethene (C 2H 4) on Pt(1 1 1) and the Pt 3Sn/Pt(1 1 1) and Pt 2Sn/Pt(1 1 1) surface alloys has been investigated experimentally by high-resolution electron energy loss spectroscopy and temperature programmed desorption. The experimental results have been compared with density functional theory (DFT) calculations allowing us to perform a complete assignment of all vibration modes and loss features to the species present on the surfaces. On Pt(1 1 1) as well as on the Pt-Sn surface alloys an η2 di-σ-bonded conformation of ethene has been found to be the most stable adsorbed form. In addition to this majority species a minor amount of π-bonded ethene has been identified, which is more abundant on the Pt 2Sn surface alloy than on the other surfaces. Additionally the HREELS spectra of ethene on Pt(1 1 1) and the Pt-Sn surface alloys differ only slightly in terms of the energetic positions of the loss peaks.

  12. Probing the solvent shell with 195Pt chemical shifts: density functional theory molecular dynamics study of Pt(II) and Pt(IV) anionic complexes in aqueous solution.

    PubMed

    Truflandier, Lionel A; Autschbach, Jochen

    2010-03-17

    Ab initio molecular dynamics (aiMD) simulations based on density functional theory (DFT) were performed on a set of five anionic platinum complexes in aqueous solution. (195)Pt nuclear magnetic shielding constants were computed with DFT as averages over the aiMD trajectories, using the two-component relativistic zeroth-order regular approximation (ZORA) in order to treat relativistic effects on the Pt shielding tensors. The chemical shifts obtained from the aiMD averages are in good agreement with experimental data. For Pt(II) and Pt(IV) halide complexes we found an intermediate solvent shell interacting with the complexes that causes pronounced solvent effects on the Pt chemical shifts. For these complexes, the magnitude of solvent effects on the Pt shielding constant can be correlated with the surface charge density. For square-planar Pt complexes the aiMD simulations also clearly demonstrate the influence of closely coordinated non-equatorial water molecules on the Pt chemical shift, relating the structure of the solution around the complex to the solvent effects on the metal NMR chemical shift. For the complex [Pt(CN)(4)](2-), the solvent effects on the Pt shielding constant are surprisingly small. PMID:20166712

  13. An evaluation of Pt sulfite acid (PSA) as precursor for supported Pt catalysts

    SciTech Connect

    Regalbuto, J.R.; Ansel, O.; Miller, J.T.

    2010-11-12

    As a catalyst precursor, platinum sulfite acid (PSA) is easy to use and not relatively expensive, and is a potentially attractive precursor for many types of supported catalysts. The ultimate usefulness for many catalyst applications will depend on the extent that Pt can be dispersed and sulfur eliminated. To our knowledge, there exists no detailed characterization in the catalysis literature of PSA and the nanoparticulate Pt phases derived from it during catalyst pretreatment. To this end a series of supports including alumina, silica, magnesia, niobia, titania, magnesia and carbon were contacted with PSA solutions and subsequently analyzed with extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) analysis, and x-ray photoelectron spectroscopy (XPS) to characterize the Pt species formed upon impregnation, calcination, and reduction. While all catalysts show retention of some S, reasonably small particle sizes with relatively little Pt-S can in some instances be produced using PSA. The amount of retained sulfur appears to decrease with decreasing surface acidity, although even the most acidic supports (niobia and silica) display some storage of S even while only Pt-O bands are observed after calcination or reoxidation. More sulfur was eliminated by high temperature calcinations followed by reduction in hydrogen, at the expense of increasing Pt particle size.

  14. Modification of Pt/Co/Pt film properties by ion irradiation

    NASA Astrophysics Data System (ADS)

    Avchaciov, K. A.; Ren, W.; Djurabekova, F.; Nordlund, K.; Sveklo, I.; Maziewski, A.

    2015-09-01

    We studied the structural modifications of a Pt/Co/Pt trilayer epitaxial film under Ga+ 30-keV ion irradiation by means of classical molecular dynamics and Monte Carlo simulations. The semiclassical tight-binding second-moment approximation potential was adjusted to reproduce the enthalpies of formation, the lattice constants, and the order-disorder transition temperatures for Co-Pt alloys. We found that during irradiation, the sandwich-type Pt(fcc)/Co(hcp)/Pt(fcc) film structure underwent a transition to the new solid solution α -Co /Pt (fcc ) phase. Our analysis of the short-range order indicates the formation, within a nanosecond time scale, of a homogeneous chemically disordered solution. The longer time-scale simulations employing a Monte Carlo algorithm demonstrated that the transition from the disordered phase to the ordered L 10 and L 12 phases was also possible but not significant for the changes in perpendicular magnetic anisotropy (PMA) observed experimentally. The strain analysis showed that the Co layer was under tensile strain in the lateral direction at the fluences of 1.5 ×1014-3.5 ×1014ionscm -2 ; this range of fluences corresponds to the appearance of PMA. This strain was induced in the initially relaxed hcp Co layer due to its partial transformation to the fcc phase and to the influence of atomic layers with larger lattice constants at upper/lower interfaces.

  15. Structural investigation of ultrathin Pt/Co/Pt trilayer films under EUV irradiation

    NASA Astrophysics Data System (ADS)

    Dynowska, E.; Pelka, J. B.; Klinger, D.; Minikayev, R.; Bartnik, A.; Dluzewski, P.; Jakubowski, M.; Klepka, M.; Petruczik, A.; Seeck, O. H.; Sobierajski, R.; Sveklo, I.; Wawro, A. A.; Maziewski, A.

    2015-12-01

    Trilayer systems containing ultrathin (3 nm) cobalt layer grown on 5 nm thick Pt buffer layer and covered with 3 nm thick Pt cap layer grown at room temperature by molecular beam epitaxy on the Al2O3(00.1) substrate have been irradiated by nanosecond extreme ultraviolet light pulses. It was previously evidenced that light irradiation induced irreversible change of direction of magnetization in such nanostructures. In order to understand the reasons of such behavior the structural studies with the use of X-ray diffraction and transmission electron microscopy of the as-grown and irradiated samples have been done. It was found that irradiation leads to intermixing of cobalt with platinum giving rise to creation of Pt1-xCox disordered alloy. The methodology of determination of the strain state of the layers, relaxed lattice parameter of the unit cell and the composition of Pt1-xCox alloys has been developed and described in details. The results of structural studies of the as grown Pt/Co/Pt nanostructures as well as those modified by irradiation are presented in this paper.

  16. Compositional superlattices based on PtCl/PtBr MX materials

    SciTech Connect

    Saxena, A.; Huang, X.Z.; Bishop, A.R.

    1992-01-01

    We consider theoretically a novel class of compositional superlattices consisting of alternating layers of quasi-one-dimensional (QlD) MX (halogen-bridged, transition metal) chain materials. In particular, we have studied a superlattice based on the PtCl/PtBr unit where the Peierls band gap for PtCl is [approximately]2.4 eV and [approximately]1.5 eV for PtBr. We have calculated electronic properties, optical absorption and vibrational properties (e.g. Raman spectrum) of an MX superlattice using a discrete, two-band, tight-binding Peierls-Hubbard model. The electronic band structure reveals a typical subband structure and varies with the relative lengths of the constituent PtCl and PtBr units. The MX superlattice can be thought of as an analog of a GaAs/GaAl[sub x]As[sub 1-x] compositional superlattice but with the added feature that the optical, transport and various other physical properties are modified due to presence of nonlinear excitations (e.g. polarons) in the doped samples.

  17. The Mechanism of Direct Formic Acid Fuel Cell Using Pd, Pt and Pt-Ru

    NASA Astrophysics Data System (ADS)

    Kamiya, Nobuyuki; Liu, Yan; Mitsushima, Shigenori; Ota, Ken-Ichiro; Tsutsumi, Yasuyuki; Ogawa, Naoya; Kon, Norihiro; Eguchi, Mika

    The electro-oxidation of formic acid, 2-propanol and methanol on Pd black, Pd/C, Pt-Ru/C and Pt/C has been investigated to clear the reaction mechanism. It was suggested that the formic acid is dehydrogenated on Pd surface and the hydrogen is occluded in the Pd lattice. Thus obtained hydrogen acts like pure hydrogen supplied from the outside and the cell performance of the direct formic acid fuel cell showed as high as that of a hydrogen-oxygen fuel cell. 2-propanol did not show such dehydrogenation reaction on Pd catalyst. Platinum and Pt-Ru accelerated the oxidation of C-OH of 2-propanol and methanol. Slow scan voltammogram (SSV) and chronoamperometry measurements showed that the activity of formic acid oxidation increased in the following order: Pd black > Pd 30wt.%/C > Pt50wt.%/C > 27wt.%Pt-13wt.%Ru/C. A large oxidation current for formic acid was found at a low overpotential on the palladium electrocatalysts. These results indicate that formic acid is mainly oxidized through a dehydrogenation reaction. For the oxidation of 2-propanol and methanol, palladium was not effective, and 27wt.%Pt-13wt.%Ru/C showed the best oxidation activity.

  18. One-Step Synthesis of Pt/Graphene Composites from Pt Acid Dissolved Ethanol via Microwave Plasma Spray Pyrolysis.

    PubMed

    Jo, Eun Hee; Chang, Hankwon; Kim, Sun Kyung; Choi, Ji-Hyuk; Park, Su-Ryeon; Lee, Chong Min; Jang, Hee Dong

    2016-01-01

    Pt nanoparticles-laden graphene (Pt/GR) composites were synthesized in the gas phase from a mixture of ethanol and Pt precursor by microwave plasma spray pyrolysis. The morphology of Pt/GR composites has the shape of wrinkled sheets of paper, while Pt nanoparticles (Pt NPs) that are less than 2.6 nm in the mean diameter are uniformly well deposited on the surface of GR sheets stacked in only three layers. The Pt/GR composite prepared with 20 wt% of Pt had the highest specific surface area and electrochemical surface area of up to 402 m(2) g(-1) and 77 m(2) g(-1) (Pt), respectively. In addition, the composite showed superior electrocatalytic activity compared with commercial Pt-carbon black. The excellent electrocatalytic activity was attributed to the high specific surface area and electrochemical surface area of the Pt/GR composite directly produced by microwave plasma spray pyrolysis. Thus, it is clearly expected that the Pt/GR composite is a promising material for DMFC catalysts. PMID:27622908

  19. Investigation of the electrocatalysis for oxygen reduction reaction by Pt and binary Pt alloys: an XRD, XAS and electrochemical study

    SciTech Connect

    Mukerjee, S.; McBreen, J.; Srinivasan, S.

    1995-12-31

    Electrocatalysis for the oxygen reduction reaction (ORR) on five binary Pt alloy electrocatalysts (PtCr/C, PtMn/C, PtFe/C, PtCo/C and PtNi/C) supported on carbon have been investigated. The electrochemical characteristics for ORR in a proton conducting fuel cell environment has been correlated with the electronic and structural parameters determined under in situ conditions using XANES and EXAFS technique respectively. Results indicate that all the alloys possess higher Pt 5d band vacancies as compared to Pt/C. There is also evidence of lattice contraction in the alloys (supported by XRD results). Further, the Pt/C shows increase in Pt 5 d band vacancies during potential transitions from 0.54 to 0.84 V vs. RHE, which has been ration@ on the basis of OH type adsorption. In contrast to this, the alloys do not exhibit such an enhancement. Detailed EXAFS analysis supports the presence of OH species on Pt/C and its relative absence in the alloys. Correlation of the electrochemical results with bond distances and d-band vacancies show a volcano type behavior with the PtCr/C on top of the curve.

  20. Surface enrichment of Pt in Ga2O3 films grown on liquid Pt/Ga alloys

    NASA Astrophysics Data System (ADS)

    Grabau, Mathias; Krick Calderón, Sandra; Rietzler, Florian; Niedermaier, Inga; Taccardi, Nicola; Wasserscheid, Peter; Maier, Florian; Steinrück, Hans-Peter; Papp, Christian

    2016-09-01

    The formation of surface Ga2O3 films on liquid samples of Ga, and Pt-Ga alloys with 0.7 and 1.8 at.% Pt was examined using near-ambient pressure (NAP) X-ray photoelectron spectroscopy (XPS). Thickness, composition and growth of the oxide films were deduced as a function of temperature and Pt content of the alloys, in ultra-high vacuum and at oxygen pressures of 3 × 10- 7, 3 × 10- 3 and 1 mbar. We examined oxide layers up to a thickness of 37 Å. Different growth modes were found for oxidation at low and high pressures. The formed Ga2O3 oxide films showed an increased Pt content, while the pristine GaPt alloy showed a surface depletion of Pt at the examined temperatures. Upon growth of Ga2O3 on Pt/Ga alloys a linear increase of Pt content was observed, due to the incorporation of 3.6 at.% Pt in the Ga2O3. The Pt content in Ga2O3, at the examined temperatures and bulk Pt concentrations is found to be independent of pressure, temperature and the nominal Pt content of the metallic alloy.

  1. Granular nanostructures and magnetic characteristics of FePt-TiO{sub 2}/FePt-C stacked granular films

    SciTech Connect

    Ono, Takuya Moriya, Tomohiro; Hatayama, Masatoshi; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2014-05-07

    To realize a granular film composed of L1{sub 0}-FePt grains with high uniaxial magnetic anisotropy energy, K{sub u}, and segregants for heat-assisted magnetic recording, the FePt-TiO{sub 2}/FePt-C stacked film was investigated. The FePt-TiO{sub 2}/FePt-C stacked film has well-isolated granular structure with average grain size of 6.7 nm because the FePt-TiO{sub 2} film follows the FePt-C template film in microstructural growth. However, the K{sub u} value is quite low for total thickness of 9 nm: 5 × 10{sup 6} erg/cm{sup 3}. Exploration of the thickness dependence of L1{sub 0}-FePt(001) peaks in XRD spectra and cross-sectional TEM images suggest that degradation of the L1{sub 0} ordering appears near the middle of the FePt-TiO{sub 2} layer. The EDX-STEM mapping reveals that Ti atoms exist within the FePt grains in addition to the grain boundary. This indicates the possibility that TiO{sub 2} tends to be incorporated into the FePt grains and that it prevents L1{sub 0}-ordering of the FePt grains along the normal-to-plane direction.

  2. New Crystal Structures Identified for PtO and PtO2 using Density Functional Theory Calculations

    NASA Astrophysics Data System (ADS)

    da Silva, Juarez L. F.; Nomiyama, Ricardo K.; Piotrowski, Mauricio J.

    2012-02-01

    Platinum plays an important role in catalysis and electrochemistry, and it has been known that the direct interaction of oxygen with Pt surfaces can lead to the formation of platinum oxides (PtOx), which can affects the reactivity. To contribute to the atomistic understanding of the atomic structure of PtOx, we report a density functional theory study of the atomic structure of bulk PtOx (1 <=x <=2). From our calculations, we identified a lowest energy structure (GeS-type, space group Pnma) for PtO, which is 0.181 eV lower in energy than the structure suggested by Moore and Pauling (PtS-type). Furthermore, two atomic structures were identified for PtO2, which are almost degenerate in energy with the lowest energy structure reported so far for PtO2 (CaCl2-type). Based on our results and analysis, we suggest that Pt and O atoms tends to form octahedron motifs in PtOx even at lower O composition by the formation of Pt-Pt bonds.

  3. Non-Saccharomyces and Saccharomyces strains co-fermentation increases acetaldehyde accumulation: effect on anthocyanin-derived pigments in Tannat red wines.

    PubMed

    Medina, Karina; Boido, Eduardo; Fariña, Laura; Dellacassa, Eduardo; Carrau, Francisco

    2016-07-01

    During fermentation, Saccharomyces cerevisiae releases into the medium secondary metabolic products, such as acetaldehyde, able to react with anthocyanins, producing more stable derived pigments. However, very limited reports are found about non-Saccharomyces effects on grape fermentation. In this study, six non-Saccharomyces yeast strains, belonging to the genera Metschnikowia and Hanseniaspora, were screened for their effect on red wine colour and wine-making capacity under pure culture conditions and mixed with Saccharomyces. An artificial red grape must was prepared, containing a phenolic extract of Tannat grapes that allows monitoring changes of key phenol parameters during fermentation, but without skin solids in the medium. When fermented in pure cultures, S. cerevisiae produced higher concentrations of acetaldehyde and vitisin B (acetaldehyde reaction-dependent) compared to M. pulcherrima M00/09G, Hanseniaspora guillermondii T06/09G, H. opuntiae T06/01G, H. vineae T02/05F and H. clermontiae (A10/82Fand C10/54F). However, co-fermentation of H. vineae and H. clermontiae with S. cerevisiae resulted in a significantly higher concentration of acetaldehyde compared with the pure S. cerevisiae control. HPLC-DAD-MS analysis confirmed an increased formation of vitisin B in co-fermentation treatments when compared to pure Saccharomyces fermentation, suggesting the key role of acetaldehyde. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26888345

  4. High-Temperature Regeneration of Perpendicular Exchange Bias in a Pt/Co/Pt/α-Cr2O3/Pt Thin Film System

    NASA Astrophysics Data System (ADS)

    Shiratsuchi, Yu; Takechi, Yuichiro; Toyoki, Kentaro; Nakano, Yuuta; Onoue, Satoshi; Mitsumata, Chiharu; Nakatani, Ryoichi

    2013-12-01

    We found the regeneration of perpendicular exchange bias at high temperature in the Pt-capping/Co/Pt-spacer/α-Cr2O3/Pt-buffer thin film with an ultrathin (0.2 nm) Pt-spacer layer after the disappearance at low temperature. Abrupt changes in the coercivity accompany the abrupt disappearance and regeneration of exchange bias. The direction of the regenerated exchange bias could be reversed by altering the ferromagnetic spin orientation during temperature rise. The exchange bias did not regenerate when the Pt spacer layer was grown at a slow growth rate, suggesting that the growth mode of Pt on the α-Cr2O3 layer affects the regeneration feature.

  5. Adsorbed water and CO on Pt electrode modified with Ru

    NASA Astrophysics Data System (ADS)

    Futamata, Masayuki; Luo, Liqiang

    Highly sensitive ATR-SEIRA spectroscopy was exploited to elucidate water, CO and electrolyte anions adsorbed on the Ru modified Pt film electrode. CO on Ru domains was oxidized below ca. +0.3 V, followed by pronounced water adsorption. Since the oxidation potential of CO on Pt domain was significantly reduced compared to bare Pt, these water molecules on Ru obviously prompt CO oxidation on adjacent Pt surface as consistent with the bifunctional mechanism. Diffusion of adsorbate from Ru to Pt surfaces was indicated in dilute CH 3OH solution by spectral changes with potential.

  6. Exactly solvable PT -symmetric models in two dimensions

    NASA Astrophysics Data System (ADS)

    Agarwal, Kaustubh S.; Pathak, Rajeev K.; Joglekar, Yogesh N.

    2015-11-01

    Non-Hermitian, PT -symmetric Hamiltonians, experimentally realized in optical systems, accurately model the properties of open, bosonic systems with balanced, spatially separated gain and loss. We present a family of exactly solvable, two-dimensional, PT potentials for a non-relativistic particle confined in a circular geometry. We show that the PT -symmetry threshold can be tuned by introducing a second gain-loss potential or its Hermitian counterpart. Our results explicitly demonstrate that PT breaking in two dimensions has a rich phase diagram, with multiple re-entrant PT -symmetric phases.

  7. Magnetic properties of ultrathin Ni/Co/Pt(111) films

    NASA Astrophysics Data System (ADS)

    Su, C. W.; Shern, C. S.; Yao, Y. D.

    2004-06-01

    Magnetic properties of one monolayer (ML) Ni/1 ML Co/Pt(111) film upon thermal annealing were investigated. Increases in polar Kerr rotation correspond to the topmost Ni layer incorporated with the second Co layer on Pt, and the further alloying of Co-Pt during the annealing. Interestingly, Curie temperature shifted dramatically to 325 K when the film was annealed at 830 K. The alloy formation of Ni-Pt and top-layer enrichment of Pt may be the main reason causing the great shift of Curie temperature.

  8. Intracellular ethanol accumulation in Saccharomyces cerevisiae during fermentation.

    PubMed

    D'Amore, T; Panchal, C J; Stewart, G G

    1988-01-01

    An intracellular accumulation of ethanol in Saccharomyces cerevisiae was observed during the early stages of fermentation (3 h). However, after 12 h of fermentation, the intracellular and extracellular ethanol concentrations were similar. Increasing the osmotic pressure of the medium caused an increase in the ratio of intracellular to extracellular ethanol concentrations at 3 h of fermentation. As in the previous case, the intracellular and extracellular ethanol concentrations were similar after 12 h of fermentation. Increasing the osmotic pressure also caused a decrease in yeast cell growth and fermentation activities. However, nutrient supplementation of the medium increased the extent of growth and fermentation, resulting in complete glucose utilization, even though intracellular ethanol concentrations were unaltered. These results suggest that nutrient limitation is a major factor responsible for the decreased growth and fermentation activities observed in yeast cells at higher osmotic pressures. PMID:3278685

  9. Mutants of Saccharomyces cerevisiae with defective vacuolar function

    SciTech Connect

    Kitamoto, K.; Yoshizawa, K.; Ohsumi, Y.; Anraku, Y.

    1988-06-01

    Mutants of the yeast Saccharomyces cerevisiae that have a small vacuolar lysine pool were isolated and characterized. Mutant KL97 (lys1 slp1-1) and strain KL197-1A (slp1-1), a prototrophic derivative of KL97, did not grow well in synthetic medium supplemented with 10 mM lysine. Genetic studies indicated that the slp1-1mutation (for small lysine pool) is recessive and is due to a single chromosomal mutation. Mutant KL97 shows the following pleiotropic defects in vacuolar functions. (i) It has small vacuolar pools for lysine, arginine, and histidine. (ii) Its growth is sensitive to lysine, histidine, Ca/sup 2 +/, heavy metal ions, and antibiotics. (iii) It has many small vesicles but no large central vacuole. (iv) It has a normal amount of the vacuolar membrane marker ..cap alpha..-mannosidase but shows reduced activities of the vacuole sap markers proteinase A, proteinase B, and carboxypeptidase Y.

  10. Bent DNA functions as a replication enhancer in Saccharomyces cerevisiae.

    PubMed Central

    Williams, J S; Eckdahl, T T; Anderson, J N

    1988-01-01

    Previous studies have demonstrated that bent DNA is a conserved property of Saccharomyces cerevisiae autonomously replicating sequences (ARSs). Here we showed that bending elements are contained within ARS subdomains identified by others as replication enhancers. To provide a direct test for the function of this unusual structure, we analyzed the ARS activity of plasmids that contained synthetic bent DNA substituted for the natural bending element in yeast ARS1. The results demonstrated that deletion of the natural bending locus impaired ARS activity which was restored to a near wild-type level with synthetic bent DNA. Since the only obvious common features of the natural and synthetic bending elements are the sequence patterns that give rise to DNA bending, the results suggest that the bent structure per se is crucial for ARS function. Images PMID:3043195

  11. Asynchronous spore germination in isogenic natural isolates of Saccharomyces paradoxus.

    PubMed

    Stelkens, Rike B; Miller, Eric L; Greig, Duncan

    2016-05-01

    Spores from wild yeast isolates often show great variation in the size of colonies they produce, for largely unknown reasons. Here we measure the colonies produced from single spores from six different wild Saccharomyces paradoxus strains. We found remarkable variation in spore colony sizes, even among spores that were genetically identical. Different strains had different amounts of variation in spore colony sizes, and variation was not affected by the number of preceding meioses, or by spore maturation time. We used time-lapse photography to show that wild strains also have high variation in spore germination timing, providing a likely mechanism for the variation in spore colony sizes. When some spores from a laboratory strain make small colonies, or no colonies, it usually indicates a genetic or meiotic fault. Here, we demonstrate that in wild strains spore colony size variation is normal. We discuss and assess potential adaptive and non-adaptive explanations for this variation. PMID:26880797

  12. Interorganelle signaling is a determinant of longevity in Saccharomyces cerevisiae.

    PubMed Central

    Kirchman, P A; Kim, S; Lai, C Y; Jazwinski, S M

    1999-01-01

    Replicative capacity, which is the number of times an individual cell divides, is the measure of longevity in the yeast Saccharomyces cerevisiae. In this study, a process that involves signaling from the mitochondrion to the nucleus, called retrograde regulation, is shown to determine yeast longevity, and its induction resulted in postponed senescence. Activation of retrograde regulation, by genetic and environmental means, correlated with increased replicative capacity in four different S. cerevisiae strains. Deletion of a gene required for the retrograde response, RTG2, eliminated the increased replicative capacity. RAS2, a gene previously shown to influence longevity in yeast, interacts with retrograde regulation in setting yeast longevity. The molecular mechanism of aging elucidated here parallels the results of genetic studies of aging in nematodes and fruit flies, as well as the caloric restriction paradigm in mammals, and it underscores the importance of metabolic regulation in aging, suggesting a general applicability. PMID:10224252

  13. Identity elements of Saccharomyces cerevisiae tRNA(His).

    PubMed Central

    Nameki, N; Asahara, H; Shimizu, M; Okada, N; Himeno, H

    1995-01-01

    Recognition of tRNA(His) by Saccharomyces cerevisiae histidyl-tRNA synthetase was studied using in vitro transcripts. Histidine tRNA is unique in possessing an extra nucleotide, G-1, at the 5' end. Mutation studies indicate that this irregular secondary structure at the end of the acceptor stem is important for aminoacylation with histidine, while the requirement of either base of this extra base pair is smaller than that in Escherichia coli. The anticodon was also found to be required for histidylation. The regions involved in histidylation are essentially the same as those in E.coli, whereas the proportion of the contributions of the two portions distant from each other, the anticodon and the end of the acceptor stem, makes a substantial difference between the two systems. PMID:7885835

  14. Hormetic Effect of H2O2 in Saccharomyces cerevisiae

    PubMed Central

    Valishkevych, Bohdana V.

    2016-01-01

    In this study, we investigated the relationship between target of rapamycin (TOR) and H2O2-induced hormetic response in the budding yeast Saccharomyces cerevisiae grown on glucose or fructose. In general, our data suggest that: (1) hydrogen peroxide (H2O2) induces hormesis in a TOR-dependent manner; (2) the H2O2-induced hormetic dose–response in yeast depends on the type of carbohydrate in growth medium; (3) the concentration-dependent effect of H2O2 on yeast colony growth positively correlates with the activity of glutathione reductase that suggests the enzyme involvement in the H2O2-induced hormetic response; and (4) both TOR1 and TOR2 are involved in the reciprocal regulation of the activity of glucose-6-phosphate dehydrogenase and glyoxalase 1. PMID:27099601

  15. Bioaccumulation of cadmium by growing Zygosaccharomyces rouxii and Saccharomyces cerevisiae.

    PubMed

    Li, Chunsheng; Jiang, Wei; Ma, Ning; Zhu, Yinglian; Dong, Xiaoyan; Wang, Dongfeng; Meng, Xianghong; Xu, Ying

    2014-03-01

    Bioaccumulation via growing cells is a potential technique for heavy metal removal from food materials. The cadmium bioaccumulation characteristics by growing Zygosaccharomyces rouxii and Saccharomyces cerevisiae were investigated. Z. rouxii displayed powerful cadmium removal ability at low cadmium concentrations, which mainly depended on the intracellular cadmium bioaccumulation. The percentage of intracellular cadmium bioaccumulation of both yeasts obviously decreased with the increase of initial biomass and cadmium concentrations. Low pH and elevated concentrations of zinc and copper significantly decreased the intracellular cadmium bioaccumulation of both yeasts but improved the cadmium tolerance and the cell-surface cadmium bioaccumulation of Z. rouxii. Cadmium removal of Z. rouxii was improved by zinc and copper conditionally. Z. rouxii that possessed more powerful cadmium tolerance and removal ability at low pH and high concentration of competing ions can be developed into a potential cadmium removal agent using in complex food environment in future. PMID:24440489

  16. MPS3 mediates meiotic bouquet formation in Saccharomyces cerevisiae.

    PubMed

    Conrad, Michael N; Lee, Chih-Ying; Wilkerson, Joseph L; Dresser, Michael E

    2007-05-22

    In meiotic prophase, telomeres associate with the nuclear envelope and accumulate adjacent to the centrosome/spindle pole to form the chromosome bouquet, a well conserved event that in Saccharomyces cerevisiae requires the meiotic telomere protein Ndj1p. Ndj1p interacts with Mps3p, a nuclear envelope SUN domain protein that is required for spindle pole body duplication and for sister chromatid cohesion. Removal of the Ndj1p-interaction domain from MPS3 creates an ndj1 Delta-like separation-of-function allele, and Ndj1p and Mps3p are codependent for stable association with the telomeres. SUN domain proteins are found in the nuclear envelope across phyla and are implicated in mediating interactions between the interior of the nucleus and the cytoskeleton. Our observations indicate a general mechanism for meiotic telomere movements. PMID:17495028

  17. The Influence of Microgravity on Invasive Growth in Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Van Mulders, Sebastiaan E.; Stassen, Catherine; Daenen, Luk; Devreese, Bart; Siewers, Verena; van Eijsden, Rudy G. E.; Nielsen, Jens; Delvaux, Freddy R.; Willaert, Ronnie

    2011-01-01

    This study investigates the effects of microgravity on colony growth and the morphological transition from single cells to short invasive filaments in the model eukaryotic organism Saccharomyces cerevisiae. Two-dimensional spreading of the yeast colonies grown on semi-solid agar medium was reduced under microgravity in the Σ1278b laboratory strain but not in the CMBSESA1 industrial strain. This was supported by the Σ1278b proteome map under microgravity conditions, which revealed upregulation of proteins linked to anaerobic conditions. The Σ1278b strain showed a reduced invasive growth in the center of the yeast colony. Bud scar distribution was slightly affected, with a switch toward more random budding. Together, microgravity conditions disturb spatially programmed budding patterns and generate strain-dependent growth differences in yeast colonies on semi-solid medium.

  18. [Tolerance of Saccharomyces cerevisiae to monoterpenes--a review].

    PubMed

    Liu, Jidong; Zhou, Jingwen; Chen, Jian

    2013-06-01

    Tolerance of Saccharomyces cerevisiae to monoterpenes is important in both metabolic engineering of the yeast to produce these chemicals de novo and efficient use of biomass containing these chemicals. Understanding the mechanisms in the tolerance of S. cerevisiae to monoterpenes could facilitate the construction of yeast strains with enhanced monoterpenes resistance, and therefore improve related bioprocesses. Monoterpenes could disturb the redox balance in S. cerevisiae, therefore increase the accumulation of reactive oxygen species (ROS) and result in cell death. S. cerevisiae has to systematically improve its antioxidative ability to deal with the ROS induced damage. The current review summarized the recent developments in demonstration of the tolerance of S. cerevisiae to different typical monoterpenes mainly from the aspect of the antioxidative mechanisms. Based on the analysis of the previous works, further attempts to demonstrate the mechanisms were proposed. PMID:24028054

  19. Heterologous biosynthesis of artemisinic acid in Saccharomyces cerevisiae.

    PubMed

    Li, C; Li, J; Wang, G; Li, X

    2016-06-01

    Artemisinic acid is a precursor of antimalarial compound artemisinin. The titre of biosynthesis of artemisinic acid using Saccharomyces cerevisiae platform has been achieved up to 25 g l(-1) ; however, the performance of platform cells is still industrial unsatisfied. Many strategies have been proposed to improve the titre of artemisinic acid. The traditional strategies mainly focused on partial target sites, simple up-regulation key genes or repression competing pathways in the total synthesis route. However, this may result in unbalance of carbon fluxes and dysfunction of metabolism. In this review, the recent advances on the promising methods in silico and in vivo for biosynthesis of artemisinic acid have been discussed. The bioinformatics and omics techniques have brought a great prospect for improving production of artemisinin and other pharmacal compounds in heterologous platform. PMID:26743771

  20. Advanced biofuel production by the yeast Saccharomyces cerevisiae.

    PubMed

    Buijs, Nicolaas A; Siewers, Verena; Nielsen, Jens

    2013-06-01

    Replacement of conventional transportation fuels with biofuels will require production of compounds that can cover the complete fuel spectrum, ranging from gasoline to kerosene. Advanced biofuels are expected to play an important role in replacing fossil fuels because they have improved properties compared with ethanol and some of these may have the energy density required for use in heavy duty vehicles, ships, and aviation. Moreover, advanced biofuels can be used as drop-in fuels in existing internal combustion engines. The yeast cell factory Saccharomyces cerevisiae can be turned into a producer of higher alcohols (1-butanol and isobutanol), sesquiterpenes (farnesene and bisabolene), and fatty acid ethyl esters (biodiesel), and here we discusses progress in metabolic engineering of S. cerevisiae for production of these advanced biofuels. PMID:23628723

  1. Translation initiation factor-dependent extracts from Saccharomyces cerevisiae.

    PubMed

    Altmann, M; Blum, S; Pelletier, J; Sonenberg, N; Wilson, T M; Trachsel, H

    1990-08-27

    Translation initiation factor 4A- and 4E-dependent extracts were developed from Saccharomyces cerevisiae and used to study factor requirements for translation of individual mRNAs in vitro. Whereas all mRNAs tested required eIF-4A, mRNAs devoid of secondary structure in their 5' untranslated region did not require exogenous eIF-4E for translation. The latter included alfalfa mosaic virus RNA4, mRNA containing the untranslated region of tobacco mosaic virus RNA and mRNA containing part of the untranslated region of poliovirus RNA. Furthermore, initiation of translation on mRNAs containing part of the untranslated region of poliovirus RNA is most likely internal. PMID:2169890

  2. Availability of substratum enhances ethanol production in Saccharomyces cerevisiae.

    PubMed

    Sankh, Santosh N; Arvindekar, Akalpita U

    2004-12-01

    Novel additives that act as substratum for attachment of the yeast cells, increased ethanol production in Saccharomyces cerevisiae. The addition of 2 g rice husk, straw, wood shavings, plastic pieces or silica gel to 100 ml medium enhanced ethanol production by 30-40 (v/v). Six distillery strains showed an average enhancement of 34 from 4.1 (v/v) in control to 5.5 (v/v) on addition of rice husk. The cell wall bound glycogen increased by 40-50 mg g (-1) dry yeast while intracellular glycogen decreased by 10-12 mg g(-1) dry yeast in cells grown in presence of substratum. PMID:15672221

  3. Yap1: a DNA damage responder in Saccharomyces cerevisiae.

    PubMed

    Rowe, Lori A; Degtyareva, Natalya; Doetsch, Paul W

    2012-04-01

    Activation of signaling pathways in response to genotoxic stress is crucial for cells to properly repair DNA damage. In response to DNA damage, intracellular levels of reactive oxygen species increase. One important function of such a response could be to initiate signal transduction processes. We have employed the model eukaryote Saccharomyces cerevisiae to delineate DNA damage sensing mechanisms. We report a novel, unanticipated role for the transcription factor Yap1 as a DNA damage responder, providing direct evidence that reactive oxygen species are an important component of the DNA damage signaling process. Our findings reveal an epistatic link between Yap1 and the DNA base excision repair pathway. Corruption of the Yap1-mediated DNA damage response influences cell survival and genomic stability in response to exposure to genotoxic agents. PMID:22433435

  4. Electrophysiology in the eukaryotic model cell Saccharomyces cerevisiae.

    PubMed

    Bertl, A; Bihler, H; Kettner, C; Slayman, C L

    1998-11-01

    Since the mid-1980s, use of the budding yeast, Saccharomyces cerevisiae, for expression of heterologous (foreign) genes and proteins has burgeoned for several major purposes, including facile genetic manipulation, large-scale production of specific proteins, and preliminary functional analysis. Expression of heterologous membrane proteins in yeast has not kept pace with expression of cytoplasmic proteins for two principal reasons: (1) although plant and fungal proteins express and function easily in yeast membranes, animal proteins do not, at least yet; and (2) the yeast plasma membrane is generally regarded as a difficult system to which to apply the standard electrophysiological techniques for detailed functional analysis of membrane proteins. Especially now, since completion of the genome-sequencing project for Saccharomyces, yeast membranes themselves can be seen as an ample source of diverse membrane proteins - including ion channels, pumps, and cotransporters - which lend themselves to electrophysiological analysis, and specifically to patch-clamping. Using some of these native proteins for assay, we report systematic methods to prepare both the yeast plasma membrane and the yeast vacuolar membrane (tonoplast) for patch-clamp experiments. We also describe optimized ambient conditions - such as electrode preparation, buffer solutions, and time regimens - which facilitate efficient patch recording from Saccharomyces membranes. There are two main keys to successful patch-clamping with Saccharomyces. The first is patience; the second is scrupulous cleanliness. Large cells, such as provided by polyploid strains, are also useful in yeast patch recording, especially while the skill required for gigaseal formation is being learned. Cleanliness is aided by (1) osmotic extrusion of protoplasts, after minimal digestion of yeast walls; (2) use of a rather spare suspension of protoplasts in the recording chamber; (3) maintenance of continuous chamber perfusion prior to

  5. Protein disorder reduced in Saccharomyces cerevisiae to survive heat shock.

    PubMed

    Vicedo, Esmeralda; Gasik, Zofia; Dong, Yu-An; Goldberg, Tatyana; Rost, Burkhard

    2015-01-01

    Recent experiments established that a culture of Saccharomyces cerevisiae (baker's yeast) survives sudden high temperatures by specifically duplicating the entire chromosome III and two chromosomal fragments (from IV and XII). Heat shock proteins (HSPs) are not significantly over-abundant in the duplication. In contrast, we suggest a simple algorithm to " postdict " the experimental results: Find a small enough chromosome with minimal protein disorder and duplicate this region. This algorithm largely explains all observed duplications. In particular, all regions duplicated in the experiment reduced the overall content of protein disorder. The differential analysis of the functional makeup of the duplication remained inconclusive. Gene Ontology (GO) enrichment suggested over-representation in processes related to reproduction and nutrient uptake. Analyzing the protein-protein interaction network (PPI) revealed that few network-central proteins were duplicated. The predictive hypothesis hinges upon the concept of reducing proteins with long regions of disorder in order to become less sensitive to heat shock attack. PMID:26673203

  6. Higher-order structure of Saccharomyces cerevisiae chromatin

    SciTech Connect

    Lowary, P.T.; Widom, J. )

    1989-11-01

    We have developed a method for partially purifying chromatin from Saccharomyces cerevisiae (baker's yeast) to a level suitable for studies of its higher-order folding. This has required the use of yeast strains that are free of the ubiquitous yeast killer virus. Results from dynamic light scattering, electron microscopy, and x-ray diffraction show that the yeast chromatin undergoes a cation-dependent folding into 30-nm filaments that resemble those characteristic of higher-cell chromatin; moreover, the packing of nucleosomes within the yeast 30-nm filaments is similar to that of higher cells. These results imply that yeast has a protein or protein domain that serves the role of the histone H 1 found in higher cells; physical and genetic studies of the yeast activity could help elucidate the structure and function of H 1. Images of the yeast 30-nm filaments can be used to test crossed-linker models for 30-nm filament structure.

  7. Local Nanomechanical Motion of the Cell Wall of Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Pelling, Andrew E.; Sehati, Sadaf; Gralla, Edith B.; Valentine, Joan S.; Gimzewski, James K.

    2004-08-01

    We demonstrate that the cell wall of living Saccharomyces cerevisiae (baker's yeast) exhibits local temperature-dependent nanomechanical motion at characteristic frequencies. The periodic motions in the range of 0.8 to 1.6 kHz with amplitudes of ~3 nm were measured using the cantilever of an atomic force microscope (AFM). Exposure of the cells to a metabolic inhibitor causes the periodic motion to cease. From the strong frequency dependence on temperature, we derive an activation energy of 58 kJ/mol, which is consistent with the cell's metabolism involving molecular motors such as kinesin, dynein, and myosin. The magnitude of the forces observed (~10 nN) suggests concerted nanomechanical activity is operative in the cell.

  8. Construction of a flocculent Saccharomyces cerevisiae fermenting lactose.

    PubMed

    Domingues, L; Teixeira, J A; Lima, N

    1999-05-01

    A flocculent Saccharomyces cerevisiae strain with the ability to express both the LAC4 (coding for beta-galactosidase) and LAC12 (coding for lactose permease) genes of Kluyveromyces marxianus was constructed. This recombinant strain is not only able to grow on lactose, but it can also ferment this substrate. To our knowledge this is the first time that a recombinant S. cervisiae has been found to ferment lactose in a way comparable to that of the existing lactose-fermenting yeast strains. Moreover, the flocculating capacity of the strain used in this work gives the process several advantages. On the one hand, it allows for operation in a continuous mode at high cell concentration, thus increasing the system's overall productivity; on the other hand, the biomass concentration in the effluent is reduced, thus decreasing product separation/purification costs. PMID:10390820

  9. Diversity and adaptive evolution of Saccharomyces wine yeast: a review

    PubMed Central

    Marsit, Souhir; Dequin, Sylvie

    2015-01-01

    Saccharomyces cerevisiae and related species, the main workhorses of wine fermentation, have been exposed to stressful conditions for millennia, potentially resulting in adaptive differentiation. As a result, wine yeasts have recently attracted considerable interest for studying the evolutionary effects of domestication. The widespread use of whole-genome sequencing during the last decade has provided new insights into the biodiversity, population structure, phylogeography and evolutionary history of wine yeasts. Comparisons between S. cerevisiae isolates from various origins have indicated that a variety of mechanisms, including heterozygosity, nucleotide and structural variations, introgressions, horizontal gene transfer and hybridization, contribute to the genetic and phenotypic diversity of S. cerevisiae. This review will summarize the current knowledge on the diversity and evolutionary history of wine yeasts, focusing on the domestication fingerprints identified in these strains. PMID:26205244

  10. Direct evidence for a xylose metabolic pathway in Saccharomyces cerevisiae

    SciTech Connect

    Batt, C.A.; Carvallo, S.; Easson, D.D.; Akedo, M.; Sinskey, A.J.

    1986-04-01

    Xylose transport, xylose reductase, and xylitol dehydrogenase activities are demonstrated in Saccharomyces cerevisiae. The enzymes in the xylose catabolic pathway necessary for the conversion of xylose xylulose are present, although S. cerevisiae cannot grow on xylose as a sole carbon source. Xylose transport is less efficient than glucose transport, and its rate is dependent upon aeration. Xylose reductase appears to be a xylose inducible enzyme and xylitol dehydrogenase activity is constitutive, although both are repressed by glucose. Both xylose reductase and xylitol dehydrogenase activities are five- to tenfold lower in S. cerevisie as compared to Candida utilis. In vivo conversion of /sup 14/C-xylose in S. cerevisiage is demonstrated and xylitol is detected, although no significant levels of any other /sup 14/C-labeled metabolites (e.g., ethanol) are observed. 22 references.

  11. Phenotypic effects of membrane protein overexpression in Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Melén, Karin; Blomberg, Anders; von Heijne, Gunnar

    2006-07-01

    Large-scale protein overexpression phenotype screens provide an important complement to the more common gene knockout screens. Here, we have targeted the so far poorly understood Saccharomyces cerevisiae membrane proteome and report growth phenotypes for a strain collection overexpressing 600 C-terminally tagged integral membrane proteins grown both under normal and three different stress conditions. Although overexpression of most membrane proteins reduce the growth rate in synthetic defined medium, we identify a large number of proteins that, when overexpressed, confer specific resistance to various stress conditions. Our data suggest that regulation of glycosylphosphatidylinositol anchor biosynthesis and the Na+/K+ homeostasis system constitute major downstream targets of the yeast PKA/RAS pathway and point to a possible connection between the early secretory pathway and the cells' response to oxidative stress. We also have quantified the expression levels for >550 membrane proteins, facilitating the choice of well expressing proteins for future functional and structural studies. caffeine | paraquat | salt tolerance | yeast

  12. Purification of fluorescently labeled Saccharomyces cerevisiae Spindle Pole Bodies

    PubMed Central

    Davis, Trisha N.

    2016-01-01

    Centrosomes are components of the mitotic spindle responsible for organizing microtubules and establishing a bipolar spindle for accurate chromosome segregation. In budding yeast, Saccharomyces cerevisiae, the centrosome is called the spindle pole body, a highly organized tri-laminar structure embedded in the nuclear envelope. Here we describe a detailed protocol for the purification of fluorescently labeled spindle pole bodes from S. cerevisiae. Spindle pole bodies are purified from yeast using a TAP-tag purification followed by velocity sedimentation. This highly reproducible TAP-tag purification method improves upon previous techniques and expands the scope of in vitro characterization of yeast spindle pole bodies. The genetic flexibility of this technique allows for the study of spindle pole body mutants as well as the study of spindle pole bodies during different stages of the cell cycle. The ease and reproducibility of the technique makes it possible to study spindle pole bodies using a variety of biochemical, biophysical, and microscopic techniques. PMID:27193850

  13. Production of natural products through metabolic engineering of Saccharomyces cerevisiae.

    PubMed

    Krivoruchko, Anastasia; Nielsen, Jens

    2015-12-01

    Many high-value metabolites are produced in nature by organisms that are not ideal for large-scale production. Therefore, interest exists in expressing the biosynthetic pathways of these compounds in organisms that are more suitable for industrial production. Recent years have seen developments in both the discovery of various biosynthetic pathways, as well as development of metabolic engineering tools that allow reconstruction of complex pathways in microorganisms. In the present review we discuss recent advances in reconstruction of the biosynthetic pathways of various high-value products in the yeast Saccharomyces cerevisiae, a commonly used industrial microorganism. Key achievements in the production of different isoprenoids, aromatics and polyketides are presented and the metabolic engineering strategies underlying these accomplishments are discussed. PMID:25544013

  14. Mutations in Ran system affected telomere silencing in Saccharomyces cerevisiae

    SciTech Connect

    Hayashi, Naoyuki Kobayashi, Masahiko; Shimizu, Hiroko; Yamamoto, Ken-ichi; Murakami, Seishi; Nishimoto, Takeharu

    2007-11-23

    The Ran GTPase system regulates the direction and timing of several cellular events, such as nuclear-cytosolic transport, centrosome formation, and nuclear envelope assembly in telophase. To gain insight into the Ran system's involvement in chromatin formation, we investigated gene silencing at the telomere in several mutants of the budding yeast Saccharomyces cerevisiae, which had defects in genes involved in the Ran system. A mutation of the RanGAP gene, rna1-1, caused reduced silencing at the telomere, and partial disruption of the nuclear Ran binding factor, yrb2-{delta}2, increased this silencing. The reduced telomere silencing in rna1-1 cells was suppressed by a high dosage of the SIR3 gene or the SIT4 gene. Furthermore, hyperphosphorylated Sir3 protein accumulated in the rna1-1 mutant. These results suggest that RanGAP is required for the heterochromatin structure at the telomere in budding yeast.

  15. Domestication and Divergence of Saccharomyces cerevisiae Beer Yeasts.

    PubMed

    Gallone, Brigida; Steensels, Jan; Prahl, Troels; Soriaga, Leah; Saels, Veerle; Herrera-Malaver, Beatriz; Merlevede, Adriaan; Roncoroni, Miguel; Voordeckers, Karin; Miraglia, Loren; Teiling, Clotilde; Steffy, Brian; Taylor, Maryann; Schwartz, Ariel; Richardson, Toby; White, Christopher; Baele, Guy; Maere, Steven; Verstrepen, Kevin J

    2016-09-01

    Whereas domestication of livestock, pets, and crops is well documented, it is still unclear to what extent microbes associated with the production of food have also undergone human selection and where the plethora of industrial strains originates from. Here, we present the genomes and phenomes of 157 industrial Saccharomyces cerevisiae yeasts. Our analyses reveal that today's industrial yeasts can be divided into five sublineages that are genetically and phenotypically separated from wild strains and originate from only a few ancestors through complex patterns of domestication and local divergence. Large-scale phenotyping and genome analysis further show strong industry-specific selection for stress tolerance, sugar utilization, and flavor production, while the sexual cycle and other phenotypes related to survival in nature show decay, particularly in beer yeasts. Together, these results shed light on the origins, evolutionary history, and phenotypic diversity of industrial yeasts and provide a resource for further selection of superior strains. PAPERCLIP. PMID:27610566

  16. Energy-dependent effects of resveratrol in Saccharomyces cerevisiae.

    PubMed

    Madrigal-Perez, Luis Alberto; Canizal-Garcia, Melina; González-Hernández, Juan Carlos; Reynoso-Camacho, Rosalia; Nava, Gerardo M; Ramos-Gomez, Minerva

    2016-06-01

    The metabolic effects induced by resveratrol have been associated mainly with the consumption of high-calorie diets; however, its effects with standard or low-calorie diets remain unclear. To better understand the interactions between resveratrol and cellular energy levels, we used Saccharomyces cerevisiae as a model. Herein it is shown that resveratrol: (a) decreased cell viability in an energy-dependent manner; (b) lessening of cell viability occurred specifically when cells were under cellular respiration; and (c) inhibition of oxygen consumption in state 4 occurred at low and standard energy levels, whereas at high energy levels oxygen consumption was promoted. These findings indicate that the effects of resveratrol are dependent on the cellular energy status and linked to metabolic respiration. Importantly, our study also revealed that S. cerevisiae is a suitable and useful model to elucidate the molecular targets of resveratrol under different nutritional statuses. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26945517

  17. ROG1 encodes a monoacylglycerol lipase in Saccharomyces cerevisiae.

    PubMed

    Vishnu Varthini, Lakshmanaperumal; Selvaraju, Kandasamy; Srinivasan, Malathi; Nachiappan, Vasanthi

    2015-01-01

    Lipid metabolism is extensively studied in Saccharomyces cerevisiae. Here, we report that revertant of glycogen synthase kinase mutation-1 (Rog1p) possesses monoacylglycerol (MAG) lipase activity in S. cerevisiae. The lipase activity of Rog1p was confirmed in two ways: through analysis of a strain with a double deletion of ROG1 and monoglyceride lipase YJU3 (yju3Δrog1Δ) and by site-directed mutagenesis of the ROG1 lipase motif (GXSXG). Rog1p is localized in both the cytosol and the nucleus. Overexpression of ROG1 in a ROG1-deficient strain resulted in an accumulation of reactive oxygen species. These results suggest that Rog1p is a MAG lipase that regulates lipid homeostasis. PMID:25433290

  18. Exposure to benzene metabolites causes oxidative damage in Saccharomyces cerevisiae.

    PubMed

    Raj, Abhishek; Nachiappan, Vasanthi

    2016-06-01

    Hydroquinone (HQ) and benzoquinone (BQ) are known benzene metabolites that form reactive intermediates such as reactive oxygen species (ROS). This study attempts to understand the effect of benzene metabolites (HQ and BQ) on the antioxidant status, cell morphology, ROS levels and lipid alterations in the yeast Saccharomyces cerevisiae. There was a reduction in the growth pattern of wild-type cells exposed to HQ/BQ. Exposure of yeast cells to benzene metabolites increased the activity of the anti-oxidant enzymes catalase, superoxide dismutase and glutathione peroxidase but lead to a decrease in ascorbic acid and reduced glutathione. Increased triglyceride level and decreased phospholipid levels were observed with exposure to HQ and BQ. These results suggest that the enzymatic antioxidants were increased and are involved in the protection against macromolecular damage during oxidative stress; presumptively, these enzymes are essential for scavenging the pro-oxidant effects of benzene metabolites. PMID:27016252

  19. Tolerance of budding yeast Saccharomyces cerevisiae to ultra high pressure

    NASA Astrophysics Data System (ADS)

    Shibata, M.; Torigoe, M.; Matsumoto, Y.; Yamamoto, M.; Takizawa, N.; Hada, Y.; Mori, Y.; Takarabe, K.; Ono, F.

    2014-05-01

    Our studies on the tolerance of plants and animals against very high pressure of several GPa have been extended to a smaller sized fungus, the budding yeast Saccharomyces cerevisiae. Several pieces of budding yeast (dry yeast) were sealed in a small teflon capsule with a liquid pressure medium fluorinate, and exposed to 7.5 GPa by using a cubic anvil press. The pressure was kept constant for various duration of time from 2 to 24 h. After the pressure was released, the specimens were brought out from the teflon capsule, and they were cultivated on a potato dextrose agar. It was found that the budding yeast exposed to 7.5 GPa for up to 6 h showed multiplication. However, those exposed to 7.5 GPa for longer than 12 h were found dead. The high pressure tolerance of budding yeast is a little weaker than that of tardigrades.

  20. Functional attributes of the Saccharomyces cerevisiae meiotic recombinase Dmc1.

    PubMed

    Busygina, Valeria; Gaines, William A; Xu, Yuanyuan; Kwon, Youngho; Williams, Gareth J; Lin, Sheng-Wei; Chang, Hao-Yen; Chi, Peter; Wang, Hong-Wei; Sung, Patrick

    2013-09-01

    The role of Dmc1 as a meiosis-specific general recombinase was first demonstrated in Saccharomyces cerevisiae. Progress in understanding the biochemical mechanism of ScDmc1 has been hampered by its tendency to form inactive aggregates. We have found that the inclusion of ATP during protein purification prevents Dmc1 aggregation. ScDmc1 so prepared is capable of forming D-loops and responsive to its accessory factors Rad54 and Rdh54. Negative staining electron microscopy and iterative helical real-space reconstruction revealed that the ScDmc1-ssDNA nucleoprotein filament harbors 6.5 protomers per turn with a pitch of ∼106Å. The ScDmc1 purification procedure and companion molecular analyses should facilitate future studies on this recombinase. PMID:23769192

  1. Characterization of Encapsulated Berberine in Yeast Cells of Saccharomyces cerevisiae

    PubMed Central

    Salari, Roshanak; Rajabi, Omid; Khashyarmanesh, Zahra; Fathi Najafi, Mohsen; Fazly Bazzaz, BiBi Sedigheh

    2015-01-01

    Berberine was loaded in yeast cells of Saccharomyces cerevisiaeas a novel pharmaceutical carrier to improve the treatment ofmany diseases. The yeast-encapsulated active materialsshowedhigh stability and bioavailability due to the enhanced solubility and sustained releasing. In this study, different characteristics of prepared berberine loaded yeast cells (loading capacity, release kinetic order, MIC and stability) were evaluatedby different analytical methods (fluorescence spectroscopy, HPLC and SEM).The loading capacity was about 78% ± 0.6%.Berberine release patterns of microcapsules happened in two different stages and followed by zero and first-order kinetic,respectively. About 99% of all active material released during 34 h. MIC was improved by berberine loaded microcapsules in comparison withberberine powder. The microcapsules were completely stable. Berberine loaded Sac. Cerevisiae could be considered as a favorite sustained release drug delivery system. The yeast would be applied as an efficient carrier to improve various properties of different active materials. PMID:26664393

  2. Pt skin on Pd-Co-Zn/C ternary nanoparticles with enhanced Pt efficiency toward ORR

    NASA Astrophysics Data System (ADS)

    Xiao, Weiping; Zhu, Jing; Han, Lili; Liu, Sufen; Wang, Jie; Wu, Zexing; Lei, Wen; Xuan, Cuijuan; Xin, Huolin L.; Wang, Deli

    2016-08-01

    Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, a highly active, durable, carbon supported, and monolayer Pt coated Pd-Co-Zn nanoparticle is synthesized via a simple impregnation-reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition-activity volcano curve for the Pd-Co-Zn nanoparticles and determined that Pd : Co : Zn = 8 : 1 : 1 is the optimal composition. Compared with pure Pd/C, the Pd8CoZn/C nanoparticles show a substantial enhancement in both the catalytic activity and the durability toward the ORR. Moreover, the durability and activity are further enhanced by forming a Pt skin on Pd8CoZn/C nanocatalysts. Interestingly, after 10 000 potential cycles in N2-saturated 0.1 M HClO4 solution, Pd8CoZn@Pt/C shows improved mass activity (2.62 A mg-1Pt) and specific activity (4.76 A m-2total), which are about 1.4 and 4.4 times higher than the initial values, and 37.4 and 5.5 times higher than those of Pt/C catalysts, respectively. After accelerated stability testing in O2-saturated 0.1 M HClO4 solution for 30 000 potential cycles, the half-wave potential negatively shifts about 6 mV. The results show that the Pt skin plays an important role in enhancing the activity as well as preventing degradation.Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, a highly active, durable, carbon supported, and monolayer Pt coated Pd-Co-Zn nanoparticle is synthesized via a simple impregnation-reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition-activity volcano curve for the Pd-Co-Zn nanoparticles and determined that Pd : Co : Zn = 8

  3. Experimental measurements of the heats of formation of Fe{sub 3}Pt, FePt, and FePt{sub 3} using differential scanning calorimetry

    SciTech Connect

    Wang, B.; Berry, D. C.; Chiari, Y.; Barmak, K.

    2011-07-01

    Using differential scanning calorimetry (DSC), the heats of formation of Fe{sub 3}Pt, FePt, and FePt{sub 3} were determined from the reaction of sputter deposited Fe/Pt multilayer thin-films with a periodicity of 200 nm but different overall compositions. Film compositions were measured by energy dispersive x-ray spectrometry. The phases present along the reaction path were identified by x-ray diffraction. For the most Fe-rich phase, namely, Fe{sub 3}Pt, the measured enthalpy of formation was -9.3 {+-} 1.3 kJ/mol in a film with a composition of 70.4:29.6 ({+-}0.2 at. %) Fe:Pt. For FePt, the measured enthalpy of formation was -27.2 {+-} 2.2 kJ/g-atom in a 49.0:51.0 ({+-}0.5 at. %) Fe:Pt film. For FePt{sub 3}, which is the most Pt rich intermetallic phase, the measured enthalpy of formation was -23.7 {+-} 2.2 in a film with a composition of 22.2:77.8 ({+-}0.6 at. %) Fe:Pt. The reaction enthalpies for films with Fe:Pt compositions of 44.5:55.5 ({+-}0.3 at. %) and 38.5:61.5 ({+-}0.4 at. %) were -26.9 {+-} 1.0 and -26.6 {+-} 0.6 kJ/g-atom, respectively, which taken together with the value for the 49.0:51.0 film demonstrate the relative insensitivity of the reaction enthalpy to film composition over a broad composition range in the vicinity of the equiatomic composition. The experimental heats of formation are compared with two sets of reported first-principles calculated values for each of the three phases at exact stoichiometry.

  4. Proteomic characterization of a wild-type wine strain of Saccharomyces cerevisiae.

    PubMed

    Trabalzini, Lorenza; Paffetti, Alessandro; Ferro, Elisa; Scaloni, Andrea; Talamo, Fabio; Millucci, Lia; Martelli, Paola; Santucci, Annalisa

    2003-12-01

    Saccharomyces cerevisiae is the optimal eukaryotic model system to study mammalian biological responses. At the same time Saccharomyces cerevisiae is also widely utilized as a biotechnological tool in the food industry. Enological Saccharomyces cerevisiae strains have been so far routinely analyzed for their microbiological aspects. Nevertheless, wine yeasts are gaining an increasing interest in the last years since they strongly affect both the vinification process and the organoleptic properties of the final product wine. The protein repertoire is responsible of such features and, consequently, 2D-PAGE can be an useful tool to evaluate and select optimal wine yeast strains. We present here the first proteomic map of a wild-type wine Saccharomyces cerevisiae strain selected for the guided fermentation of very high quality wines. PMID:15141481

  5. Synthesis And Characterization of Pt Clusters in Aqueous Solutions

    SciTech Connect

    Siani, A.; Wigal, K.R.; Alexeev, O.S.; Amiridis, M.D.

    2009-05-26

    Extended X-ray absorption fine structure (EXAFS) and UV-visible (UV-vis) spectroscopies were used to monitor the various steps involved in the synthesis of unprotected and poly(vinyl alcohol) (PVA)-protected aqueous colloidal Pt suspensions. The results indicate that on hydrolysis of the H{sub 2}PtCl{sub 6} precursor, the Cl{sup -} ligands were partially replaced by aquo ligands in the first coordination shell of Pt to form [PtCl{sub 2}(H{sub 2}O){sub 4}]{sup 2+}. Treatment of these species with NaBH{sub 4} under controlled pH conditions led to the formation of nearly uniform Pt{sub 4} and Pt{sub 6} clusters in the absence and presence of PVA, respectively. These highly dispersed colloidal Pt suspensions were stable for several months. The addition of 2-propanol (IPA) to both types of Pt suspensions led to some sintering of the Pt clusters, although both suspensions retained their colloidal nature. Less sintering was evident in the PVA-protected Pt suspension. Both the unprotected and the PVA-protected colloidal Pt suspensions were catalytically active for the liquid-phase selective oxidation of 2-propanol to acetone, with the unprotected suspension exhibiting the highest activity.

  6. Copper Tolerance and Biosorption of Saccharomyces cerevisiae during Alcoholic Fermentation

    PubMed Central

    Liu, Ling-ling; Jia, Bo; Zhao, Fang; Huang, Wei-dong; Zhan, Ji-cheng

    2015-01-01

    At high levels, copper in grape mash can inhibit yeast activity and cause stuck fermentations. Wine yeast has limited tolerance of copper and can reduce copper levels in wine during fermentation. This study aimed to understand copper tolerance of wine yeast and establish the mechanism by which yeast decreases copper in the must during fermentation. Three strains of Saccharomyces cerevisiae (lab selected strain BH8 and industrial strains AWRI R2 and Freddo) and a simple model fermentation system containing 0 to 1.50 mM Cu2+ were used. ICP-AES determined Cu ion concentration in the must decreasing differently by strains and initial copper levels during fermentation. Fermentation performance was heavily inhibited under copper stress, paralleled a decrease in viable cell numbers. Strain BH8 showed higher copper-tolerance than strain AWRI R2 and higher adsorption than Freddo. Yeast cell surface depression and intracellular structure deformation after copper treatment were observed by scanning electron microscopy and transmission electron microscopy; electronic differential system detected higher surface Cu and no intracellular Cu on 1.50 mM copper treated yeast cells. It is most probably that surface adsorption dominated the biosorption process of Cu2+ for strain BH8, with saturation being accomplished in 24 h. This study demonstrated that Saccharomyces cerevisiae strain BH8 has good tolerance and adsorption of Cu, and reduces Cu2+ concentrations during fermentation in simple model system mainly through surface adsorption. The results indicate that the strain selected from China’s stress-tolerant wine grape is copper tolerant and can reduce copper in must when fermenting in a copper rich simple model system, and provided information for studies on mechanisms of heavy metal stress. PMID:26030864

  7. Optical studies of Pt-rich π--conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Drori, Tomer; Tong, M.; Gambetti, A.; Singh, S.; Yang, C.; Vardeny, Z. V.; Tretiak, S.

    2008-03-01

    We have used a variety of steady state and ultrafast spectroscopies for studying the photophysics of platinum-containing conjugated polymers, which have potential applications as the active layer of light-emitting diodes. The heavy metal Pt atom that is incorporated in the polymer chain dramatically increases the spin-orbit coupling, and this influences both the intersystem crossing time, TISC, and the phosphorescence emission intensity. The Pt-polymers were newly synthesized, where the intrachain Pt atom was incorporated into the polymer either in each (Pt-1) or in every three (Pt-3) monomer units. We will discuss an interesting effect for the photoexcited triplets, which dramatically influence the phosphorescence spectral shape vs. temperature. We also observed the existence of circular polarization memory of the phosphorescence emission in Pt-1 polymers, in which the platinum atoms are separated by only one phenyl ring; but not in Pt-3.

  8. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides.

    PubMed

    Lu, Shuanglong; Eid, Kamel; Li, Weifeng; Cao, Xueqin; Pan, Yue; Guo, Jun; Wang, Liang; Wang, Hongjing; Gu, Hongwei

    2016-01-01

    Tailoring the morphology of Pt nanocrystals (NCs) is of great concern for their enhancement in catalytic activity and durability. In this article, a novel synthetic strategy is developed to selectively prepare porous dendritic Pt NCs with different structures for oxygen reduction reaction (ORR) assisted by NH3 gas and halides (F(-), Cl(-), Br(-)). The NH3 gas plays critical roles on tuning the morphology. Previously, H2 and CO gas are reported to assist the shape control of metallic nanocrystals. This is the first demonstration that NH3 gas assists the Pt anisotropic growth. The halides also play important role in the synthetic strategy to regulate the formation of Pt NCs. As-made porous dendritic Pt NCs, especially when NH4F is used as a regulating reagent, show superior catalytic activity for ORR compared with commercial Pt/C catalyst and other previously reported Pt-based NCs. PMID:27184228

  9. Synthesis and Characterization of Cu-Pt Bimetallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Zheng, Xusheng; Liu, Shoujie; Chen, Xing; Cheng, Jie; Si, Cheng; Pan, Zhiyun; Marcelli, Augosto; Chu, Wangsheng; Wu, Ziyu

    2013-04-01

    Pt-based alloys have recently triggered a lot of attentions due to their important potential industrial applications. They provide great opportunities for the development of low-cost and high-performance fuel-cell catalysts. Many studies have already pointed out the excellent physico-chemical properties of Pt-based alloys, intimately related to their internal structure. Great efforts have been spent to characterize shape, homogeneity, dispersion, alloying extent and kinetic growth of Pt-based nano-particles. Here, we present Cu-Pt bimetallic nano-particles synthesized by the thermal decomposition method under oleylamine and OE coordination. HRTEM images show that Cu-Pt nanostructures having size of about 1.2 nm includes about 35 atoms capped by the surfactant with OA. Accurate structural information of this system has been obtained by XRD and XAFS. A charge transfer mechanism has been observed and Pt occupied Cu sites in these Cu-Pt nanoparticles.

  10. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides

    PubMed Central

    Lu, Shuanglong; Eid, Kamel; Li, Weifeng; Cao, Xueqin; Pan, Yue; Guo, Jun; Wang, Liang; Wang, Hongjing; Gu, Hongwei

    2016-01-01

    Tailoring the morphology of Pt nanocrystals (NCs) is of great concern for their enhancement in catalytic activity and durability. In this article, a novel synthetic strategy is developed to selectively prepare porous dendritic Pt NCs with different structures for oxygen reduction reaction (ORR) assisted by NH3 gas and halides (F−, Cl−, Br−). The NH3 gas plays critical roles on tuning the morphology. Previously, H2 and CO gas are reported to assist the shape control of metallic nanocrystals. This is the first demonstration that NH3 gas assists the Pt anisotropic growth. The halides also play important role in the synthetic strategy to regulate the formation of Pt NCs. As-made porous dendritic Pt NCs, especially when NH4F is used as a regulating reagent, show superior catalytic activity for ORR compared with commercial Pt/C catalyst and other previously reported Pt-based NCs. PMID:27184228

  11. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides

    NASA Astrophysics Data System (ADS)

    Lu, Shuanglong; Eid, Kamel; Li, Weifeng; Cao, Xueqin; Pan, Yue; Guo, Jun; Wang, Liang; Wang, Hongjing; Gu, Hongwei

    2016-05-01

    Tailoring the morphology of Pt nanocrystals (NCs) is of great concern for their enhancement in catalytic activity and durability. In this article, a novel synthetic strategy is developed to selectively prepare porous dendritic Pt NCs with different structures for oxygen reduction reaction (ORR) assisted by NH3 gas and halides (F‑, Cl‑, Br‑). The NH3 gas plays critical roles on tuning the morphology. Previously, H2 and CO gas are reported to assist the shape control of metallic nanocrystals. This is the first demonstration that NH3 gas assists the Pt anisotropic growth. The halides also play important role in the synthetic strategy to regulate the formation of Pt NCs. As-made porous dendritic Pt NCs, especially when NH4F is used as a regulating reagent, show superior catalytic activity for ORR compared with commercial Pt/C catalyst and other previously reported Pt-based NCs.

  12. Magnetic hardening in FePt nanostructured films

    SciTech Connect

    Liu, J.P.; Liu, Y.; Luo, C.P.; Shan, Z.S.; Sellmyer, D.J.

    1997-04-01

    FePt films have been prepared by sputtering Fe/Pt multilayers onto glass or silicon substrates. The thickness of the Fe and Pt layers was adjusted with the Fe:Pt atomic ratio from about 1:1 to 2:1. Magnetic hardening is observed after heat treatment at elevated temperatures, which led to coercivity values exceeding 20 kOe in samples with an Fe:Pt ratio around 1.2:1. The hardening originates from the formation of the tetragonal FePt phase with high magnetocrystalline anisotropy and a favorable microstructure. Two-phase composite films containing hard and soft phases were obtained when the Fe:Pt ratio increased. Under optimized processing conditions, composite films with energy products larger than 30 MGOe at room temperature have been successfully produced. {copyright} {ital 1997 American Institute of Physics.}

  13. Magnetic hardening in FePt nanostructured films

    NASA Astrophysics Data System (ADS)

    Liu, J. P.; Liu, Y.; Luo, C. P.; Shan, Z. S.; Sellmyer, D. J.

    1997-04-01

    FePt films have been prepared by sputtering Fe/Pt multilayers onto glass or silicon substrates. The thickness of the Fe and Pt layers was adjusted with the Fe:Pt atomic ratio from about 1:1 to 2:1. Magnetic hardening is observed after heat treatment at elevated temperatures, which led to coercivity values exceeding 20 kOe in samples with an Fe:Pt ratio around 1.2:1. The hardening originates from the formation of the tetragonal FePt phase with high magnetocrystalline anisotropy and a favorable microstructure. Two-phase composite films containing hard and soft phases were obtained when the Fe:Pt ratio increased. Under optimized processing conditions, composite films with energy products larger than 30 MG Oe at room temperature have been successfully produced.

  14. Pt skin on Pd-Co-Zn/C ternary nanoparticles with enhanced Pt efficiency toward ORR.

    PubMed

    Xiao, Weiping; Zhu, Jing; Han, Lili; Liu, Sufen; Wang, Jie; Wu, Zexing; Lei, Wen; Xuan, Cuijuan; Xin, Huolin L; Wang, Deli

    2016-08-21

    Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, a highly active, durable, carbon supported, and monolayer Pt coated Pd-Co-Zn nanoparticle is synthesized via a simple impregnation-reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition-activity volcano curve for the Pd-Co-Zn nanoparticles and determined that Pd : Co : Zn = 8 : 1 : 1 is the optimal composition. Compared with pure Pd/C, the Pd8CoZn/C nanoparticles show a substantial enhancement in both the catalytic activity and the durability toward the ORR. Moreover, the durability and activity are further enhanced by forming a Pt skin on Pd8CoZn/C nanocatalysts. Interestingly, after 10 000 potential cycles in N2-saturated 0.1 M HClO4 solution, Pd8CoZn@Pt/C shows improved mass activity (2.62 A mg(-1)Pt) and specific activity (4.76 A m(-2)total), which are about 1.4 and 4.4 times higher than the initial values, and 37.4 and 5.5 times higher than those of Pt/C catalysts, respectively. After accelerated stability testing in O2-saturated 0.1 M HClO4 solution for 30 000 potential cycles, the half-wave potential negatively shifts about 6 mV. The results show that the Pt skin plays an important role in enhancing the activity as well as preventing degradation. PMID:27445114

  15. Water treatment process and system for metals removal using Saccharomyces cerevisiae

    DOEpatents

    Krauter, Paula A. W.; Krauter, Gordon W.

    2002-01-01

    A process and a system for removal of metals from ground water or from soil by bioreducing or bioaccumulating the metals using metal tolerant microorganisms Saccharomyces cerevisiae. Saccharomyces cerevisiae is tolerant to the metals, able to bioreduce the metals to the less toxic state and to accumulate them. The process and the system is useful for removal or substantial reduction of levels of chromium, molybdenum, cobalt, zinc, nickel, calcium, strontium, mercury and copper in water.

  16. Effect of nitrogen upon structural and magnetic properties of FePt in FePt/AlN multilayer structures

    SciTech Connect

    Gao, Tenghua Zhang, Cong; Sannomiya, Takumi; Muraishi, Shinji; Nakamura, Yoshio; Shi, Ji

    2014-09-01

    This paper investigates the effect of the addition of nitrogen in FePt layers for ultrathin FePt/AlN multilayer structures. X-ray diffraction results reveal that a compressive stress relaxation occurs after annealing owing to the release of interstitial nitrogen atoms in the FePt layers. The introduction of nitrogen also induces a large in-plane compressive strain during grain growth not seen in FePt deposited without nitrogen. This strain is considered to decrease the driving force for (111) grain growth and FePt ordering.

  17. Transforming AdaPT to Ada

    NASA Technical Reports Server (NTRS)

    Goldsack, Stephen J.; Holzbach-Valero, A. A.; Waldrop, Raymond S.; Volz, Richard A.

    1991-01-01

    This paper describes how the main features of the proposed Ada language extensions intended to support distribution, and offered as possible solutions for Ada9X can be implemented by transformation into standard Ada83. We start by summarizing the features proposed in a paper (Gargaro et al, 1990) which constitutes the definition of the extensions. For convenience we have called the language in its modified form AdaPT which might be interpreted as Ada with partitions. These features were carefully chosen to provide support for the construction of executable modules for execution in nodes of a network of loosely coupled computers, but flexibly configurable for different network architectures and for recovery following failure, or adapting to mode changes. The intention in their design was to provide extensions which would not impact adversely on the normal use of Ada, and would fit well in style and feel with the existing standard. We begin by summarizing the features introduced in AdaPT.

  18. Adsorption of maleic anhydride on Pt(111)

    NASA Astrophysics Data System (ADS)

    Sinha, Godhuli; Heikkinen, Olli; Vestberg, Matias; Mether, Lotta; Nordlund, Kai; Lahtinen, Jouko

    2014-02-01

    The surface chemistry of maleic anhydride (MA) has been studied on Pt(111) with temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Adsorption of MA takes place at 170 K forming multilayers. We have studied the behavior of distinct carbon and oxygen species of MA depending on the surface temperature. MA-TPD indicates three main desorption temperatures; at 240 K, approximately 60% of total MA on the surface shows molecular desorption. At high temperatures (360 and 550 K) MA shows dissociative decomposition with production of C2H2, CO and CO2 fragments. A plausible decomposition pathway of MA on the Pt(111) surface is discussed. DFT calculations provide details of the adsorption geometry.

  19. Integrability of PT-symmetric dimers

    NASA Astrophysics Data System (ADS)

    Pickton, J.; Susanto, H.

    2013-12-01

    The coupled discrete linear and Kerr nonlinear Schrödinger equations with gain and loss describing transport on dimers with parity-time (PT)-symmetric potentials are considered. The model is relevant among others to experiments in optical couplers and proposals on Bose-Einstein condensates in PT-symmetric double-well potentials. It is known that the models are integrable. Here, the integrability is exploited further to construct the phase portraits of the system. A pendulum equation with a linear potential and a constant force for the phase difference between the fields is obtained, which explains the presence of unbounded solutions above a critical threshold parameter. The behavior of all solutions of the system, including changes in the topological structure of the phase plane, is then discussed.

  20. Magnetic properties of ordered NiPt

    NASA Astrophysics Data System (ADS)

    Brommer, P. E.; Franse, J. J. M.

    1988-04-01

    Thermal expansion, forced volume magnetostriction and high magnetic field data are presented on the ordered equiatomic NiPt compound. Values are derived for the magnetovolume parameter κC (≃3 × 10 -6kg2A-2m-4), and for the electronic and lattice Grüneisen parameters (Γ e ≊ 5.6; Γ latt ≊ 2.5) . Ordering effects on the magnetoelastic properties are studied for alloys containing 40-60 at % Ni.

  1. Evidence for Divergent Evolution of Growth Temperature Preference in Sympatric Saccharomyces Species

    PubMed Central

    Gonçalves, Paula; Valério, Elisabete; Correia, Cláudia; de Almeida, João M. G. C. F.; Sampaio, José Paulo

    2011-01-01

    The genus Saccharomyces currently includes eight species in addition to the model yeast Saccharomyces cerevisiae, most of which can be consistently isolated from tree bark and soil. We recently found sympatric pairs of Saccharomyces species, composed of one cryotolerant and one thermotolerant species in oak bark samples of various geographic origins. In order to contribute to explain the occurrence in sympatry of Saccharomyces species, we screened Saccharomyces genomic data for protein divergence that might be correlated to distinct growth temperature preferences of the species, using the dN/dS ratio as a measure of protein evolution rates and pair-wise species comparisons. In addition to proteins previously implicated in growth at suboptimal temperatures, we found that glycolytic enzymes were among the proteins exhibiting higher than expected divergence when one cryotolerant and one thermotolerant species are compared. By measuring glycolytic fluxes and glycolytic enzymatic activities in different species and at different temperatures, we subsequently show that the unusual divergence of glycolytic genes may be related to divergent evolution of the glycolytic pathway aligning its performance to the growth temperature profiles of the different species. In general, our results support the view that growth temperature preference is a trait that may have undergone divergent selection in the course of ecological speciation in Saccharomyces. PMID:21674061

  2. Interface induced manipulation of perpendicular exchange bias in Pt/Co/(Pt,Cr)/CoO thin films

    NASA Astrophysics Data System (ADS)

    Akdoğan, N.; Yağmur, A.; Öztürk, M.; Demirci, E.; Öztürk, O.; Erkovan, M.

    2015-01-01

    Perpendicular exchange bias has been manipulated by changing ferromagnetic film thickness and spacer layer in Pt/Co/(Pt,Cr)/CoO thin films. The exchange bias characteristics, blocking temperature, and magnetization of thin films strongly depend on the spacer layer (Pt,Cr) between ferromagnetic and antiferromagnetic layers. While Pt/Co/Pt/CoO thin films show perpendicular exchange bias, Pt/Co/Cr/CoO has exchange bias with easy magnetization axis in the film plane. We have also observed very small hysteretic behavior from the hard axis magnetization curve of Pt/Co/Cr/CoO film. This can be attributed to misalignment of the sample or small perpendicular contribution from Pt/Co bottom interface. We have also investigated the temperature and spacer layer dependent exchange bias properties of the samples. We observed higher HEB and HC for the thicker Co layer in the Pt/Co/Pt/CoO sample. In addition, onset of exchange bias effect starts at much lower temperatures for Pt/Co/Cr/CoO thin film. This clearly shows that Cr spacer layer not only removes the perpendicular exchange bias, but also reduces the exchange interaction between Co and CoO and thus lowers the TB.

  3. First principles calculations of the effect of Pt on NiAl surfaceenergy and the site preference of Pt

    SciTech Connect

    Yu, Rong; Hou, Peggy Y.

    2007-03-08

    Pt-modified NiAl is widely used as a coating material in industry. In this study, the surface energies of NiAl with and without Pt are investigated using first-principles calculations. The presence of Pt in NiAl takes the surface electronic states to higher energies, resulting in an increased surface energy, which explains some of the beneficial effects of Pt on the oxidation resistance of NiAl. The electronic structure of NiAl-Pt alloys is also analyzed in terms of the site preference of Pt in NiAl. Results show that Pt bonds strongly to Al, giving its site preference on the Ni site.

  4. Interlayer exchange coupling in [Pt/Co]n/MgO/[Co/Pt]2 perpendicular magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Li, Lei; Han, Dong; Lei, Wenguang; Liu, Zhongyuan; Zhang, Fang; Mao, Xiaonan; Wang, Pengwei; Hou, Hongmiao

    2014-09-01

    In this paper, we present further study on the interlayer exchange coupling of [Pt/Co]n/MgO/[Co/Pt]2 perpendicular magnetic tunnel junctions. Antiferromagnetic interlayer couplings in [Pt/Co]n/MgO/[Co/Pt]2 are observed. The strength of antiferromagnetic coupling oscillates irregularly with the repetition number n, that may be related to the Ruderman-Kittel-Kasuya-Yosida (RKKY)-type ferromagnetic interlayer coupling existing in the [Pt/Co]n hard layer. The interlayer coupling of [Pt/Co]9/MgO(22 Å)/[Co/Pt]2 magnetic tunnel junction reaches a maximum at 200 K, and decreases gradually with increasing temperature. This thermal behavior of interlayer coupling may be related to the enhanced perpendicular magnetic anisotropy of hard layer with decreasing temperature.

  5. Magic number Pt13 and misshapen Pt12 clusters: which one is the better catalyst?

    PubMed

    Imaoka, Takane; Kitazawa, Hirokazu; Chun, Wang-Jae; Omura, Saori; Albrecht, Ken; Yamamoto, Kimihisa

    2013-09-01

    A relationship between the size of metal particles and their catalytic activity has been established over a nanometer scale (2-10 nm). However, application on a subnanometer scale (0.5-2 nm) is difficult, a possible reason being that the activity no longer relies on the size but rather the geometric structure as a cluster (or superatomic) compound. We now report that the catalytic activity for the oxygen reduction reaction (ORR) significantly increased when only one atom was removed from a magic number cluster composed of 13-platinum atoms (Pt13). The synthesis with an atomic-level precision was successfully achieved by using a dendrimer ligand as the macromolecular template strictly defining the number of metal atoms. It was quite surprising that the Pt12 cluster exhibited more than 2-fold catalytic activity compared with that of the Pt13 cluster. ESI-TOF-mass and EXAFS analyses provided information about the structures. These analyses suggested that the Pt12 has a deformed coordination, while the Pt13 has a well-known icosahedral atomic coordination as part of the stable cluster series. Theoretical analyses based on density functional theory (DFT) also supported this idea. The present results suggest potential activity of the metastable clusters although they have been "missing" species in conventional statistical synthesis. PMID:23902457

  6. Atomic-scale redistribution of Pt during reactive diffusion in Ni (5% Pt)-Si contacts.

    PubMed

    Cojocaru-Mirédin, O; Cadel, E; Blavette, D; Mangelinck, D; Hoummada, K; Genevois, C; Deconihout, B

    2009-06-01

    The NiSi silicide that forms by reactive diffusion between Ni and Si active regions of nanotransistors is used nowadays as contacts in nanoelectronics because of its low resistivity. Pt is added to the Ni film in order to stabilise the NiSi phase against the formation of the high-resistivity NiSi(2) phase and agglomeration. In situ X-ray diffraction (XRD) experiments performed on material aged at 350 degrees C (under vacuum) showed the complete consumption of the Ni (5 at% Pt) phase, the regression of Ni(2)Si phase as well as the growth of the NiSi phase after 48 min. Pt distribution for this heat treatment has been analysed by laser-assisted tomographic atom probe (LATAP). An enrichment of platinum in the middle of the NiSi phase suggests that Pt is almost immobile during the growth of NiSi at the two interfaces: Ni(2)Si/NiSi and NiSi/Si. In the peak, platinum was found to substitute for Ni in the NiSi phase. Very small amounts of Pt were also found in the Ni(2)Si phase close to the surface and at the NiSi/Si interface. PMID:19339118

  7. Pd surface and Pt subsurface segregation in Pt1-c Pd c nanoalloys.

    PubMed

    De Clercq, A; Giorgio, S; Mottet, C

    2016-02-17

    The structure and chemical arrangement of Pt1-c Pd c nanoalloys with the icosahedral and face centered cubic symmetry are studied using Monte Carlo simulations with a tight binding interatomic potential fitted to density-functional theory calculations. Pd surface segregation from the lowest to the highest coordinated sites is predicted by the theory together with a Pt enrichment at the subsurface, whatever the structure and the size of the nanoparticles, and which subsists when increasing the temperature. The onion-shell chemical configuration is found for both symmetries and is initiated from the Pd surface segregation. It is amplified in the icosahedral symmetry and small sizes but when considering larger sizes, the oscillating segregation profile occurs near the surface on about three to four shells whatever the structure. Pd segregation results from the significant lower cohesive energy of Pd as compared to Pt and the weak ordering tendency leads to the Pt subsurface segregation. The very weak size mismatch does not prevent the bigger atoms (Pt) from occupying subsurface sites which are in compression whereas the smaller ones (Pd) occupy the central site of the icosahedra where the compression is an order of magnitude higher. PMID:26795206

  8. Pd surface and Pt subsurface segregation in Pt1-c Pd c nanoalloys

    NASA Astrophysics Data System (ADS)

    De Clercq, A.; Giorgio, S.; Mottet, C.

    2016-02-01

    The structure and chemical arrangement of Pt1-c Pd c nanoalloys with the icosahedral and face centered cubic symmetry are studied using Monte Carlo simulations with a tight binding interatomic potential fitted to density-functional theory calculations. Pd surface segregation from the lowest to the highest coordinated sites is predicted by the theory together with a Pt enrichment at the subsurface, whatever the structure and the size of the nanoparticles, and which subsists when increasing the temperature. The onion-shell chemical configuration is found for both symmetries and is initiated from the Pd surface segregation. It is amplified in the icosahedral symmetry and small sizes but when considering larger sizes, the oscillating segregation profile occurs near the surface on about three to four shells whatever the structure. Pd segregation results from the significant lower cohesive energy of Pd as compared to Pt and the weak ordering tendency leads to the Pt subsurface segregation. The very weak size mismatch does not prevent the bigger atoms (Pt) from occupying subsurface sites which are in compression whereas the smaller ones (Pd) occupy the central site of the icosahedra where the compression is an order of magnitude higher.

  9. Xylose Isomerase Improves Growth and Ethanol Production Rates from Biomass Sugars for Both Saccharomyces Pastorianus and Saccharomyces Cerevisiae

    PubMed Central

    Miller, Kristen P.; Gowtham, Yogender Kumar; Henson, J. Michael; Harcum, Sarah W.

    2013-01-01

    The demand for biofuel ethanol made from clean, renewable nonfood sources is growing. Cellulosic biomass, such as switch grass (Panicum virgatum L.), is an alternative feedstock for ethanol production; however, cellulosic feedstock hydrolysates contain high levels of xylose, which needs to be converted to ethanol to meet economic feasibility. In this study, the effects of xylose isomerase on cell growth and ethanol production from biomass sugars representative of switch grass were investigated using low cell density cultures. The lager yeast species Saccharomyces pastorianus was grown with immobilized xylose isomerase in the fermentation step to determine the impact of the glucose and xylose concentrations on the ethanol production rates. Ethanol production rates were improved due to xylose isomerase; however, the positive effect was not due solely to the conversion of xylose to xylulose. Xylose isomerase also has glucose isomerase activity, so to better understand the impact of the xylose isomerase on S. pastorianus, growth and ethanol production were examined in cultures provided fructose as the sole carbon. It was observed that growth and ethanol production rates were higher for the fructose cultures with xylose isomerase even in the absence of xylose. To determine whether the positive effects of xylose isomerase extended to other yeast species, a side-by-side comparison of S. pastorianus and Saccharomyces cerevisiae was conducted. These comparisons demonstrated that the xylose isomerase increased ethanol productivity for both the yeast species by increasing the glucose consumption rate. These results suggest that xylose isomerase can contribute to improved ethanol productivity, even without significant xylose conversion. PMID:22866331

  10. Ecological Success of a Group of Saccharomyces cerevisiae/Saccharomyces kudriavzevii Hybrids in the Northern European Wine-Making Environment

    PubMed Central

    Erny, C.; Raoult, P.; Alais, A.; Butterlin, G.; Delobel, P.; Matei-Radoi, F.; Casaregola, S.

    2012-01-01

    The hybrid nature of lager-brewing yeast strains has been known for 25 years; however, yeast hybrids have only recently been described in cider and wine fermentations. In this study, we characterized the hybrid genomes and the relatedness of the Eg8 industrial yeast strain and of 24 Saccharomyces cerevisiae/Saccharomyces kudriavzevii hybrid yeast strains used for wine making in France (Alsace), Germany, Hungary, and the United States. An array-based comparative genome hybridization (aCGH) profile of the Eg8 genome revealed a typical chimeric profile. Measurement of hybrids DNA content per cell by flow cytometry revealed multiple ploidy levels (2n, 3n, or 4n), and restriction fragment length polymorphism analysis of 22 genes indicated variable amounts of S. kudriavzevii genetic content in three representative strains. We developed microsatellite markers for S. kudriavzevii and used them to analyze the diversity of a population isolated from oaks in Ardèche (France). This analysis revealed new insights into the diversity of this species. We then analyzed the diversity of the wine hybrids for 12 S. cerevisiae and 7 S. kudriavzevii microsatellite loci and found that these strains are the products of multiple hybridization events between several S. cerevisiae wine yeast isolates and various S. kudriavzevii strains. The Eg8 lineage appeared remarkable, since it harbors strains found over a wide geographic area, and the interstrain divergence measured with a (δμ)2 genetic distance indicates an ancient origin. These findings reflect the specific adaptations made by S. cerevisiae/S. kudriavzevii cryophilic hybrids to winery environments in cool climates. PMID:22344648

  11. Ecological success of a group of Saccharomyces cerevisiae/Saccharomyces kudriavzevii hybrids in the northern european wine-making environment.

    PubMed

    Erny, C; Raoult, P; Alais, A; Butterlin, G; Delobel, P; Matei-Radoi, F; Casaregola, S; Legras, J L

    2012-05-01

    The hybrid nature of lager-brewing yeast strains has been known for 25 years; however, yeast hybrids have only recently been described in cider and wine fermentations. In this study, we characterized the hybrid genomes and the relatedness of the Eg8 industrial yeast strain and of 24 Saccharomyces cerevisiae/Saccharomyces kudriavzevii hybrid yeast strains used for wine making in France (Alsace), Germany, Hungary, and the United States. An array-based comparative genome hybridization (aCGH) profile of the Eg8 genome revealed a typical chimeric profile. Measurement of hybrids DNA content per cell by flow cytometry revealed multiple ploidy levels (2n, 3n, or 4n), and restriction fragment length polymorphism analysis of 22 genes indicated variable amounts of S. kudriavzevii genetic content in three representative strains. We developed microsatellite markers for S. kudriavzevii and used them to analyze the diversity of a population isolated from oaks in Ardèche (France). This analysis revealed new insights into the diversity of this species. We then analyzed the diversity of the wine hybrids for 12 S. cerevisiae and 7 S. kudriavzevii microsatellite loci and found that these strains are the products of multiple hybridization events between several S. cerevisiae wine yeast isolates and various S. kudriavzevii strains. The Eg8 lineage appeared remarkable, since it harbors strains found over a wide geographic area, and the interstrain divergence measured with a (δμ)(2) genetic distance indicates an ancient origin. These findings reflect the specific adaptations made by S. cerevisiae/S. kudriavzevii cryophilic hybrids to winery environments in cool climates. PMID:22344648

  12. A comparative theoretical study for the methanol dehydrogenation to CO over Pt3 and PtAu2 clusters.

    PubMed

    Zhong, Wenhui; Liu, Yuxia; Zhang, Dongju

    2012-07-01

    The density functional theory (DFT) calculations are carried out to study the mechanism details and the ensemble effect of methanol dehydrogenation over Pt(3) and PtAu(2) clusters, which present the smallest models of pure Pt clusters and bimetallic PtAu clusters. The energy diagrams are drawn out along both the initial O-H and C-H bond scission pathways via the four sequential dehydrogenation processes, respectively, i.e., CH(3)OH → CH(2)OH → CH(2)O → CHO → CO and CH(3)OH → CH(3)O → CH(2)O → CHO → CO, respectively. It is revealed that the reaction kinetics over PtAu(2) is significantly different from that over Pt(3). For the Pt(3)-mediated reaction, the C-H bond scission pathway, where an ensemble composed of two Pt atoms is required to complete methanol dehydrogenation, is energetically more favorable than the O-H bond scission pathway, and the maximum barrier along this pathway is calculated to be 12.99 kcal mol(-1). In contrast, PtAu(2) cluster facilitates the reaction starting from the O-H bond scission, where the Pt atom acts as the active center throughout each elementary step of methanol dehydrogenation, and the initial O-H bond scission with a barrier of 21.42 kcal mol(-1) is the bottom-neck step of methanol decomposition. Importantly, it is shown that the complete dehydrogenation product of methanol, CO, can more easily dissociate from PtAu(2) cluster than from Pt(3) cluster. The calculated results over the model clusters provide assistance to some extent for understanding the improved catalytic activity of bimetal PtAu catalysts toward methanol oxidation in comparison with pure Pt catalysts. PMID:22160734

  13. Spatially Resolved Electronic Alterations As Seen by in Situ 195Pt and 13CO NMR in Ru@Pt and Au@Pt Core-Shell Nanoparticles

    SciTech Connect

    Atienza, Dianne O.; Allison, Thomas C.; Tong, Yu ye J.

    2012-12-20

    Pt-based core-shell (M@Pt where M stands for core element) nanoparticles (NPs) have recently been under increasing scrutiny in the fields of fuel cell and lithium air battery electrocatalysis due to their promising prospects in optimizing catalytic activity, reducing Pt loading and consequently lowering its cost. To achieve the latter, delineating spatially resolved local (surface) elemental distribution and associated variations in electronic properties under working condition (i.e., in situ) is arguably a prerequisite of fundamental importance in investigating electrocatalysis but unfortunately is still sorely missing. In this regard, in situ 195Pt electrochemical NMR (EC-NMR) of Pt-based NPs is unique in terms of accessing such information, particularly the spatially resolved partition between the sand d-like Fermi level local density of states (Ef-LDOS) modified by the core elements. In this paper, we report a comparative in situ 195Pt EC-NMR investigation of Ru@Pt vs Au@Pt NPs which was complemented by in situ 13C EC-NMR of the 13CO adsorbed on the respective NPs generated via dissociation of methanol and by ab initio DFT calculations. The obtained results showed opposing electronic effect between Ru vs Au cores: the former reduced substantially the s-like but not the d-like Ef-LDOS of the Pt shell while the latter did the opposite. According to recent quantum calculations, a reduction in d-like partition would weaken the Pt-O bond while a reduction in s-like partition would weaken the Pt-H bond, which is largely in agreement with experimental observations.

  14. High Anisotropy CoPtCrB Magnetic Recording Media

    SciTech Connect

    Toney, Michael F

    2003-06-17

    We describe the synthesis, magnetism and structure of CoPtCrB alloys with Pt concentrations from 10-43%. The Cr concentration in the alloys was 15-17% and the B concentration was 9-11%. The magnetic anisotropy and coercivity increase with increasing Pt up to {approx} 30%, plateau at {approx} 35,000 Oe and {approx} 6000 Oe, respectively, and then decrease. Transmission electron microscopy results show the media form fine, isolated grains for all Pt concentrations. X-ray diffraction measurements show that with increasing Pt an fcc Co-alloy phase is progressively formed at the expense of the hcp Co-alloy and that this fraction becomes significant for > 35% Pt. The formation of the fcc phase likely causes the behavior in the anisotropy. No Pt concentration dependence is observed for the stacking fault density. The X-ray data show that with increasing Pt the CoPtCrB alloy lattice parameters exhibit two distinct regions with the slope changing at 16% Pt. The presence of these two regions is discussed.

  15. Monodispersed Fe-Pt nanoparticles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Kim, Do Kyung; Kan, Ding; Veres, Teodor; Normadin, Francois; Liao, James K.; Kim, Hyung Hwan; Lee, Se-Hee; Zahn, Markus; Muhammed, Mamoun

    2005-05-01

    Monodispersed Fe-Pt nanoparticles are promising candidates for biomedical applications with an average particle diameter of 6.9nmFe48Pt52, 3.3nmFe52Pt48, and 4.2nmFe70Pt30. They are prepared by simultaneous chemical reduction of Pt(acac)2 and thermal decomposition of Fe(CO)5 in the presence of surfactant as an anti-oxidation reagent and amine as a stabilizer. The blocking temperatures, Tb, of 9 K for Fe70Pt30, 11 K for Fe52Pt48 and 14.4 K for Fe48Pt52 and the mean diameter of the spherical magnetic particles were estimated from the calculated volume to be 3.6, 3.1, and 3.8 nm. The cytotoxicity of unmodified Fe-Pt nanoparticles was performed in brain endothelial cells. Fe48Pt52 nanoparticles were not found to have any significant toxicity on bEnd3 cells during a 24 h period.

  16. Alcohol electrooxidation at Pt and Pt-Ru sputtered electrodes under elevated temperature and pressurized conditions

    NASA Astrophysics Data System (ADS)

    Umeda, Minoru; Sugii, Hiromasa; Uchida, Isamu

    2008-05-01

    The electrooxidation properties of methanol and 2-propanol, which are both promising candidates for direct alcohol fuel cells (DAFCs), have been studied under elevated temperature and pressurized conditions. Sputter-deposited Pt and Pt-Ru electrodes were well-characterized and utilized for the electrochemical measurement of the alcohol oxidation at 25-100 °C. The Pt electrode prepared at 600 °C had a flat surface, and the Pt-Ru formed an alloy. The electrochemical measurements were carried out in a gas-tight cell under elevated temperature, which accompanies the pressurized condition. This is a representative example of the DAFC rising temperature operation. As a result, at 25 °C, the onset potential of the 2-propanol oxidation is about 400 mV more negative than that of the methanol oxidation, and current density of the 2-propanol oxidation exceeds that of the methanol oxidation. Conversely, at 100 °C, the methanol oxidation current density overcomes that of 2-propanol, and the onset potentials of the two are almost the same. The highest current density for the methanol oxidation is obtained at the Pt:Ru = 50:50 electrode, whereas at the Pt:Ru = 35:65 for the 2-propanol oxidation. A Tafel plot analysis was employed to investigate the reaction mechanism. For the methanol oxidation, the number of electrons transferred during the rate-determining process is estimated to be 1 at 25 °C and 2 at 100 °C. This suggests that the methanol reaction mechanism differs at 25 and 100 °C. In contrast, the rate-determining process of the 2-propanol oxidation at 25 and 100 °C was expected to be 1-electron transfer which accompanies the proton-elimination reaction to produce acetone. Consequently, it is deduced that methanol and 2-propanol have an advantage under the rising temperature and room temperature operation, respectively.

  17. The mechanism of charge density wave in Pt-based layered superconductors: SrPt2As2 and LaPt2Si2

    PubMed Central

    Kim, Sooran; Kim, Kyoo; Min, B. I.

    2015-01-01

    The intriguing coexistence of the charge density wave (CDW) and superconductivity in SrPt2As2 and LaPt2Si2 has been investigated based on the ab initio density functional theory band structure and phonon calculations. We have found that the CDW instabilities for both cases arise from the q-dependent electron-phonon coupling with quasi-nesting feature of the Fermi surface. The band structure obtained by the band-unfolding technique reveals the sizable q-dependent electron-phonon coupling responsible for the CDW instability. The local split distortions of Pt atoms in the [As-Pt-As] layers play an essential role in driving the five-fold supercell CDW instability as well as the phonon softening instability in SrPt2As2. By contrast, the CDW and phonon softening instabilities in LaPt2Si2 occur without split distortions of Pt atoms. The phonon calculations suggest that the CDW and the superconductivity coexist in [X-Pt-X] layers (X = As or Si) for both cases. PMID:26449877

  18. The mechanism of charge density wave in Pt-based layered superconductors: SrPt2As2 and LaPt2Si2.

    PubMed

    Kim, Sooran; Kim, Kyoo; Min, B I

    2015-01-01

    The intriguing coexistence of the charge density wave (CDW) and superconductivity in SrPt2As2 and LaPt2Si2 has been investigated based on the ab initio density functional theory band structure and phonon calculations. We have found that the CDW instabilities for both cases arise from the q-dependent electron-phonon coupling with quasi-nesting feature of the Fermi surface. The band structure obtained by the band-unfolding technique reveals the sizable q-dependent electron-phonon coupling responsible for the CDW instability. The local split distortions of Pt atoms in the [As-Pt-As] layers play an essential role in driving the five-fold supercell CDW instability as well as the phonon softening instability in SrPt2As2. By contrast, the CDW and phonon softening instabilities in LaPt2Si2 occur without split distortions of Pt atoms. The phonon calculations suggest that the CDW and the superconductivity coexist in [X-Pt-X] layers (X = As or Si) for both cases. PMID:26449877

  19. Impedance spectroscopy of resistance switching in a Pt/NiO/Pt capacitor

    NASA Astrophysics Data System (ADS)

    Na, Sang-Chul; Chun, Min Chul; Kim, Jae-Jun; Shon, Jungwook; Jo, Sunkak; Kim, Hyunjin; Kang, Bo Soo

    2013-12-01

    A unipolar resistance switching (URS) Pt/NiO/Pt thin film structure was successfully deposited by sputtering. Each state was analyzed by using impedance spectroscopy. The equivalent circuit of the pristine state consists of resistor-capacitor parallel circuit. The low-resistance state could be described by using a single resistor. The high-resistance state comprised parallelly-connected resistor and constant-phase element, plus a serial inductor. Our results are in good agreement with a model for the formation/rupture of conducting filaments in the URS phenomenon.

  20. Nanoporous PtAg and PtCu alloys with hollow ligaments for enhanced electrocatalysis and glucose biosensing.

    PubMed

    Xu, Caixia; Liu, Yunqing; Su, Fa; Liu, Aihua; Qiu, Huajun

    2011-09-15

    Nanoporous silver (NPS) and copper (NPC) obtained by dealloying AgAl and CuAl alloys, respectively, were used as both three-dimensional templates and reducing agents for the fabrication of nanoporous PtAg (NPS-Pt) and PtCu (NPC-Pt) alloys with hollow ligaments by a simple galvanic replacement reaction with H(2)PtCl(6). Electron microscopy and X-ray diffraction characterizations demonstrate that NPS and NPC with similar ligament sizes (30-50 nm) have different effects on the formed hollow nanostructures. For NPS-Pt, the shell of the hollow ligament is seamless. However, the shell of NPC-Pt is comprised of small pores and alloy nanoparticles with a size of ∼3 nm. The as-prepared NPS-Pt and NPC-Pt exhibit remarkably improved electrocatalytic activities towards the oxidation of ethanol and H(2)O(2) compared with state-of-the-art Pt/C catalyst, and can be used for sensitive electrochemical sensing applications. The hierarchical nanoporous structure also provides a good microenvironment for enzymes. After immobilization of glucose oxidase (GOx), the enzyme modified nanoporous electrode can sensitively detect glucose in a wide linear range (0.6-20 mM). PMID:21778046

  1. Facet-controlled {100}Rh-Pt and {100}Pt-Pt dendritic nanostructures by transferring the {100} facet nature of the core nanocube to the branch nanocubes

    NASA Astrophysics Data System (ADS)

    Khi, Nguyen Tien; Park, Jongsik; Baik, Hionsuck; Lee, Hyunkyung; Sohn, Jeong-Hun; Lee, Kwangyeol

    2015-02-01

    Facet-controlled dendritic nanostructures are expected to exhibit excellent catalytic properties because both aggregation-free nature and controlled facet-originated activity and selectivity can be accomplished. However, such examples are extremely rare due to the incompatibility of the dendrite formation process with the usage of surface-stabilizing moieties, which are typically used to control facets. Herein, we demonstrate that regiospecific growth on a facet-controlled core nanoparticle can induce the facet-control of the branch nanoparticles. Specifically, facet-controlled dendritic nanostructures of {100}Rh-Pt and {100}Pt-Pt can be conveniently prepared by transferring the crystallographic behaviour of the {100}Pt dendritic core nanocube to the {100}Rh or {100}Pt branch nanocubes.Facet-controlled dendritic nanostructures are expected to exhibit excellent catalytic properties because both aggregation-free nature and controlled facet-originated activity and selectivity can be accomplished. However, such examples are extremely rare due to the incompatibility of the dendrite formation process with the usage of surface-stabilizing moieties, which are typically used to control facets. Herein, we demonstrate that regiospecific growth on a facet-controlled core nanoparticle can induce the facet-control of the branch nanoparticles. Specifically, facet-controlled dendritic nanostructures of {100}Rh-Pt and {100}Pt-Pt can be conveniently prepared by transferring the crystallographic behaviour of the {100}Pt dendritic core nanocube to the {100}Rh or {100}Pt branch nanocubes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07049f

  2. New Magnetic Nanodot Memory with FePt Nanodots

    NASA Astrophysics Data System (ADS)

    Yin, Cheng-Kuan; Murugesan, Mariappan; Bea, Ji-Chel; Oogane, Mikihiko; Fukushima, Takafumi; Tanaka, Tetsu; Kono, Shozo; Samukawa, Seiji; Koyanagi, Mitsumasa

    2007-04-01

    A new magnetic nanodot (MND) memory with FePt nanodots was proposed. The FePt nanodots dispersed in SiO2 insulating film was successfully fabricated by self-assembled nanodot deposition (SAND). The size of the FePt nanodot can be controlled by SAND with a different target area ratio of the FePt pellets area in the SiO2 target. Thermal annealing converts the magnetic properties of the FePt nanodots from antiferromagnetic into high coercivity ferromagnetic without thermal agglomeration. An L10 face-centered tetragonal (fct) FePt MND film was successfully formed which acted as a charge retention layer. Furthermore, the fundamental characteristics of the MND memory were investigated using magnetic metal oxide semiconductor (MOS) capacitor devices.

  3. Surface diffusion of xenon on Pt(111)

    NASA Astrophysics Data System (ADS)

    Meixner, D. Laurence; George, Steven M.

    1993-06-01

    The surface diffusion of xenon on the Pt(111) surface was investigated using laser induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. The surface diffusion coefficient at 80 K decreased dramatically from D=8×10-7 cm2/s at θ=0.05θs to approximately D=2×10-8 cm2/s at θ=θs, where θs denotes the saturation coverage at 85 K, corresponding to a commensurate monolayer coverage of 5.0×1014 xenon atoms/cm2. This coverage dependence was consistent with attractive interactions between the adsorbed xenon atoms and the existence of two-dimensional condensed phases of xenon on Pt(111). The kinetic parameters for surface diffusion at θ=θs were Edif=1.3±0.1 kcal/mol and D0=1.1×10-4±0.2 cm2/s. The magnitude of Edif at θ=θs represented the combined effect of the intrinsic corrugation of the adsorbate-surface potential and attractive interactions between the adsorbed xenon atoms. LITD experiments at θ=0.25 θs revealed diffusion kinetic parameters of Edif=1.2±0.2 kcal/mol and D0=3.4×10-4±0.5 cm2/s. The constant Edif at low and high coverage was attributed to the ``breakaway'' of xenon atoms from the edges of condensed phase xenon islands. The coverage dependence of the surface diffusion coefficient for Xe/Pt(111) was explained by a multiple site diffusion mechanism, where collisions with xenon islands limit diffusional motion. Thermal desorption kinetics for xenon on Pt(111) were determined using TPD experiments. Using the variation of heating rates method, the desorption parameters were Edes=6.6±0.2 kcal/mol and νdes=1.3×1013±0.4 s-1, in good agreement with previous studies. The xenon TPD peak shifted to higher temperature versus initial coverage at a fixed heating rate, providing further evidence for attractive interactions between the adsorbed xenon atoms.

  4. Laser cleanup of Pt group metals

    SciTech Connect

    Chen, H.L.

    1980-10-28

    Due to increasing interest in chemical and fuel synthesis from syngas, the feasibility and practicality of purifying Pt group metals (Pd, Ru, Rh) using LIS technologies have been re-evaluated. Findings for the selective removal of /sup 107/Pd from Pd metal are described here. The selectivity of this technique is based on the angular momentum selection rules for atomic absorption of circularly polarized light. In principle, it is possible to selectively excite isotopes with non-zero nuclear spin, using two circularly polarized laser pulses, while leaving the isotopes with zero nuclear spin unexcited. The excited atom can then be ionized using a third photon of appropriate energy.

  5. Superconductivity in Pd, Ir, and Pt chalcogenide

    NASA Astrophysics Data System (ADS)

    Oh, Yoon Seok; Yang, Junjie; Choi, Y. J.; Hogan, A.; Horibe, Y.; Cheong, S.-W.

    2012-02-01

    Large spin-orbit coupling in materials with heavy chalcogens can result in unique quantum states or functional properties such as topological insulator, giant thermoelectric power, and superconductivity. When materials contain heavy cations in addition to heavy chalcogens, spin-orbit coupling can be further enhanced. For these reasons, we have studied the superconductivity of Pd, Ir, and Pt tellurides and selenides. In the exploration of these chalcogenides, we have focused on the competition between superconductivity and charge density wave that is associated with superlattice reflections.

  6. Self-Diffusion Along Step-Bottoms on Pt(111)

    SciTech Connect

    Feibelman, P.J.

    1999-04-05

    First-principles total energies of periodic vicinals are used to estimate barriers for Pt-adatom diffusion along straight and kinked steps on Pt(111), and around a corner where straight steps intersect. In all cases studied, hopping diffusion has a lower barrier than concerted substitution. In conflict with simulations of dendritic Pt island formation on Pt(111), hopping from a corner site to a step whose riser is a (111)-micro facet is predicted to be more facile than to one whose riser is a (100).

  7. Passive PT -symmetric couplers without complex optical potentials

    NASA Astrophysics Data System (ADS)

    Lee, Yi-Chan; Liu, Jibing; Chuang, You-Lin; Hsieh, Min-Hsiu; Lee, Ray-Kuang

    2015-11-01

    In addition to the implementation of parity-time-(PT -) symmetric optical systems by carefully and actively controlling the gain and loss, we show that a 2 ×2 PT -symmetric Hamiltonian has a unitarily equivalent representation without complex optical potentials in the resulting optical coupler. Through the Naimark dilation in operator algebra, passive PT -symmetric couplers can thus be implemented with a refractive index of real values and asymmetric coupling coefficients. This opens up the possibility to implement general PT -symmetric systems with state-of-the-art asymmetric slab waveguides, dissimilar optical fibers, or cavities with chiral mirrors.

  8. Nanoscale PtSi Tips for Conducting Probe Technologies

    NASA Astrophysics Data System (ADS)

    Bhaskaran, Harish; Sebastian, Abu; Despont, Michel

    2009-01-01

    A method to improve the conduction and wear properties of nanometric conducting tips by forming silicides of Pt at the tip apex is presented. Tips with PtSi apexes are fabricated in conjunction with standard Si tips. Wear measurements are carried out on both tip types of similar geometries, and a one-on-one comparison between Si and PtSi at the nanoscale is shown for the first time. Both the wear properties on tetrahedral amorphous carbon and the conduction on Au of the PtSi tip apexes are shown to be superior to the Si tips.

  9. A novel method to evaluate spin diffusion length of Pt

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-qing; Sun, Niu-yi; Che, Wen-ru; Shan, Rong; Zhu, Zhen-gang

    2016-05-01

    Spin diffusion length of Pt is evaluated via proximity effect of spin orbit coupling (SOC) and anomalous Hall effect (AHE) in Pt/Co2FeAl bilayers. By varying the thicknesses of Pt and Co2FeAl layer, the thickness dependences of AHE parameters can be obtained, which are theoretically predicted to be proportional to the square of the SOC strength. According to the physical image of the SOC proximity effect, the spin diffusion length of Pt can easily be identified from these thickness dependences. This work provides a novel method to evaluate spin diffusion length in a material with a small value.

  10. Distributions of noble metal Pd and Pt in mesoporous silica

    NASA Astrophysics Data System (ADS)

    Arbiol, J.; Cabot, A.; Morante, J. R.; Chen, Fanglin; Liu, Meilin

    2002-10-01

    Mesoporous silica nanostructures have been synthesized and loaded with Pd and Pt catalytic noble metals. It is found that Pd forms small nanoclusters (3-5 nm) on the surface of the mesoporous structure whereas Pt impregnation results in the inclusion of Pt nanostructures within the silica hexagonal pores (from nanoclusters to nanowires). It is observed that these materials have high catalytic properties for CO-CH4 combustion, even in a thick film form. In particular, results indicate that the Pt and Pd dispersed in mesoporous silica are catalytically active as a selective filter for gas sensors.

  11. Layer-Resolved Magnetic Moments in Ni/Pt Multilayers

    NASA Astrophysics Data System (ADS)

    Wilhelm, F.; Poulopoulos, P.; Ceballos, G.; Wende, H.; Baberschke, K.; Srivastava, P.; Benea, D.; Ebert, H.; Angelakeris, M.; Flevaris, N. K.; Niarchos, D.; Rogalev, A.; Brookes, N. B.

    2000-07-01

    The magnetic moments in Ni/Pt multilayers are thoroughly studied by combining experimental and ab initio theoretical techniques. SQUID magnetometry probes the samples' magnetizations. X-ray magnetic circular dichroism separates the contribution of Ni and Pt and provides a layer-resolved magnetic moment profile for the whole system. The results are compared to band-structure calculations. Induced Pt magnetic moments localized mostly at the interface are revealed. No magnetically ``dead'' Ni layers are found. The magnetization per Ni volume is slightly enhanced compared to bulk NiPt alloys.

  12. Jarzynski equality in PT-symmetric quantum mechanics

    SciTech Connect

    Deffner, Sebastian; Saxena, Avadh

    2015-04-13

    We show that the quantum Jarzynski equality generalizes to PT -symmetric quantum mechanics with unbroken PT -symmetry. In the regime of broken PT -symmetry the Jarzynski equality does not hold as also the CPT -norm is not preserved during the dynamics. These findings are illustrated for an experimentally relevant system – two coupled optical waveguides. It turns out that for these systems the phase transition between the regimes of unbroken and broken PT -symmetry is thermodynamically inhibited as the irreversible work diverges at the critical point.

  13. Local PT symmetry violates the no-signaling principle.

    PubMed

    Lee, Yi-Chan; Hsieh, Min-Hsiu; Flammia, Steven T; Lee, Ray-Kuang

    2014-04-01

    Bender et al. [Phys. Rev. Lett. 80, 5243 (1998)] have developed PT-symmetric quantum theory as an extension of quantum theory to non-Hermitian Hamiltonians. We show that when this model has a local PT symmetry acting on composite systems, it violates the nonsignaling principle of relativity. Since the case of global PT symmetry is known to reduce to standard quantum mechanics A. Mostafazadeh [J. Math. Phys. 43, 205 (2001)], this shows that the PT-symmetric theory is either a trivial extension or likely false as a fundamental theory. PMID:24745396

  14. Factors affecting the spontaneous adsorption of Bi(III) onto Pt and PtRu nanoparticles

    NASA Astrophysics Data System (ADS)

    Sawy, Ehab N. El; Khan, M. Akhtar; Pickup, Peter G.

    2016-02-01

    The influence of Bi(III) concentration and pH on the spontaneous adsorption of Bi species onto Pt nanoparticles has been systematically investigated in order to identify the adsorbing species, determine whether the nature of the adsorbing species changes, and investigate whether the activities of the resulting Bi decorated particles for formic acid oxidation can be influenced. The adsorption of Bi follows a Temkin-type isotherm, with a pH dependence indicating that the adsorbing species is [Bi6O4(OH)4]6+. Activities of Bi decorated Pt nanoparticles for formic acid oxidation are strongly influenced by the Bi coverage, with a maximum enhancement of a factor of ca. 60 at a coverage of 70%, but not by the Bi(III) concentration or pH used to adsorb the Bi species, other than through their influence on Bi coverage. These results support the conclusion that the adsorbing species is [Bi6O4(OH)4]6+ under all conditions investigated. Adsorbed Bi also activates PtRu nanoparticles for formic acid oxidation, although the effect is not as strong as for Pt. The maximum enhancement observed was only a factor of ca. 7. This has been attributed to attenuation of the effects of Bi adatoms that are adsorbed at Ru sites.

  15. Cycloheximide Chase Analysis of Protein Degradation in Saccharomyces cerevisiae.

    PubMed

    Buchanan, Bryce W; Lloyd, Michael E; Engle, Sarah M; Rubenstein, Eric M

    2016-01-01

    Regulation of protein abundance is crucial to virtually every cellular process. Protein abundance reflects the integration of the rates of protein synthesis and protein degradation. Many assays reporting on protein abundance (e.g., single-time point western blotting, flow cytometry, fluorescence microscopy, or growth-based reporter assays) do not allow discrimination of the relative effects of translation and proteolysis on protein levels. This article describes the use of cycloheximide chase followed by western blotting to specifically analyze protein degradation in the model unicellular eukaryote, Saccharomyces cerevisiae (budding yeast). In this procedure, yeast cells are incubated in the presence of the translational inhibitor cycloheximide. Aliquots of cells are collected immediately after and at specific time points following addition of cycloheximide. Cells are lysed, and the lysates are separated by polyacrylamide gel electrophoresis for western blot analysis of protein abundance at each time point. The cycloheximide chase procedure permits visualization of the degradation kinetics of the steady state population of a variety of cellular proteins. The procedure may be used to investigate the genetic requirements for and environmental influences on protein degradation. PMID:27167179

  16. Heritable capture of heterochromatin dynamics in Saccharomyces cerevisiae

    PubMed Central

    Dodson, Anne E; Rine, Jasper

    2015-01-01

    Heterochromatin exerts a heritable form of eukaryotic gene repression and contributes to chromosome segregation fidelity and genome stability. However, to date there has been no quantitative evaluation of the stability of heterochromatic gene repression. We designed a genetic strategy to capture transient losses of gene silencing in Saccharomyces as permanent, heritable changes in genotype and phenotype. This approach revealed rare transcription within heterochromatin that occurred in approximately 1/1000 cell divisions. In concordance with multiple lines of evidence suggesting these events were rare and transient, single-molecule RNA FISH showed that transcription was limited. The ability to monitor fluctuations in heterochromatic repression uncovered previously unappreciated roles for Sir1, a silencing establishment factor, in the maintenance and/or inheritance of silencing. In addition, we identified the sirtuin Hst3 and its histone target as contributors to the stability of the silenced state. These approaches revealed dynamics of a heterochromatin function that have been heretofore inaccessible. DOI: http://dx.doi.org/10.7554/eLife.05007.001 PMID:25581000

  17. TOR and RAS pathways regulate desiccation tolerance in Saccharomyces cerevisiae

    PubMed Central

    Welch, Aaron Z.; Gibney, Patrick A.; Botstein, David; Koshland, Douglas E.

    2013-01-01

    Tolerance to desiccation in cultures of Saccharomyces cerevisiae is inducible; only one in a million cells from an exponential culture survive desiccation compared with one in five cells in stationary phase. Here we exploit the desiccation sensitivity of exponentially dividing cells to understand the stresses imposed by desiccation and their stress response pathways. We found that induction of desiccation tolerance is cell autonomous and that there is an inverse correlation between desiccation tolerance and growth rate in glucose-, ammonia-, or phosphate-limited continuous cultures. A transient heat shock induces a 5000–fold increase in desiccation tolerance, whereas hyper-ionic, -reductive, -oxidative, or -osmotic stress induced much less. Furthermore, we provide evidence that the Sch9p-regulated branch of the TOR and Ras-cAMP pathway inhibits desiccation tolerance by inhibiting the stress response transcription factors Gis1p, Msn2p, and Msn4p and by activating Sfp1p, a ribosome biogenesis transcription factor. Among 41 mutants defective in ribosome biogenesis, a subset defective in 60S showed a dramatic increase in desiccation tolerance independent of growth rate. We suggest that reduction of a specific intermediate in 60S biogenesis, resulting from conditions such as heat shock and nutrient deprivation, increases desiccation tolerance. PMID:23171550

  18. Membrane trafficking in the yeast Saccharomyces cerevisiae model.

    PubMed

    Feyder, Serge; De Craene, Johan-Owen; Bär, Séverine; Bertazzi, Dimitri L; Friant, Sylvie

    2015-01-01

    The yeast Saccharomyces cerevisiae is one of the best characterized eukaryotic models. The secretory pathway was the first trafficking pathway clearly understood mainly thanks to the work done in the laboratory of Randy Schekman in the 1980s. They have isolated yeast sec mutants unable to secrete an extracellular enzyme and these SEC genes were identified as encoding key effectors of the secretory machinery. For this work, the 2013 Nobel Prize in Physiology and Medicine has been awarded to Randy Schekman; the prize is shared with James Rothman and Thomas Südhof. Here, we present the different trafficking pathways of yeast S. cerevisiae. At the Golgi apparatus newly synthesized proteins are sorted between those transported to the plasma membrane (PM), or the external medium, via the exocytosis or secretory pathway (SEC), and those targeted to the vacuole either through endosomes (vacuolar protein sorting or VPS pathway) or directly (alkaline phosphatase or ALP pathway). Plasma membrane proteins can be internalized by endocytosis (END) and transported to endosomes where they are sorted between those targeted for vacuolar degradation and those redirected to the Golgi (recycling or RCY pathway). Studies in yeast S. cerevisiae allowed the identification of most of the known effectors, protein complexes, and trafficking pathways in eukaryotic cells, and most of them are conserved among eukaryotes. PMID:25584613

  19. Transcriptional regulation by ergosterol in the yeast Saccharomyces cerevisiae.

    PubMed Central

    Smith, S J; Crowley, J H; Parks, L W

    1996-01-01

    Sterol biosynthesis in the yeast Saccharomyces cerevisiae is an energy-expensive, aerobic process, requiring heme and molecular oxygen. Heme, also synthesized exclusively during aerobic growth, not only acts as an enzymatic cofactor but also is directly and indirectly responsible for the transcriptional control of several yeast genes. Because of their biosynthetic similarities, we hypothesized that ergosterol, like heme, may have a regulatory function. Sterols are known to play a structural role in membrane integrity, but regulatory roles have not been characterized. To test possible regulatory roles of sterol, the promoter for the ERG3 gene, encoding the sterol C-5 desaturase, was fused to the bacterial lacZ reporter gene. This construct was placed in strains making aberrant sterols, and the effect of altered sterol composition on gene expression was monitored by beta-galactosidase activity. The absence of ergosterol resulted in a 35-fold increase in the expression of ERG3 as measured by beta-galactosidase activity. The level of ERG3 mRNA was increased as much as ninefold in erg mutant strains or wild-type strains inhibited in ergosterol biosynthesis by antifungal agents. The observed regulatory effects of ergosterol on ERG3 are specific for ergosterol, as several ergosterol derivatives failed to elicit the same controlling effect. These results demonstrate for the first time that ergosterol exerts a regulatory effect on gene transcription in S. cerevisiae. PMID:8816455

  20. CRISPR-Cas9 Genome Engineering in Saccharomyces cerevisiae Cells.

    PubMed

    Ryan, Owen W; Poddar, Snigdha; Cate, Jamie H D

    2016-01-01

    This protocol describes a method for CRISPR-Cas9-mediated genome editing that results in scarless and marker-free integrations of DNA into Saccharomyces cerevisiae genomes. DNA integration results from cotransforming (1) a single plasmid (pCAS) that coexpresses the Cas9 endonuclease and a uniquely engineered single guide RNA (sgRNA) expression cassette and (2) a linear DNA molecule that is used to repair the chromosomal DNA damage by homology-directed repair. For target specificity, the pCAS plasmid requires only a single cloning modification: replacing the 20-bp guide RNA sequence within the sgRNA cassette. This CRISPR-Cas9 protocol includes methods for (1) cloning the unique target sequence into pCAS, (2) assembly of the double-stranded DNA repair oligonucleotides, and (3) cotransformation of pCAS and linear repair DNA into yeast cells. The protocol is technically facile and requires no special equipment. It can be used in any S. cerevisiae strain, including industrial polyploid isolates. Therefore, this CRISPR-Cas9-based DNA integration protocol is achievable by virtually any yeast genetics and molecular biology laboratory. PMID:27250940

  1. Chromatin remodeling during Saccharomyces cerevisiae ADH2 gene activation.

    PubMed

    Verdone, L; Camilloni, G; Di Mauro, E; Caserta, M

    1996-05-01

    We have analyzed at both low and high resolution the distribution of nucleosomes over the Saccharomyces cerevisiae ADH2 promoter region in its chromosomal location, both under repressing (high-glucose) conditions and during derepression. Enzymatic treatments (micrococcal nuclease and restriction endonucleases) were used to probe the in vivo chromatin structure during ADH2 gene activation. Under glucose-repressed conditions, the ADH2 promoter was bound by a precise array of nucleosomes, the principal ones positioned at the RNA initiation sites (nucleosome +1), at the TATA box (nucleosome -1), and upstream of the ADR1-binding site (UAS1) (nucleosome -2). The UAS1 sequence and the adjacent UAS2 sequence constituted a nucleosome-free region. Nucleosomes -1 and +1 were destabilized soon after depletion of glucose and had become so before the appearance of ADH2 mRNA. When the transcription rate was high, nucleosomes -2 and +2 also underwent rearrangement. When spheroplasts were prepared from cells grown in minimal medium, detection of this chromatin remodeling required the addition of a small amount of glucose. Cells lacking the ADR1 protein did not display any of these chromatin modifications upon glucose depletion. Since the UAS1 sequence to which Adr1p binds is located immediately upstream of nucleosome -1, Adr1p is presumably required for destabilization of this nucleosome and for aiding the TATA-box accessibility to the transcription machinery. PMID:8628264

  2. Tanshinones extend chronological lifespan in budding yeast Saccharomyces cerevisiae.

    PubMed

    Wu, Ziyun; Song, Lixia; Liu, Shao Quan; Huang, Dejian

    2014-10-01

    Natural products with anti-aging property have drawn great attention recently but examples of such compounds are exceedingly scarce. By applying a high-throughput assay based on yeast chronological lifespan measurement, we screened the anti-aging activity of 144 botanical materials and found that dried roots of Salvia miltiorrhiza Bunge have significant anti-aging activity. Tanshinones isolated from the plant including cryptotanshione, tanshinone I, and tanshinone IIa, are the active components. Among them, cryptotanshinone can greatly extend the budding yeast Saccharomyces cerevisiae chronological lifespan (up to 2.5 times) in a dose- and the-time-of-addition-dependent manner at nanomolar concentrations without disruption of cell growth. We demonstrate that cryptotanshinone prolong chronological lifespan via a nutrient-dependent regime, especially essential amino acid sensing, and three conserved protein kinases Tor1, Sch9, and Gcn2 are required for cryptotanshinone-induced lifespan extension. In addition, cryptotanshinone significantly increases the lifespan of SOD2-deleted mutants. Altogether, those data suggest that cryptotanshinone might be involved in the regulation of, Tor1, Sch9, Gcn2, and Sod2, these highly conserved longevity proteins modulated by nutrients from yeast to humans. PMID:24970458

  3. Tor1 regulates protein solubility in Saccharomyces cerevisiae

    PubMed Central

    Peters, Theodore W.; Rardin, Matthew J.; Czerwieniec, Gregg; Evani, Uday S.; Reis-Rodrigues, Pedro; Lithgow, Gordon J.; Mooney, Sean D.; Gibson, Bradford W.; Hughes, Robert E.

    2012-01-01

    Accumulation of insoluble protein in cells is associated with aging and aging-related diseases; however, the roles of insoluble protein in these processes are uncertain. The nature and impact of changes to protein solubility during normal aging are less well understood. Using quantitative mass spectrometry, we identify 480 proteins that become insoluble during postmitotic aging in Saccharomyces cerevisiae and show that this ensemble of insoluble proteins is similar to those that accumulate in aging nematodes. SDS-insoluble protein is present exclusively in a nonquiescent subpopulation of postmitotic cells, indicating an asymmetrical distribution of this protein. In addition, we show that nitrogen starvation of young cells is sufficient to cause accumulation of a similar group of insoluble proteins. Although many of the insoluble proteins identified are known to be autophagic substrates, induction of macroautophagy is not required for insoluble protein formation. However, genetic or chemical inhibition of the Tor1 kinase is sufficient to promote accumulation of insoluble protein. We conclude that target of rapamycin complex 1 regulates accumulation of insoluble proteins via mechanisms acting upstream of macroautophagy. Our data indicate that the accumulation of proteins in an SDS-insoluble state in postmitotic cells represents a novel autophagic cargo preparation process that is regulated by the Tor1 kinase. PMID:23097491

  4. Saccharomyces cerevisiae: a nomadic yeast with no niche?

    PubMed Central

    Goddard, Matthew R.; Greig, Duncan

    2015-01-01

    Different species are usually thought to have specific adaptations, which allow them to occupy different ecological niches. But recent neutral ecology theory suggests that species diversity can simply be the result of random sampling, due to finite population sizes and limited dispersal. Neutral models predict that species are not necessarily adapted to specific niches, but are functionally equivalent across a range of habitats. Here, we evaluate the ecology of Saccharomyces cerevisiae, one of the most important microbial species in human history. The artificial collection, concentration and fermentation of large volumes of fruit for alcohol production produce an environment in which S. cerevisiae thrives, and therefore it is assumed that fruit is the ecological niche that S. cerevisiae inhabits and has adapted to. We find very little direct evidence that S. cerevisiae is adapted to fruit, or indeed to any other specific niche. We propose instead a neutral nomad model for S. cerevisiae, which we believe should be used as the starting hypothesis in attempting to unravel the ecology of this important microbe. PMID:25725024

  5. mRNA transcription in nuclei isolated from Saccharomyces cerevisiae.

    PubMed Central

    Jerome, J F; Jaehning, J A

    1986-01-01

    We developed an improved method for the isolation of transcriptionally active nuclei from Saccharomyces cerevisiae, which allows analysis of specific transcripts. When incubated with alpha-32P-labeled ribonucleoside triphosphates in vitro, nuclei isolated from haploid or diploid cells transcribed rRNA, tRNA, and mRNAs in a strand-specific manner, as shown by slot blot hybridization of the in vitro synthesized RNA to cloned genes encoding 5.8S, 18S and 28S rRNAs, tRNATyr, and GAL7, URA3, TY1 and HIS3 mRNAs. A yeast strain containing a high-copy-number plasmid which overproduced GAL7 mRNA was initially used to facilitate detection of a discrete message. We optimized conditions for the transcription of genes expressed by each of the three yeast nuclear RNA polymerases. Under optimal conditions, labeled transcripts could be detected from single-copy genes normally expressed at low levels in the cells (HIS3 and URA3). We determined that the alpha-amanitin sensitivity of transcript synthesis in the isolated nuclei paralleled the sensitivity of the corresponding purified RNA polymerases; in particular, mRNA synthesis was 50% sensitive to 1 microgram of alpha-amanitin per ml, establishing transcription of mRNA by RNA polymerase II. Images PMID:3537708

  6. Efficient expression of a Paenibacillus barcinonensis endoglucanase in Saccharomyces cerevisiae.

    PubMed

    Mormeneo, María; Pastor, Fi Javier; Zueco, Jesús

    2012-01-01

    The endoglucanase coded by celA (GenBank Access No. Y12512) from Paenibacillus barcinonensis, an enzyme with good characteristics for application on paper manufacture from agricultural fibers, was expressed in Saccharomyces cerevisiae by using different domains of the cell wall protein Pir4 as translational fusion partners, to achieve either secretion or cell wall retention of the recombinant enzyme. Given the presence of five potential N-glycosylation sites in the amino acid sequence coded by celA, the effect of glycosylation on the enzymatic activity of the recombinant enzyme was investigated by expressing the recombinant fusion proteins in both, standard and glycosylation-deficient strains of S. cerevisiae. Correct targeting of the recombinant fusion proteins was confirmed by Western immunoblot using Pir-specific antibodies, while enzymatic activity on carboxymethyl cellulose was demonstrated on plate assays, zymographic analysis and colorimetric assays. Hyperglycosylation of the enzyme when expressed in the standard strain of S. cerevisiae did not affect activity, and values of 1.2 U/ml were obtained in growth medium supernatants in ordinary batch cultures after 24 h. These values compare quite favorably with those described for other recombinant endoglucanases expressed in S. cerevisiae. This is one of the few reports describing the expression of Bacillus cellulases in S. cerevisiae, since yeast expressed recombinant cellulases have been mostly of fungal origin. It is also the first report of the yeast expression of this particular endoglucanase. PMID:21701899

  7. Dual Effects of Plant Steroidal Alkaloids on Saccharomyces cerevisiae†

    PubMed Central

    Simons, Veronika; Morrissey, John P.; Latijnhouwers, Maita; Csukai, Michael; Cleaver, Adam; Yarrow, Carol; Osbourn, Anne

    2006-01-01

    Many plant species accumulate sterols and triterpenes as antimicrobial glycosides. These secondary metabolites (saponins) provide built-in chemical protection against pest and pathogen attack and can also influence induced defense responses. In addition, they have a variety of important pharmacological properties, including anticancer activity. The biological mechanisms underpinning the varied and diverse effects of saponins on microbes, plants, and animals are only poorly understood despite the ecological and pharmaceutical importance of this major class of plant secondary metabolites. Here we have exploited budding yeast (Saccharomyces cerevisiae) to investigate the effects of saponins on eukaryotic cells. The tomato steroidal glycoalkaloid α-tomatine has antifungal activity towards yeast, and this activity is associated with membrane permeabilization. Removal of a single sugar from the tetrasaccharide chain of α-tomatine results in a substantial reduction in antimicrobial activity. Surprisingly, the complete loss of sugars leads to enhanced antifungal activity. Experiments with α-tomatine and its aglycone tomatidine indicate that the mode of action of tomatidine towards yeast is distinct from that of α-tomatine and does not involve membrane permeabilization. Investigation of the effects of tomatidine on yeast by gene expression and sterol analysis indicate that tomatidine inhibits ergosterol biosynthesis. Tomatidine-treated cells accumulate zymosterol rather than ergosterol, which is consistent with inhibition of the sterol C24 methyltransferase Erg6p. However, erg6 and erg3 mutants (but not erg2 mutants) have enhanced resistance to tomatidine, suggesting a complex interaction of erg mutations, sterol content, and tomatidine resistance. PMID:16870766

  8. Multiparameter analysis of apoptosis in puromycin-treated Saccharomyces cerevisiae.

    PubMed

    Citterio, Barbara; Albertini, Maria Cristina; Ghibelli, Lina; Falcieri, Elisabetta; Battistelli, Michela; Canonico, Barbara; Rocchi, Marco B L; Teodori, Laura; Ciani, Maurizio; Piatti, Elena

    2015-08-01

    In Saccharomyces cerevisiae, a typical apoptotic phenotype is induced by some stress factors such as sugars, acetic acid, hydrogen peroxide, aspirin and age. Nevertheless, no data have been reported for apoptosis induced by puromycin, a damaging agent known to induce apoptosis in mammalian cells. We treated S. cerevisiae with puromycin to induce apoptosis and evaluated the percentage of dead cells by using Hoechst 33342 staining, transmission electron microscopy (TEM) and Annexin V flow cytometry (FC) analysis. Hoechst 33342 fluorescence images were processed to acquire parameters to use for multiparameter analysis [and perform a principal component analysis, (PCA)]. Cell viability was evaluated by Rhodamine 123 (Rh 123) and Acridine Orange microscope fluorescence staining. The results show puromycin-induced apoptosis in S. cerevisiae, and the PCA analysis indicated that the increasing percentage of apoptotic cells delineated a well-defined graph profile. The results were supported by TEM and FC. This study gives new insights into yeast apoptosis using puromycin as inducer agent, and PCA analysis may complement molecular analysis facilitating further studies to its detection. PMID:25868793

  9. Assembly of evolved ligninolytic genes in Saccharomyces cerevisiae

    PubMed Central

    Gonzalez-Perez, David; Alcalde, Miguel

    2014-01-01

    The ligninolytic enzymatic consortium produced by white-rot fungi is one of the most efficient oxidative systems found in nature, with many potential applications that range from the production of 2nd generation biofuels to chemicals synthesis. In the current study, two high redox potential oxidoreductase fusion genes (laccase -Lac- and versatile peroxidase -Vp-) that had been evolved in the laboratory were re-assembled in Saccharomyces cerevisiae. First, cell viability and secretion were assessed after co-transforming the Lac and Vp genes into yeast. Several expression cassettes were inserted in vivo into episomal bi-directional vectors in order to evaluate inducible promoter and/or terminator pairs of different strengths in an individual and combined manner. The synthetic white-rot yeast model harboring Vp(GAL1/CYC1)-Lac(GAL10/ADH1) displayed up to 1000 and 100 Units per L of peroxidase and laccase activity, respectively, representing a suitable point of departure for future synthetic biology studies. PMID:24830983

  10. Isolation, identification and characterization of regional indigenous Saccharomyces cerevisiae strains.

    PubMed

    Šuranská, Hana; Vránová, Dana; Omelková, Jiřina

    2016-01-01

    In the present work we isolated and identified various indigenous Saccharomyces cerevisiae strains and screened them for the selected oenological properties. These S. cerevisiae strains were isolated from berries and spontaneously fermented musts. The grape berries (Sauvignon blanc and Pinot noir) were grown under the integrated and organic mode of farming in the South Moravia (Czech Republic) wine region. Modern genotyping techniques such as PCR-fingerprinting and interdelta PCR typing were employed to differentiate among indigenous S. cerevisiae strains. This combination of the methods provides a rapid and relatively simple approach for identification of yeast of S. cerevisiae at strain level. In total, 120 isolates were identified and grouped by molecular approaches and 45 of the representative strains were tested for selected important oenological properties including ethanol, sulfur dioxide and osmotic stress tolerance, intensity of flocculation and desirable enzymatic activities. Their ability to produce and utilize acetic/malic acid was examined as well; in addition, H2S production as an undesirable property was screened. The oenological characteristics of indigenous isolates were compared to a commercially available S. cerevisiae BS6 strain, which is commonly used as the starter culture. Finally, some indigenous strains coming from organically treated grape berries were chosen for their promising oenological properties and these strains will be used as the starter culture, because application of a selected indigenous S. cerevisiae strain can enhance the regional character of the wines. PMID:26887243

  11. Regulation of the Saccharomyces cerevisiae DNA repair gene RAD16.

    PubMed Central

    Bang, D D; Timmermans, V; Verhage, R; Zeeman, A M; van de Putte, P; Brouwer, J

    1995-01-01

    The RAD16 gene product has been shown to be essential for the repair of the silenced mating type loci [Bang et al. (1992) Nucleic Acids Res. 20, 3925-3931]. More recently we demonstrated that the RAD16 and RAD7 proteins are also required for repair of non-transcribed strands of active genes in Saccharomyces cerevisiae [Waters et al. (1993) Mol. Gen. Genet. 239, 28-32]. We have studied the regulation of the RAD16 gene and found that the RAD16 transcript levels increased up to 7-fold upon UV irradiation. Heat shock at 42 degrees C also results in elevated levels of RAD16 mRNA. In sporulating MAT alpha/MATa diploid cells RAD16 mRNA is also induced. The basal level of the RAD16 transcript is constant during the mitotic cell cycle. G1-arrested cells show normal induction of RAD16 mRNA upon UV irradiation demonstrating that the induction is not a secondary consequence of G2 cell cycle arrest following UV irradiation. However, in cells arrested in G1 the induction of RAD16 mRNA after UV irradiation is not followed by a rapid decline as occurs in normal growing cells suggesting that the down regulation of RAD16 transcription is dependent on progression into the cell cycle. Images PMID:7784171

  12. Dynamics of the Saccharomyces cerevisiae Transcriptome during Bread Dough Fermentation

    PubMed Central

    Aslankoohi, Elham; Zhu, Bo; Rezaei, Mohammad Naser; Voordeckers, Karin; De Maeyer, Dries; Marchal, Kathleen; Dornez, Emmie

    2013-01-01

    The behavior of yeast cells during industrial processes such as the production of beer, wine, and bioethanol has been extensively studied. In contrast, our knowledge about yeast physiology during solid-state processes, such as bread dough, cheese, or cocoa fermentation, remains limited. We investigated changes in the transcriptomes of three genetically distinct Saccharomyces cerevisiae strains during bread dough fermentation. Our results show that regardless of the genetic background, all three strains exhibit similar changes in expression patterns. At the onset of fermentation, expression of glucose-regulated genes changes dramatically, and the osmotic stress response is activated. The middle fermentation phase is characterized by the induction of genes involved in amino acid metabolism. Finally, at the latest time point, cells suffer from nutrient depletion and activate pathways associated with starvation and stress responses. Further analysis shows that genes regulated by the high-osmolarity glycerol (HOG) pathway, the major pathway involved in the response to osmotic stress and glycerol homeostasis, are among the most differentially expressed genes at the onset of fermentation. More importantly, deletion of HOG1 and other genes of this pathway significantly reduces the fermentation capacity. Together, our results demonstrate that cells embedded in a solid matrix such as bread dough suffer severe osmotic stress and that a proper induction of the HOG pathway is critical for optimal fermentation. PMID:24056467

  13. Characterization of Saccharomyces cerevisiae mutants supersensitive to aminoglycoside antibiotics.

    PubMed Central

    Ernst, J F; Chan, R K

    1985-01-01

    We describe mutants of Saccharomyces cerevisiae that are more sensitive than the wild type to the aminoglycoside antibiotics G418, hygromycin B, destomycin A, and gentamicin X2. In addition, the mutants are sensitive to apramycin, kanamycin B, lividomycin A, neamine, neomycin, paromomycin, and tobramycin--antibiotics which do not inhibit wild-type strains. Mapping studies suggest that supersensitivity is caused by mutations in at least three genes, denoted AGS1, AGS2, and AGS3 (for aminoglycoside antibiotic sensitivity). Mutations in all three genes are required for highest antibiotic sensitivity; ags1 ags2 double mutants have intermediate antibiotic sensitivity. AGS1 was mapped 8 centimorgans distal from LEU2 on chromosome III. Analyses of yeast strains transformed with vectors carrying antibiotic resistance genes revealed that G418, gentamicin X2, kanamycin B, lividomycin A, neamine, and paromomycin are inactivated by the Tn903 phosphotransferase and that destomycin A is inactivated by the hygromycin B phosphotransferase. ags strains are improved host strains for vectors carrying the phosphotransferase genes because a wide spectrum of aminoglycoside antibiotics can be used to select for plasmid maintenance. PMID:2989254

  14. Characterization of the Biotin Transport System in Saccharomyces cerevisiae1

    PubMed Central

    Rogers, Thomas O.; Lichstein, Herman C.

    1969-01-01

    The characteristics of the biotin transport mechanism of Saccharomyces cerevisiae were investigated in nonproliferating cells. Microbiological and radioisotope assays were employed to measure biotin uptake. The vitamin existed intracellularly in both free and bound forms. Free biotin was extracted by boiling water. Chromatography of the free extract showed it to consist entirely of d-biotin. Cellular bound biotin was released by treating cells with 6 n H2SO4. The rate of biotin uptake was linear with time for 10 min, reaching a maximum at about 20 min followed by a gradual loss of accumulated free vitamin from the cells. Biotin was not degraded or converted to vitamers during uptake. Transport was temperature- and pH-dependent, optimum conditions for uptake being 30 C and pH 4.0. Glucose markedly stimulated biotin transport. In its presence, large intracellular free-biotin concentration gradients were established. Iodoacetate inhibited the glucose stimulation of biotin uptake. The rate of vitamin transport increased in a linear fashion with increasing cell mass. The transport system was saturated with increasing concentrations of the vitamin. The apparent Km for uptake was 3.23 × 10−7m. Uptake of radioactive biotin was inhibited by unlabeled biotin and a number of analogues including homobiotin, desthiobiotin, oxybiotin, norbiotin, and biotin sulfone. Proline, hydroxyproline, and 7,8-diaminopelargonic acid did not inhibit uptake. Unlabeled biotin and desthiobiotin exchanged with accumulated intracellular 14C-biotin, whereas hydroxyproline did not. PMID:5354931

  15. The Saccharomyces Genome Database: Advanced Searching Methods and Data Mining.

    PubMed

    Cherry, J Michael

    2015-12-01

    At the core of the Saccharomyces Genome Database (SGD) are chromosomal features that encode a product. These include protein-coding genes and major noncoding RNA genes, such as tRNA and rRNA genes. The basic entry point into SGD is a gene or open-reading frame name that leads directly to the locus summary information page. A keyword describing function, phenotype, selective condition, or text from abstracts will also provide a door into the SGD. A DNA or protein sequence can be used to identify a gene or a chromosomal region using BLAST. Protein and DNA sequence identifiers, PubMed and NCBI IDs, author names, and function terms are also valid entry points. The information in SGD has been gathered and is maintained by a group of scientific biocurators and software developers who are devoted to providing researchers with up-to-date information from the published literature, connections to all the major research resources, and tools that allow the data to be explored. All the collected information cannot be represented or summarized for every possible question; therefore, it is necessary to be able to search the structured data in the database. This protocol describes the YeastMine tool, which provides an advanced search capability via an interactive tool. The SGD also archives results from microarray expression experiments, and a strategy designed to explore these data using the SPELL (Serial Pattern of Expression Levels Locator) tool is provided. PMID:26631124

  16. The Saccharomyces Genome Database: Exploring Genome Features and Their Annotations.

    PubMed

    Cherry, J Michael

    2015-12-01

    Genomic-scale assays result in data that provide information over the entire genome. Such base pair resolution data cannot be summarized easily except via a graphical viewer. A genome browser is a tool that displays genomic data and experimental results as horizontal tracks. Genome browsers allow searches for a chromosomal coordinate or a feature, such as a gene name, but they do not allow searches by function or upstream binding site. Entry into a genome browser requires that you identify the gene name or chromosomal coordinates for a region of interest. A track provides a representation for genomic results and is displayed as a row of data shown as line segments to indicate regions of the chromosome with a feature. Another type of track presents a graph or wiggle plot that indicates the processed signal intensity computed for a particular experiment or set of experiments. Wiggle plots are typical for genomic assays such as the various next-generation sequencing methods (e.g., chromatin immunoprecipitation [ChIP]-seq or RNA-seq), where it represents a peak of DNA binding, histone modification, or the mapping of an RNA sequence. Here we explore the browser that has been built into the Saccharomyces Genome Database (SGD). PMID:26631126

  17. Protective Effects of Arginine on Saccharomyces cerevisiae Against Ethanol Stress

    PubMed Central

    Cheng, Yanfei; Du, Zhaoli; Zhu, Hui; Guo, Xuena; He, Xiuping

    2016-01-01

    Yeast cells are challenged by various environmental stresses in the process of industrial fermentation. As the currently main organism for bio-ethanol production, Saccharomyces cerevisiae suffers from ethanol stress. Some amino acids have been reported to be related to yeast tolerance to stresses. Here the relationship between arginine and yeast response to ethanol stress was investigated. Marked inhibitions of ethanol on cell growth, expression of genes involved in arginine biosynthesis and intracellular accumulation of arginine were observed. Furthermore, extracellular addition of arginine can abate the ethanol damage largely. To further confirm the protective effects of arginine on yeast cells, yeast strains with different levels of arginine content were constructed by overexpression of ARG4 involved in arginine biosynthesis or CAR1 encoding arginase. Intracellular arginine was increased by 18.9% or 13.1% respectively by overexpression of ARG4 or disruption of CAR1, which enhanced yeast tolerance to ethanol stress. Moreover, a 41.1% decrease of intracellular arginine was observed in CAR1 overexpressing strain, which made yeast cells keenly sensitive to ethanol. Further investigations indicated that arginine protected yeast cells from ethanol damage by maintaining the integrity of cell wall and cytoplasma membrane, stabilizing the morphology and function of organellae due to low ROS generation. PMID:27507154

  18. Distribution and regulation of stochasticity and plasticity in Saccharomyces cerevisiae

    SciTech Connect

    Dar, R. D.; Karig, D. K.; Cooke, J. F.; Cox, C. D.; Simpson, M. L.

    2010-09-01

    Stochasticity is an inherent feature of complex systems with nanoscale structure. In such systems information is represented by small collections of elements (e.g. a few electrons on a quantum dot), and small variations in the populations of these elements may lead to big uncertainties in the information. Unfortunately, little is known about how to work within this inherently noisy environment to design robust functionality into complex nanoscale systems. Here, we look to the biological cell as an intriguing model system where evolution has mediated the trade-offs between fluctuations and function, and in particular we look at the relationships and trade-offs between stochastic and deterministic responses in the gene expression of budding yeast (Saccharomyces cerevisiae). We find gene regulatory arrangements that control the stochastic and deterministic components of expression, and show that genes that have evolved to respond to stimuli (stress) in the most strongly deterministic way exhibit the most noise in the absence of the stimuli. We show that this relationship is consistent with a bursty 2-state model of gene expression, and demonstrate that this regulatory motif generates the most uncertainty in gene expression when there is the greatest uncertainty in the optimal level of gene expression.

  19. Distribution and regulation of stochasticity and plasticity in Saccharomyces cerevisiae

    DOE PAGESBeta

    Dar, R. D.; Karig, D. K.; Cooke, J. F.; Cox, C. D.; Simpson, M. L.

    2010-09-01

    Stochasticity is an inherent feature of complex systems with nanoscale structure. In such systems information is represented by small collections of elements (e.g. a few electrons on a quantum dot), and small variations in the populations of these elements may lead to big uncertainties in the information. Unfortunately, little is known about how to work within this inherently noisy environment to design robust functionality into complex nanoscale systems. Here, we look to the biological cell as an intriguing model system where evolution has mediated the trade-offs between fluctuations and function, and in particular we look at the relationships and trade-offsmore » between stochastic and deterministic responses in the gene expression of budding yeast (Saccharomyces cerevisiae). We find gene regulatory arrangements that control the stochastic and deterministic components of expression, and show that genes that have evolved to respond to stimuli (stress) in the most strongly deterministic way exhibit the most noise in the absence of the stimuli. We show that this relationship is consistent with a bursty 2-state model of gene expression, and demonstrate that this regulatory motif generates the most uncertainty in gene expression when there is the greatest uncertainty in the optimal level of gene expression.« less

  20. MAP kinase pathways in the yeast Saccharomyces cerevisiae

    NASA Technical Reports Server (NTRS)

    Gustin, M. C.; Albertyn, J.; Alexander, M.; Davenport, K.; McIntire, L. V. (Principal Investigator)

    1998-01-01

    A cascade of three protein kinases known as a mitogen-activated protein kinase (MAPK) cascade is commonly found as part of the signaling pathways in eukaryotic cells. Almost two decades of genetic and biochemical experimentation plus the recently completed DNA sequence of the Saccharomyces cerevisiae genome have revealed just five functionally distinct MAPK cascades in this yeast. Sexual conjugation, cell growth, and adaptation to stress, for example, all require MAPK-mediated cellular responses. A primary function of these cascades appears to be the regulation of gene expression in response to extracellular signals or as part of specific developmental processes. In addition, the MAPK cascades often appear to regulate the cell cycle and vice versa. Despite the success of the gene hunter era in revealing these pathways, there are still many significant gaps in our knowledge of the molecular mechanisms for activation of these cascades and how the cascades regulate cell function. For example, comparison of different yeast signaling pathways reveals a surprising variety of different types of upstream signaling proteins that function to activate a MAPK cascade, yet how the upstream proteins actually activate the cascade remains unclear. We also know that the yeast MAPK pathways regulate each other and interact with other signaling pathways to produce a coordinated pattern of gene expression, but the molecular mechanisms of this cross talk are poorly understood. This review is therefore an attempt to present the current knowledge of MAPK pathways in yeast and some directions for future research in this area.

  1. Metabolic engineering of Saccharomyces cerevisiae to improve 1-hexadecanol production.

    PubMed

    Feng, Xueyang; Lian, Jiazhang; Zhao, Huimin

    2015-01-01

    Fatty alcohols are important components of a vast array of surfactants, lubricants, detergents, pharmaceuticals and cosmetics. We have engineered Saccharomyces cerevisiae to produce 1-hexadecanol by expressing a fatty acyl-CoA reductase (FAR) from barn owl (Tyto alba). In order to improve fatty alcohol production, we have manipulated both the structural genes and the regulatory genes in yeast lipid metabolism. The acetyl-CoA carboxylase gene (ACC1) was over-expressed, which improved 1-hexadecanol production by 56% (from 45mg/L to 71mg/L). Knocking out the negative regulator of the INO1 gene in phospholipid metabolism, RPD3, further enhanced 1-hexadecanol production by 98% (from 71mg/L to 140mg/L). The cytosolic acetyl-CoA supply was next engineered by expressing a heterologous ATP-dependent citrate lyase, which increased the production of 1-hexadecanol by an additional 136% (from 140mg/L to 330mg/L). Through fed-batch fermentation using resting cells, over 1.1g/L 1-hexadecanol can be produced in glucose minimal medium, which represents the highest titer reported in yeast to date. PMID:25466225

  2. Functional Profiling Using the Saccharomyces Genome Deletion Project Collections.

    PubMed

    Nislow, Corey; Wong, Lai Hong; Lee, Amy Huei-Yi; Giaever, Guri

    2016-01-01

    The ability to measure and quantify the fitness of an entire organism requires considerably more complex approaches than simply using traditional "omic" methods that examine, for example, the abundance of RNA transcripts, proteins, or metabolites. The yeast deletion collections represent the only systematic, comprehensive set of null alleles for any organism in which such fitness measurements can be assayed. Generated by the Saccharomyces Genome Deletion Project, these collections allow the systematic and parallel analysis of gene functions using any measurable phenotype. The unique 20-bp molecular barcodes engineered into the genome of each deletion strain facilitate the massively parallel analysis of individual fitness. Here, we present functional genomic protocols for use with the yeast deletion collections. We describe how to maintain, propagate, and store the deletion collections and how to perform growth fitness assays on single and parallel screening platforms. Phenotypic fitness analyses of the yeast mutants, described in brief here, provide important insights into biological functions, mechanisms of drug action, and response to environmental stresses. It is important to bear in mind that the specific assays described in this protocol represent some of the many ways in which these collections can be assayed, and in this description particular attention is paid to maximizing throughput using growth as the phenotypic measure. PMID:27587776

  3. MAP Kinase Pathways in the Yeast Saccharomyces cerevisiae

    PubMed Central

    Gustin, Michael C.; Albertyn, Jacobus; Alexander, Matthew; Davenport, Kenneth

    1998-01-01

    A cascade of three protein kinases known as a mitogen-activated protein kinase (MAPK) cascade is commonly found as part of the signaling pathways in eukaryotic cells. Almost two decades of genetic and biochemical experimentation plus the recently completed DNA sequence of the Saccharomyces cerevisiae genome have revealed just five functionally distinct MAPK cascades in this yeast. Sexual conjugation, cell growth, and adaptation to stress, for example, all require MAPK-mediated cellular responses. A primary function of these cascades appears to be the regulation of gene expression in response to extracellular signals or as part of specific developmental processes. In addition, the MAPK cascades often appear to regulate the cell cycle and vice versa. Despite the success of the gene hunter era in revealing these pathways, there are still many significant gaps in our knowledge of the molecular mechanisms for activation of these cascades and how the cascades regulate cell function. For example, comparison of different yeast signaling pathways reveals a surprising variety of different types of upstream signaling proteins that function to activate a MAPK cascade, yet how the upstream proteins actually activate the cascade remains unclear. We also know that the yeast MAPK pathways regulate each other and interact with other signaling pathways to produce a coordinated pattern of gene expression, but the molecular mechanisms of this cross talk are poorly understood. This review is therefore an attempt to present the current knowledge of MAPK pathways in yeast and some directions for future research in this area. PMID:9841672

  4. Post-Transcriptional Regulation of Iron Homeostasis in Saccharomyces cerevisiae

    PubMed Central

    Martínez-Pastor, María Teresa; de Llanos, Rosa; Romero, Antonia María; Puig, Sergi

    2013-01-01

    Iron is an essential micronutrient for all eukaryotic organisms because it participates as a redox cofactor in a wide variety of biological processes. Recent studies in Saccharomyces cerevisiae have shown that in response to iron deficiency, an RNA-binding protein denoted Cth2 coordinates a global metabolic rearrangement that aims to optimize iron utilization. The Cth2 protein contains two Cx8Cx5Cx3H tandem zinc fingers (TZFs) that specifically bind to adenosine/uridine-rich elements within the 3′ untranslated region of many mRNAs to promote their degradation. The Cth2 protein shuttles between the nucleus and the cytoplasm. Once inside the nucleus, Cth2 binds target mRNAs and stimulates alternative 3′ end processing. A Cth2/mRNA-containing complex is required for export to the cytoplasm, where the mRNA is degraded by the 5′ to 3′ degradation pathway. This post-transcriptional regulatory mechanism limits iron utilization in nonessential pathways and activates essential iron-dependent enzymes such as ribonucleotide reductase, which is required for DNA synthesis and repair. Recent findings indicate that the TZF-containing tristetraprolin protein also functions in modulating human iron homeostasis. Elevated iron concentrations can also be detrimental for cells. The Rnt1 RNase III exonuclease protects cells from excess iron by promoting the degradation of a subset of the Fe acquisition system when iron levels rise. PMID:23903042

  5. Water-Transfer Slows Aging in Saccharomyces cerevisiae

    PubMed Central

    Cohen, Aviv; Weindling, Esther; Rabinovich, Efrat; Nachman, Iftach; Fuchs, Shai; Chuartzman, Silvia; Gal, Lihi; Schuldiner, Maya; Bar-Nun, Shoshana

    2016-01-01

    Transferring Saccharomyces cerevisiae cells to water is known to extend their lifespan. However, it is unclear whether this lifespan extension is due to slowing the aging process or merely keeping old yeast alive. Here we show that in water-transferred yeast, the toxicity of polyQ proteins is decreased and the aging biomarker 47Q aggregates at a reduced rate and to a lesser extent. These beneficial effects of water-transfer could not be reproduced by diluting the growth medium and depended on de novo protein synthesis and proteasomes levels. Interestingly, we found that upon water-transfer 27 proteins are downregulated, 4 proteins are upregulated and 81 proteins change their intracellular localization, hinting at an active genetic program enabling the lifespan extension. Furthermore, the aging-related deterioration of the heat shock response (HSR), the unfolded protein response (UPR) and the endoplasmic reticulum-associated protein degradation (ERAD), was largely prevented in water-transferred yeast, as the activities of these proteostatic network pathways remained nearly as robust as in young yeast. The characteristics of young yeast that are actively maintained upon water-transfer indicate that the extended lifespan is the outcome of slowing the rate of the aging process. PMID:26862897

  6. Functional Diversity of Haloacid Dehalogenase Superfamily Phosphatases from Saccharomyces cerevisiae

    PubMed Central

    Kuznetsova, Ekaterina; Nocek, Boguslaw; Brown, Greg; Makarova, Kira S.; Flick, Robert; Wolf, Yuri I.; Khusnutdinova, Anna; Evdokimova, Elena; Jin, Ke; Tan, Kemin; Hanson, Andrew D.; Hasnain, Ghulam; Zallot, Rémi; de Crécy-Lagard, Valérie; Babu, Mohan; Savchenko, Alexei; Joachimiak, Andrzej; Edwards, Aled M.; Koonin, Eugene V.; Yakunin, Alexander F.

    2015-01-01

    The haloacid dehalogenase (HAD)-like enzymes comprise a large superfamily of phosphohydrolases present in all organisms. The Saccharomyces cerevisiae genome encodes at least 19 soluble HADs, including 10 uncharacterized proteins. Here, we biochemically characterized 13 yeast phosphatases from the HAD superfamily, which includes both specific and promiscuous enzymes active against various phosphorylated metabolites and peptides with several HADs implicated in detoxification of phosphorylated compounds and pseudouridine. The crystal structures of four yeast HADs provided insight into their active sites, whereas the structure of the YKR070W dimer in complex with substrate revealed a composite substrate-binding site. Although the S. cerevisiae and Escherichia coli HADs share low sequence similarities, the comparison of their substrate profiles revealed seven phosphatases with common preferred substrates. The cluster of secondary substrates supporting significant activity of both S. cerevisiae and E. coli HADs includes 28 common metabolites that appear to represent the pool of potential activities for the evolution of novel HAD phosphatases. Evolution of novel substrate specificities of HAD phosphatases shows no strict correlation with sequence divergence. Thus, evolution of the HAD superfamily combines the conservation of the overall substrate pool and the substrate profiles of some enzymes with remarkable biochemical and structural flexibility of other superfamily members. PMID:26071590

  7. Mead production: selection and characterization assays of Saccharomyces cerevisiae strains.

    PubMed

    Pereira, Ana Paula; Dias, Teresa; Andrade, João; Ramalhosa, Elsa; Estevinho, Letícia M

    2009-08-01

    Mead is a traditional drink, which results from the alcoholic fermentation of diluted honey carried out by yeasts. However, when it is produced in a homemade way, mead producers find several problems, namely, the lack of uniformity in the final product, delayed and arrested fermentations, and the production of "off-flavours" by the yeasts. These problems are usually associated with the inability of yeast strains to respond and adapt to unfavourable and stressful growth conditions. The main objectives of this work were to evaluate the capacity of Saccharomyces cerevisiae strains, isolated from honey of the Trás-os-Montes (Northeast Portugal), to produce mead. Five strains from honey, as well as one laboratory strain and one commercial wine strain, were evaluated in terms of their fermentation performance under ethanol, sulphur dioxide and osmotic stress. All the strains showed similar behaviour in these conditions. Two yeasts strains isolated from honey and the commercial wine strain were further tested for mead production, using two different honey (a dark and a light honey), enriched with two supplements (one commercial and one developed by the research team), as fermentation media. The results obtained in this work show that S. cerevisiae strains isolated from honey, are appropriate for mead production. However it is of extreme importance to take into account the characteristics of the honey, and supplements used in the fermentation medium formulation, in order to achieve the best results in mead production. PMID:19481129

  8. A novel selection system for chromosome translocations in Saccharomyces cerevisiae.

    PubMed Central

    Tennyson, Rachel B; Ebran, Nathalie; Herrera, Anissa E; Lindsley, Janet E

    2002-01-01

    Chromosomal translocations are common genetic abnormalities found in both leukemias and solid tumors. While much has been learned about the effects of specific translocations on cell proliferation, much less is known about what causes these chromosome rearrangements. This article describes the development and use of a system that genetically selects for rare translocation events using the yeast Saccharomyces cerevisiae. A translocation YAC was created that contains the breakpoint cluster region from the human MLL gene, a gene frequently involved in translocations in leukemia patients, flanked by positive and negative selection markers. A translocation between the YAC and a yeast chromosome, whose breakpoint falls within the MLL DNA, physically separates the markers and forms the basis for the selection. When RAD52 is deleted, essentially all of the selected and screened cells contain simple translocations. The detectable translocation rates are the same in haploids and diploids, although the mechanisms involved and true translocation rates may be distinct. A unique double-strand break induced within the MLL sequences increases the number of detectable translocation events 100- to 1000-fold. This novel system provides a tractable assay for answering basic mechanistic questions about the development of chromosomal translocations. PMID:11973293

  9. Water-Transfer Slows Aging in Saccharomyces cerevisiae.

    PubMed

    Cohen, Aviv; Weindling, Esther; Rabinovich, Efrat; Nachman, Iftach; Fuchs, Shai; Chuartzman, Silvia; Gal, Lihi; Schuldiner, Maya; Bar-Nun, Shoshana

    2016-01-01

    Transferring Saccharomyces cerevisiae cells to water is known to extend their lifespan. However, it is unclear whether this lifespan extension is due to slowing the aging process or merely keeping old yeast alive. Here we show that in water-transferred yeast, the toxicity of polyQ proteins is decreased and the aging biomarker 47Q aggregates at a reduced rate and to a lesser extent. These beneficial effects of water-transfer could not be reproduced by diluting the growth medium and depended on de novo protein synthesis and proteasomes levels. Interestingly, we found that upon water-transfer 27 proteins are downregulated, 4 proteins are upregulated and 81 proteins change their intracellular localization, hinting at an active genetic program enabling the lifespan extension. Furthermore, the aging-related deterioration of the heat shock response (HSR), the unfolded protein response (UPR) and the endoplasmic reticulum-associated protein degradation (ERAD), was largely prevented in water-transferred yeast, as the activities of these proteostatic network pathways remained nearly as robust as in young yeast. The characteristics of young yeast that are actively maintained upon water-transfer indicate that the extended lifespan is the outcome of slowing the rate of the aging process. PMID:26862897

  10. Metabolic engineering of Saccharomyces cerevisiae for itaconic acid production.

    PubMed

    Blazeck, John; Miller, Jarrett; Pan, Anny; Gengler, Jon; Holden, Clinton; Jamoussi, Mariam; Alper, Hal S

    2014-10-01

    Renewable alternatives for petroleum-derived chemicals are achievable through biosynthetic production. Here, we utilize Saccharomyces cerevisiae to enable the synthesis of itaconic acid, a molecule with diverse applications as a petrochemical replacement. We first optimize pathway expression within S. cerevisiae through the use of a hybrid promoter. Next, we utilize sequential, in silico computational genome-scanning to identify beneficial genetic perturbations that are metabolically distant from the itaconic acid synthesis pathway. In this manner, we successfully identify three non-obvious genetic targets (∆ade3 ∆bna2 ∆tes1) that successively improve itaconic acid titer. We establish that focused manipulations of upstream pathway enzymes (localized refactoring) and enzyme re-localization to both mitochondria and cytosol fail to improve itaconic acid titers. Finally, we establish a higher cell density fermentation that ultimately achieves itaconic acid titer of 168 mg/L, a sevenfold improvement over initial conditions. This work represents an attempt to increase itaconic acid production in yeast and demonstrates the successful utilization of computationally guided genetic manipulation to increase metabolic capacity. PMID:24997118

  11. Biochemical basis of mitochondrial acetaldehyde dismutation in Saccharomyces cerevisiae.

    PubMed Central

    Thielen, J; Ciriacy, M

    1991-01-01

    As reported previously, Saccharomyces cerevisiae cells deficient in all four known genes coding for alcohol dehydrogenases (ADH1 through ADH4) produce considerable amounts of ethanol during aerobic growth on glucose. It has been suggested that ethanol production in such adh0 cells is a corollary of acetaldehyde dismutation in mitochondria. This could be substantiated further by showing that mitochondrial ethanol formation requires functional electron transport, while the proton gradient or oxidative phosphorylation does not interfere with reduction of acetaldehyde in isolated mitochondria. This acetaldehyde-reducing activity is different from classical alcohol dehydrogenases in that it is associated with the inner mitochondrial membrane and also is unable to carry out ethanol oxidation. The putative cofactor is NADH + H+ generated by a soluble, matrix-located aldehyde dehydrogenase upon acetaldehyde oxidation to acetate. This enzyme has been purified from mitochondria of glucose-grown cells. It is clearly different from the known mitochondrial aldehyde dehydrogenase, which is absent in glucose-grown cells. Both acetaldehyde-reducing and acetaldehyde-oxidizing activities are also present in the mitochondrial fraction of fermentation-proficient (ADH+) cells. Mitochondrial acetaldehyde dismutation may have some significance in the removal of surplus acetaldehyde and in the formation of acetate in mitochondria during aerobic glucose fermentation. Images FIG. 4 PMID:1938903

  12. Electroinduced release of recombinant β-galactosidase from Saccharomyces cerevisiae.

    PubMed

    Ganeva, Valentina; Stefanova, Debora; Angelova, Boyana; Galutzov, Bojidar; Velasco, Isabel; Arévalo-Rodríguez, Miguel

    2015-10-10

    Yeasts are one of the most commonly used systems for recombinant protein production. When the protein is intracelullarly expressed the first step comprises a cell lysis, achieved usually by a mechanical disintegration. This leads to non-selective liberation of the cytoplasmic content, which complicates the following downstream process. Here, we present a new approach suitable for more selective and efficient recovery of large intracellular proteins from yeast, based on the combination of electropermeabilisation and subsequent treatment with lytic enzyme. The experiments were performed with Saccharomyces cerevisiae strains expressing LYTAG-β-galactosidase from Escherichia coli. The permeabilzation of plasma membrane was induced by application of rectangular electric pulses, with 1.25ms duration and field intensity of 4.3-5.4kV/cm. In the presence of a reducing agent the cells released approximately 80% of the total protein 4h after electrical treatment. At the same conditions the release of the recombinant protein was very slow, reaching 45% from total activity 20h after pulse application. The great difference in the release kinetics enabled to remove a part of the total protein, without significant loss of β-galactosidase activity, only by substituting the incubation buffer. The subsequent addition of lyticase (1-2U/ml) led to recovery of approximately 70% from the recombinant enzyme, with a factor of purification 2.6, without provoking a significant cell lysis. The applicability of similar protocol for liberation of large recombinant and native proteins from yeast is discussed. PMID:26142064

  13. Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

    PubMed Central

    Orlean, Peter

    2012-01-01

    The wall gives a Saccharomyces cerevisiae cell its osmotic integrity; defines cell shape during budding growth, mating, sporulation, and pseudohypha formation; and presents adhesive glycoproteins to other yeast cells. The wall consists of β1,3- and β1,6-glucans, a small amount of chitin, and many different proteins that may bear N- and O-linked glycans and a glycolipid anchor. These components become cross-linked in various ways to form higher-order complexes. Wall composition and degree of cross-linking vary during growth and development and change in response to cell wall stress. This article reviews wall biogenesis in vegetative cells, covering the structure of wall components and how they are cross-linked; the biosynthesis of N- and O-linked glycans, glycosylphosphatidylinositol membrane anchors, β1,3- and β1,6-linked glucans, and chitin; the reactions that cross-link wall components; and the possible functions of enzymatic and nonenzymatic cell wall proteins. PMID:23135325

  14. Biogeographical characterization of Saccharomyces cerevisiae wine yeast by molecular methods

    PubMed Central

    Tofalo, Rosanna; Perpetuini, Giorgia; Schirone, Maria; Fasoli, Giuseppe; Aguzzi, Irene; Corsetti, Aldo; Suzzi, Giovanna

    2013-01-01

    Biogeography is the descriptive and explanatory study of spatial patterns and processes involved in the distribution of biodiversity. Without biogeography, it would be difficult to study the diversity of microorganisms because there would be no way to visualize patterns in variation. Saccharomyces cerevisiae, “the wine yeast,” is the most important species involved in alcoholic fermentation, and in vineyard ecosystems, it follows the principle of “everything is everywhere.” Agricultural practices such as farming (organic versus conventional) and floor management systems have selected different populations within this species that are phylogenetically distinct. In fact, recent ecological and geographic studies highlighted that unique strains are associated with particular grape varieties in specific geographical locations. These studies also highlighted that significant diversity and regional character, or ‘terroir,’ have been introduced into the winemaking process via this association. This diversity of wild strains preserves typicity, the high quality, and the unique flavor of wines. Recently, different molecular methods were developed to study population dynamics of S. cerevisiae strains in both vineyards and wineries. In this review, we will provide an update on the current molecular methods used to reveal the geographical distribution of S. cerevisiae wine yeast. PMID:23805132

  15. Assembly of evolved ligninolytic genes in Saccharomyces cerevisiae.

    PubMed

    Gonzalez-Perez, David; Alcalde, Miguel

    2014-01-01

    The ligninolytic enzymatic consortium produced by white-rot fungi is one of the most efficient oxidative systems found in nature, with many potential applications that range from the production of 2nd generation biofuels to chemicals synthesis. In the current study, two high redox potential oxidoreductase fusion genes (laccase -Lac- and versatile peroxidase -Vp-) that had been evolved in the laboratory were re-assembled in Saccharomyces cerevisiae. First, cell viability and secretion were assessed after co-transforming the Lac and Vp genes into yeast. Several expression cassettes were inserted in vivo into episomal bi-directional vectors in order to evaluate inducible promoter and/or terminator pairs of different strengths in an individual and combined manner. The synthetic white-rot yeast model harboring Vp(GAL1/CYC1)-Lac(GAL10/ADH1) displayed up to 1000 and 100 Units per L of peroxidase and laccase activity, respectively, representing a suitable point of departure for future synthetic biology studies. PMID:24830983

  16. Endocytosis in Saccharomyces cerevisiae: internalization of enveloped viruses into spheroplasts.

    PubMed Central

    Makarow, M

    1985-01-01

    When vesicular stomatitis virus was incubated with Saccharomyces cerevisiae spheroplasts at 37 degrees C, part of the virus was internalized by the spheroplasts as shown by the following criteria. (i) The spheroplast-associated virus was protected from proteinase K digestion, which releases surface-bound virus by degrading the envelope glycoproteins. (ii) The spheroplast-associated virus was resistant to mild Triton X-100 treatment, which readily solubilizes the virus. The same results were obtained with Semliki Forest virus. Internalization of the two viruses followed linear kinetics up to 90 min at 37 degrees C. Internalization was concentration- and temperature-dependent. At 11 degrees C no uptake could be detected for at least 2 h. Homogenization and organelle fractionation protocols were designed for the S. cerevisiae spheroplasts to study the compartments into which the virions were internalized. Three compartments containing both marker viruses could be separated in density gradients. One coincided with vacuole markers, one banded at a slightly higher and one at a similar density to the plasma membrane markers. Thus, S. cerevisiae spheroplasts appear to have the capability of endocytosing particulate markers like viruses. The companion paper describes internalization of two soluble macromolecules, alpha-amylase and fluorescent dextran, into intact cells. Images Fig. 2. Fig. 4. PMID:2992948

  17. Growth characteristics of Saccharomyces rouxii isolated from chocolate syrup.

    PubMed Central

    Restaino, L; Bills, S; Tscherneff, K; Lenovich, L M

    1983-01-01

    We investigated the growth parameters of Saccharomyces rouxii isolated from spoiled chocolate syrup. The optimum pH range for S. rouxii was 3.5 to 5.5, whereas the minimum and maximum pH values that permitted growth were 1.5 and 10.5, respectively. For cells grown in 0 and 60% sucrose the optimum water activity (aw) values were 0.97 and 0.96, respectively. The optimum temperature for S. rouxii increased with a decreasing aw regardless of whether glucose or sucrose was used as the humectant. The optimum temperatures for S. rouxii were 28 degrees C at an aw of greater than 0.995 and 35 degrees C at an aw of 0.96 to 0.90 in 2 X potato dextrose broth with sucrose. Increasing the sorbate concentration (from 0.03 to 0.10%) caused the growth of S. rouxii to become more inhibited between aws of greater than 0.995 and 0.82. S. rouxii did not grow when the sorbate level was 0.12% (wt/vol). At lower sorbate levels, the effect of sorbate on the growth of S. rouxii depended on the aw level. Lowering the aw enhanced the resistance of S. rouxii to increasing concentrations of potassium sorbate. Permeability and polyol production are discussed with respect to sorbate tolerance of S. rouxii at different aw levels. PMID:6615600

  18. [Production of β-carotene by metabolically engineered Saccharomyces cerevisiae].

    PubMed

    Wang, Beibei; Shi, Mingyu; Wang, Dong; Xu, Jiaoyang; Liu, Yi; Yang, Hongjiang; Dai, Zhubo; Zhang, Xueli

    2014-08-01

    β-carotene has a wide range of application in food, pharmaceutical and cosmetic industries. For microbial production of β-carotene in Saccharomyces cerevisiae, the supply of geranylgeranyl diphosphate (GGPP) was firstly increased in S. cerevisiae BY4742 to obtain strain BY4742-T2 through over-expressing truncated 3-hydroxy-3-methylglutaryl-CoA reductase (tHMGR), which is the major rate-limiting enzyme in the mevalonate (MVA) pathway, and GGPP synthase (GGPS), which is a key enzyme in the diterpenoid synthetic pathway. The β-carotene synthetic genes of Pantoea agglomerans and Xanthophyllomyces dendrorhous were further integrated into strain BY4742-T2 for comparing β-carotene production. Over-expression of tHMGR and GGPS genes led to 26.0-fold increase of β-carotene production. In addition, genes from X. dendrorhous was more efficient than those from P. agglomerans for β-carotene production in S. cerevisiae. Strain BW02 was obtained which produced 1.56 mg/g (dry cell weight) β-carotene, which could be used further for constructing cell factories for β-carotene production. PMID:25507473

  19. [Production of β-carotene by metabolically engineered Saccharomyces cerevisiae].

    PubMed

    Wang, Beibei; Shi, Mingyu; Wang, Dong; Xu, Jiaoyang; Liu, Yi; Yang, Hongjiang; Dai, Zhubo; Zhang, Xueli

    2014-08-01

    β-carotene has a wide range of application in food, pharmaceutical and cosmetic industries. For microbial production of β-carotene in Saccharomyces cerevisiae, the supply of geranylgeranyl diphosphate (GGPP) was firstly increased in S. cerevisiae BY4742 to obtain strain BY4742-T2 through over-expressing truncated 3-hydroxy-3-methylglutaryl-CoA reductase (tHMGR), which is the major rate-limiting enzyme in the mevalonate (MVA) pathway, and GGPP synthase (GGPS), which is a key enzyme in the diterpenoid synthetic pathway. The β-carotene synthetic genes of Pantoea agglomerans and Xanthophyllomyces dendrorhous were further integrated into strain BY4742-T2 for comparing β-carotene production. Over-expression of tHMGR and GGPS genes led to 26.0-fold increase of β-carotene production. In addition, genes from X. dendrorhous was more efficient than those from P. agglomerans for β-carotene production in S. cerevisiae. Strain BW02 was obtained which produced 1.56 mg/g (dry cell weight) β-carotene, which could be used further for constructing cell factories for β-carotene production. PMID:25423750

  20. Functional studies of aldo-keto reductases in Saccharomyces cerevisiae*

    PubMed Central

    Chang, Qing; Griest, Terry A.; Harter, Theresa M.; Petrash, J. Mark

    2007-01-01

    SUMMARY We utilized the budding yeast Saccharomyces cerevisiae as a model to systematically explore physiological roles for yeast and mammalian aldo-keto reductases. Six open reading frames encoding putative aldo-keto reductases were identified when the yeast genome was queried against the sequence for human aldose reductase, the prototypical mammalian aldo-keto reductase. Recombinant proteins produced from five of these yeast open reading frames demonstrated NADPH-dependent reductase activity with a variety of aldehyde and ketone substrates. A triple aldo-keto reductase null mutant strain demonstrated a glucose-dependent heat shock phenotype which could be rescued by ectopic expression of human aldose reductase. Catalytically-inactive mutants of human or yeast aldo-keto reductases failed to effect a rescue of the heat shock phenotype, suggesting that the phenotype results from either an accumulation of one or more unmetabolized aldo-keto reductase substrates or a synthetic deficiency of aldo-keto reductase products generated in response to heat shock stress. These results suggest that multiple aldo-keto reductases fulfill functionally redundant roles in the stress response in yeast. PMID:17140678

  1. Systematic Identification of Balanced Transposition Polymorphisms in Saccharomyces cerevisiae

    PubMed Central

    Faddah, Dina A.; Ganko, Eric W.; McCoach, Caroline; Pickrell, Joseph K.; Hanlon, Sean E.; Mann, Frederick G.; Mieczkowska, Joanna O.; Jones, Corbin D.; Lieb, Jason D.; Vision, Todd J.

    2009-01-01

    High-throughput techniques for detecting DNA polymorphisms generally do not identify changes in which the genomic position of a sequence, but not its copy number, varies among individuals. To explore such balanced structural polymorphisms, we used array-based Comparative Genomic Hybridization (aCGH) to conduct a genome-wide screen for single-copy genomic segments that occupy different genomic positions in the standard laboratory strain of Saccharomyces cerevisiae (S90) and a polymorphic wild isolate (Y101) through analysis of six tetrads from a cross of these two strains. Paired-end high-throughput sequencing of Y101 validated four of the predicted rearrangements. The transposed segments contained one to four annotated genes each, yet crosses between S90 and Y101 yielded mostly viable tetrads. The longest segment comprised 13.5 kb near the telomere of chromosome XV in the S288C reference strain and Southern blotting confirmed its predicted location on chromosome IX in Y101. Interestingly, inter-locus crossover events between copies of this segment occurred at a detectable rate. The presence of low-copy repetitive sequences at the junctions of this segment suggests that it may have arisen through ectopic recombination. Our methodology and findings provide a starting point for exploring the origins, phenotypic consequences, and evolutionary fate of this largely unexplored form of genomic polymorphism. PMID:19503594

  2. Population genetics of the wild yeast Saccharomyces paradoxus.

    PubMed Central

    Johnson, Louise J; Koufopanou, Vassiliki; Goddard, Matthew R; Hetherington, Richard; Schäfer, Stefanie M; Burt, Austin

    2004-01-01

    Saccharomyces paradoxus is the closest known relative of the well-known S. cerevisiae and an attractive model organism for population genetic and genomic studies. Here we characterize a set of 28 wild isolates from a 10-km(2) sampling area in southern England. All 28 isolates are homothallic (capable of mating-type switching) and wild type with respect to nutrient requirements. Nine wild isolates and two lab strains of S. paradoxus were surveyed for sequence variation at six loci totaling 7 kb, and all 28 wild isolates were then genotyped at seven polymorphic loci. These data were used to calculate nucleotide diversity and number of segregating sites in S. paradoxus and to investigate geographic differentiation, population structure, and linkage disequilibrium. Synonymous site diversity is approximately 0.3%. Extensive incompatibilities between gene genealogies indicate frequent recombination between unlinked loci, but there is no evidence of recombination within genes. Some localized clonal growth is apparent. The frequency of outcrossing relative to inbreeding is estimated at 1.1% on the basis of heterozygosity. Thus, all three modes of reproduction known in the lab (clonal replication, inbreeding, and outcrossing) have been important in molding genetic variation in this species. PMID:15020405

  3. Potential immobilized Saccharomyces cerevisiae as heavy metal removal

    NASA Astrophysics Data System (ADS)

    Raffar, Nur Izzati Abdul; Rahman, Nadhratul Nur Ain Abdul; Alrozi, Rasyidah; Senusi, Faraziehan; Chang, Siu Hua

    2015-05-01

    Biosorption of copper ion using treated and untreated immobilized Saccharomyces cerevisiae from aqueous solution was investigate in this study. S.cerevisiae has been choosing as biosorbent due to low cost, easy and continuously available from various industries. In this study, the ability of treated and untreated immobilized S.cerevisiae in removing copper ion influence by the effect of pH solution, and initial concentration of copper ion with contact time. Besides, adsorption isotherm and kinetic model also studied. The result indicated that the copper ion uptake on treated and untreated immobilized S.cerevisiae was increased with increasing of contact time and initial concentration of copper ion. The optimum pH for copper ion uptake on untreated and treated immobilized S.cerevisiae at 4 and 6. From the data obtained of copper ion uptake, the adsorption isotherm was fitted well by Freundlich model for treated immobilized S.cerevisiae and Langmuir model for untreated immobilized S.cerevisiae according to high correlation coefficient. Meanwhile, the pseudo second order was described as suitable model present according to high correlation coefficient. Since the application of biosorption process has been received more attention from numerous researchers as a potential process to be applied in the industry, future study will be conducted to investigate the potential of immobilized S.cerevisiae in continuous process.

  4. Adaptation of a Saccharomyces cerevisiae strain to high copper concentrations.

    PubMed

    Sarais, I; Manzano, M; De Bertoldi, M; Romandini, P; Beltramini, M; Salvato, B; Rocco, G P

    1994-07-01

    A strain of Saccharomyces cerevisiae has been adapted to increasing concentrations of copper at two different pH values. The growth curve at pH 5.5 is characterized by a time generation increasing with the amount of added copper. A significant decrease of cell volume as compared with the control is also observed. At pH 3 the cells grow faster than at pH 5.5 and resist higher copper concentrations (3.8 against 1.2 mM). Experimental evidence indicates that, after copper treatment, the metal is not bound to the cell wall, but is localized intracellularly. A significant precipitation of copper salts in the medium was observed only at pH 5.5. Increased levels of superoxide dismutase (SOD) activity were observed in copper-treated cells and which persisted after 20 subsequent inocula in a medium without added metal. On the contrary, catalase activity was not stimulated by copper treatment and, hence, not correlated with SOD levels. The mechanism of copper resistance, therefore, probably involves a persistent induction of SOD, but not of catalase, and it is strongly pH-dependent. PMID:8043987

  5. Effects of spaceflight on polysaccharides of Saccharomyces cerevisiae cell wall.

    PubMed

    Liu, Hong-Zhi; Wang, Qiang; Liu, Xiao-Yong; Tan, Sze-Sze

    2008-12-01

    Freeze-dried samples of four Saccharomyces cerevisiae strains, namely, FL01, FL03, 2.0016, and 2.1424, were subjected to spaceflight. After the satellite's landing on Earth, the samples were recovered and changes in yeast cell wall were analyzed. Spaceflight strains of all S. cerevisiae strains showed significant changes in cell wall thickness (P < 0.05). One mutant of S. cerevisiae 2.0016 with increased biomass, cell wall thickness, and cell wall glucan was isolated (P < 0.05). The spaceflight mutant of S. cerevisiae 2.0016 showed 46.7%, 62.6%, and 146.0% increment in biomass, cell wall thickness and beta-glucan content, respectively, when compared to the ground strain. Moreover, growth curve analysis showed spaceflight S. cerevisiae 2.0016 had a faster growth rate, shorter lag phase periods, higher final biomass, and higher content of beta-glucan. Genetic stability analysis showed that prolonged subculturing of spaceflight strain S. cerevisiae 2.0016 did not lead to the appearance of variants, indicating that the genetic stability of S. cerevisiae 2.0016 mutant could be sufficient for its exploitation of beta-glucan production. PMID:18797865

  6. Protective Effects of Arginine on Saccharomyces cerevisiae Against Ethanol Stress.

    PubMed

    Cheng, Yanfei; Du, Zhaoli; Zhu, Hui; Guo, Xuena; He, Xiuping

    2016-01-01

    Yeast cells are challenged by various environmental stresses in the process of industrial fermentation. As the currently main organism for bio-ethanol production, Saccharomyces cerevisiae suffers from ethanol stress. Some amino acids have been reported to be related to yeast tolerance to stresses. Here the relationship between arginine and yeast response to ethanol stress was investigated. Marked inhibitions of ethanol on cell growth, expression of genes involved in arginine biosynthesis and intracellular accumulation of arginine were observed. Furthermore, extracellular addition of arginine can abate the ethanol damage largely. To further confirm the protective effects of arginine on yeast cells, yeast strains with different levels of arginine content were constructed by overexpression of ARG4 involved in arginine biosynthesis or CAR1 encoding arginase. Intracellular arginine was increased by 18.9% or 13.1% respectively by overexpression of ARG4 or disruption of CAR1, which enhanced yeast tolerance to ethanol stress. Moreover, a 41.1% decrease of intracellular arginine was observed in CAR1 overexpressing strain, which made yeast cells keenly sensitive to ethanol. Further investigations indicated that arginine protected yeast cells from ethanol damage by maintaining the integrity of cell wall and cytoplasma membrane, stabilizing the morphology and function of organellae due to low ROS generation. PMID:27507154

  7. Genetic dissection of acetic acid tolerance in Saccharomyces cerevisiae.

    PubMed

    Geng, Peng; Xiao, Yin; Hu, Yun; Sun, Haiye; Xue, Wei; Zhang, Liang; Shi, Gui-Yang

    2016-09-01

    Dissection of the hereditary architecture underlying Saccharomyces cerevisiae tolerance to acetic acid is essential for ethanol fermentation. In this work, a genomics approach was used to dissect hereditary variations in acetic acid tolerance between two phenotypically different strains. A total of 160 segregants derived from these two strains were obtained. Phenotypic analysis indicated that the acetic acid tolerance displayed a normal distribution in these segregants, and suggested that the acetic acid tolerant traits were controlled by multiple quantitative trait loci (QTLs). Thus, 220 SSR markers covering the whole genome were used to detect QTLs of acetic acid tolerant traits. As a result, three QTLs were located on chromosomes 9, 12, and 16, respectively, which explained 38.8-65.9 % of the range of phenotypic variation. Furthermore, twelve genes of the candidates fell into the three QTL regions by integrating the QTL analysis with candidates of acetic acid tolerant genes. These results provided a novel avenue to obtain more robust strains. PMID:27430512

  8. Lactose fermentation by engineered Saccharomyces cerevisiae capable of fermenting cellobiose.

    PubMed

    Liu, Jing-Jing; Zhang, Guo-Chang; Oh, Eun Joong; Pathanibul, Panchalee; Turner, Timothy L; Jin, Yong-Su

    2016-09-20

    Lactose is an inevitable byproduct of the dairy industry. In addition to cheese manufacturing, the growing Greek yogurt industry generates excess acid whey, which contains lactose. Therefore, rapid and efficient conversion of lactose to fuels and chemicals would be useful for recycling the otherwise harmful acid whey. Saccharomyces cerevisiae, a popular metabolic engineering host, cannot natively utilize lactose. However, we discovered that an engineered S. cerevisiae strain (EJ2) capable of fermenting cellobiose can also ferment lactose. This finding suggests that a cellobiose transporter (CDT-1) can transport lactose and a β-glucosidase (GH1-1) can hydrolyze lactose by acting as a β-galactosidase. While the lactose fermentation by the EJ2 strain was much slower than the cellobiose fermentation, a faster lactose-fermenting strain (EJ2e8) was obtained through serial subcultures on lactose. The EJ2e8 strain fermented lactose with a consumption rate of 2.16g/Lh. The improved lactose fermentation by the EJ2e8 strain was due to the increased copy number of cdt-1 and gh1-1 genes. Looking ahead, the EJ2e8 strain could be exploited for the production of other non-ethanol fuels and chemicals from lactose through further metabolic engineering. PMID:27457698

  9. Purification, characterization, and immunofluorescence localization of Saccharomyces cerevisiae capping protein.

    PubMed

    Amatruda, J F; Cooper, J A

    1992-06-01

    Capping protein binds the barbed ends of actin filaments and nucleates actin filament assembly in vitro. We purified capping protein from Saccharomyces cervisiae. One of the two subunits is the product of the CAP2 gene, which we previously identified as the gene encoding the beta subunit of capping protein based on its sequence similarity to capping protein beta subunits in chicken and Dictyostelium (Amatruda, J. F., J. F. Cannon, K. Tatchell, C. Hug, and J. A. Cooper. 1990. Nature (Lond.) 344:352-354). Yeast capping protein has activity in critical concentration and low-shear viscometry assays consistent with barbed-end capping activity. Like chicken capping protein, yeast capping protein is inhibited by PIP2. By immunofluorescence microscopy yeast capping protein colocalizes with cortical actin spots at the site of bud emergence and at the tips of growing buds and shmoos. In contrast, capping protein does not colocalize with actin cables or with actin rings at the site of cytokinesis. PMID:1315784

  10. Bread, beer and wine: Saccharomyces cerevisiae diversity reflects human history.

    PubMed

    Legras, Jean-Luc; Merdinoglu, Didier; Cornuet, Jean-Marie; Karst, Francis

    2007-05-01

    Fermented beverages and foods have played a significant role in most societies worldwide for millennia. To better understand how the yeast species Saccharomyces cerevisiae, the main fermenting agent, evolved along this historical and expansion process, we analysed the genetic diversity among 651 strains from 56 different geographical origins, worldwide. Their genotyping at 12 microsatellite loci revealed 575 distinct genotypes organized in subgroups of yeast types, i.e. bread, beer, wine, sake. Some of these groups presented unexpected relatedness: Bread strains displayed a combination of alleles intermediate between beer and wine strains, and strains used for rice wine and sake were most closely related to beer and bread strains. However, up to 28% of genetic diversity between these technological groups was associated with geographical differences which suggests local domestications. Focusing on wine yeasts, a group of Lebanese strains were basal in an F(ST) tree, suggesting a Mesopotamia-based origin of most wine strains. In Europe, migration of wine strains occurred through the Danube Valley, and around the Mediterranean Sea. An approximate Bayesian computation approach suggested a postglacial divergence (most probable period 10,000-12,000 bp). As our results suggest intimate association between man and wine yeast across centuries, we hypothesize that yeast followed man and vine migrations as a commensal member of grapevine flora. PMID:17498234

  11. Metabolic Engineering of Saccharomyces cerevisiae for Caffeine and Theobromine Production

    PubMed Central

    Jin, Lu; Bhuiya, Mohammad Wadud; Li, Mengmeng; Liu, XiangQi; Han, Jixiang; Deng, WeiWei; Wang, Min; Yu, Oliver; Zhang, Zhengzhu

    2014-01-01

    Caffeine (1, 3, 7-trimethylxanthine) and theobromine (3, 7-dimethylxanthine) are the major purine alkaloids in plants, e.g. tea (Camellia sinensis) and coffee (Coffea arabica). Caffeine is a major component of coffee and is used widely in food and beverage industries. Most of the enzymes involved in the caffeine biosynthetic pathway have been reported previously. Here, we demonstrated the biosynthesis of caffeine (0.38 mg/L) by co-expression of Coffea arabica xanthosine methyltransferase (CaXMT) and Camellia sinensis caffeine synthase (TCS) in Saccharomyces cerevisiae. Furthermore, we endeavored to develop this production platform for making other purine-based alkaloids. To increase the catalytic activity of TCS in an effort to increase theobromine production, we identified four amino acid residues based on structural analyses of 3D-model of TCS. Two TCS1 mutants (Val317Met and Phe217Trp) slightly increased in theobromine accumulation and simultaneously decreased in caffeine production. The application and further optimization of this biosynthetic platform are discussed. PMID:25133732

  12. Phosphatidylcholine Supply to Peroxisomes of the Yeast Saccharomyces cerevisiae.

    PubMed

    Flis, Vid V; Fankl, Ariane; Ramprecht, Claudia; Zellnig, Günther; Leitner, Erich; Hermetter, Albin; Daum, Günther

    2015-01-01

    In the yeast Saccharomyces cerevisiae, phosphatidylcholine (PC), the major phospholipid (PL) of all organelle membranes, is synthesized via two different pathways. Methylation of phosphatidylethanolamine (PE) catalyzed by the methyl transferases Cho2p/Pem1p and Opi3p/Pem2p as well as incorporation of choline through the CDP (cytidine diphosphate)-choline branch of the Kennedy pathway lead to PC formation. To determine the contribution of these two pathways to the supply of PC to peroxisomes (PX), yeast mutants bearing defects in the two pathways were cultivated under peroxisome inducing conditions, i.e. in the presence of oleic acid, and subjected to biochemical and cell biological analyses. Phenotype studies revealed compromised growth of both the cho20Δopi3Δ (mutations in the methylation pathway) and the cki1Δdpl1Δeki1Δ (mutations in the CDP-choline pathway) mutant when grown on oleic acid. Analysis of peroxisomes from the two mutant strains showed that both pathways produce PC for the supply to peroxisomes, although the CDP-choline pathway seemed to contribute with higher efficiency than the methylation pathway. Changes in the peroxisomal lipid pattern of mutants caused by defects in the PC biosynthetic pathways resulted in changes of membrane properties as shown by anisotropy measurements with fluorescent probes. In summary, our data define the origin of peroxisomal PC and demonstrate the importance of PC for peroxisome membrane formation and integrity. PMID:26241051

  13. Phosphatidylcholine Supply to Peroxisomes of the Yeast Saccharomyces cerevisiae

    PubMed Central

    Ramprecht, Claudia; Zellnig, Günther; Leitner, Erich; Hermetter, Albin; Daum, Günther

    2015-01-01

    In the yeast Saccharomyces cerevisiae, phosphatidylcholine (PC), the major phospholipid (PL) of all organelle membranes, is synthesized via two different pathways. Methylation of phosphatidylethanolamine (PE) catalyzed by the methyl transferases Cho2p/Pem1p and Opi3p/Pem2p as well as incorporation of choline through the CDP (cytidine diphosphate)-choline branch of the Kennedy pathway lead to PC formation. To determine the contribution of these two pathways to the supply of PC to peroxisomes (PX), yeast mutants bearing defects in the two pathways were cultivated under peroxisome inducing conditions, i.e. in the presence of oleic acid, and subjected to biochemical and cell biological analyses. Phenotype studies revealed compromised growth of both the cho20Δopi3Δ (mutations in the methylation pathway) and the cki1Δdpl1Δeki1Δ (mutations in the CDP-choline pathway) mutant when grown on oleic acid. Analysis of peroxisomes from the two mutant strains showed that both pathways produce PC for the supply to peroxisomes, although the CDP-choline pathway seemed to contribute with higher efficiency than the methylation pathway. Changes in the peroxisomal lipid pattern of mutants caused by defects in the PC biosynthetic pathways resulted in changes of membrane properties as shown by anisotropy measurements with fluorescent probes. In summary, our data define the origin of peroxisomal PC and demonstrate the importance of PC for peroxisome membrane formation and integrity. PMID:26241051

  14. Endomitotic effect of a cell cycle mutation of Saccharomyces cerevisiae

    SciTech Connect

    Schild, D.; Ananthaswamy, H.N.; Mortimer, R.K.

    1981-03-01

    A recessive temperature-sensitive mutation of Saccharomyces cerevisiae has been isolated and shown to cause an increase in ploidy in both haploids and diploids. Genetic analysis revealed that the strain carrying the mutation was an aa diploid, although MNNG mutagenesis had been done on an a haploid strain. When the mutant strain was crossed with an ..cap alpha cap alpha.. diploid and the resultant tetraploid sporulated, some of the meiotic progeny of this tetraploid were themselves tetraploid, as shown by both genetic analysis and DNA measurements, instead of diploid as expected of tetraploid meiosis. The ability of these tetraploids to continue to produce tetraploid meiotic progeny was followed for four generations. It was found that tetraploidization was independent of sporulation temperature, but was dependent on the temperature of germination and the growth of the spores. Increase in ploidy occurred when the spores were germinated and grown at 30/sup 0/, but did not occur at 23/sup 0/. Two cycles of sporulation and growth at 23/sup 0/ resulted in haploids, which were shown to diploidize within 24 hr when grown at 30/sup 0/.

  15. Transcriptional regulatory network shapes the genome structure of Saccharomyces cerevisiae

    PubMed Central

    Li, Songling; Heermann, Dieter W.

    2013-01-01

    Among cellular processes gene transcription is central. More and more evidence is mounting that transcription is tightly connected with the spatial organization of the chromosomes. Spatial proximity of genes sharing transcriptional machinery is one of the consequences of this organization. Motivated by information on the physical relationship among genes identified via chromosomal conformation capture methods, we complement the spatial organization with the idea that genes under similar transcription factor control, but possible scattered throughout the genome, might be in physically proximity to facilitate the access of their commonly used transcription factors. Unlike the transcription factory model, “interacting” genes in our “Gene Proximity Model” are not necessarily immediate physical neighbors but are in spatial proximity. Considering the stochastic nature of TF-promoter binding, this local condensation mechanism could serve as a tie to recruit co-regulated genes to guarantee the swiftness of biological reactions. We tested this idea with a simple eukaryotic organism, Saccharomyces cerevisiae. Chromosomal interaction patterns and folding behavior generated by our model re-construct those obtained from experiments. We show that the transcriptional regulatory network has a close linkage with the genome organization in budding yeast, which is fundamental and instrumental to later studies on other more complex eukaryotes. PMID:23674068

  16. Data on dynamic study of cytoophidia in Saccharomyces cerevisiae.

    PubMed

    Li, Hui; Huang, Yong; Wang, Peng-Ye; Ye, Fangfu; Liu, Ji-Long

    2016-09-01

    The data in this paper are related to the research article entitled "Filamentation of metabolic enzymes in Saccharomyces cerevisiae" Q.J. Shen et al. (2016) [1]. Cytoophidia are filamentous structures discovered in fruit flies (doi:10.1016/S1673-8527(09)60046-1) J.L. Liu (2010) [2], bacteria (doi:10.1038/ncb2087) M. Ingerson-Mahar et al. (2010) [3], yeast (doi:10.1083/jcb.201003001; doi:10.1242/bio.20149613) C. Noree et al. (2010) and J. Zhang, L. Hulme, J.L. Liu (2014) [4], [5] and human cells (doi:10.1371/journal.pone.0029690; doi:10.1016/j.jgg.2011.08.004) K. Chen et al. (2011) and W.C. Carcamo et al. (2011) ( [6], [7]. However, there is little research on the motility of the cytoophidia. Here we selected cytoophidia formed by 6 filament-forming proteins in the budding yeast S. cerevisiae, and performed living-cell imaging of cells expressing the proteins fused with GFP. The dynamic features of the six types of cytoophidia were analyzed. In the data, both raw movies and analysed results of the dynamics of cytoophidia are presented. PMID:27274529

  17. Characterization of Alcohol-induced Filamentous Growth in Saccharomyces cerevisiae

    PubMed Central

    Lorenz, Michael C.; Cutler, N. Shane; Heitman, Joseph

    2000-01-01

    Diploid cells of the budding yeast Saccharomyces cerevisiae starved for nitrogen differentiate into a filamentous growth form. Poor carbon sources such as starches can also stimulate filamentation, whereas haploid cells undergo a similar invasive growth response in rich medium. Previous work has demonstrated a role for various alcohols, by-products of amino acid metabolism, in altering cellular morphology. We found that several alcohols, notably isoamyl alcohol and 1-butanol, stimulate filamentous growth in haploid cells in which this differentiation is normally repressed. Butanol also induces cell elongation and changes in budding pattern, leading to a pseudohyphal morphology, even in liquid medium. The filamentous colony morphology and cell elongation require elements of the pheromone-responsive MAPK cascade and TEC1, whereas components of the nutrient-sensing machinery, such as MEP2, GPA2, and GPR1, do not affect this phenomenon. A screen for 1-butanol–insensitive mutants identified additional proteins that regulate polarized growth (BUD8, BEM1, BEM4, and FIG1), mitochondrial function (MSM1, MRP21, and HMI1), and a transcriptional regulator (CHD1). Furthermore, we have also found that ethanol stimulates hyperfilamentation in diploid cells, again in a MAPK-dependent manner. Together, these results suggest that yeast may sense a combination of nutrient limitation and metabolic by-products to regulate differentiation. PMID:10637301

  18. Genetic determinants for enhanced glycerol growth of Saccharomyces cerevisiae.

    PubMed

    Swinnen, Steve; Ho, Ping-Wei; Klein, Mathias; Nevoigt, Elke

    2016-07-01

    The yeast Saccharomyces cerevisiae generally shows a low natural capability to utilize glycerol as the sole source of carbon, particularly when synthetic medium is used and complex supplements are omitted. Nevertheless, wild type isolates have been identified that show a moderate growth under these conditions. In the current study we made use of intraspecies diversity to identify targets suitable for reverse metabolic engineering of the non-growing laboratory strain CEN.PK113-1A. A genome-wide genetic mapping experiment using pooled-segregant whole-genome sequence analysis was conducted, and one major and several minor genetic loci were identified responsible for the superior glycerol growth phenotype of the previously selected S. cerevisiae strain CBS 6412-13A. Downscaling of the major locus by fine-mapping and reciprocal hemizygosity analysis allowed the parallel identification of two superior alleles (UBR2CBS 6412-13A and SSK1CBS 6412-13A). These alleles together with the previously identified GUT1CBS 6412-13A allele were used to replace the corresponding alleles in the strain CEN.PK113-1A. In this way, glycerol growth could be established reaching a maximum specific growth rate of 0.08h(-1). Further improvement to a maximum specific growth rate of 0.11h(-1) could be achieved by heterologous expression of the glycerol facilitator FPS1 from Cyberlindnera jadinii. PMID:26971668

  19. Combinatorial metabolic engineering of Saccharomyces cerevisiae for terminal alkene production.

    PubMed

    Chen, Binbin; Lee, Dong-Yup; Chang, Matthew Wook

    2015-09-01

    Biological production of terminal alkenes has garnered a significant interest due to their industrial applications such as lubricants, detergents and fuels. Here, we engineered the yeast Saccharomyces cerevisiae to produce terminal alkenes via a one-step fatty acid decarboxylation pathway and improved the alkene production using combinatorial engineering strategies. In brief, we first characterized eight fatty acid decarboxylases to enable and enhance alkene production. We then increased the production titer 7-fold by improving the availability of the precursor fatty acids. We additionally increased the titer about 5-fold through genetic cofactor engineering and gene expression tuning in rich medium. Lastly, we further improved the titer 1.8-fold to 3.7 mg/L by optimizing the culturing conditions in bioreactors. This study represents the first report of terminal alkene biosynthesis in S. cerevisiae, and the abovementioned combinatorial engineering approaches collectively increased the titer 67.4-fold. We envision that these approaches could provide insights into devising engineering strategies to improve the production of fatty acid-derived biochemicals in S. cerevisiae. PMID:26164646

  20. In vivo Reconstitution of Algal Triacylglycerol Production in Saccharomyces cerevisiae

    PubMed Central

    Hung, Chun-Hsien; Kanehara, Kazue; Nakamura, Yuki

    2016-01-01

    The current fascination with algal biofuel production stems from a high lipid biosynthetic capacity and little conflict with land plant cultivation. However, the mechanisms which enable algae to accumulate massive oil remain elusive. An enzyme for triacylglycerol (TAG) biosynthesis in Chlamydomonas reinhardtii, CrDGTT2, can produce a large amount of TAG when expressed in yeast or higher plants, suggesting a unique ability of CrDGTT2 to enhance oil production in a heterologous system. Here, we performed metabolic engineering in Saccharomyces cerevisiae by taking advantage of CrDGTT2. We suppressed membrane phospholipid biosynthesis at the log phase by mutating OPI3, enhanced TAG biosynthetic pathway at the stationary phase by overexpressing PAH1 and CrDGTT2, and suppressed TAG hydrolysis on growth resumption from the stationary phase by knocking out DGK1. The resulting engineered yeast cells accumulated about 70-fold of TAG compared with wild type cells. Moreover, TAG production was sustainable. Our results demonstrated the enhanced and sustainable TAG production in the yeast synthetic platform. PMID:26913021

  1. Redundant Regulation of Cdk1 Tyrosine Dephosphorylation in Saccharomyces cerevisiae.

    PubMed

    Kennedy, Erin K; Dysart, Michael; Lianga, Noel; Williams, Elizabeth C; Pilon, Sophie; Doré, Carole; Deneault, Jean-Sebastien; Rudner, Adam D

    2016-03-01

    Cdk1 activity drives both mitotic entry and the metaphase-to-anaphase transition in all eukaryotes. The kinase Wee1 and the phosphatase Cdc25 regulate the mitotic activity of Cdk1 by the reversible phosphorylation of a conserved tyrosine residue. Mutation of cdc25 in Schizosaccharomyces pombe blocks Cdk1 dephosphorylation and causes cell cycle arrest. In contrast, deletion of MIH1, the cdc25 homolog in Saccharomyces cerevisiae, is viable. Although Cdk1-Y19 phosphorylation is elevated during mitosis in mih1∆ cells, Cdk1 is dephosphorylated as cells progress into G1, suggesting that additional phosphatases regulate Cdk1 dephosphorylation. Here we show that the phosphatase Ptp1 also regulates Cdk1 dephosphorylation in vivo and can directly dephosphorylate Cdk1 in vitro. Using a novel in vivo phosphatase assay, we also show that PP2A bound to Rts1, the budding yeast B56-regulatory subunit, regulates dephosphorylation of Cdk1 independently of a function regulating Swe1, Mih1, or Ptp1, suggesting that PP2A(Rts1) either directly dephosphorylates Cdk1-Y19 or regulates an unidentified phosphatase. PMID:26715668

  2. Sucrose and Saccharomyces cerevisiae: a relationship most sweet.

    PubMed

    Marques, Wesley Leoricy; Raghavendran, Vijayendran; Stambuk, Boris Ugarte; Gombert, Andreas Karoly

    2016-02-01

    Sucrose is an abundant, readily available and inexpensive substrate for industrial biotechnology processes and its use is demonstrated with much success in the production of fuel ethanol in Brazil. Saccharomyces cerevisiae, which naturally evolved to efficiently consume sugars such as sucrose, is one of the most important cell factories due to its robustness, stress tolerance, genetic accessibility, simple nutrient requirements and long history as an industrial workhorse. This minireview is focused on sucrose metabolism in S. cerevisiae, a rather unexplored subject in the scientific literature. An analysis of sucrose availability in nature and yeast sugar metabolism was performed, in order to understand the molecular background that makes S. cerevisiae consume this sugar efficiently. A historical overview on the use of sucrose and S. cerevisiae by humans is also presented considering sugarcane and sugarbeet as the main sources of this carbohydrate. Physiological aspects of sucrose consumption are compared with those concerning other economically relevant sugars. Also, metabolic engineering efforts to alter sucrose catabolism are presented in a chronological manner. In spite of its extensive use in yeast-based industries, a lot of basic and applied research on sucrose metabolism is imperative, mainly in fields such as genetics, physiology and metabolic engineering. PMID:26658003

  3. Investigation of Batten disease with the yeast Saccharomyces cerevisiae.

    PubMed

    Pearce, D A; Sherman, F

    1999-04-01

    The CLN3 gene, which encodes the protein whose absence is responsible for Batten disease, the most common inherited neurovisceral storage disease of childhood, was identified in 1995. The function of the protein, Cln3p, still remains elusive. We previously cloned the Saccharomyces cerevisiae homolog to the human CLN3 gene, designated BTN1, whose product is 39% identical and 59% similar to Cln3p. We report that yeast strains lacking Btn1p, btn1-Delta deletion yeast strains, are more resistant to d-(-)-threo-2-amino-1-[p-nitrophenyl]-1,3-propanediol (ANP), in a pH-dependent manner. This phenotype is complemented in yeast by the human CLN3 gene. In addition, point mutations characterized in CLN3 from individuals with less severe forms of Batten disease, when introduced into BTN1, altered the degree of ANP resistance. Severity of Batten disease due to mutations in CLN3 and the degree of ANP resistance in yeast are related when the equivalent amino acid replacements in Cln3p and Btn1p are compared. These results indicate that yeast can be used as a model for the study of Batten disease. PMID:10191120

  4. Brazilian propolis protects Saccharomyces cerevisiae cells against oxidative stress

    PubMed Central

    de Sá, Rafael A.; de Castro, Frederico A.V.; Eleutherio, Elis C.A.; de Souza, Raquel M.; da Silva, Joaquim F.M.; Pereira, Marcos D.

    2013-01-01

    Propolis is a natural product widely used for humans. Due to its complex composition, a number of applications (antimicrobial, antiinflammatory, anesthetic, cytostatic and antioxidant) have been attributed to this substance. Using Saccharomyces cerevisiae as a eukaryotic model we investigated the mechanisms underlying the antioxidant effect of propolis from Guarapari against oxidative stress. Submitting a wild type (BY4741) and antioxidant deficient strains (ctt1Δ, sod1Δ, gsh1Δ, gtt1Δ and gtt2Δ) either to 15 mM menadione or to 2 mM hydrogen peroxide during 60 min, we observed that all strains, except the mutant sod1Δ, acquired tolerance when previously treated with 25 μg/mL of alcoholic propolis extract. Such a treatment reduced the levels of ROS generation and of lipid peroxidation, after oxidative stress. The increase in Cu/Zn-Sod activity by propolis suggests that the protection might be acting synergistically with Cu/Zn-Sod. PMID:24516431

  5. Carboxylic Acids Plasma Membrane Transporters in Saccharomyces cerevisiae.

    PubMed

    Casal, Margarida; Queirós, Odília; Talaia, Gabriel; Ribas, David; Paiva, Sandra

    2016-01-01

    This chapter covers the functionally characterized plasma membrane carboxylic acids transporters Jen1, Ady2, Fps1 and Pdr12 in the yeast Saccharomyces cerevisiae, addressing also their homologues in other microorganisms, as filamentous fungi and bacteria. Carboxylic acids can either be transported into the cells, to be used as nutrients, or extruded in response to acid stress conditions. The secondary active transporters Jen1 and Ady2 can mediate the uptake of the anionic form of these substrates by a H(+)-symport mechanism. The undissociated form of carboxylic acids is lipid-soluble, crossing the plasma membrane by simple diffusion. Furthermore, acetic acid can also be transported by facilitated diffusion via Fps1 channel. At the cytoplasmic physiological pH, the anionic form of the acid prevails and it can be exported by the Pdr12 pump. This review will highlight the mechanisms involving carboxylic acids transporters, and the way they operate according to the yeast cell response to environmental changes, as carbon source availability, extracellular pH and acid stress conditions. PMID:26721276

  6. Global landscape of protein complexes in the yeast Saccharomyces cerevisiae.

    PubMed

    Krogan, Nevan J; Cagney, Gerard; Yu, Haiyuan; Zhong, Gouqing; Guo, Xinghua; Ignatchenko, Alexandr; Li, Joyce; Pu, Shuye; Datta, Nira; Tikuisis, Aaron P; Punna, Thanuja; Peregrín-Alvarez, José M; Shales, Michael; Zhang, Xin; Davey, Michael; Robinson, Mark D; Paccanaro, Alberto; Bray, James E; Sheung, Anthony; Beattie, Bryan; Richards, Dawn P; Canadien, Veronica; Lalev, Atanas; Mena, Frank; Wong, Peter; Starostine, Andrei; Canete, Myra M; Vlasblom, James; Wu, Samuel; Orsi, Chris; Collins, Sean R; Chandran, Shamanta; Haw, Robin; Rilstone, Jennifer J; Gandi, Kiran; Thompson, Natalie J; Musso, Gabe; St Onge, Peter; Ghanny, Shaun; Lam, Mandy H Y; Butland, Gareth; Altaf-Ul, Amin M; Kanaya, Shigehiko; Shilatifard, Ali; O'Shea, Erin; Weissman, Jonathan S; Ingles, C James; Hughes, Timothy R; Parkinson, John; Gerstein, Mark; Wodak, Shoshana J; Emili, Andrew; Greenblatt, Jack F

    2006-03-30

    Identification of protein-protein interactions often provides insight into protein function, and many cellular processes are performed by stable protein complexes. We used tandem affinity purification to process 4,562 different tagged proteins of the yeast Saccharomyces cerevisiae. Each preparation was analysed by both matrix-assisted laser desorption/ionization-time of flight mass spectrometry and liquid chromatography tandem mass spectrometry to increase coverage and accuracy. Machine learning was used to integrate the mass spectrometry scores and assign probabilities to the protein-protein interactions. Among 4,087 different proteins identified with high confidence by mass spectrometry from 2,357 successful purifications, our core data set (median precision of 0.69) comprises 7,123 protein-protein interactions involving 2,708 proteins. A Markov clustering algorithm organized these interactions into 547 protein complexes averaging 4.9 subunits per complex, about half of them absent from the MIPS database, as well as 429 additional interactions between pairs of complexes. The data (all of which are available online) will help future studies on individual proteins as well as functional genomics and systems biology. PMID:16554755

  7. Bioflavour production from orange peel hydrolysate using immobilized Saccharomyces cerevisiae.

    PubMed

    Lalou, Sofia; Mantzouridou, Fani; Paraskevopoulou, Adamantini; Bugarski, Branko; Levic, Steva; Nedovic, Victor

    2013-11-01

    The rising trend of bioflavour synthesis by microorganisms is hindered by the high manufacturing costs, partially attributed to the cost of the starting material. To overcome this limitation, in the present study, dilute-acid hydrolysate of orange peel was employed as a low-cost, rich in fermentable sugars substrate for the production of flavour-active compounds by Saccharomyces cerevisiae. With this purpose, the use of immobilized cell technology to protect cells against the various inhibitory compounds present in the hydrolysate was evaluated with regard to yeast viability, carbon and nitrogen consumption and cell ability to produce flavour active compounds. For cell immobilization the encapsulation in Ca alginate beads was used. The results were compared with those obtained using free-cell system. Based on the data obtained immobilized cells showed better growth performance and increased ability for de novo synthesis of volatile esters of "fruity" aroma (phenylethyl acetate, ethyl hexanoate, octanoate, decanoate and dodecanoate) than those of free cells. The potential for in situ production of new formulations containing flavour-active compounds derive from yeast cells and also from essential oil of orange peel (limonene, α-terpineol) was demonstrated by the fact that bioflavour mixture was found to accumulate within the beads. Furthermore, the ability of the immobilized yeast to perform efficiently repeated batch fermentations of orange peel hydrolysate for bioflavour production was successfully maintained after six consecutive cycles of a total period of 240 h. PMID:23995224

  8. Characterization of a mitochondrial inorganic pyrophosphatase in Saccharomyces cerevisiae.

    PubMed

    Lundin, M; Deopujari, S W; Lichko, L; da Silva, L P; Baltscheffsky, H

    1992-01-16

    We have studied a mitochondrial inorganic pyrophosphatase (PPase) in the yeast Saccharomyces cerevisiae. The uncoupler FCCP (carbonyl cyanide p-trifluoromethoxyphenylhydrazone) and the ionophores valinomycin and nigericin stimulate the PPase activity of repeatedly washed yeast mitochondria 2-3-fold. We have previously cloned a yeast gene, PPA2, encoding the catalytic subunit of a mitochondrial PPase. Uncouplers stimulate the PPase activity several-fold in mitochondria from both cells that overexpress PPA2 from a high copy number plasmid and cells with normal expression. These results indicate that the PPA2 polypeptide functions as an energy linked and membrane associated PPase. The stimulation of mitochondrial PPase activity by FCCP, but not by valinomycin and nigericin, was greatly enhanced by the presence of DTT. The antibiotics Dio-9, equisetin and the F0F1-ATPase inhibitor oligomycin also increase mitochondrial PPase activity several fold. This stimulation is much higher, whereas basal PPase activity is lower, in isotonic than in hypotonic solution, which indicates that intact membranes are a prerequisite for maximal effects. PMID:1309654

  9. D-xylulose fermentation to ethanol by Saccharomyces cerevisiae

    SciTech Connect

    Chiang, L.C.; Gong, C.S.; Chen, L.F.; Tsao, G.T.

    1981-08-01

    Commercial bakers' yeast (Saccharomyces cerevisiae) was used to study the conversion of D-xylulose to ethanol in the presence of D-xylose. The rate of ethanol production increased with an increase in yeast cell density. The optimal temperature for D-xylulose fermentation was 35 degrees Celcius, and the optimal pH range was 4 to 6. The fermentation of D-xylulose by yeast resulted in the production of ethanol as the major product; small amounts of xylitol and glycerol were also produced. The production of xylitol was influenced by pH as well as temperature. High pH values and low temperatures enhanced xylitol production. The rate of D-xylulose fermentation decreased when the production of ethanol yielded concentrations of 4% or more. The slow conversion rate of D-xylulose to ethanol was increased by increasing the yeast cell density. The overall production of ethanol from D-xylulose by yeast cells under optimal conditions was 90% of the theoretical yield. (Refs. 21).

  10. Symmetric cell division in pseudohyphae of the yeast Saccharomyces cerevisiae.

    PubMed Central

    Kron, S J; Styles, C A; Fink, G R

    1994-01-01

    Laboratory strains of Saccharomyces cerevisiae are dimorphic; in response to nitrogen starvation they switch from a yeast form (YF) to a filamentous pseudohyphal (PH) form. Time-lapse video microscopy of dividing cells reveals that YF and PH cells differ in their cell cycles and budding polarity. The YF cell cycle is controlled at the G1/S transition by the cell-size checkpoint Start. YF cells divide asymmetrically, producing small daughters from full-sized mothers. As a result, mothers and daughters bud asynchronously. Mothers bud immediately but daughters grow in G1 until they achieve a critical cell size. By contrast, PH cells divide symmetrically, restricting mitosis until the bud grows to the size of the mother. Thus, mother and daughter bud synchronously in the next cycle, without a G1 delay before Start. YF and PH cells also exhibit distinct bud-site selection patterns. YF cells are bipolar, producing their second and subsequent buds at either pole. PH cells are unipolar, producing their second and subsequent buds only from the end opposite the junction with their mother. We propose that in PH cells a G2 cell-size checkpoint delays mitosis until bud size reaches that of the mother cell. We conclude that yeast and PH forms are distinct cell types each with a unique cell cycle, budding pattern, and cell shape. Images PMID:7841518

  11. Complete nucleotide sequence of Saccharomyces cerevisiae chromosome X.

    PubMed Central

    Galibert, F; Alexandraki, D; Baur, A; Boles, E; Chalwatzis, N; Chuat, J C; Coster, F; Cziepluch, C; De Haan, M; Domdey, H; Durand, P; Entian, K D; Gatius, M; Goffeau, A; Grivell, L A; Hennemann, A; Herbert, C J; Heumann, K; Hilger, F; Hollenberg, C P; Huang, M E; Jacq, C; Jauniaux, J C; Katsoulou, C; Karpfinger-Hartl, L

    1996-01-01

    The complete nucleotide sequence of Saccharomyces cerevisiae chromosome X (745 442 bp) reveals a total of 379 open reading frames (ORFs), the coding region covering approximately 75% of the entire sequence. One hundred and eighteen ORFs (31%) correspond to genes previously identified in S. cerevisiae. All other ORFs represent novel putative yeast genes, whose function will have to be determined experimentally. However, 57 of the latter subset (another 15% of the total) encode proteins that show significant analogy to proteins of known function from yeast or other organisms. The remaining ORFs, exhibiting no significant similarity to any known sequence, amount to 54% of the total. General features of chromosome X are also reported, with emphasis on the nucleotide frequency distribution in the environment of the ATG and stop codons, the possible coding capacity of at least some of the small ORFs (<100 codons) and the significance of 46 non-canonical or unpaired nucleotides in the stems of some of the 24 tRNA genes recognized on this chromosome. Images PMID:8641269

  12. Transformations of inorganic mercury by Candida albicans and Saccharomyces cerevisiae

    SciTech Connect

    Yannai, S.; Berdicevsky, I.; Duek, L. )

    1991-01-01

    Saccharomyces cerevisiae and Candida albicans were incubated with 0.25, 0.5, or 0.75 {mu}g of Hg (as HgCl{sub 2}) per ml of Nelson's medium in the presence of trace amounts of oxygen at 28{degree}C for 12 days. Two control media were used, one without added Hg and one without yeast inoculum. Yeast cell growth was estimated after 1, 2, 3, and 8 days of incubation. The contents of organomercury in the system and of elemental mercury released from the media and collected in traps were determined at the end of the experiments. The results were as follows: (1) C. albicans was the more mercury-resistant species, but both yeast species failed to grown in the media containing 0.75 {mu}g of Hg per ml.; (2) The amounts of organomercury produced by the two species were proportional to the amount of HgCl{sub 2} added to the medium. In all cases C. albicans produced considerably larger amounts of methylmercury than S. cerevisiae; (3) The amounts of elemental Hg produced were inversely proportional to the HgCl{sub 2} level added in the case of S. cerevisiae but were all similar in the case of C. albicans;and (4) Neither organomercury nor elemental Hg was produced in any of the control media.

  13. Oxygen requirements of yeasts. [Saccharomyces cerevisiae; Candida tropicalis

    SciTech Connect

    Visser, W.; Scheffers, W.A.; Batenburg-Van Der Vegte, W.H.; Van Dijken, J.P. )

    1990-12-01

    Type species of 75 yeast genera were examined for their ability to grow anaerobically in complex and mineral media. To define anaerobic conditions, we added a redox indicator, resazurin, to the media to determine low redox potentials. All strains tested were capable of fermenting glucose to ethanol in oxygen-limited shake-flask cultures, even those of species generally regarded as nonfermentative. However, only 23% of the yeast species tested grew under anaerobic conditions. A comparative study with a number of selected strains revealed that Saccharomyces cerevisiae stands out as a yeast capable of rapid growth at low redox potentials. Other yeasts, such as Torulaspora delbrueckii and Candida tropicalis, grew poorly ({mu}{sub max}, 0.03 and 0.05 h{sup {minus}1}, respectively) under anaerobic conditions in mineral medium supplemented with Tween 80 and ergosterol. The latter organisms grew rapidly under oxygen limitation and then displayed a high rate of alcoholic fermentation. It can be concluded that these yeasts have hitherto-unidentified oxygen requirements for growth.

  14. Xylose Fermentation by Saccharomyces cerevisiae: Challenges and Prospects

    PubMed Central

    Moysés, Danuza Nogueira; Reis, Viviane Castelo Branco; de Almeida, João Ricardo Moreira; de Moraes, Lidia Maria Pepe; Torres, Fernando Araripe Gonçalves

    2016-01-01

    Many years have passed since the first genetically modified Saccharomyces cerevisiae strains capable of fermenting xylose were obtained with the promise of an environmentally sustainable solution for the conversion of the abundant lignocellulosic biomass to ethanol. Several challenges emerged from these first experiences, most of them related to solving redox imbalances, discovering new pathways for xylose utilization, modulation of the expression of genes of the non-oxidative pentose phosphate pathway, and reduction of xylitol formation. Strategies on evolutionary engineering were used to improve fermentation kinetics, but the resulting strains were still far from industrial application. Lignocellulosic hydrolysates proved to have different inhibitors derived from lignin and sugar degradation, along with significant amounts of acetic acid, intrinsically related with biomass deconstruction. This, associated with pH, temperature, high ethanol, and other stress fluctuations presented on large scale fermentations led the search for yeasts with more robust backgrounds, like industrial strains, as engineering targets. Some promising yeasts were obtained both from studies of stress tolerance genes and adaptation on hydrolysates. Since fermentation times on mixed-substrate hydrolysates were still not cost-effective, the more selective search for new or engineered sugar transporters for xylose are still the focus of many recent studies. These challenges, as well as under-appreciated process strategies, will be discussed in this review. PMID:26927067

  15. Regulation of protein synthesis during early limitation of Saccharomyces cerevisiae.

    PubMed Central

    Swedes, J S; Dial, M E; McLaughlin, C S

    1979-01-01

    Arsenate, a competitive inhibitor with phosphate in phosphorylation reactions, has been used to lower adenine and guanine nucleotide levels in Saccharomyces cerevisiae to study nucleotide effects on protein synthesis. By measuring polysome levels, we have shown that initiation of protein synthesis is much more sensitive than elongation or termination to inhibition when the ATP/ADP, GTP/GDP ratios are low. When the arsenate-phosphate molar ratio was 0.27, protein synthesis was inhibited by about 85% and the kinetics of polysome decay was similar to that observed with the initiation inhibitor, verrucarin-76, or with the protein synthesis initiation mutant, ts187, at the restrictive temperature. With this level of arsenate, the adenylate energy charge dropped from 0.9 to 0.7 and the ATP/ADP and GTP/GDP ratios dropped from 6 to 2. The observed correlations between nucleotide ratio changes and inhibition of protein synthesis suggest that the former may be a control signal for the latter. The significance of these in vivo correlations will have to be tested with an in vitro protein synthesizing system. Higher arsenate levels resulted in even lower ATP/ADP, GTP/GDP ratios and in a slower decay of polysomes, implying that, eventually, elongation (in addition to initiation) was being inhibited. PMID:374362

  16. Nutrient sensing and signaling in the yeast Saccharomyces cerevisiae

    PubMed Central

    Conrad, Michaela; Schothorst, Joep; Kankipati, Harish Nag; Van Zeebroeck, Griet; Rubio-Texeira, Marta; Thevelein, Johan M

    2014-01-01

    The yeast Saccharomyces cerevisiae has been a favorite organism for pioneering studies on nutrient-sensing and signaling mechanisms. Many specific nutrient responses have been elucidated in great detail. This has led to important new concepts and insight into nutrient-controlled cellular regulation. Major highlights include the central role of the Snf1 protein kinase in the glucose repression pathway, galactose induction, the discovery of a G-protein-coupled receptor system, and role of Ras in glucose-induced cAMP signaling, the role of the protein synthesis initiation machinery in general control of nitrogen metabolism, the cyclin-controlled protein kinase Pho85 in phosphate regulation, nitrogen catabolite repression and the nitrogen-sensing target of rapamycin pathway, and the discovery of transporter-like proteins acting as nutrient sensors. In addition, a number of cellular targets, like carbohydrate stores, stress tolerance, and ribosomal gene expression, are controlled by the presence of multiple nutrients. The protein kinase A signaling pathway plays a major role in this general nutrient response. It has led to the discovery of nutrient transceptors (transporter receptors) as nutrient sensors. Major shortcomings in our knowledge are the relationship between rapid and steady-state nutrient signaling, the role of metabolic intermediates in intracellular nutrient sensing, and the identity of the nutrient sensors controlling cellular growth. PMID:24483210

  17. Long-chain alkane production by the yeast Saccharomyces cerevisiae.

    PubMed

    Buijs, Nicolaas A; Zhou, Yongjin J; Siewers, Verena; Nielsen, Jens

    2015-06-01

    In the past decade industrial-scale production of renewable transportation biofuels has been developed as an alternative to fossil fuels, with ethanol as the most prominent biofuel and yeast as the production organism of choice. However, ethanol is a less efficient substitute fuel for heavy-duty and maritime transportation as well as aviation due to its low energy density. Therefore, new types of biofuels, such as alkanes, are being developed that can be used as drop-in fuels and can substitute gasoline, diesel, and kerosene. Here, we describe for the first time the heterologous biosynthesis of long-chain alkanes by the yeast Saccharomyces cerevisiae. We show that elimination of the hexadecenal dehydrogenase Hfd1 and expression of a redox system are essential for alkane biosynthesis in yeast. Deletion of HFD1 together with expression of an alkane biosynthesis pathway resulted in the production of the alkanes tridecane, pentadecane, and heptadecane. Our study provides a proof of principle for producing long-chain alkanes in the industrial workhorse S. cerevisiae, which was so far limited to bacteria. We anticipate that these findings will be a key factor for further yeast engineering to enable industrial production of alkane based drop-in biofuels, which can allow the biofuel industry to diversify beyond bioethanol. PMID:25545362

  18. Membrane Trafficking in the Yeast Saccharomyces cerevisiae Model

    PubMed Central

    Feyder, Serge; De Craene, Johan-Owen; Bär, Séverine; Bertazzi, Dimitri L.; Friant, Sylvie

    2015-01-01

    The yeast Saccharomyces cerevisiae is one of the best characterized eukaryotic models. The secretory pathway was the first trafficking pathway clearly understood mainly thanks to the work done in the laboratory of Randy Schekman in the 1980s. They have isolated yeast sec mutants unable to secrete an extracellular enzyme and these SEC genes were identified as encoding key effectors of the secretory machinery. For this work, the 2013 Nobel Prize in Physiology and Medicine has been awarded to Randy Schekman; the prize is shared with James Rothman and Thomas Südhof. Here, we present the different trafficking pathways of yeast S. cerevisiae. At the Golgi apparatus newly synthesized proteins are sorted between those transported to the plasma membrane (PM), or the external medium, via the exocytosis or secretory pathway (SEC), and those targeted to the vacuole either through endosomes (vacuolar protein sorting or VPS pathway) or directly (alkaline phosphatase or ALP pathway). Plasma membrane proteins can be internalized by endocytosis (END) and transported to endosomes where they are sorted between those targeted for vacuolar degradation and those redirected to the Golgi (recycling or RCY pathway). Studies in yeast S. cerevisiae allowed the identification of most of the known effectors, protein complexes, and trafficking pathways in eukaryotic cells, and most of them are conserved among eukaryotes. PMID:25584613

  19. Quantifying separation and similarity in a Saccharomyces cerevisiae metapopulation

    PubMed Central

    Knight, Sarah; Goddard, Matthew R

    2015-01-01

    Eukaryotic microbes are key ecosystem drivers; however, we have little theory and few data elucidating the processes influencing their observed population patterns. Here we provide an in-depth quantitative analysis of population separation and similarity in the yeast Saccharomyces cerevisiae with the aim of providing a more detailed account of the population processes occurring in microbes. Over 10 000 individual isolates were collected from native plants, vineyards and spontaneous ferments of fruit from six major regions spanning 1000 km across New Zealand. From these, hundreds of S. cerevisiae genotypes were obtained, and using a suite of analytical methods we provide comprehensive quantitative estimates for both population structure and rates of gene flow or migration. No genetic differentiation was detected within geographic regions, even between populations inhabiting native forests and vineyards. We do, however, reveal a picture of national population structure at scales above ∼100 km with distinctive populations in the more remote Nelson and Central Otago regions primarily contributing to this. In addition, differential degrees of connectivity between regional populations are observed and correlate with the movement of fruit by the New Zealand wine industry. This suggests some anthropogenic influence on these observed population patterns. PMID:25062126

  20. Saccharomyces pastorianus: genomic insights inspiring innovation for industry.

    PubMed

    Gibson, Brian; Liti, Gianni

    2015-01-01

    A combination of biological and non-biological factors has led to the interspecific hybrid yeast species Saccharomyces pastorianus becoming one of the world's most important industrial organisms. This yeast is used in the production of lager-style beers, the fermentation of which requires very low temperatures compared to other industrial fermentation processes. This group of organisms has benefited from both the whole-genome duplication in its ancestral lineage and the subsequent hybridization event between S. cerevisiae and S. eubayanus, resulting in strong fermentative ability. The hybrid has key traits, such as cold tolerance and good maltose- and maltotriose-utilizing ability, inherited either from the parental species or originating from genetic interactions between the parent genomes. Instability in the nascent allopolyploid hybrid genome may have contributed to rapid evolution of the yeast to tolerate conditions prevalent in the brewing environment. The recent discovery of S. eubayanus has provided new insights into the evolutionary history of S. pastorianus and may offer new opportunities for generating novel industrially-beneficial lager yeast strains. PMID:25088523

  1. Reciprocal translocations in Saccharomyces cerevisiae formed by nonhomologous end joining.

    PubMed

    Yu, Xin; Gabriel, Abram

    2004-02-01

    Reciprocal translocations are common in cancer cells, but their creation is poorly understood. We have developed an assay system in Saccharomyces cerevisiae to study reciprocal translocation formation in the absence of homology. We induce two specific double-strand breaks (DSBs) simultaneously on separate chromosomes with HO endonuclease and analyze the subsequent chromosomal rearrangements among surviving cells. Under these conditions, reciprocal translocations via nonhomologous end joining (NHEJ) occur at frequencies of approximately 2-7 x 10(-5)/cell exposed to the DSBs. Yku80p is a component of the cell's NHEJ machinery. In its absence, reciprocal translocations still occur, but the junctions are associated with deletions and extended overlapping sequences. After induction of a single DSB, translocations and inversions are recovered in wild-type and rad52 strains. In these rearrangements, a nonrandom assortment of sites have fused to the DSB, and their junctions show typical signs of NHEJ. The sites tend to be between open reading frames or within Ty1 LTRs. In some cases the translocation partner is formed by a break at a cryptic HO recognition site. Our results demonstrate that NHEJ-mediated reciprocal translocations can form in S. cerevisiae as a consequence of DSB repair. PMID:15020464

  2. Metabolomic approach for improving ethanol stress tolerance in Saccharomyces cerevisiae.

    PubMed

    Ohta, Erika; Nakayama, Yasumune; Mukai, Yukio; Bamba, Takeshi; Fukusaki, Eiichiro

    2016-04-01

    The budding yeast Saccharomyces cerevisiae is widely used for brewing and ethanol production. The ethanol sensitivity of yeast cells is still a serious problem during ethanol fermentation, and a variety of genetic approaches (e.g., random mutant screening under selective pressure of ethanol) have been developed to improve ethanol tolerance. In this study, we developed a strategy for improving ethanol tolerance of yeast cells based on metabolomics as a high-resolution quantitative phenotypic analysis. We performed gas chromatography-mass spectrometry analysis to identify and quantify 36 compounds on 14 mutant strains including knockout strains for transcription factor and metabolic enzyme genes. A strong relation between metabolome of these mutants and their ethanol tolerance was observed. Data mining of the metabolomic analysis showed that several compounds (such as trehalose, valine, inositol and proline) contributed highly to ethanol tolerance. Our approach successfully detected well-known ethanol stress related metabolites such as trehalose and proline thus, to further prove our strategy, we focused on valine and inositol as the most promising target metabolites in our study. Our results show that simultaneous deletion of LEU4 and LEU9 (leading to accumulation of valine) or INM1 and INM2 (leading to reduction of inositol) significantly enhanced ethanol tolerance. This study shows the potential of the metabolomic approach to identify target genes for strain improvement of S. cerevisiae with higher ethanol tolerance. PMID:26344121

  3. Nutritional and environmental factors in ethanol fermentation by Saccharomyces cerevisiae

    SciTech Connect

    Wong, H.; Wilke, C.R.; Blanch, H.W.

    1983-05-01

    Using Saccharomyces cerevisiae as a model system, a basic study of the nutritional and environmental factors in ethanol fermentation was carried out to provide fundamental and practical bases for design of fermentation media and culture conditions. The requirements for all active medium components need to be determined in order to establish balanced media, which are important to reduce raw materials costs and to minimize inhibition from buildup of excess feed components in recycle processes with selective ethanol removal. Pulse injection of nutrients into continuous cultures was an effective method for screening active nutrients. In a systematic sensitivity analysis the effect of feed concentration of these individual nutrients was then determined and allowed formulation of media optimal with respect to the major fermentation parameters. Biotin, pantothenate, myo-inositol, potassium and phosphates appeared to stimulate growth preferentially to ethanol production. In contrast, thiamine and pyridoxine appeared to enhance specific ethanol productivity. The effect of ammonium sulfate depended on concentration. A conceptual model was proposed to relate the effects of these nutrients to biochemical pathways and functions. With these data and model the minimum cost combination of raw materials to achieve a medium of well defined components can be determined with a linear program. This computer program shows that many growth factors and minerals can be added to media more economically as pure components than as fractions of complex factors. 225 references, 61 figures, 54 tables.

  4. Nutritional and environmental factors in ethanol fermentation by Saccharomyces cerevisiae

    SciTech Connect

    Wong, H.

    1983-01-01

    Using Saccharomyces cerevisiae as a model system, a basic study of the nutritional and environmental factors in ethanol fermentation was carried out to provide fundamental and practical bases for design of fermentation media and culture conditions. The requirements for all active medium components need to be determined in order to establish balanced media, which are important to reduce raw materials costs and to minimize inhibition from build-up of excess feed components in recycle processes with selective ethanol removal. The effect of feed concentration of individual nutrients was determined and allowed formulation of media optimal with respect to the major fermentation parameters. Biotin, pantothenate, myoinositol, potassium, and phosphates appeared to stimulate growth preferentially to ethanol production. Thiamine and pyridoxine appeared to have the opposite effect. A conceptual model was proposed to relate the effects of these nutrients to biochemical pathways and functions. The minimum cost combination of raw materials to achieve a medium of well defined components can be determined with a linear program. The effect of dissolved oxygen was studied from essentially zero to 346 mm Hg oxygen tension, showing a continuous decline in specific ethanol productivity with increasing oxygen over this range. Long term continuous cultures resulted in decreased media requirements for growth factors and increased tolerance for ethanol inhibition, most probably through adaptation. An ethanol productivity of 5.6 g/l-hr in continuous culture was achieved with a completely synthetic medium with the improved culture.

  5. Systems biology of GAL regulon in Saccharomyces cerevisiae.

    PubMed

    Pannala, Venkat Reddy; Bhat, Paike Jayadeva; Bhartiya, Sharad; Venkatesh, K V

    2010-01-01

    Evolutionary success of an organism depends on its ability to express or adapt to constantly changing environmental conditions. Saccharomyces cerevisiae has evolved an elaborate genetic circuit to regulate the expression of galactose-metabolizing enzymes in the presence of galactose but in the absence of glucose. The circuit possesses molecular mechanisms such as multiple binding sites, cooperativity, autoregulation, nucleocytoplasmic shuttling, and substrate sensing mechanism. Furthermore, the GAL system consists of two positive (activating) feedback and one negative (repressing) feedback loops. These individual mechanisms, elucidated through experimental approach, can be integrated to obtain a system-wide behavior. Mathematical models in conjunction with guided experiments have demonstrated system-level properties such as ultrasensitivity, memory, noise attenuation, rapid response, and sensitive response arising out of the molecular interactions. These system-level properties allow S. cerevisiae to adapt and grow in a galactose medium under noisy and changing environments. This review focuses on system-level models and properties of the GAL regulon. PMID:20836013

  6. Sphingolipids are potential heat stress signals in Saccharomyces.

    PubMed

    Dickson, R C; Nagiec, E E; Skrzypek, M; Tillman, P; Wells, G B; Lester, R L

    1997-11-28

    The ability of organisms to quickly respond to stresses requires the activation of many intracellular signal transduction pathways. The sphingolipid intermediate ceramide is thought to be particularly important for activating and coordinating signaling pathways during mammalian stress responses. Here we present the first evidence that ceramide and other sphingolipid intermediates are signaling molecules in the Saccharomyces cerevisiae heat stress response. Our data show a 2-3-fold transient increase in the concentration of C18-dihydrosphingosine and C18-phytosphingosine, more than a 100-fold transient increase in C20-dihydrosphingosine and C20-phytosphingosine, and a more stable 2-fold increase in ceramide containing C18-phytosphingosine and a 5-fold increase in ceramide containing C20-phytosphingosine following heat stress. Treatment of cells with dihydrosphingosine activates transcription of the TPS2 gene encoding a subunit of trehalose synthase and causes trehalose, a known thermoprotectant, to accumulate. Dihydrosphingosine induces expression of a STRE-LacZ reporter gene, showing that the global stress response element, STRE, found in many yeast promoter sequences can be activated by sphingolipid signals. The TPS2 promoter contains four STREs that may mediate dihydrosphingosine responsiveness. Using genetic and other approaches it should be possible to identify sphingolipid signaling pathways in S. cerevisiae and quantify the importance of each during heat stress. PMID:9374502

  7. Transcriptional Response of Saccharomyces cerevisiae to Desiccation and Rehydration†

    PubMed Central

    Singh, Jatinder; Kumar, Deept; Ramakrishnan, Naren; Singhal, Vibha; Jervis, Jody; Garst, James F.; Slaughter, Stephen M.; DeSantis, Andrea M.; Potts, Malcolm; Helm, Richard F.

    2005-01-01

    A transcriptional analysis of the response of Saccharomyces cerevisiae strain BY4743 to controlled air-drying (desiccation) and subsequent rehydration under minimal glucose conditions was performed. Expression of genes involved in fatty acid oxidation and the glyoxylate cycle was observed to increase during drying and remained in this state during the rehydration phase. When the BY4743 expression profile for the dried sample was compared to that of a commercially prepared dry active yeast, strikingly similar expression changes were observed. The fact that these two samples, dried by different means, possessed very similar transcriptional profiles supports the hypothesis that the response to desiccation is a coordinated event independent of the particular conditions involved in water removal. Similarities between “stationary-phase-essential genes” and those upregulated during desiccation were also noted, suggesting commonalities in different routes to reduced metabolic states. Trends in extracellular and intracellular glucose and trehalose levels suggested that the cells were in a “holding pattern” during the rehydration phase, a concept that was reinforced by cell cycle analyses. Application of a “redescription mining” algorithm suggested that sulfur metabolism is important for cell survival during desiccation and rehydration. PMID:16332871

  8. Genomic Analysis of ATP Efflux in Saccharomyces cerevisiae

    PubMed Central

    Peters, Theodore W.; Miller, Aaron W.; Tourette, Cendrine; Agren, Hannah; Hubbard, Alan; Hughes, Robert E.

    2015-01-01

    Adenosine triphosphate (ATP) plays an important role as a primary molecule for the transfer of chemical energy to drive biological processes. ATP also functions as an extracellular signaling molecule in a diverse array of eukaryotic taxa in a conserved process known as purinergic signaling. Given the important roles of extracellular ATP in cell signaling, we sought to comprehensively elucidate the pathways and mechanisms governing ATP efflux from eukaryotic cells. Here, we present results of a genomic analysis of ATP efflux from Saccharomyces cerevisiae by measuring extracellular ATP levels in cultures of 4609 deletion mutants. This screen revealed key cellular processes that regulate extracellular ATP levels, including mitochondrial translation and vesicle sorting in the late endosome, indicating that ATP production and transport through vesicles are required for efflux. We also observed evidence for altered ATP efflux in strains deleted for genes involved in amino acid signaling, and mitochondrial retrograde signaling. Based on these results, we propose a model in which the retrograde signaling pathway potentiates amino acid signaling to promote mitochondrial respiration. This study advances our understanding of the mechanism of ATP secretion in eukaryotes and implicates TOR complex 1 (TORC1) and nutrient signaling pathways in the regulation of ATP efflux. These results will facilitate analysis of ATP efflux mechanisms in higher eukaryotes. PMID:26585826

  9. Human acylphosphatase cannot replace phosphoglycerate kinase in Saccharomyces cerevisiae.

    PubMed

    Van Hoek, P; Modesti, A; Ramponi, G; Kötter, P; van Dijken, J P; Pron, J T

    2001-10-01

    Human acylphosphatase (h-AP, EC 3.6.1.7) has been reported to catalyse the hydrolysis of the 1-phosphate group of 1,3-diphosphoglycerate. In vivo operation of this reaction in the yeast Saccharomyces cerevisiae would bypass phosphoglycerate kinase and thus reduce the ATP yield from glycolysis. To investigate whether h-AP can indeed replace the S. cerevisiae phosphoglycerate kinase, a multi-copy plasmid carrying the h-AP gene under control of the yeast TDH3 promoter was introduced into a pgk1 delta mutant of S. cerevisiae. A strain carrying the expression vector without the h-AP cassette was used as a reference. For both strains, steady-state carbon- and energy-limited chemostat cultures were obtained at a dilution rate of 0.10 h(-1) on a medium containing a mixture of glucose and ethanol (15% and 85% on a carbon basis, respectively). Although the h-AP strain exhibited a high acylphosphatase activity in cell extracts, switching to glucose as sole carbon and energy source resulted in a complete arrest of glucose consumption and growth. The lack of a functional glycolytic pathway was further evident from the absence of ethanol formation in the presence of excess glucose in the culture. As h-AP cannot replace yeast phosphoglycerate kinase in vivo, the enzyme is not a useful tool to modify the ATP yield of glycolysis in S. cerevisiae. PMID:11761363

  10. The postmitotic Saccharomyces cerevisiae after spaceflight showed higher viability

    NASA Astrophysics Data System (ADS)

    Yi, Zong-Chun; Li, Xiao-Fei; Wang, Yan; Wang, Jie; Sun, Yan; Zhuang, Feng-Yuan

    2011-06-01

    The budding yeast Saccharomyces cerevisiae has been proposed as an ideal model organism for clarifying the biological effects caused by spaceflight conditions. The postmitotic S. cerevisiae cells onboard Practice eight recoverable satellite were subjected to spaceflight for 15 days. After recovery, the viability, the glycogen content, the activities of carbohydrate metabolism enzymes, the DNA content and the lipid peroxidation level in yeast cells were analyzed. The viability of the postmitotic yeast cells after spaceflight showed a three-fold increase as compared with that of the ground control cells. Compared to the ground control cells, the lipid peroxidation level in the spaceflight yeast cells markedly decreased. The spaceflight yeast cells also showed an increase in G2/M cell population and a decrease in Sub-G1 cell population. The glycogen content and the activities of hexokinase and succinate dehydrogenase significantly decreased in the yeast cells after spaceflight. In contrast, the activity of malate dehydrogenase showed an obvious increase after spaceflight. These results suggested that microgravity or spaceflight could promote the survival of postmitotic S. cerevisiae cells through regulating carbohydrate metabolism, ROS level and cell cycle progression.

  11. Identification of Genes Affecting Vacuole Membrane Fragmentation in Saccharomyces cerevisiae

    PubMed Central

    Michaillat, Lydie; Mayer, Andreas

    2013-01-01

    The equilibrium of membrane fusion and fission influences the volume and copy number of organelles. Fusion of yeast vacuoles has been well characterized but their fission and the mechanisms determining vacuole size and abundance remain poorly understood. We therefore attempted to systematically characterize factors necessary for vacuole fission. Here, we present results of an in vivo screening for deficiencies in vacuolar fragmentation activity of an ordered collection deletion mutants, representing 4881 non-essential genes of the yeast Saccharomyces cerevisiae. The screen identified 133 mutants with strong defects in vacuole fragmentation. These comprise numerous known fragmentation factors, such as the Fab1p complex, Tor1p, Sit4p and the V-ATPase, thus validating the approach. The screen identified many novel factors promoting vacuole fragmentation. Among those are 22 open reading frames of unknown function and three conspicuous clusters of proteins with known function. The clusters concern the ESCRT machinery, adaptins, and lipases, which influence the production of diacylglycerol and phosphatidic acid. A common feature of these factors of known function is their capacity to change membrane curvature, suggesting that they might promote vacuole fragmentation via this property. PMID:23383298

  12. Copper oxide nanoparticles inhibit the metabolic activity of Saccharomyces cerevisiae.

    PubMed

    Mashock, Michael J; Kappell, Anthony D; Hallaj, Nadia; Hristova, Krassimira R

    2016-01-01

    Copper oxide nanoparticles (CuO NPs) are used increasingly in industrial applications and consumer products and thus may pose risk to human and environmental health. The interaction of CuO NPs with complex media and the impact on cell metabolism when exposed to sublethal concentrations are largely unknown. In the present study, the short-term effects of 2 different sized manufactured CuO NPs on metabolic activity of Saccharomyces cerevisiae were studied. The role of released Cu(2+) during dissolution of NPs in the growth media and the CuO nanostructure were considered. Characterization showed that the 28 nm and 64 nm CuO NPs used in the present study have different primary diameter, similar hydrodynamic diameter, and significantly different concentrations of dissolved Cu(2+) ions in the growth media released from the same initial NP mass. Exposures to CuO NPs or the released Cu(2+) fraction, at doses that do not have impact on cell viability, showed significant inhibition on S. cerevisiae cellular metabolic activity. A greater CuO NP effect on the metabolic activity of S. cerevisiae growth under respiring conditions was observed. Under the tested conditions the observed metabolic inhibition from the NPs was not explained fully by the released Cu ions from the dissolving NPs. PMID:26178758

  13. Metabolic Impact of Increased NADH Availability in Saccharomyces cerevisiae▿

    PubMed Central

    Hou, Jin; Scalcinati, Gionata; Oldiges, Marco; Vemuri, Goutham N.

    2010-01-01

    Engineering the level of metabolic cofactors to manipulate metabolic flux is emerging as an attractive strategy for bioprocess applications. We present the metabolic consequences of increasing NADH in the cytosol and the mitochondria of Saccharomyces cerevisiae. In a strain that was disabled in formate metabolism, we either overexpressed the native NAD+-dependent formate dehydrogenase in the cytosol or directed it into the mitochondria by fusing it with the mitochondrial signal sequence encoded by the CYB2 gene. Upon exposure to formate, the mutant strains readily consumed formate and induced fermentative metabolism even under conditions of glucose derepression. Cytosolic overexpression of formate dehydrogenase resulted in the production of glycerol, while when this enzyme was directed into the mitochondria, we observed glycerol and ethanol production. Clearly, these results point toward different patterns of compartmental regulation of redox homeostasis. When pulsed with formate, S. cerevisiae cells growing in a steady state on glucose immediately consumed formate. However, formate consumption ceased after 20 min. Our analysis revealed that metabolites at key branch points of metabolic pathways were affected the most by the genetic perturbations and that the intracellular concentrations of sugar phosphates were specifically affected by time. In conclusion, the results have implications for the design of metabolic networks in yeast for industrial applications. PMID:20023106

  14. Isolation, identification and characterization of regional indigenous Saccharomyces cerevisiae strains

    PubMed Central

    Šuranská, Hana; Vránová, Dana; Omelková, Jiřina

    2016-01-01

    In the present work we isolated and identified various indigenous Saccharomyces cerevisiae strains and screened them for the selected oenological properties. These S. cerevisiae strains were isolated from berries and spontaneously fermented musts. The grape berries (Sauvignon blanc and Pinot noir) were grown under the integrated and organic mode of farming in the South Moravia (Czech Republic) wine region. Modern genotyping techniques such as PCR-fingerprinting and interdelta PCR typing were employed to differentiate among indigenous S. cerevisiae strains. This combination of the methods provides a rapid and relatively simple approach for identification of yeast of S. cerevisiae at strain level. In total, 120 isolates were identified and grouped by molecular approaches and 45 of the representative strains were tested for selected important oenological properties including ethanol, sulfur dioxide and osmotic stress tolerance, intensity of flocculation and desirable enzymatic activities. Their ability to produce and utilize acetic/malic acid was examined as well; in addition, H2S production as an undesirable property was screened. The oenological characteristics of indigenous isolates were compared to a commercially available S. cerevisiae BS6 strain, which is commonly used as the starter culture. Finally, some indigenous strains coming from organically treated grape berries were chosen for their promising oenological properties and these strains will be used as the starter culture, because application of a selected indigenous S. cerevisiae strain can enhance the regional character of the wines. PMID:26887243

  15. Xylose Fermentation by Saccharomyces cerevisiae: Challenges and Prospects.

    PubMed

    Moysés, Danuza Nogueira; Reis, Viviane Castelo Branco; de Almeida, João Ricardo Moreira; de Moraes, Lidia Maria Pepe; Torres, Fernando Araripe Gonçalves

    2016-01-01

    Many years have passed since the first genetically modified Saccharomyces cerevisiae strains capable of fermenting xylose were obtained with the promise of an environmentally sustainable solution for the conversion of the abundant lignocellulosic biomass to ethanol. Several challenges emerged from these first experiences, most of them related to solving redox imbalances, discovering new pathways for xylose utilization, modulation of the expression of genes of the non-oxidative pentose phosphate pathway, and reduction of xylitol formation. Strategies on evolutionary engineering were used to improve fermentation kinetics, but the resulting strains were still far from industrial application. Lignocellulosic hydrolysates proved to have different inhibitors derived from lignin and sugar degradation, along with significant amounts of acetic acid, intrinsically related with biomass deconstruction. This, associated with pH, temperature, high ethanol, and other stress fluctuations presented on large scale fermentations led the search for yeasts with more robust backgrounds, like industrial strains, as engineering targets. Some promising yeasts were obtained both from studies of stress tolerance genes and adaptation on hydrolysates. Since fermentation times on mixed-substrate hydrolysates were still not cost-effective, the more selective search for new or engineered sugar transporters for xylose are still the focus of many recent studies. These challenges, as well as under-appreciated process strategies, will be discussed in this review. PMID:26927067

  16. Rapid identification of chemical genetic interactions in Saccharomyces cerevisiae.

    PubMed

    Dilworth, David; Nelson, Christopher J

    2015-01-01

    Determining the mode of action of bioactive chemicals is of interest to a broad range of academic, pharmaceutical, and industrial scientists. Saccharomyces cerevisiae, or budding yeast, is a model eukaryote for which a complete collection of ~6,000 gene deletion mutants and hypomorphic essential gene mutants are commercially available. These collections of mutants can be used to systematically detect chemical-gene interactions, i.e. genes necessary to tolerate a chemical. This information, in turn, reports on the likely mode of action of the compound. Here we describe a protocol for the rapid identification of chemical-genetic interactions in budding yeast. We demonstrate the method using the chemotherapeutic agent 5-fluorouracil (5-FU), which has a well-defined mechanism of action. Our results show that the nuclear TRAMP RNA exosome and DNA repair enzymes are needed for proliferation in the presence of 5-FU, which is consistent with previous microarray based bar-coding chemical genetic approaches and the knowledge that 5-FU adversely affects both RNA and DNA metabolism. The required validation protocols of these high-throughput screens are also described. PMID:25867090

  17. Biotransformation of malachite green by Saccharomyces cerevisiae MTCC 463.

    PubMed

    Jadhav, J P; Govindwar, S P

    2006-03-01

    In recent years, use of microbial biomass for decolourization of textile industry wastewater is becoming a promising alternative in which some bacteria and fungi are used to replace present treatment processes. Saccharomyces cerevisiae MTCC 463 decolourized the triphenylmethane dyes (malachite green, cotton blue, methyl violet and crystal violet) by biosorption, showing different decolourization patterns. However, malachite green decolourized by biosorption at the initial stage and further biodegradation occurred, about 85% in plain distilled water within 7 h, and about 95.5% in 5% glucose medium within 4 h, under aerobic conditions and at room temperature. Decolourization of malachite green depends on various conditions, such as concentration of dye, concentration of cells, composition of medium and agitation. HPLC, UV-VIS, FTIR and TLC analysis of samples extracted with ethyl acetate from decolourized culture flasks confirmed the biodegradation of malachite green into several metabolites. A study of the enzymes responsible for the biodegradation of malachite green in the control and cells obtained after decolourization showed the activities of laccase, lignin peroxidase, NADH-DCIP reductase, malachite green reductase and aminopyrine N-demethylase in control cells. A significant increase in the activities of NADH-DCIP reductase and MG reductase was observed in the cells obtained after decolourization, indicating a major involvement of reductases in malachite green degradation. PMID:16544273

  18. Genomic Evolution of Saccharomyces cerevisiae under Chinese Rice Wine Fermentation

    PubMed Central

    Li, Yudong; Zhang, Weiping; Zheng, Daoqiong; Zhou, Zhan; Yu, Wenwen; Zhang, Lei; Feng, Lifang; Liang, Xinle; Guan, Wenjun; Zhou, Jingwen; Chen, Jian; Lin, Zhenguo

    2014-01-01

    Rice wine fermentation represents a unique environment for the evolution of the budding yeast, Saccharomyces cerevisiae. To understand how the selection pressure shaped the yeast genome and gene regulation, we determined the genome sequence and transcriptome of a S. cerevisiae strain YHJ7 isolated from Chinese rice wine (Huangjiu), a popular traditional alcoholic beverage in China. By comparing the genome of YHJ7 to the lab strain S288c, a Japanese sake strain K7, and a Chinese industrial bioethanol strain YJSH1, we identified many genomic sequence and structural variations in YHJ7, which are mainly located in subtelomeric regions, suggesting that these regions play an important role in genomic evolution between strains. In addition, our comparative transcriptome analysis between YHJ7 and S288c revealed a set of differentially expressed genes, including those involved in glucose transport (e.g., HXT2, HXT7) and oxidoredutase activity (e.g., AAD10, ADH7). Interestingly, many of these genomic and transcriptional variations are directly or indirectly associated with the adaptation of YHJ7 strain to its specific niches. Our molecular evolution analysis suggested that Japanese sake strains (K7/UC5) were derived from Chinese rice wine strains (YHJ7) at least approximately 2,300 years ago, providing the first molecular evidence elucidating the origin of Japanese sake strains. Our results depict interesting insights regarding the evolution of yeast during rice wine fermentation, and provided a valuable resource for genetic engineering to improve industrial wine-making strains. PMID:25212861

  19. Mating-Type Genes and MAT Switching in Saccharomyces cerevisiae

    PubMed Central

    Haber, James E.

    2012-01-01

    Mating type in Saccharomyces cerevisiae is determined by two nonhomologous alleles, MATa and MATα. These sequences encode regulators of the two different haploid mating types and of the diploids formed by their conjugation. Analysis of the MATa1, MATα1, and MATα2 alleles provided one of the earliest models of cell-type specification by transcriptional activators and repressors. Remarkably, homothallic yeast cells can switch their mating type as often as every generation by a highly choreographed, site-specific homologous recombination event that replaces one MAT allele with different DNA sequences encoding the opposite MAT allele. This replacement process involves the participation of two intact but unexpressed copies of mating-type information at the heterochromatic loci, HMLα and HMRa, which are located at opposite ends of the same chromosome-encoding MAT. The study of MAT switching has yielded important insights into the control of cell lineage, the silencing of gene expression, the formation of heterochromatin, and the regulation of accessibility of the donor sequences. Real-time analysis of MAT switching has provided the most detailed description of the molecular events that occur during the homologous recombinational repair of a programmed double-strand chromosome break. PMID:22555442

  20. Pressure treatment of Saccharomyces cerevisiae in low-moisture environments.

    PubMed

    Moussa, Marwen; Espinasse, Vincent; Perrier-Cornet, Jean-Marie; Gervais, Patrick

    2009-11-01

    We investigated the influence of cell hydration on the ability of Saccharomyces cerevisiae CBS 1171 to withstand extreme hydrostatic pressure in order to determine the mechanisms involved in cell resistance. Hydration conditions were modified in two different ways. We first modulated the chemical potential of water by adding glycerol in cell suspensions. Another procedure consisted in dehydrating cells aerobically and immersing them in perfluorooctane, an innocuous hydrophobic liquid used as a pressure-transmitting medium, prior to pressure treatments. This original method made it possible to transmit isostatic pressure to yeast powders without changing the initial water activity (aw) level at which cells had been equilibrated. The aw ranged between 0.11 and 0.99. Pressure treatments were applied at levels of up to 600 MPa for 10 min, 24 h, and 6 days. The dehydration of cells was found to strongly limit, or even prevent, cell inactivation under pressure. Notably, cells suspended in a water-glycerol mixture with aw levels of 0.71 or below were completely protected against all pressure treatments. Moreover, cells dehydrated aerobically survived for 6 days at 600 MPa even when aw levels were relatively high (up to 0.94). We highlighted the crucial role of water content in determining cellular damage under pressure. When water is available in a sufficient amount, high pressure induces membrane permeabilization, causing uncontrolled mass transfers that could lead to death during a prolonged holding under pressure. Possible mechanisms of membrane permeabilization are discussed. PMID:19633838

  1. Adsorption of aromatics on the (111) surface of PtM and PtM3 (M = Fe, Ni) alloys

    SciTech Connect

    Hensley, Alyssa; Schneider, Sebastian; Wang, Yong; McEwen, Jean-Sabin

    2015-09-18

    The adsorption of benzene and phenol was studied on PtM and PtM3 (111) surfaces, with M being either Ni or Fe. Under vacuum, the most favorable near surface structures showed an enrichment in Pt over the M species. An analysis of the electronic structure of the metal species in the clean surfaces with different near surface structures was done with the d-band model and showed that the Pt's d-states are significantly shifted away from the Fermi level due to the Pt-M interactions while the M species' d-states were less affected, with Ni's d-band shifting closer to the Fermi level and Fe's d-band shifting away from the Fermi level. The adsorption of aromatics, benzene and phenol, on several near surface structures for the PtM and PtM3 (111) surfaces showed that higher surface M concentrations resulted in a stronger adsorption due to the larger amount of charge transferred between the adsorbate and surface. However, compared to the adsorption of benzene and phenol on monometallic surfaces, the adsorption of these species on the PtM and PtM3 (111) surfaces was significantly weakened. Overall, our results show that the observed behavior of these Pt/Fe and Pt/Ni alloys is similar to that seen for the previously studied Pd/Fe surfaces. Furthermore, balancing the weakly adsorbing Pt surface species with the more strongly interacting Fe or Ni species can lead to the tailored adsorption of aromatics with applications in both hydrodeoxygenation and hydrogenation reactions by increasing the desorption rate of wanted aromatic products.

  2. Resolving Sulfur Oxidation and Removal from Pt and Pt3Co Electrocatalysts Using in Situ X-ray Absorption Spectroscopy

    SciTech Connect

    Ramaker, D.; Gatewood, D; Korovina, A; Garsany, Y; Swider-Lyons, K

    2010-01-01

    Adsorbed sulfur is a poison to the Pt catalysts used in proton exchange membrane fuel cells, but it can be removed by potential cycling. This process is studied for S{sub x}-poisoned nanoscale Pt- and Pt{sub 3}Co- on Vulcan carbon (Pt/VC and Pt{sub 3}Co/VC) in perchloric acid electrolyte using the {Delta}{mu} adsorbate isolation technique for in situ X-ray absorption spectroscopy. The {Delta}{mu} technique is modified to better distinguish the {Delta}{mu} signatures for H, O, and Sx on Pt. The resulting {Delta}{mu} analysis suggests that SO{sub 2} on nanoscale Pt is oxidized to bisulfate or sulfate species in two regions, near 1.05 V on the cluster edges of the Pt nanoparticle, and at higher potentials from the Pt(111) faces where oxygen is less strongly bound. The bisulfate or sulfate species desorb from the Pt surface at high potentials due to O(OH) adsorption/replacement and at low potentials due to loss of the Coulomb attraction between the bisulfate anion and the Pt. A similar oxidation process occurs for S{sub x}-poisoned Pt{sub 3}Co/VC, but at lower potentials because a ligand effect coming from Co shifts the oxidization potential of adsorbed SO{sub 2} to lower potentials while pushing OH adsorption to higher potentials. The spectroscopic results give insights into cyclic voltammetry data and are consistent with electrochemical cycling procedures for removing the sulfur.

  3. Genetic and phenotypic characterization of Saccharomyces spp. strains isolated in distillery plants.

    PubMed

    Úbeda, Juan F; Chacón-Ocaña, Maria; Díaz-Hellín, Patricia; Ramírez-Pérez, Hector; Briones, Ana

    2016-06-01

    In this study, the biodiversity and some interesting phenotypic properties of Saccharomyces wild yeasts isolated in distilleries, at least 100 years old, located in La Mancha (Spain), were determined. Strains were genetically characterized by RFLP-mtDNA, which confirmed a great genetic biodiversity with 73% of strains with different mtDNA profiles, highlighting the large variability found in sweet and fermented piquette substrata. The predominant species identified was S. cerevisiae, followed by S. paradoxus and S. bayanus Due to the residual sugar-alcohol extraction process using warm water, a great number of thermophilic Saccharomyces strains with a great cell vitality were found to have potential use as starters in distillery plants. Interesting technological properties such as cell vitality and growth rate at different temperatures were studied. The thermal washing process for the extraction of alcohol and reducing sugars of some raw materials contributes to the presence of Saccharomyces strains with technologically interesting properties, especially in terms of vitality and resistance to high temperatures. Due to the fact that fermentation is spontaneous, the yeast biota of these environments, Saccharomyces and non-Saccharomyces, is very varied so these ecological niches are microbial reserves of undoubted biotechnological interest. PMID:27189361

  4. First-principles study of oxygen and hydrogen adsorption on Pt(111) and PtML/Pd(111) surfaces

    NASA Astrophysics Data System (ADS)

    Nie, J. L.; Ao, L.; Zu, X. T.

    2015-11-01

    In this paper, first-principles calculations based on density functional theory (DFT) have been performed to investigate the adsorption of oxygen and hydrogen on Pt(111) and Pd(111) surfaces covered by monolayer (ML) of Pt(PtML/Pd(111)). The results have shown that the oxygen molecule tends to adsorb on fcc site on both surfaces at the coverage of 0.25 ML, which becomes degeneration with hcp site when the coverage increases to 1 ML. For both oxygen and hydrogen, the adsorption on PtML/Pd(111) surface are stronger than those on Pt(111) surface. The adsorption energy difference for oxygen on the two surfaces is ˜0.2 eV at the coverage of 1 ML, which increases to ˜0.6 eV with the coverage decreasing to 0.25 ML. The similar energy difference was also found for hydrogen adsorption. The density of states analysis have demonstrated the chemical interaction of adsorbed oxygen with both pure Pt(111) and PtML/Pd(111) surfaces with certain shift of O2p states to lower level compared to isolated oxygen. For hydrogen adsorption, the hybridization of H1s with Pt5d states were observed for both surfaces, indicating the covalent bonding component of H-Pt bond.

  5. L10 phase transformation and magnetic behaviors of (Fe, FePt, FePtCu)-C nanocomposite films

    NASA Astrophysics Data System (ADS)

    Mi, W. B.; Liu, Hui; Li, Z. Q.; Wu, P.; Jiang, E. Y.; Bai, H. L.

    2005-06-01

    As-deposited (Fe, FePt, FePtCu)-C nanocomposite films with fixed C atomic fraction xc=47 fabricated using facing-target sputtering method at room temperature are composed of ˜2-3-nm amorphous metal granules buried in a-C matrix. Annealing at high temperatures turns the amorphous granules into α-Fe, α-Fe- and L10-structured FePt, and L10-ordered FePtCu for Fe-C, FePt-C, and FePtCu-C films, respectively, and makes a-C preferential graphitization. As-deposited granules are superparamagnetic at 300K, and ferromagnetic at 5K. The zero-field-cooled (ZFC) and field-cooled (FC) curves reveal that there exist strong intergranular interactions at temperatures below 300K, and the size distribution of granules becomes broad by Pt and Cu addition. The M-H loop of annealed Fe31Pt22C47 films exhibits a two-step saturation behavior because of the coexistence of soft and hard ferromagnetic phases. As the Cu atomic fraction is 14%, the coercivity of annealed Fe23Pt16Cu14C47 films reaches a large value of ˜11.2kOe at 5K and decreases to ˜7.2kOe at 300K.

  6. Pt and Pt-Ru/Carbon Nanotube Nanocomposites Synthesized in Supercritical Fluid as Electrocatalysts for Low-Temperature Fuel Cells

    SciTech Connect

    Lin, Yuehe; Cui, Xiaoli; Wang, Jun; Yen, Clive; Wai, Chien M.

    2006-06-01

    In recent years, the use of supercritical fluids (SCFs) for the synthesis and processing of nanomaterials has proven to be a rapid, direct, and clean approach to develop nanomaterials and nanocomposites. The application of supercritical fluid technology can result in products (and processes) that are cleaner, less expensive, and of higher quality than those that are produced using conventional technologies and solvents. In this work, carbon nanotube (CNT)-supported Pt and Pt-Ru nanoparticles catalysts have been synthesized in supercritical carbon dioxide (scCO2). The experimental results demonstrate that Pt, Pt-Ru/CNT nanocomposites synthesized in supercritical carbon dioxide are effective electrocatalysts for low-temperature fuel cells.

  7. Surface relaxation of Pt(1 1 1) and Cu/Pt(1 1 1) revealed by DEPES

    NASA Astrophysics Data System (ADS)

    Miszczuk, A.; Morawski, I.; Kucharczyk, R.; Nowicki, M.

    2016-06-01

    In this paper, we report the results of surface relaxation investigations for a clean Pt(1 1 1) as well as Pt(1 1 1) covered with a pseudomorphic monolayer of Cu. The pseudomorphic (1 × 1) Cu overlayer on Pt(1 1 1) was formed upon continuous copper adsorption at the substrate temperature equal to 450 K. Considerations include both the experimental and theoretical studies employing directional elastic peak electron spectroscopy (DEPES), multiple scattering (MS) formalism, and density functional theory (DFT). A quantitative analysis of two-dimensional DEPES intensity distributions is presented and the contribution of consecutive subsurface Pt atomic layers to the measured signal is identified. The experimental DEPES distributions are compared with theoretical maps MS-simulated for a variable separation between the outermost atomic planes. For the clean Pt(1 1 1), the best fit is obtained assuming the outward relaxation of the surface layer by +0.7% with respect to the interplanar distance in the bulk, confirming the slight expansion of the Pt(1 1 1) surface. Similar analysis performed for the Cu/Pt(1 1 1) adsorption system indicates the inward shift of the pseudomorphic Cu overlayer by -6.9% with respect to the substrate lattice continuation sites. Such DEPES-determined surface relaxations of Pt(1 1 1) and Cu/Pt(1 1 1) agree with the values predicted by the corresponding DFT computations.

  8. Identification and quantification of oxygen species adsorbed on Pt(111) single-crystal and polycrystalline Pt electrodes by photoelectron spectroscopy.

    PubMed

    Wakisaka, Mitsuru; Suzuki, Hirokazu; Mitsui, Satoshi; Uchida, Hiroyuki; Watanabe, Masahiro

    2009-02-17

    We have positively identified oxygen species on Pt(111) single-crystal and polycrystalline Pt electrodes in N2-purged 0.1 M HF solution by X-ray photoelectron spectroscopy combined with an electrochemical cell. Four oxygen species (Oad, OHad, and two types of water molecules) were distinguished. The binding energies of each species were nearly constant over the whole potential region and independent of the single- or polycrystalline electrodes. The coverages, however, varied considerably and were dependent on the electrode potential. We have for the first time demonstrated clear differences in the surface oxidation processes for Pt(111) and polycrystalline Pt electrodes. PMID:19152331

  9. Mechanistic examination of aerobic Pt oxidation: insertion of molecular oxygen into Pt-H bonds through a radical chain mechanism.

    PubMed

    Keith, Jason M; Ye, Yixin; Wei, Haochuan; Buck, Matthew R

    2016-07-19

    DFT calculations were performed in an effort to evaluate the mechanism of O2 insertion into the Pt-H bond of Tp(Me2)Pt(IV)Me2H catalyzed by AIBN or light. Results are consistent with a radical chain mechanism involving H˙ loss to form a Pt(III)˙ species followed by addition of O2 to form Pt(III)OO˙. Subsequent radical propagation involving this Pt(III)OO˙ species and an additional equivalent of the Pt(IV) starting material result in the formation of the observed Pt(IV)OOH and regeneration of the Pt(III)˙. In addition examination of the reaction between AIBN and the Pt(IV) hydroperoxo product demonstrates that radical initiation reactions involving the product occur with a lower barrier than with the initial starting material supporting the idea of autoacceleration in this reaction. Other possible mechanisms were examined in an effort to understand the limited reactivity reported in the absence of light or radical initiators. TDDFT calculations were performed in an effort to understand the reported parallel photo-induced reaction. These calculations found the reactant to be transparent in the relevant light range. An experimental UV-Vis spectrum was obtained and is in agreement with the calculations. PMID:27364984

  10. Activation of Homolytic Si-Zn and Si-Hg Bond Cleavage, Mediated by a Pt(0) Complex, via Novel Pt-Zn and Pt-Hg Compounds.

    PubMed

    Kratish, Yosi; Molev, Gregory; Kostenko, Arseni; Sheberla, Dennis; Tumanskii, Boris; Botoshansky, Mark; Shimada, Shigeru; Bravo-Zhivotovskii, Dmitry; Apeloig, Yitzhak

    2015-09-28

    The thermally stable [(tBuMe2 Si)2 M] (M=Zn, Hg) generate R3 Si(.) radicals in the presence of [(dmpe)Pt(PEt3 )2 ] at 60-80 °C. The reaction proceeds via hexacoordinate Pt complexes, (M=Zn (2 a and 2 b), M=Hg (3 a and 3 b)) which were isolated and characterized. Mild warming or photolysis of 2 or 3 lead to homolytic dissociation of the Pt-MSiR3 bond generating silyl radicals and novel unstable pentacoordinate platinum paramagnetic complexes (M=Zn (5), Hg (6)) whose structures were determined by EPR spectroscopy and DFT calculations. PMID:26288342

  11. Past and Future of Non-Saccharomyces Yeasts: From Spoilage Microorganisms to Biotechnological Tools for Improving Wine Aroma Complexity.

    PubMed

    Padilla, Beatriz; Gil, José V; Manzanares, Paloma

    2016-01-01

    It is well established that non-Saccharomyces wine yeasts, considered in the past as undesired or spoilage yeasts, can enhance the analytical composition, and aroma profile of the wine. The contribution of non-Saccharomyces yeasts, including the ability to secret enzymes and produce secondary metabolites, glycerol and ethanol, release of mannoproteins or contributions to color stability, is species- and strain-specific, pointing out the key importance of a clever strain selection. The use of mixed starters of selected non-Saccharomyces yeasts with strains of Saccharomyces cerevisiae represents an alternative to both spontaneous and inoculated wine fermentations, taking advantage of the potential positive role that non-Saccharomyces wine yeast species play in the organoleptic characteristics of wine. In this context mixed starters can meet the growing demand for new and improved wine yeast strains adapted to different types and styles of wine. With the aim of presenting old and new evidences on the potential of non-Saccharomyces yeasts to address this market trend, we mainly review the studies focused on non-Saccharomyces strain selection and design of mixed starters directed to improve primary and secondary aroma of wines. The ability of non-Saccharomyces wine yeasts to produce enzymes and metabolites of oenological relevance is also discussed. PMID:27065975

  12. Past and Future of Non-Saccharomyces Yeasts: From Spoilage Microorganisms to Biotechnological Tools for Improving Wine Aroma Complexity

    PubMed Central

    Padilla, Beatriz; Gil, José V.; Manzanares, Paloma

    2016-01-01

    It is well established that non-Saccharomyces wine yeasts, considered in the past as undesired or spoilage yeasts, can enhance the analytical composition, and aroma profile of the wine. The contribution of non-Saccharomyces yeasts, including the ability to secret enzymes and produce secondary metabolites, glycerol and ethanol, release of mannoproteins or contributions to color stability, is species- and strain-specific, pointing out the key importance of a clever strain selection. The use of mixed starters of selected non-Saccharomyces yeasts with strains of Saccharomyces cerevisiae represents an alternative to both spontaneous and inoculated wine fermentations, taking advantage of the potential positive role that non-Saccharomyces wine yeast species play in the organoleptic characteristics of wine. In this context mixed starters can meet the growing demand for new and improved wine yeast strains adapted to different types and styles of wine. With the aim of presenting old and new evidences on the potential of non-Saccharomyces yeasts to address this market trend, we mainly review the studies focused on non-Saccharomyces strain selection and design of mixed starters directed to improve primary and secondary aroma of wines. The ability of non-Saccharomyces wine yeasts to produce enzymes and metabolites of oenological relevance is also discussed. PMID:27065975

  13. Modeling surface segregation phenomena in the (111) surface of ordered Pt3Ti crystal

    NASA Astrophysics Data System (ADS)

    Duan, Zhiyao; Zhong, Jun; Wang, Guofeng

    2010-09-01

    We investigated the surface segregation phenomena in the (111) surface of ordered Pt3Ti crystal using density functional theory (DFT) calculation (with no configuration sampling) and Monte Carlo (MC) simulation method (employing modified embedded atom method potentials and with extensive configuration sampling). Our DFT study suggested that the off-stoichiometric effect (specifically, a Pt concentration higher than 75 at. %) accounted for the experimentally observed Pt segregation to the outermost layer of the Pt3Ti (111). Our MC simulations predicted that in a Pt3Ti (111) sample with a Pt concentration slightly above 75 at. %, Pt atoms would segregate to the surface to form a pure Pt outermost layer, while the ordered Pt3Ti crystal structure would be maintained in the second layer and below. Moreover, our DFT calculations revealed that the d-band center of the Pt-segregated Pt3Ti (111) surface would downshift by 0.21 eV as compared to that of a pure Pt (111) surface. As a result, O adsorption energy on the Pt-segregated Pt3Ti (111) surface was found to be at least 0.16 eV weaker than that on the pure Pt (111) surface. Thus, we theoretically modeled the geometric and electronic structures of the Pt-segregated Pt3Ti (111) surface and further suggested that the Pt surface segregation could lead to enhanced catalytic activity for oxygen reduction reactions on Pt3Ti alloy catalysts.

  14. PT-symmetry breaking in resonant tunneling heterostructures

    NASA Astrophysics Data System (ADS)

    Gorbatsevich, A. A.; Shubin, N. M.

    2016-06-01

    We present fermionic model based on symmetric resonant tunneling heterostructure, which demonstrates spontaneous symmetry breaking in respect to combined operations of space inversion (P) and time reversal (T). PT-symmetry breaking manifests itself in resonance coalescence (collapse of resonances). We show that resonant energies are determined by eigenvalues of auxiliary pseudo-Hermitian PT-invariant Hamiltonian.

  15. Adsorption of molecular hydrogen on Pd(Pt) decorated graphene

    NASA Astrophysics Data System (ADS)

    Adhikari, Narayan; Khaniya, Asim; Lamichhane, Saran; Pantha, Nurapati

    2015-03-01

    We have performed the first-principles based Density Functional Theory (DFT) calculations to study the stability, geometrical structures, and electronic properties of a Pd(Pt) atom adsorbed graphene to investigate the possibility of using Pd(Pt) decorated graphene as energy storage materials with reference to pristine graphene. The London dispersion forces have been incorporated by the DFT-D2 levels of calculations implemented in Quantum Espresso packages. Our findings show that Pd and Pt both adsorb on graphene at Bridge site. The electronic structures of Pd(Pt) adsorbed graphene possesses band gap opening due to breaking of the symmetry of graphene. Further we have studied the adsorption of moelcular hydrogen ((H 2) n , n = 1-7) on the Pd(Pt)-graphene system. The adatom Pd(Pt) enhances the binding energy per hydrogen molecule in Pd(Pt)-graphene system in comparison to that in the pristine graphene. The binding energy per hydrogen molecule of the adatom-graphene system decreases as the number of H 2 molecules increases and finally it saturates to 0.15 eV (0.16 eV) per hydrogen molecule for Pd-graphene (Pt-graphene) systems respectively. ICTP-NET 56/TWAS.

  16. Limited Genetic Diversity in Salmonella enterica Serovar Enteritidis PT13

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Salmonella enterica serovar Enteritidis has emerged as a significant food-borne pathogen throughout the world and it is commonly characterized by phage typing (PT). In Canada, PT4, 8 and 13 are the predominant PTs. Epidemiological subtyping of Salmonella is typically done by PFGE but plasmid profil...

  17. Thermochemistry of Pt-Fullerene Complexes: Semiempirical Study

    NASA Astrophysics Data System (ADS)

    Voityuk, Alexander A.

    2009-07-01

    Modified Neglect of Differential Overlap (MNDO) and MNDO/d based semiempirical methods are widely employed to explore structure and thermochemistry of molecular systems. In this work, the AM1/d method has been parametrized for systems containing platinum. The proposed scheme delivers excellent performance for binding energies of Pt complexes with ethylene and large π conjugated hydrocarbons. The estimated bond energies accurately reproduce the results of MP4(SDQ) calculations and show significant improvement over DFT (B3LYP and M05) data. We apply the AM1/d scheme to explore the structure and thermochemistry of several Pt compounds with C60 and C70. The calculated binding energies of bare Pt atoms and [Pt(PH3)2] units to the fullerenes are 75 and 45 kcal/mol, respectively. We find that coordination of a single metal center to C60 activates the fullerene cage making subsequent coordination of Pt more favorable. The bond energy [C60-PtC60] is calculated to be 65 kcal/mol. The estimated reaction enthalpies are useful for exploring the stability of PtxC60 polymer systems and their interaction with phosphines. AM1/d predicts a very low barrier to rotation of the coordinated fullerenes in [Pt(C60)2]. The AM1/d scheme is computationally very efficient and can be employed to obtain fast quantitative estimates for binding energies and structural parameters of Pt complexes with large π conjugated systems like fullerenes and carbon nanotubes.

  18. Limited genetic diversity in Salmonella enterica Serovar Enteritidis PT13

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Salmonella enterica serovar Enteritidis has emerged as a significant foodborne pathogen throughout the world and is commonly characterized by phage typing. In Canada phage types (PT) 4, 8 and 13 predominate and in 2005 a large foodborne PT13 outbreak occurred in the province of Ontario. The ability ...

  19. Dilepton pT Distribution Through the Color Glass Condensate

    SciTech Connect

    Betemps, M.A.; Gay Ducati, M.B.

    2004-12-02

    We investigate the dilepton production in proton-nucleus collisions at the forward rapidity region using the Color Glass Condensate approach. We focus our attention on the dilepton transverse momentum distribution (pT), more precisely in the low pT region where the saturation effects are expected to be increasingly large.

  20. Controlled Synthesis and Assembly of FePt Nanoparticles

    SciTech Connect

    Toney, Michael F

    2003-06-20

    Monodisperse 4 nm FePt magnetic nanoparticles were synthesized by superhydride reduction of FeCl{sub 2} and Pt(acac){sub 2} at high temperature, and thin assemblies of FePt nanoparticles with controlled thickness were formed through polymer mediated self-assembly. Adding superhydride (LiBEt{sub 3}H) to the organic solution of FeCl{sub 2} and Pt(acac){sub 2} in the presence of oleic acid, oleylamine and 1,2-hexadecanediol at 200 C, followed by refluxing at 263 C led to monodisperse 4 nm FePt nanoparticles. The initial molar ratio of the metal precursors was retained during the synthesis; and the final FePt composition of the particles was readily tuned. Alternatively absorbing a layer of polyethylenimine (PEI) and the FePt nanoparticles onto a solid substrate resulted in nanoparticle assemblies with tunable thickness. Chemical analysis of the assemblies revealed that more iron oxide was present in the thinner assemblies annealed at lower temperature or for shorter time. Thermal annealing induced the internal particle structure change from chemically disordered fee to chemically ordered fct and transformed the thin assembly from superparamagnetic to ferromagnetic. This controlled synthesis and assembly can be used to fabricate FePt nanoparticle-based functional devices for future nanomagnetic applications.

  1. Modifying exchange-spring behavior of CoPt/NiFe bilayer by inserting a Pt or Ru spacer

    SciTech Connect

    Hsu, Jen-Hwa Tsai, C. L.; Lee, C.-M.; Saravanan, P.

    2015-05-07

    We herein explore the possibility of obtaining tunable tilted magnetic anisotropy in ordered-CoPt (5 nm)/NiFe(t{sub NiFe}) bilayers through modifying their exchange spring behavior by inserting Pt and Ru-spacers. The tuning process of tilt angle magnetization of NiFe-layer was systematically investigated by varying the Pt or Ru thickness (t{sub Pt} or t{sub Ru}) from 0 to 8 nm at different thicknesses of NiFe (t{sub NiFe} = 1.5, 4.0, and 6.0 nm). Polar magneto-optic Kerr effect (p-MOKE) studies reveal that the bilayers grown in absence of spacers exhibit almost a rectangular hysteresis loop. With the insertion of Pt-spacer, the loop becomes more and more tilted as t{sub Pt} increases; whereas, in the case of Ru-spacer, the nature of the loops is not simply changing in one direction. The estimated SQR{sub ⊥} (= θ{sub r}/θ{sub s}) values from the p-MOKE loops are found to monotonically decrease with increasing t{sub Pt} when t{sub Pt} ≦ 4 nm. In contrast, in the case of Ru-spacer, an oscillatory behavior for the SQR{sub ⊥} values is apparent when t{sub Ru} ≦ 4 nm. As a result, an oscillatory tilted angle of NiFe spin configuration was obtained in the case of Ru-spacer; while a decoupling effect was prominent for the Pt-spacer. The results of present study reveal that the insertion of Pt and Ru-spacers as an appropriate means for realizing tunable tilted magnetic anisotropy in the CoPt/NiFe exchange springs.

  2. Graphene oxide aerogel-supported Pt electrocatalysts for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Duan, Jialin; Zhang, Xuelin; Yuan, Weijian; Chen, Hailong; Jiang, Shan; Liu, Xiaowei; Zhang, Yufeng; Chang, Limin; Sun, Zhiyuan; Du, Juan

    2015-07-01

    Graphene oxide aerogel (GOA) was prepared to serve as catalyst support for Pt nanoparticles for methanol electro-oxidation. Analyses by X-ray diffraction (XRD) and scanning electron microscopy (SEM) were conducted to physically characterize the Pt/GOA catalyst. The results show that Pt/GOA has a 3D macroporous structure, which can not only accelerate mass transfer but also provide a larger efficient surface area for methanol oxidation. The results of electrochemical tests reveal that Pt/GOA has an electrochemical surface area as large as 95.5 m2 g-1, and its peak current density toward methanol oxidation is as high as 876 mA mg-1Pt.

  3. Strong spin Hall effect in the antiferromagnet PtMn

    NASA Astrophysics Data System (ADS)

    Ou, Yongxi; Shi, Shengjie; Ralph, D. C.; Buhrman, R. A.

    2016-06-01

    Effectively manipulating magnetism in ferromagnet (FM) thin-film nanostructures with an in-plane current has become feasible since the determination of a "giant" spin Hall effect (SHE) in certain heavy metal/FM systems. Recently, both theoretical and experimental reports indicate that metallic antiferromagnet materials can have both a large anomalous Hall effect and a strong SHE. Here we report a systematic study of the SHE in PtMn with several PtMn/FM systems. By using interface engineering to reduce the "spin memory loss" we obtain, in the best instance, a spin-torque efficiency ξDLPtMn≡TintθSHPtMn≃0.24 , where Tint is the effective interface spin transparency. This is more than twice the previously reported spin-torque efficiency for PtMn. We also find that the apparent spin diffusion length in PtMn is surprisingly long, λsPtMn≈2.3 nm .

  4. Topological States in Partially-PT-Symmetric Azimuthal Potentials.

    PubMed

    Kartashov, Yaroslav V; Konotop, Vladimir V; Torner, Lluis

    2015-11-01

    We introduce partially-parity-time (pPT)-symmetric azimuthal potentials composed from individual PT-symmetric cells located on a ring, where two azimuthal directions are nonequivalent in a sense that in such potential excitations carrying topological dislocations exhibit different dynamics for different directions of energy circulation in the initial field distribution. Such nonconservative ratchetlike structures support rich families of stable vortex solitons in cubic nonlinear media, whose properties depend on the sign of the topological charge due to the nonequivalence of azimuthal directions. In contrast, oppositely charged vortex solitons remain equivalent in similar fully-PT-symmetric potentials. The vortex solitons in the pPT- and PT-symmetric potentials are shown to feature qualitatively different internal current distributions, which are described by different discrete rotation symmetries of the intensity profiles. PMID:26588383

  5. PtRu/C electrocatalysts prepared using γ-irradiation

    NASA Astrophysics Data System (ADS)

    Silva, Dionísio F.; Neto, Almir Oliveira; Pino, Eddy S.; Linardi, Marcelo; Spinacé, Estevam V.

    PtRu/C electrocatalysts (carbon-supported PtRu nanoparticles) were prepared submitting water/ethylene glycol solutions containing Pt(IV) and Ru(III) ions and the carbon support to γ-irradiation. The water/ethylene glycol ratio (v/v) and the total dose (kGy) were evaluated as synthesis parameters. The electrocatalysts were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts were more active for methanol electro-oxidation than the commercial PtRu/C electrocatalyst at ambient temperature and the electrocatalytic activity depends on the water/ethylene glycol ratio used in the preparation.

  6. Anomalous Hall effect in YIG|Pt bilayers

    SciTech Connect

    Meyer, Sibylle Schlitz, Richard; Geprägs, Stephan; Opel, Matthias; Huebl, Hans; Goennenwein, Sebastian T. B.; Gross, Rudolf

    2015-03-30

    We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet|platinum (YIG|Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall effect like voltage in Pt, which is sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing conductance G{sub i} plays a crucial role in YIG|Pt bilayers. In particular, our data suggest a sign change in G{sub i} between 10 K and 300 K. Additionally, we report a higher order Hall effect contribution, which appears in thin Pt films on YIG at low temperatures.

  7. Comparative proteomic analysis of Saccharomyces cerevisiae under different nitrogen sources.

    PubMed

    Zhao, Shaohui; Zhao, Xinrui; Zou, Huijun; Fu, Jianwei; Du, Guocheng; Zhou, Jingwen; Chen, Jian

    2014-04-14

    In cultures containing multiple sources of nitrogen, Saccharomyces cerevisiae exhibits a sequential use of nitrogen sources through a mechanism known as nitrogen catabolite repression (NCR). To identify proteins differentially expressed due to NCR, proteomic analysis of S. cerevisiae S288C under different nitrogen source conditions was performed using two-dimensional gel electrophoresis (2-DE), revealing 169 candidate protein spots. Among these 169 protein spots, 121 were identified by matrix assisted laser desorption ionization-time of flight/time of flight mass spectrometry (MALDI-TOF/TOF). The identified proteins were closely associated with four main biological processes through Gene Ontology (GO) categorical analysis. The identification of the potential proteins and cellular processes related to NCR offer a global overview of changes elicited by different nitrogen sources, providing clues into how yeast adapt to different nutritional conditions. Moreover, by comparing our proteomic data with corresponding mRNA data, proteins regulated at the transcriptional and post-transcriptional level could be distinguished. Biological significance In S. cerevisiae, different nitrogen sources provide different growth characteristics and generate different metabolites. The nitrogen catabolite repression (NCR) process plays an important role for S. cerevisiae in the ordinal utilization of different nitrogen sources. NCR process can result in significant shift of global metabolic networks. Previous works on NCR primarily focused on transcriptomic level. The results obtained in this study provided a global atlas of the proteome changes triggered by different nitrogen sources and would facilitate the understanding of mechanisms for how yeast could adapt to different nutritional conditions. PMID:24530623

  8. Nanofiltration concentration of extracellular glutathione produced by engineered Saccharomyces cerevisiae.

    PubMed

    Sasaki, Kengo; Hara, Kiyotaka Y; Kawaguchi, Hideo; Sazuka, Takashi; Ogino, Chiaki; Kondo, Akihiko

    2016-01-01

    This study aimed to optimize extracellular glutathione production by a Saccharomyces cerevisiae engineered strain and to concentrate the extracellular glutathione by membrane separation processes, including ultrafiltration (UF) and nanofiltration (NF). Synthetic defined (SD) medium containing 20 g L(-1) glucose was fermented for 48 h; the fermentation liquid was passed through an UF membrane to remove macromolecules. Glutathione in this permeate was concentrated for 48 h to 545.1 ± 33.6 mg L(-1) using the NF membrane; this was a significantly higher concentration than that obtained with yeast extract peptone dextrose (YPD) medium following 96 h NF concentration (217.9 ± 57.4 mg L(-1)). This higher glutathione concentration results from lower cellular growth in SD medium (final OD600 = 6.9 ± 0.1) than in YPD medium (final OD600 = 11.0 ± 0.6) and thus higher production of extracellular glutathione (16.0 ± 1.3 compared to 9.2 ± 2.1 mg L(-1) in YPD medium, respectively). Similar fermentation and membrane processing of sweet sorghum juice containing 20 g L(-1) total sugars provided 240.3 ± 60.6 mg L(-1) glutathione. Increased extracellular production of glutathione by this engineered strain in SD medium and subsequent UF permeation and NF concentration in shortend time may help realize industrial recovery of extracellular glutathione. PMID:26105794

  9. Saccharomyces cerevisiae Genes Involved in Survival of Heat Shock

    PubMed Central

    Jarolim, Stefanie; Ayer, Anita; Pillay, Bethany; Gee, Allison C.; Phrakaysone, Alex; Perrone, Gabriel G.; Breitenbach, Michael; Dawes, Ian W.

    2013-01-01

    The heat-shock response in cells, involving increased transcription of a specific set of genes in response to a sudden increase in temperature, is a highly conserved biological response occurring in all organisms. Despite considerable attention to the processes activated during heat shock, less is known about the role of genes in survival of a sudden temperature increase. Saccharomyces cerevisiae genes involved in the maintenance of heat-shock resistance in exponential and stationary phase were identified by screening the homozygous diploid deletants in nonessential genes and the heterozygous diploid mutants in essential genes for survival after a sudden shift in temperature from 30 to 50°. More than a thousand genes were identified that led to altered sensitivity to heat shock, with little overlap between them and those previously identified to affect thermotolerance. There was also little overlap with genes that are activated or repressed during heat-shock, with only 5% of them regulated by the heat-shock transcription factor. The target of rapamycin and protein kinase A pathways, lipid metabolism, vacuolar H+-ATPase, vacuolar protein sorting, and mitochondrial genome maintenance/translation were critical to maintenance of resistance. Mutants affected in l-tryptophan metabolism were heat-shock resistant in both growth phases; those affected in cytoplasmic ribosome biogenesis and DNA double-strand break repair were resistant in stationary phase, and in mRNA catabolic processes in exponential phase. Mutations affecting mitochondrial genome maintenance were highly represented in sensitive mutants. The cell division transcription factor Swi6p and Hac1p involved in the unfolded protein response also play roles in maintenance of heat-shock resistance. PMID:24142923

  10. Human G protein-coupled receptor studies in Saccharomyces cerevisiae.

    PubMed

    Liu, Rongfang; Wong, Winsy; IJzerman, Adriaan P

    2016-08-15

    G protein-coupled receptors (GPCRs) are one of the largest families of membrane proteins, with approximately 800 different GPCRs in the human genome. Signaling via GPCRs regulates many biological processes, such as cell proliferation, differentiation, and development. In addition, many receptors have a pivotal role in immunophysiology. Many hormones and neurotransmitters are ligands for these receptors, and hence it is not surprising that many drugs, either mimicking or blocking the action of the bodily substances, have been developed. It is estimated that 30-40% of current drugs on the market target GPCRs. Further identifying and elucidating the functions of GPCRs will provide opportunities for novel drug discovery, including for immunotherapy. The budding yeast Saccharomyces cerevisiae (S. cerevisiae) is a very important and useful platform in this respect. There are many advantages of using a yeast assay system, as it is cheap, safe and stable; it is also convenient for rapid feasibility and optimization studies. Moreover, it offers a "null" background when studying human GPCRs. New developments regarding human GPCRs expressed in a yeast platform are providing insight into GPCR activation and signaling, and facilitate agonist and antagonist identification. In this review we summarize the latest findings regarding human G-protein-coupled receptors in studies using S. cerevisiae, ever since the year 2005 when we last published a review on this topic. We describe 11 families of GPCRs in detail, while including the principles and developments of each yeast system applied to these different GPCRs and highlight and generalize the experimental findings of GPCR function in these systems. PMID:26920251

  11. The plasma membrane of Saccharomyces cerevisiae: structure, function, and biogenesis.

    PubMed

    van der Rest, M E; Kamminga, A H; Nakano, A; Anraku, Y; Poolman, B; Konings, W N

    1995-06-01

    The composition of phospholipids, sphingolipids, and sterols in the plasma membrane has a strong influence on the activity of the proteins associated or embedded in the lipid bilayer. Since most lipid-synthesizing enzymes in Saccharomyces cerevisiae are located in intracellular organelles, an extensive flux of lipids from these organelles to the plasma membrane is required. Although the pathway of protein traffic to the plasma membrane is similar to that of most of the lipids, the bulk flow of lipids is separate from vesicle-mediated protein transport. Recent advances in the analysis of membrane budding and membrane fusion indicate that the mechanisms of protein transport from the endoplasmic reticulum to the Golgi and from the Golgi to plasma membrane are similar. The majority of plasma membrane proteins transport solutes across the membrane. A number of ATP-dependent export systems have been detected that couple the hydrolysis of ATP to transport of molecules out of the cell. The hydrolysis of ATP by the plasma membrane H(+)-ATPase generates a proton motive force which is used to drive secondary transport processes. In S. cerevisiae, many substrates are transported by more than one system. Transport of monosaccharide is catalyzed by uniport systems, while transport of disaccharides, amino acids, and nucleosides is mediated by proton symport systems. Transport activity can be regulated at the level of transcription, e.g., induction and (catabolite) repression, but transport proteins can also be affected posttranslationally by a process termed catabolite inactivation. Catabolite inactivation is triggered by the addition of fermentable sugars, intracellular acidification, stress conditions, and/or nitrogen starvation. Phosphorylation and/or ubiquitination of the transport proteins has been proposed as an initial step in the controlled inactivation and degradation of the target enzyme. The use of artificial membranes, like secretory vesicles and plasma membranes

  12. Mating-type Gene Switching in Saccharomyces cerevisiae.

    PubMed

    Lee, Cheng-Sheng; Haber, James E

    2015-04-01

    The budding yeast Saccharomyces cerevisiae has two alternative mating types designated MATa and MATα. These are distinguished by about 700 bp of unique sequences, Ya or Yα, including divergent promoter sequences and part of the open reading frames of genes that regulate mating phenotype. Homothallic budding yeast, carrying an active HO endonuclease gene, HO, can switch mating type through a recombination process known as gene conversion, in which a site-specific double-strand break (DSB) created immediately adjacent to the Y region results in replacement of the Y sequences with a copy of the opposite mating type information, which is harbored in one of two heterochromatic donor loci, HMLα or HMRa. HO gene expression is tightly regulated to ensure that only half of the cells in a lineage switch to the opposite MAT allele, thus promoting conjugation and diploid formation. Study of the silencing of these loci has provided a great deal of information about the role of the Sir2 histone deacetylase and its associated Sir3 and Sir4 proteins in creating heterochromatic regions. MAT switching has been examined in great detail to learn about the steps in homologous recombination. MAT switching is remarkably directional, with MATa recombining preferentially with HMLα and MATα using HMRa. Donor preference is controlled by a cis-acting recombination enhancer located near HML. RE is turned off in MATα cells but in MATa binds multiple copies of the Fkh1 transcription factor whose forkhead-associated phosphothreonine binding domain localizes at the DSB, bringing HML into conjunction with MATa. PMID:26104712

  13. Ergosterol production from molasses by genetically modified Saccharomyces cerevisiae.

    PubMed

    He, Xiuping; Guo, Xuena; Liu, Nan; Zhang, Borun

    2007-05-01

    Ergosterol is an economically important metabolite produced by fungi. Recombinant Saccharomyces cerevisiae YEH56(pHXA42) with increased capacity of ergosterol formation was constructed by combined overexpression of sterol C-24(28) reductase and sterol acyltransferase in the yeast strain YEH56. The production of ergosterol by this recombinant strain using cane molasses (CM) as an inexpensive carbon source was investigated. An ergosterol content of 52.6 mg/g was obtained with 6.1 g/l of biomass from CM medium containing 60 g/l of total sugar in 30 h in shake flask. The ergosterol yield was enhanced through the increasing cell biomass by supplementation of urea to a concentration of 6 g/l in molasses medium. Fermentation was performed in 5-l bioreactor using the optimized molasses medium. In batch fermentation, the effect of agitation velocity on ergosterol production was examined. The highest ergosterol yield was obtained at 400 rpm that increased 60.4 mg/l in comparison with the shake flask culture. In fed-batch fermentation, yeast cells were cultivated, firstly, in the starting medium containing molasses with 20 g/l of total sugar, 1.68 g/l of phosphate acid, and 6 g/l of urea (pH 5.4) for 5 h, then molasses containing 350 g/l of total sugar was fed exponentially into the bioreactor to keep the ethanol level in the broth below 0.5%. After 40 h of cultivation, the ergosterol yield reached 1,707 mg/l, which was 3.1-fold of that in the batch fermentation. PMID:17225097

  14. A vector set for systematic metabolic engineering in Saccharomyces cerevisiae

    PubMed Central

    Fang, Fang; Salmon, Kirsty; Shen, Michael W. Y.; Aeling, Kimberly A.; Ito, Elaine; Irwin, Becky; Tran, Uyen Phuong C.; Hatfield, G. Wesley; Da Silva, Nancy A.; Sandmeyer, Suzanne

    2011-01-01

    A set of shuttle vectors was constructed to facilitate expression of genes for metabolic engineering in Saccharomyces cerevisiae. Selectable markers include the URA3, TRP1, MET15, LEU2-d8, HIS3 and CAN1 genes. Differential expression of genes can be achieved as each marker is available on both CEN/ARS- and 2 μ-containing plasmids. Unique restriction sites downstream of TEF1, PGK1 or HXT7-391 promoters and upstream of the CYC1 terminator allow insertion of open-reading frame cassettes for expression. Furthermore, a fragment appropriate for integration into the genome via homologous recombination can be readily generated in a polymerase chain reaction. Vector marker genes are flanked by loxP recognition sites for the CreA recombinase to allow efficient site-specific marker deletion and recycling. Expression and copy number were characterized for representative high- and low-copy vectors carrying the different marker and promoter sequences. Metabolic engineering typically requires the stable introduction of multiple genes and genomic integration is often preferred. This requires an expanded number of stable expression sites relative to standard gene expression studies. This study demonstrated the practicality of polymerase chain reaction amplification of an expression cassette and genetic marker, and subsequent replacement of endogenous retrotransposons by homologous recombination with flanking sequences. Such reporters were expressed comparably to those inserted at standard integration loci. This expands the number of available characterized integration sites and demonstrates that such sites provide a virtually inexhaustible pool of integration targets for stable expression of multiple genes. Together these vectors and expression loci will facilitate combinatorial gene expression for metabolic engineering. PMID:20936606

  15. Pathogenic potential of Saccharomyces strains isolated from dietary supplements.

    PubMed

    Llopis, Silvia; Hernández-Haro, Carolina; Monteoliva, Lucía; Querol, Amparo; Molina, María; Fernández-Espinar, María T

    2014-01-01

    Saccharomyces cerevisiae plays a beneficial role in health because of its intrinsic nutritional value and bio-functional properties, which is why it is also used as a dietary supplement. However, the perception that S. cerevisiae is harmless has changed due to an increasing number of infections caused by this yeast. Given this scenario, we have tested whether viable strains contained in dietary supplements displayed virulence-associated phenotypic traits that could contribute to virulence in humans. We have also performed an in vivo study of the pathogenic potential of these strains using a murine model of systemic infection by intravenous inoculation. A total of 5 strains were isolated from 22 commercial products and tested. Results highlight one strain (D14) in terms of burden levels in brains and kidneys and ability to cause death, whereas the other two strains (D2 and D4) were considered of low virulence. Our results suggest a strong relationship between some of the virulence-associated phenotypic traits (ability to grow at 39°C and pseudohyphal growth) and the in vivo virulence in a mouse model of intravenous inoculation for isolates under study. The isolate displaying greatest virulence (D14) was evaluated in an experimental murine model of gastrointestinal infection with immunosuppression and disruption of mucosal integrity, which are common risk factors for developing infection in humans, and results were compared with an avirulent strain (D23). We showed that D14 was able to spread to mesenteric nodes and distant organs under these conditions. Given the widespread consumption of dietary supplements, we recommend only safe strains be used. PMID:24879417

  16. Heat shock response improves heterologous protein secretion in Saccharomyces cerevisiae.

    PubMed

    Hou, Jin; Osterlund, Tobias; Liu, Zihe; Petranovic, Dina; Nielsen, Jens

    2013-04-01

    The yeast Saccharomyces cerevisiae is a widely used platform for the production of heterologous proteins of medical or industrial interest. However, heterologous protein productivity is often low due to limitations of the host strain. Heat shock response (HSR) is an inducible, global, cellular stress response, which facilitates the cell recovery from many forms of stress, e.g., heat stress. In S. cerevisiae, HSR is regulated mainly by the transcription factor heat shock factor (Hsf1p) and many of its targets are genes coding for molecular chaperones that promote protein folding and prevent the accumulation of mis-folded or aggregated proteins. In this work, we over-expressed a mutant HSF1 gene HSF1-R206S which can constitutively activate HSR, so the heat shock response was induced at different levels, and we studied the impact of HSR on heterologous protein secretion. We found that moderate and high level over-expression of HSF1-R206S increased heterologous α-amylase yield 25 and 70 % when glucose was fully consumed, and 37 and 62 % at the end of the ethanol phase, respectively. Moderate and high level over-expression also improved endogenous invertase yield 118 and 94 %, respectively. However, human insulin precursor was only improved slightly and this only by high level over-expression of HSF1-R206S, supporting our previous findings that the production of this protein in S. cerevisiae is not limited by secretion. Our results provide an effective strategy to improve protein secretion and demonstrated an approach that can induce ER and cytosolic chaperones simultaneously. PMID:23208612

  17. Heterologous expression of cellulase genes in natural Saccharomyces cerevisiae strains.

    PubMed

    Davison, Steffi A; den Haan, Riaan; van Zyl, Willem Heber

    2016-09-01

    Enzyme cost is a major impediment to second-generation (2G) cellulosic ethanol production. One strategy to reduce enzyme cost is to engineer enzyme production capacity in a fermentative microorganism to enable consolidated bio-processing (CBP). Ideally, a strain with a high secretory phenotype, high fermentative capacity as well as an innate robustness to bioethanol-specific stressors, including tolerance to products formed during pre-treatment and fermentation of lignocellulosic substrates should be used. Saccharomyces cerevisiae is a robust fermentative yeast but has limitations as a potential CBP host, such as low heterologous protein secretion titers. In this study, we evaluated natural S. cerevisiae isolate strains for superior secretion activity and other industrially relevant characteristics needed during the process of lignocellulosic ethanol production. Individual cellulases namely Saccharomycopsis fibuligera Cel3A (β-glucosidase), Talaromyces emersonii Cel7A (cellobiohydrolase), and Trichoderma reesei Cel5A (endoglucanase) were utilized as reporter proteins. Natural strain YI13 was identified to have a high secretory phenotype, demonstrating a 3.7- and 3.5-fold higher Cel7A and Cel5A activity, respectively, compared to the reference strain S288c. YI13 also demonstrated other industrially relevant characteristics such as growth vigor, high ethanol titer, multi-tolerance to high temperatures (37 and 40 °C), ethanol (10 % w/v), and towards various concentrations of a cocktail of inhibitory compounds commonly found in lignocellulose hydrolysates. This study accentuates the value of natural S. cerevisiae isolate strains to serve as potential robust and highly productive chassis organisms for CBP strain development. PMID:27470141

  18. Pathogenic Potential of Saccharomyces Strains Isolated from Dietary Supplements

    PubMed Central

    Monteoliva, Lucía; Querol, Amparo; Molina, María; Fernández-Espinar, María T.

    2014-01-01

    Saccharomyces cerevisiae plays a beneficial role in health because of its intrinsic nutritional value and bio-functional properties, which is why it is also used as a dietary supplement. However, the perception that S. cerevisiae is harmless has changed due to an increasing number of infections caused by this yeast. Given this scenario, we have tested whether viable strains contained in dietary supplements displayed virulence-associated phenotypic traits that could contribute to virulence in humans. We have also performed an in vivo study of the pathogenic potential of these strains using a murine model of systemic infection by intravenous inoculation. A total of 5 strains were isolated from 22 commercial products and tested. Results highlight one strain (D14) in terms of burden levels in brains and kidneys and ability to cause death, whereas the other two strains (D2 and D4) were considered of low virulence. Our results suggest a strong relationship between some of the virulence-associated phenotypic traits (ability to grow at 39°C and pseudohyphal growth) and the in vivo virulence in a mouse model of intravenous inoculation for isolates under study. The isolate displaying greatest virulence (D14) was evaluated in an experimental murine model of gastrointestinal infection with immunosuppression and disruption of mucosal integrity, which are common risk factors for developing infection in humans, and results were compared with an avirulent strain (D23). We showed that D14 was able to spread to mesenteric nodes and distant organs under these conditions. Given the widespread consumption of dietary supplements, we recommend only safe strains be used. PMID:24879417

  19. Septins localize to microtubules during nutritional limitation in Saccharomyces cerevisiae

    PubMed Central

    Pablo-Hernando, M Evangelina; Arnaiz-Pita, Yolanda; Tachikawa, Hiroyuki; del Rey, Francisco; Neiman, Aaron M; Vázquez de Aldana, Carlos R

    2008-01-01

    Background In Saccharomyces cerevisiae, nutrient limitation stimulates diploid cells to undergo DNA replication and meiosis, followed by the formation of four haploid spores. Septins are a family of proteins that assemble a ring structure at the mother-daughter neck during vegetative growth, where they control cytokinesis. In sporulating cells, the septin ring disassembles and septins relocalize to the prospore membrane. Results Here, we demonstrate that nutrient limitation triggers a change in the localization of at least two vegetative septins (Cdc10 and Cdc11) from the bud neck to the microtubules. The association of Cdc10 and Cdc11 with microtubules persists into meiosis, and they are found associated with the meiotic spindle until the end of meiosis II. In addition, the meiosis-specific septin Spr28 displays similar behavior, suggesting that this is a common feature of septins. Septin association to microtubules is a consequence of the nutrient limitation signal, since it is also observed when haploid cells are incubated in sporulation medium and when haploid or diploid cells are grown in medium containing non-fermentable carbon sources. Moreover, during meiosis II, when the nascent prospore membrane is formed, septins moved from the microtubules to this membrane. Proper organization of the septins on the membrane requires the sporulation-specific septins Spr3 and Spr28. Conclusion Nutrient limitation in S. cerevisiae triggers the sporulation process, but it also induces the disassembly of the septin bud neck ring and relocalization of the septin subunits to the nucleus. Septins remain associated with microtubules during the meiotic divisions and later, during spore morphogenesis, they are detected associated to the nascent prospore membranes surrounding each nuclear lobe. Septin association to microtubules also occurs during growth in non-fermentable carbon sources. PMID:18826657

  20. Engineering the monomer composition of polyhydroxyalkanoates synthesized in Saccharomyces cerevisiae.

    PubMed

    Zhang, Bo; Carlson, Ross; Srienc, Friedrich

    2006-01-01

    Polyhydroxyalkanoates (PHAs) have received considerable interest as renewable-resource-based, biodegradable, and biocompatible plastics with a wide range of potential applications. We have engineered the synthesis of PHA polymers composed of monomers ranging from 4 to 14 carbon atoms in either the cytosol or the peroxisome of Saccharomyces cerevisiae by harnessing intermediates of fatty acid metabolism. Cytosolic PHA production was supported by establishing in the cytosol critical beta-oxidation chemistries which are found natively in peroxisomes. This platform was utilized to supply medium-chain (C6 to C14) PHA precursors from both fatty acid degradation and synthesis to a cytosolically expressed medium-chain-length (mcl) polymerase from Pseudomonas oleovorans. Synthesis of short-chain-length PHAs (scl-PHAs) was established in the peroxisome of a wild-type yeast strain by targeting the Ralstonia eutropha scl polymerase to the peroxisome. This strain, harboring a peroxisomally targeted scl-PHA synthase, accumulated PHA up to approximately 7% of its cell dry weight. These results indicate (i) that S. cerevisiae expressing a cytosolic mcl-PHA polymerase or a peroxisomal scl-PHA synthase can use the 3-hydroxyacyl coenzyme A intermediates from fatty acid metabolism to synthesize PHAs and (ii) that fatty acid degradation is also possible in the cytosol as beta-oxidation might not be confined only to the peroxisomes. Polymers of even-numbered, odd-numbered, or a combination of even- and odd-numbered monomers can be controlled by feeding the appropriate substrates. This ability should permit the rational design and synthesis of polymers with desired material properties. PMID:16391089

  1. [Construction of Saccharomyces cerevisiae cell factories for lycopene production].

    PubMed

    Shi, Ming-Yu; Liu Yi; Wang, Dong; Lu, Fu-Ping; Huang, Lu-Qi; Dai, Zhu-Bo; Zhang, Xue-Li

    2014-10-01

    For microbial production of lycopene, the lycopene synthetic genes from Pantoea agglomerans were integrated into Saccharomyces cerevisiae strain BY4742, to obtain strain ZD-L-000 for production of 0.17 mg · L(-1) lycopene. Improving supplies of isoprenoid precursors was then investigated for increasing lycopene production. Four key genes were chosen to be overexpressed, inclu- ding truncated 3-hydroxy-3-methylglutaryl-CoA reductase gene (tHMG1), which is the major rate-limiting enzyme in the mevalonate (MVA) pathway, a mutated global regulatory factor gene (upc2.1), a fusion gene of FPP synthase (ERG20) and endogenous GGPP synthase (BTS1), which is a key enzyme in the diterpenoid synthetic pathway, and GGPP synthase gene (SaGGPS) from Sulfolobus acidocaldarius. Over-expression of upc2.1 could not improve lycopene production, while over-expression of tHMGI , BTS1-ERG20 and SaGGPS genes led to 2-, 16. 9- and20. 5-fold increase of lycopene production, respectively. In addition, three effective genes, tHMG1, BTS1-ERG20 and SaGGPS, were integrated into rDNA sites of ZD-L-000, resulting in strain ZD-L-201 for production of 13.23 mg · L(-1) lycopene, which was 77-fold higher than that of the parent strain. Finally, two-phase extractive fermentation was performed. The titer of lycopene increased 10-fold to 135.21 mg · L(-1). The engineered yeast strains obtained in this work provided the basis for fermentative production of lycopene. PMID:25751950

  2. Comprehensive Analysis of the SUL1 Promoter of Saccharomyces cerevisiae.

    PubMed

    Rich, Matthew S; Payen, Celia; Rubin, Alan F; Ong, Giang T; Sanchez, Monica R; Yachie, Nozomu; Dunham, Maitreya J; Fields, Stanley

    2016-05-01

    In the yeast Saccharomyces cerevisiae, beneficial mutations selected during sulfate-limited growth are typically amplifications of the SUL1 gene, which encodes the high-affinity sulfate transporter, resulting in fitness increases of >35% . Cis-regulatory mutations have not been observed at this locus; however, it is not clear whether this absence is due to a low mutation rate such that these mutations do not arise, or they arise but have limited fitness effects relative to those of amplification. To address this question directly, we assayed the fitness effects of nearly all possible point mutations in a 493-base segment of the gene's promoter through mutagenesis and selection. While most mutations were either neutral or detrimental during sulfate-limited growth, eight mutations increased fitness >5% and as much as 9.4%. Combinations of these beneficial mutations increased fitness only up to 11%. Thus, in the case of SUL1, promoter mutations could not induce a fitness increase similar to that of gene amplification. Using these data, we identified functionally important regions of the SUL1 promoter and analyzed three sites that correspond to potential binding sites for the transcription factors Met32 and Cbf1 Mutations that create new Met32- or Cbf1-binding sites also increased fitness. Some mutations in the untranslated region of the SUL1 transcript decreased fitness, likely due to the formation of inhibitory upstream open reading frames. Our methodology-saturation mutagenesis, chemostat selection, and DNA sequencing to track variants-should be a broadly applicable approach. PMID:26936925

  3. Enhanced lysosomal activity by overexpressed aminopeptidase Y in Saccharomyces cerevisiae.

    PubMed

    Yoon, Jihee; Sekhon, Simranjeet Singh; Kim, Yang-Hoon; Min, Jiho

    2016-06-01

    Saccharomyces cerevisiae contains vacuoles corresponding to lysosomes in higher eukaryotes. Lysosomes are dynamic (not silent) organelles in which enzymes can be easily integrated or released when exposed to stressful conditions. Changes in lysosomal enzymes have been observed due to oxidative stress, resulting in an increased function of lysosomes. The protein profiles from H2O2- and NH4Cl-treated lysosomes showed different expression patterns, observed with two-dimensional gel electrophoresis. The aminopeptidase Y protein (APE3) that conspicuously enhanced antimicrobial activity than other proteins was selected for further studies. The S. cerevisiae APE3 gene was isolated and inserted into pYES2.0 expression vector. The GFP gene was inserted downstream to the APE3 gene for confirmation of APE3 targeting to lysosomes, and S. cerevisiae was transformed to pYES2::APE3::GFP. The APE3 did not enter in lysosomes and formed an inclusion body at 30 °C, but it inserted to lysosomes as shown by the merger of GFP with lysosomes at 28 °C. Antimicrobial activity of the cloned S. cerevisiae increased about 5 to 10 % against eight strains, compared to normal cells, and galactose induction is increased more two folds than that of normal cells. Therefore, S. cerevisiae was transformed to pYES2::APE3::GFP, accumulating a large amount of APE3, resulting in increased lysosomal activity. Increase in endogenous levels of lysosomes and their activity following genetic modification can lead to its use in applications such as antimicrobial agents and apoptosis-inducing materials for cancer cells, and consequently, it may also be possible to use the organelles for improving in vitro functions. PMID:27221740

  4. Saccharomyces cerevisiae ribosomes recognize non-AUG initiation codons.

    PubMed Central

    Zitomer, R S; Walthall, D A; Rymond, B C; Hollenberg, C P

    1984-01-01

    A series of Saccharomyces cerevisiae plasmids and mutant derivatives containing fusions of the Escherichia coli galactokinase gene, galK, to the yeast iso-1-cytochrome c CYC1 transcription unit were used to study the sequences affecting the initiation of translation in S. cerevisiae. When the CYC1 AUG initiation codon preceded the galK AUG codon and coding sequence and either the two AUGs were out of frame with each other or a nonsense codon was located between them, the expression of the galK gene was extremely low. Deletion of the CYC1 AUG and its surrounding sequences resulted in a 100-fold increase in galK expression. This dependence of galK expression on the elimination of the CYC1 AUG codon was used to select mutations in that codon. Then the ability of these altered initiation codons to serve in translational initiation was determined by reconstruction of the CYC1 gene 3' to and in frame with them. Initiation was found to occur at the codons UUG and AUA, but not at the codons AAA and AUC. Furthermore the codon UUG, when preceded by an A three nucleotides upstream, served as a better initiation codon than when a U was substituted for the A. The efficiency of translation from these non-AUG codons was quantitated by using a CYC1/galK protein-coding fusion and measuring cellular galactokinase levels. Initiation at the UUG codon was 6.9% as efficient as initiation at the wild-type AUG codon when preceded by an A three nucleotides upstream, but was over 10-fold less efficient when a U was substituted for that A. Initiation at AUA was 0.5% as efficient as at AUG. The effects of the sequences preceding the initiation codon are discussed in light of these results. PMID:6390186

  5. Molecular basis of cell integrity and morphogenesis in Saccharomyces cerevisiae.

    PubMed Central

    Cid, V J; Durán, A; del Rey, F; Snyder, M P; Nombela, C; Sánchez, M

    1995-01-01

    In fungi and many other organisms, a thick outer cell wall is responsible for determining the shape of the cell and for maintaining its integrity. The budding yeast Saccharomyces cerevisiae has been a useful model organism for the study of cell wall synthesis, and over the past few decades, many aspects of the composition, structure, and enzymology of the cell wall have been elucidated. The cell wall of budding yeasts is a complex and dynamic structure; its arrangement alters as the cell grows, and its composition changes in response to different environmental conditions and at different times during the yeast life cycle. In the past few years, we have witnessed a profilic genetic and molecular characterization of some key aspects of cell wall polymer synthesis and hydrolysis in the budding yeast. Furthermore, this organism has been the target of numerous recent studies on the topic of morphogenesis, which have had an enormous impact on our understanding of the intracellular events that participate in directed cell wall synthesis. A number of components that direct polarized secretion, including those involved in assembly and organization of the actin cytoskeleton, secretory pathways, and a series of novel signal transduction systems and regulatory components have been identified. Analysis of these different components has suggested pathways by which polarized secretion is directed and controlled. Our aim is to offer an overall view of the current understanding of cell wall dynamics and of the complex network that controls polarized growth at particular stages of the budding yeast cell cycle and life cycle. PMID:7565410

  6. Modulation of efficiency of translation termination in Saccharomyces cerevisiae

    PubMed Central

    Nizhnikov, Anton A; Antonets, Kirill S; Inge-Vechtomov, Sergey G; Derkatch, Irina L

    2014-01-01

    Nonsense suppression is a readthrough of premature termination codons. It typically occurs either due to the recognition of stop codons by tRNAs with mutant anticodons, or due to a decrease in the fidelity of translation termination. In the latter case, suppressors usually promote the readthrough of different types of nonsense codons and are thus called omnipotent nonsense suppressors. Omnipotent nonsense suppressors were identified in yeast Saccharomyces cerevisiae in 1960s, and most of subsequent studies were performed in this model organism. Initially, omnipotent suppressors were localized by genetic analysis to different protein- and RNA-encoding genes, mostly the components of translational machinery. Later, nonsense suppression was found to be caused not only by genomic mutations, but also by epigenetic elements, prions. Prions are self-perpetuating protein conformations usually manifested by infectious protein aggregates. Modulation of translational accuracy by prions reflects changes in the activity of their structural proteins involved in different aspects of protein synthesis. Overall, nonsense suppression can be seen as a “phenotypic mirror” of events affecting the accuracy of the translational machine. However, the range of proteins participating in the modulation of translation termination fidelity is not fully elucidated. Recently, the list has been expanded significantly by findings that revealed a number of weak genetic and epigenetic nonsense suppressors, the effect of which can be detected only in specific genetic backgrounds. This review summarizes the data on the nonsense suppressors decreasing the fidelity of translation termination in S. cerevisiae, and discusses the functional significance of the modulation of translational accuracy. PMID:25486049

  7. In vivo rearrangement of mitochondrial DNA in Saccharomyces cerevisiae.

    PubMed Central

    Clark-Walker, G D

    1989-01-01

    A revertant (SPR1) from a high-frequency petite strain of Saccharomyces cerevisiae has been shown by mapping and sequence analysis to have a rearranged mitochondrial genome. In vivo rearrangement has occurred through a subgenomic-recombination pathway involving the initial formation of subgenomic molecules in nascent petite mutants, recombination between these molecules to form an intermediate with direct repeats, and subsequent excision of the resident or symposed duplication to yield a molecule with three novel junctions and a changed gene order. Sequencing of the novel junctions shows that intramolecular recombination in each case occurs by means of G + C-rich short direct repeats of 40-51 base pairs. Mapping and sequence analysis also reveal that the SPR1 mitochondrial genome lacks three sectors of the wild-type molecule of 4.4, 1.7, and 0.5 kilobases. Each of these sectors occurs in nontemplate, base-biased DNA, that is over 90% A + T. Absence of these sectors together with a rearranged gene order does not appear to affect the phenotype of SPR1, as colony morphology and growth rate on a number of different substrates are not detectably different from the wild type. Lack of phenotypic change suggests that mitochondrial gene expression has not been noticeably disrupted in SPR1 despite deletion of the consensus nonomer promoter upstream from the glutamic acid tRNA gene. Dispensability of DNA sectors and the presence of recombinogenic short, direct repeats are mandatory features of the subgenomic-recombination pathway for creating rearrangements in baker's yeast mtDNA. It is proposed that, in other organisms, organelle genomes containing these elements may undergo rearrangement by the same steps. Images PMID:2682661

  8. MET17 and Hydrogen Sulfide Formation in Saccharomyces cerevisiae

    PubMed Central

    Spiropoulos, Apostolos; Bisson, Linda F.

    2000-01-01

    Commercial isolates of Saccharomyces cerevisiae differ in the production of hydrogen sulfide (H2S) during fermentation, which has been attributed to variation in the ability to incorporate reduced sulfur into organic compounds. We transformed two commercial strains (UCD522 and UCD713) with a plasmid overexpressing the MET17 gene, which encodes the bifunctional O-acetylserine/O-acetylhomoserine sulfhydrylase (OAS/OAH SHLase), to test the hypothesis that the level of activity of this enzyme limits reduced sulfur incorporation, leading to H2S release. Overexpression of MET17 resulted in a 10- to 70-fold increase in OAS/OAH SHLase activity in UCD522 but had no impact on the level of H2S produced. In contrast, OAS/OAH SHLase activity was not as highly expressed in transformants of UCD713 (0.5- to 10-fold) but resulted in greatly reduced H2S formation. Overexpression of OAS/OAH SHLase activity was greater in UCD713 when grown under low-nitrogen conditions, but the impact on reduction of H2S was greater under high-nitrogen conditions. Thus, there was not a good correlation between the level of enzyme activity and H2S production. We measured cellular levels of cysteine to determine the impact of overexpression of OAS/OAH SHLase activity on sulfur incorporation. While Met17p activity was not correlated with increased cysteine production, conditions that led to elevated cytoplasmic levels of cysteine also reduced H2S formation. Our data do not support the simple hypothesis that variation in OAS/OAH SHLase activity is correlated with H2S production and release. PMID:11010893

  9. Microfluidic reactor for continuous cultivation of Saccharomyces cerevisiae.

    PubMed

    Edlich, Astrid; Magdanz, Veronika; Rasch, Detlev; Demming, Stefanie; Aliasghar Zadeh, Shobeir; Segura, Rodrigo; Kähler, Christian; Radespiel, Rolf; Büttgenbach, Stephanus; Franco-Lara, Ezequiel; Krull, Rainer

    2010-01-01

    A diffusion-based microreactor system operated with a reaction volume of 8 μL is presented and characterized to intensify the process understanding in microscale cultivations. Its potential as screening tool for biological processes is evaluated. The advantage of the designed microbioreactor is the use for the continuous cultivation mode by integrating online measurement technique for dissolved oxygen (DO) and optical density (OD). A further advantage is the broaden application for biological systems. The bioreactor geometry was chosen to achieve homogeneous flow during continuous process operation. The device consisted of a microstructured top layer made of poly(dimethylsiloxane) (PDMS), which was designed and fabricated using UV-depth and soft lithography assembled with a glass bottom. CFD simulation data used for geometry design were verified via microparticle-image-velocimetry (μPIV). In the used microreactor geometry no concentration gradients occurred along the entire reaction volume because of rapid diffusive mixing, the homogeneous medium flow inside the growth chamber of the microreactor could be realized. Undesirable bubble formation before and during operation was reduced by using degassed medium as well as moistened and moderate incident air flow above the gas permeable PDMS membrane. Because of this a passive oxygen supply of the culture medium in the device is ensured by diffusion through the PDMS membrane. The oxygen supply itself was monitored online via integrated DO sensors based on a fluorescent dye complex. An adequate overall volumetric oxygen transfer coefficient K(L)a as well as mechanical stability of the device were accomplished for a membrane thickness of 300 μm. Experimental investigations considering measurements of OD (online) and several metabolite concentrations (offline) in a modified Verduyn medium. The used model organism Saccharomyces cerevisiae DSM 2155 tended to strong reactor wall growth resembling a biofilm. PMID:20945484

  10. Metabolic Engineering of Glycerol Production in Saccharomyces cerevisiae

    PubMed Central

    Overkamp, Karin M.; Bakker, Barbara M.; Kötter, Peter; Luttik, Marijke A. H.; van Dijken, Johannes P.; Pronk, Jack T.

    2002-01-01

    Inactivation of TPI1, the Saccharomyces cerevisiae structural gene encoding triose phosphate isomerase, completely eliminates growth on glucose as the sole carbon source. In tpi1-null mutants, intracellular accumulation of dihydroxyacetone phosphate might be prevented if the cytosolic NADH generated in glycolysis by glyceraldehyde-3-phosphate dehydrogenase were quantitatively used to reduce dihydroxyacetone phosphate to glycerol. We hypothesize that the growth defect of tpi1-null mutants is caused by mitochondrial reoxidation of cytosolic NADH, thus rendering it unavailable for dihydroxyacetone-phosphate reduction. To test this hypothesis, a tpi1Δ nde1Δ nde2Δ gut2Δ quadruple mutant was constructed. NDE1 and NDE2 encode isoenzymes of mitochondrial external NADH dehydrogenase; GUT2 encodes a key enzyme of the glycerol-3-phosphate shuttle. It has recently been demonstrated that these two systems are primarily responsible for mitochondrial oxidation of cytosolic NADH in S. cerevisiae. Consistent with the hypothesis, the quadruple mutant grew on glucose as the sole carbon source. The growth on glucose, which was accompanied by glycerol production, was inhibited at high-glucose concentrations. This inhibition was attributed to glucose repression of respiratory enzymes as, in the quadruple mutant, respiratory pyruvate dissimilation is essential for ATP synthesis and growth. Serial transfer of the quadruple mutant on high-glucose media yielded a spontaneous mutant with much higher specific growth rates in high-glucose media (up to 0.10 h−1 at 100 g of glucose · liter−1). In aerated batch cultures grown on 400 g of glucose · liter−1, this engineered S. cerevisiae strain produced over 200 g of glycerol · liter−1, corresponding to a molar yield of glycerol on glucose close to unity. PMID:12039737

  11. Identification and characterization of phenylpyruvate decarboxylase genes in Saccharomyces cerevisiae.

    PubMed

    Vuralhan, Zeynep; Morais, Marcos A; Tai, Siew-Leng; Piper, Matthew D W; Pronk, Jack T

    2003-08-01

    Catabolism of amino acids via the Ehrlich pathway involves transamination to the corresponding alpha-keto acids, followed by decarboxylation to an aldehyde and then reduction to an alcohol. Alternatively, the aldehyde may be oxidized to an acid. This pathway is functional in Saccharomyces cerevisiae, since during growth in glucose-limited chemostat cultures with phenylalanine as the sole nitrogen source, phenylethanol and phenylacetate were produced in quantities that accounted for all of the phenylalanine consumed. Our objective was to identify the structural gene(s) required for the decarboxylation of phenylpyruvate to phenylacetaldehyde, the first specific step in the Ehrlich pathway. S. cerevisiae possesses five candidate genes with sequence similarity to genes encoding thiamine diphosphate-dependent decarboxylases that could encode this activity: YDR380w/ARO10, YDL080C/THI3, PDC1, PDC5, and PDC6. Phenylpyruvate decarboxylase activity was present in cultures grown with phenylalanine as the sole nitrogen source but was absent from ammonia-grown cultures. Furthermore, the transcript level of one candidate gene (ARO10) increased 30-fold when phenylalanine replaced ammonia as the sole nitrogen source. Analyses of phenylalanine catabolite production and phenylpyruvate decarboxylase enzyme assays indicated that ARO10 was sufficient to encode phenylpyruvate decarboxylase activity in the absence of the four other candidate genes. There was also an alternative activity with a higher capacity but lower affinity for phenylpyruvate. The candidate gene THI3 did not itself encode an active phenylpyruvate decarboxylase but was required along with one or more pyruvate decarboxylase genes (PDC1, PDC5, and PDC6) for the alternative activity. The K(m) and V(max) values of the two activities differed, showing that Aro10p is the physiologically relevant phenylpyruvate decarboxylase in wild-type cells. Modifications to this gene could therefore be important for metabolic engineering

  12. Isolation and characterization of a Saccharomyces cerevisiae peptide transport gene.

    PubMed Central

    Perry, J R; Basrai, M A; Steiner, H Y; Naider, F; Becker, J M

    1994-01-01

    We have cloned and characterized a Saccharomyces cerevisiae peptide transport gene (PTR2) isolated from a genomic DNA library by directly selecting for functional complementation of a peptide transport-deficient mutant. Deletion and frameshift mutageneses were used to localize the complementing activity to a 3.1-kbp region on the transforming plasmid. DNA sequencing of the complementing region identified an open reading frame spanning 1,803 bp. The deduced amino acid sequence predicts a hydrophobic peptide consisting of 601 amino acids, having a molecular mass of 68.1 kDa, composed in part of 12 hydrophobic segments, and sharing significant similarities with a nitrate transport protein encoded by the CHL1 gene of Arabidopsis thaliana. Northern (RNA) hybridization experiments demonstrated a single transcript that was 1.8 kb in length and that was transiently induced by the addition of L-leucine to the growth medium. The PTR2 gene was localized to the right arm of chromosome XI by contour-clamped homogeneous electric field gel chromosome blotting and by hybridization to known chromosome XI lambda phage clones of S. cerevisiae DNA. PTR2 was tightly linked to the UBI2 gene, with the coding sequences being separated by a 466-bp region and oriented so that the genes were transcribed convergently. A chromosomal disruption of the PTR2 gene in a haploid strain was not lethal under standard growth conditions. The cloning of PTR2 represents the first example of the molecular genetic characterization of a eucaryotic peptide transport gene. Images PMID:8264579

  13. A Computational Approach to Estimating Nondisjunction Frequency in Saccharomyces cerevisiae

    PubMed Central

    Chu, Daniel B.; Burgess, Sean M.

    2016-01-01

    Errors segregating homologous chromosomes during meiosis result in aneuploid gametes and are the largest contributing factor to birth defects and spontaneous abortions in humans. Saccharomyces cerevisiae has long served as a model organism for studying the gene network supporting normal chromosome segregation. Measuring homolog nondisjunction frequencies is laborious, and involves dissecting thousands of tetrads to detect missegregation of individually marked chromosomes. Here we describe a computational method (TetFit) to estimate the relative contributions of meiosis I nondisjunction and random-spore death to spore inviability in wild type and mutant strains. These values are based on finding the best-fit distribution of 4, 3, 2, 1, and 0 viable-spore tetrads to an observed distribution. Using TetFit, we found that meiosis I nondisjunction is an intrinsic component of spore inviability in wild-type strains. We show proof-of-principle that the calculated average meiosis I nondisjunction frequency determined by TetFit closely matches empirically determined values in mutant strains. Using these published data sets, TetFit uncovered two classes of mutants: Class A mutants skew toward increased nondisjunction death, and include those with known defects in establishing pairing, recombination, and/or synapsis of homologous chromosomes. Class B mutants skew toward random spore death, and include those with defects in sister-chromatid cohesion and centromere function. Epistasis analysis using TetFit is facilitated by the low numbers of tetrads (as few as 200) required to compare the contributions to spore death in different mutant backgrounds. TetFit analysis does not require any special strain construction, and can be applied to previously observed tetrad distributions. PMID:26747203

  14. A Computational Approach to Estimating Nondisjunction Frequency in Saccharomyces cerevisiae.

    PubMed

    Chu, Daniel B; Burgess, Sean M

    2016-03-01

    Errors segregating homologous chromosomes during meiosis result in aneuploid gametes and are the largest contributing factor to birth defects and spontaneous abortions in humans. Saccharomyces cerevisiae has long served as a model organism for studying the gene network supporting normal chromosome segregation. Measuring homolog nondisjunction frequencies is laborious, and involves dissecting thousands of tetrads to detect missegregation of individually marked chromosomes. Here we describe a computational method (TetFit) to estimate the relative contributions of meiosis I nondisjunction and random-spore death to spore inviability in wild type and mutant strains. These values are based on finding the best-fit distribution of 4, 3, 2, 1, and 0 viable-spore tetrads to an observed distribution. Using TetFit, we found that meiosis I nondisjunction is an intrinsic component of spore inviability in wild-type strains. We show proof-of-principle that the calculated average meiosis I nondisjunction frequency determined by TetFit closely matches empirically determined values in mutant strains. Using these published data sets, TetFit uncovered two classes of mutants: Class A mutants skew toward increased nondisjunction death, and include those with known defects in establishing pairing, recombination, and/or synapsis of homologous chromosomes. Class B mutants skew toward random spore death, and include those with defects in sister-chromatid cohesion and centromere function. Epistasis analysis using TetFit is facilitated by the low numbers of tetrads (as few as 200) required to compare the contributions to spore death in different mutant backgrounds. TetFit analysis does not require any special strain construction, and can be applied to previously observed tetrad distributions. PMID:26747203

  15. Interaction between Mismatch Repair and Genetic Recombination in Saccharomyces Cerevisiae

    PubMed Central

    Alani, E.; Reenan, RAG.; Kolodner, R. D.

    1994-01-01

    The yeast Saccharomyces cerevisiae encodes a set of genes that show strong amino acid sequence similarity to MutS and MutL, proteins required for mismatch repair in Escherichia coli. We examined the role of MSH2 and PMS1, yeast homologs of mutS and mutL, respectively, in the repair of base pair mismatches formed during meiotic recombination. By using specifically marked HIS4 and ARG4 alleles, we showed that msh2 mutants displayed a severe defect in the repair of all base pair mismatches as well as 1-, 2- and 4-bp insertion/deletion mispairs. The msh2 and pms1 phenotypes were indistinguishable, suggesting that the wild-type gene products act in the same repair pathway. A comparison of gene conversion events in wild-type and msh2 mutants indicated that mismatch repair plays an important role in genetic recombination. (1) Tetrad analysis at five different loci revealed that, in msh2 mutants, the majority of aberrant segregants displayed a sectored phenotype, consistent with a failure to repair mismatches created during heteroduplex formation. In wild type, base pair mismatches were almost exclusively repaired toward conversion rather than restoration. (2) In msh2 strains 10-19% of the aberrant tetrads were Ab4:4. (3) Polarity gradients at HIS4 and ARG4 were nearly abolished in msh2 mutants. The frequency of gene conversion at the 3' end of these genes was increased and was nearly the frequency observed at the 5' end. (4) Co-conversion studies were consistent with mismatch repair acting to regulate heteroduplex DNA tract length. We favor a model proposing that recombination events occur through the formation and resolution of heteroduplex intermediates and that mismatch repair proteins specifically interact with recombination enzymes to regulate the length of symmetric heteroduplex DNA. PMID:8056309

  16. The plasma membrane of Saccharomyces cerevisiae: structure, function, and biogenesis.

    PubMed Central

    van der Rest, M E; Kamminga, A H; Nakano, A; Anraku, Y; Poolman, B; Konings, W N

    1995-01-01

    The composition of phospholipids, sphingolipids, and sterols in the plasma membrane has a strong influence on the activity of the proteins associated or embedded in the lipid bilayer. Since most lipid-synthesizing enzymes in Saccharomyces cerevisiae are located in intracellular organelles, an extensive flux of lipids from these organelles to the plasma membrane is required. Although the pathway of protein traffic to the plasma membrane is similar to that of most of the lipids, the bulk flow of lipids is separate from vesicle-mediated protein transport. Recent advances in the analysis of membrane budding and membrane fusion indicate that the mechanisms of protein transport from the endoplasmic reticulum to the Golgi and from the Golgi to plasma membrane are similar. The majority of plasma membrane proteins transport solutes across the membrane. A number of ATP-dependent export systems have been detected that couple the hydrolysis of ATP to transport of molecules out of the cell. The hydrolysis of ATP by the plasma membrane H(+)-ATPase generates a proton motive force which is used to drive secondary transport processes. In S. cerevisiae, many substrates are transported by more than one system. Transport of monosaccharide is catalyzed by uniport systems, while transport of disaccharides, amino acids, and nucleosides is mediated by proton symport systems. Transport activity can be regulated at the level of transcription, e.g., induction and (catabolite) repression, but transport proteins can also be affected posttranslationally by a process termed catabolite inactivation. Catabolite inactivation is triggered by the addition of fermentable sugars, intracellular acidification, stress conditions, and/or nitrogen starvation. Phosphorylation and/or ubiquitination of the transport proteins has been proposed as an initial step in the controlled inactivation and degradation of the target enzyme. The use of artificial membranes, like secretory vesicles and plasma membranes

  17. Adaptive evolution of a lactose-consuming Saccharomyces cerevisiae recombinant.

    PubMed

    Guimarães, Pedro M R; François, Jean; Parrou, Jean Luc; Teixeira, José A; Domingues, Lucília

    2008-03-01

    The construction of Saccharomyces cerevisiae strains that ferment lactose has biotechnological interest, particularly for cheese whey fermentation. A flocculent lactose-consuming S. cerevisiae recombinant expressing the LAC12 (lactose permease) and LAC4 (beta-galactosidase) genes of Kluyveromyces lactis was constructed previously but showed poor efficiency in lactose fermentation. This strain was therefore subjected to an evolutionary engineering process (serial transfer and dilution in lactose medium), which yielded an evolved recombinant strain that consumed lactose twofold faster, producing 30% more ethanol than the original recombinant. We identified two molecular events that targeted the LAC construct in the evolved strain: a 1,593-bp deletion in the intergenic region (promoter) between LAC4 and LAC12 and a decrease of the plasmid copy number by about 10-fold compared to that in the original recombinant. The results suggest that the intact promoter was unable to mediate the induction of the transcription of LAC4 and LAC12 by lactose in the original recombinant and that the deletion established the transcriptional induction of both genes in the evolved strain. We propose that the tuning of the expression of the heterologous LAC genes in the evolved recombinant was accomplished by the interplay between the decreased copy number of both genes and the different levels of transcriptional induction for LAC4 and LAC12 resulting from the changed promoter structure. Nevertheless, our results do not exclude other possible mutations that may have contributed to the improved lactose fermentation phenotype. This study illustrates the usefulness of simple evolutionary engineering approaches in strain improvement. The evolved strain efficiently fermented threefold-concentrated cheese whey, providing an attractive alternative for the fermentation of lactose-based media. PMID:18245248

  18. Ecological and Genetic Barriers Differentiate Natural Populations of Saccharomyces cerevisiae.

    PubMed

    Clowers, Katie J; Heilberger, Justin; Piotrowski, Jeff S; Will, Jessica L; Gasch, Audrey P

    2015-09-01

    How populations that inhabit the same geographical area become genetically differentiated is not clear. To investigate this, we characterized phenotypic and genetic differences between two populations of Saccharomyces cerevisiae that in some cases inhabit the same environment but show relatively little gene flow. We profiled stress sensitivity in a group of vineyard isolates and a group of oak-soil strains and found several niche-related phenotypes that distinguish the populations. We performed bulk-segregant mapping on two of the distinguishing traits: The vineyard-specific ability to grow in grape juice and oak-specific tolerance to the cell wall damaging drug Congo red. To implicate causal genes, we also performed a chemical genomic screen in the lab-strain deletion collection and identified many important genes that fell under quantitative trait loci peaks. One gene important for growth in grape juice and identified by both the mapping and the screen was SSU1, a sulfite-nitrite pump implicated in wine fermentations. The beneficial allele is generated by a known translocation that we reasoned may also serve as a genetic barrier. We found that the translocation is prevalent in vineyard strains, but absent in oak strains, and presents a postzygotic barrier to spore viability. Furthermore, the translocation was associated with a fitness cost to the rapid growth rate seen in oak-soil strains. Our results reveal the translocation as a dual-function locus that enforces ecological differentiation while producing a genetic barrier to gene flow in these sympatric populations. PMID:25953281

  19. Saccharomyces cerevisiae Tti2 Regulates PIKK Proteins and Stress Response.

    PubMed

    Hoffman, Kyle S; Duennwald, Martin L; Karagiannis, Jim; Genereaux, Julie; McCarton, Alexander S; Brandl, Christopher J

    2016-01-01

    The TTT complex is composed of the three essential proteins Tel2, Tti1, and Tti2 The complex is required to maintain steady state levels of phosphatidylinositol 3-kinase-related kinase (PIKK) proteins, including mTOR, ATM/Tel1, ATR/Mec1, and TRRAP/Tra1, all of which serve as regulators of critical cell signaling pathways. Due to their association with heat shock proteins, and with newly synthesized PIKK peptides, components of the TTT complex may act as cochaperones. Here, we analyze the consequences of depleting the cellular level of Tti2 in Saccharomyces cerevisiae We show that yeast expressing low levels of Tti2 are viable under optimal growth conditions, but the cells are sensitive to a number of stress conditions that involve PIKK pathways. In agreement with this, depleting Tti2 levels decreased expression of Tra1, Mec1, and Tor1, affected their localization and inhibited the stress responses in which these molecules are involved. Tti2 expression was not increased during heat shock, implying that it does not play a general role in the heat shock response. However, steady state levels of Hsp42 increase when Tti2 is depleted, and tti2L187P has a synthetic interaction with exon 1 of the human Huntingtin gene containing a 103 residue polyQ sequence, suggesting a general role in protein quality control. We also find that overexpressing Hsp90 or its cochaperones is synthetic lethal when Tti2 is depleted, an effect possibly due to imbalanced stoichiometry of a complex required for PIKK assembly. These results indicate that Tti2 does not act as a general chaperone, but may have a specialized function in PIKK folding and/or complex assembly. PMID:27172216

  20. Saccharomyces cerevisiae Tti2 Regulates PIKK Proteins and Stress Response

    PubMed Central

    Hoffman, Kyle S.; Duennwald, Martin L.; Karagiannis, Jim; Genereaux, Julie; McCarton, Alexander S.; Brandl, Christopher J.

    2016-01-01

    The TTT complex is composed of the three essential proteins Tel2, Tti1, and Tti2. The complex is required to maintain steady state levels of phosphatidylinositol 3-kinase-related kinase (PIKK) proteins, including mTOR, ATM/Tel1, ATR/Mec1, and TRRAP/Tra1, all of which serve as regulators of critical cell signaling pathways. Due to their association with heat shock proteins, and with newly synthesized PIKK peptides, components of the TTT complex may act as cochaperones. Here, we analyze the consequences of depleting the cellular level of Tti2 in Saccharomyces cerevisiae. We show that yeast expressing low levels of Tti2 are viable under optimal growth conditions, but the cells are sensitive to a number of stress conditions that involve PIKK pathways. In agreement with this, depleting Tti2 levels decreased expression of Tra1, Mec1, and Tor1, affected their localization and inhibited the stress responses in which these molecules are involved. Tti2 expression was not increased during heat shock, implying that it does not play a general role in the heat shock response. However, steady state levels of Hsp42 increase when Tti2 is depleted, and tti2L187P has a synthetic interaction with exon 1 of the human Huntingtin gene containing a 103 residue polyQ sequence, suggesting a general role in protein quality control. We also find that overexpressing Hsp90 or its cochaperones is synthetic lethal when Tti2 is depleted, an effect possibly due to imbalanced stoichiometry of a complex required for PIKK assembly. These results indicate that Tti2 does not act as a general chaperone, but may have a specialized function in PIKK folding and/or complex assembly. PMID:27172216