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PubMed1982

[Arthrobacter globiformis - a new yeast-lysing bacterium].

A bacterium capable to lyse viable yeast cells was isolated from compost enriched with baker's yeast cells and was identified as Arthrobacter globiformis. The yeast lytic enzyme complex produced by shaking culture was precipitated with ammonium sulfate, dialyzed and lyophilized. The crude residue contained beta-glucanase and alpha-mannanase, yet not chitinase. Optimale carbon sources in the culture medium for a high enzyme synthesis were 0.5% beta-glucan for the production of beta-glucanase, resp., 3% alpha-mannan for the production of alpha-mannanase. Addition of 10% whole died baker's yeast cells to the culture medium effected similar results. The crude enzyme residue released among other things spheroplasts from cells of the yeast Pichia membranaefaciens, Metschnikowia pulcherrima, Hansenula anomala and Candida guilliermondii "H". However, it did not or only weakly lyse viable cells of the yeasts Rhodotorula rubra, Rhodosporidium toruloides and Sporobolomyces roseus. The mutants of Candida guilliermondii "H" with modified glucan, resp., mannan concentrations in the cell walls did not indicate differences in their susceptibility to lysis.

Arthrobacter↗
PubMed2004

Yeast involved in fermentation of Coffea arabica in East Africa determined by genotyping and by direct denaturating gradient gel electrophoresis.

Samples of Coffea arabica were collected during the different stages of the fermentation from two production sites in Tanzania. The yeasts community was identified by genotyping using ITS-PCR and sequence analysis of the D1/D2 domain of the 26S rRNA gene. For confirmation, denaturating gradient gel electrophoresis (DGGE) of PCR-amplified 26S rRNA gene was performed to detect yeast directly from coffee samples without cultivation. Yeast counts were in the range 4.0 x 10(4) - 5.0 x 10(7) CFU/g with an increase during fermentation. Three yeasts species were dominant. The predominant yeast found during fermentation and drying was Pichia kluyveri. Pichia anomala was found in high numbers during drying of coffee beans. Hanseniaspora uvarum was the predominant yeast during fermentation but decreased during drying. Kluyveromyces marxianus, Candida pseudointermedia, Issatchenkia orientalis, Pichia ohmeri and Torulaspora delbrueckii occurred in concentrations of 10(3) CFU/g or below in coffee samples. Saccharomyces cerevisiae and Candida xestobii were not isolated by cultivation, but by the DGGE technique. A good agreement was found between the sequence analysis of the D1/D2 domain of the 26S rRNA gene and sequencing of the DGGE bands.

Base Sequence↗
PubMed1998

Comparison of the conformational state and in vitro refolding of yeast chaperonin protein cpn10 with bacterial GroES.

Gel filtration studies demonstrate that the heptameric complex of yeast cpn10 (pI around 8.8) reversibly disassembles into monomers when lowering the pH to 4.5, whereas its secondary structure is retained as demonstrated by circular dichroism. Monomeric yeast cpn10 does not bind to GroEL in the presence of nucleotides, whereas under identical conditions E. coli cpn10 (GroES), having a strong sequence homology to the yeast form but a pI of 5.2, shows no pH-dependent dissociation and is able to complex with GroEL at both pH 7.5 and 4.5. Using circular dichroism it is shown that, unlike E. coli cpn10, yeast cpn10 is not able to refold spontaneously after first being fully unfolded in 8 M urea. However, refolding of yeast cpn10 to a complex that can be recognised by GroEL depends on the presence of a lipid-water interface with a specificity for negatively charged lipids. We suggest that the requirements for refolding of yeast cpn10 are related to its post-translational transport and subcellular localization.

Bacterial Proteins↗
PubMed2001

Comparison of morphogenetic networks of filamentous fungi and yeast.

Fungi generally display either of two growth modes, yeast-like or filamentous, whereas dimorphic fungi, upon environmental stimuli, are able to switch between the yeast-like and the filamentous growth mode. Signal transduction pathways have been elucidated in the budding yeast Saccharomyces cerevisiae, establishing a morphogenetic network that links cell-cycle events with cellular morphogenesis. Recent molecular genetic studies in several filamentous fungal model systems revealed key components required for distinct steps from fungal spore germination to the maintenance of polar hyphal growth, mycelium formation, and nuclear division. This allows a mechanistic comparison of yeast-like and hyphal growth and the establishment of a core model morphogenetic network for filamentous growth including signaling via the cAMP pathway, Rho modules, and cell cycle kinases. Appreciating similarities between morphogenetic networks of the unicellular yeasts and the multicellular filamentous fungi will open new research directions, help in isolating the central network components, and ultimately pave the way to elucidate the central differences (of many) that distinguish, e.g., the growth mode of filamentous fungi from that of their yeast-like relatives, the role of cAMP signaling, and nuclear division.

Aspergillus↗
PubMed1996

Toxicity of seleno-L-methionine, seleno-DL-methionine, high selenium wheat, and selenized yeast to mallard ducklings.

The toxicity of four chemical forms of selenium (seleno-L-methionine, seleno-DL-methionine, selenized yeast, and high selenium wheat) was compared in day-old mallard ducklings (Anas platyrhynchos). In the first experiment, in which the basal diet was 75% wheat, survival after 2 weeks was lower for ducklings fed 30 micrograms/g selenium as seleno-L-methionine (36%) than for ducklings fed 30 micrograms/g selenium as seleno-DL-methionine (100%) or 30 micrograms/g selenium from high selenium yeast (88%). The concentration of selenium at 2 weeks in the livers of survivors was similar for ducklings fed 15 micrograms/g selenium as seleno-DL-methionine (12 micrograms/g, wet weight), seleno-L-methionine (11 micrograms/g), and high selenium wheat (11 micrograms/g), but was lower when the selenium came from selenized yeast (6.2 micrograms/g). When fed 30 micrograms/g selenium from the various sources, the selenium concentrations in liver were 20 micrograms/g for seleno-DL-methionine, 19 micrograms/g for seleno-L-methionine, and 9.9 micrograms/g for selenized yeast. In a second experiment, in which the basal diet was a commercial duck feed, survival after 2 weeks was 100% in ducklings fed 30 micrograms/g selenium as seleno-DL-methionine, seleno-L-methionine, or selenized yeast. Selenium concentrations in liver were similar for ducklings fed the 30-micrograms/g selenium diets as the DL or L forms of selenomethionine (27 and 25 micrograms/g), but lower for ducklings fed selenized yeast (13 micrograms/g).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

The NADP(H) redox couple in yeast metabolism.

Theoretical calculations of the NADPH requirement for biomass formation indicate that in yeast this parameter is strongly dependent on the carbon and nitrogen sources used for growth. Enzyme surveys of NADPH-generating metabolic pathways and radiorespirometric studies demonstrate that in yeast the HMP pathway is the major source of NADPH. Furthermore, radiorespirometric data suggest that in yeasts the HMP pathway activities are close to the theoretical minimum. It may be concluded that the mitochondrial NADPH oxidation, which in yeasts may yield ATP, is quantitatively not an important process. The inability of C. utilis to utilize the NADH produced in formate oxidation as an extra source of NADPH strongly suggests that transhydrogenase activity is absent. Furthermore, the absence of xylose utilization under anaerobic conditions in most facultatively fermentative yeasts indicates that also in these organisms transhydrogenase activity is absent. This conclusion is supported by the observation that anaerobic xylose utilization is observed only in those yeasts which possess a high activity of an NADH-linked xylose reductase. Hence in these organisms the redox-neutral conversion of xylose to ethanol is possible, since the second step in xylose metabolism is mediated by an NAD+-linked xylitol dehydrogenase.

Adenosine Triphosphate↗
PubMed1995

Ascomycetous yeast communities of marine invertebrates in a southeast Brazilian mangrove ecosystem.

The ascomycetous yeast communities associated with 3 bivalve mollusk, and 4 crab species were studied in the mangrove at Coroa Grande on Sepetiba Bay in Rio de Janeiro, Brazil. These were made up mostly of diverse but sparse and apparently allochtonous yeast populations. The striking exception was a prevalent population of the species Kluyveromyces aestuarii, which predominated the yeast communities of 2 detritus feeding crabs, Sesarma rectum and Uca spp., and the shipworm Neoteredo reynei. However, K. aestuarii was absent from the omnivorous crabs Aratus pisonii and Goniopsis cruentata, and the clam Anomalocardia brasiliana, and was rare in the clam Tagelus plebeius from mostly submerged more sandy sediments. Pichia membranaefaciens, Candida valida-like, Candida krusei, Candida sorbosa, Candida colliculosa-like, Candida famata-like, Kloeckera spp., Candida guilliermondii, Candida albicans, Candida silvae, Geotrichum spp., Rhodotorula spp., Cryptococcus spp., and the methylotrophic yeast Candida boidinii were frequently isolated. The 322 ascomycetous yeast cultures representing 252 isolates from crabs and mollusks were classified as 40 species that fit standard descriptions, and 44 putative new species. The ascomycetous yeast communities of the mangrove ecosystem include many new biotypes that require better taxonomic definition.

Animals↗
PubMed1998

Effect of yeast extract on growth and metabolism of H2-utilizing acetogenic bacteria from the human colon.

The aim of this work was to determine the effect of yeast extract and of its vitamin contents on autotrophic and heterotrophic growth and metabolism of four acetogenic bacteria from the human colon. Yeast extract exerted a stimulatory effect on autotrophic growth of the colonic acetogens, but concentration of this compound above 1-2 g. L-1 in the medium did not enhance utilization of H2/CO2. Vitamins provided by yeast extract were shown to be essential cofactors of the reductive pathway of acetate synthesis except for one Clostridium strain. Yeast extract was also necessary to maintain heterotrophic growth and acetate synthesis from glucose in acetogenic species, except in the Streptococcus strain. In the absence of yeast extract, vitamins could efficiently restore glucose fermentation via acetate. The reductive and oxidative pathways of acetate synthesis might, therefore, depend on vitamin cofactors supplied by yeast extract in most of the human acetogenic bacteria. Non-vitaminic factors appeared also to be involved in the metabolism of some of these acetogenic species.

Acetates↗
PubMed2007

Differences in yeast intolerance between patients with Crohn's disease and ulcerative colitis.

PURPOSE: Alimentary factors, especially those modifying the intestinal flora, may influence the course of inflammatory bowel disease. It is known that T and B cells of patients with Crohn's disease can be stimulated with the yeast antigen, mannan. We evaluated the impact of eating habits with special respect to food containing yeast on the course of inflammatory bowel disease. METHODS: Questionnaires were sent to 180 German-speaking patients of the Inflammatory Bowel Disease Outpatient Clinic at the University Hospital Bern, Switzerland. The following information was obtained by the questionnaires: (1) course of disease, (2) eating habits, (3) environmental data, and (4) inflammatory bowel disease questionnaire. The survey was anonymous. RESULTS: A total of 145 patients (80.5 percent 95 with Crohn's disease, and 50 with ulcerative colitis) responded. Food items containing yeast were better tolerated by patients with ulcerative colitis than by patients with Crohn's disease. A significant difference between the two groups was observed concerning food containing raw yeast (dough, P = 0.04; and pastry, P = 0.001). CONCLUSIONS: Food items containing raw yeast led to more frequent problems for patients with Crohn's disease than for patients with ulcerative colitis. This observation supports our previous data, which showed the stimulatory effect of the yeast antigen, mannan, on B and T cells of patients with Crohn's disease but not of controls.

Chi-Square Distribution↗
PubMed2006

Polysaccharides and phenolic compounds as substrate for yeasts isolated from rotten wood and description of Cryptococcus fagi sp.nov.

Pieces of rotten wood collected in the forest were screened for the presence of yeasts. In spring time 3 tree species were sampled, followed by 9 species in summer. Yeast strains were identified by traditional methods. Identifications were confirmed by sequencing of ribosomal DNA in case of doubt. In total 14 yeast species of ascomycetous affiliation and 6 anamorphic basidiomycetous yeasts were isolated and identified. Most species were represented by only one strain, but Candida bertae by two and Trichosporon porosum by six strains, all from different wood samples. Three strains represented novel species, one of which is described as Cryptococcus fagi Middelhoven et Scorzetti. The type strain is CBS 9964 (JCM 13614). All strains were tested for growth on several polysaccharides as sole carbon source. Only some of these polymers supported growth of ascomycetous yeasts. Basidiomycetous yeasts assimilated soluble starch, pullulan, dextran, xylan, polygalacturonate, galactomannan and tannic acid or at least some of these. Cryptococcus podzolicus and T. porosum were the most active in this respect. None of the isolated strains grew on carboxymethyl cellulose, colloidal chitin, arabinogalactan and gum xanthan. Phenolic compounds were assimilated by several strains, belonging to the Trichosporonales and the Microbotryum and Stephanoascus/Blastobotrys clades, but not by members of the Tremellales (Cryptococcus musci excepted) and the Debaryomyces/Lodderomyces clade. Most of the ascomycetes assimilated n-hexadecane.

Alkanes↗
PubMed1987

Rat brain hexokinase: amino acid sequence at the substrate hexose binding site is homologous to that of yeast hexokinase.

A reactive Glc analog, N-(bromoacetyl)-D-glucosamine (GlcNBrAc), has recently been used (D. M. Schirch and J. E. Wilson (1987) Arch. Biochem. Biophys. 254, 385-396) to label the Glc binding site of rat brain Type I hexokinase. This site has been located in a 40-kDa domain at the C-terminus of the enzyme previously shown to be the location of the substrate ATP binding site (M. Nemat-Gorgani and J. E. Wilson (1986) Arch. Biochem. Biophys. 251, 97-103). In the present study, peptide mapping of hexokinase modified by radiolabeled GlcNBrAc yields three labeled peptides (Peptides I-III). Peptides I and III, as well as catalytic activity, are protected by inclusion of Glc or GlcNAc during reaction with GlcNBrAc. These two peptides show considerable homology to contiguous regions in the sequences of yeast hexokinase isozymes A and B. Peptide III is homologous to a sequence which, based on the X-ray crystallographic work by Steitz and co-workers, is located near the Glc binding site of yeast hexokinase; Peptide I is homologous to an immediately adjacent (toward the C-terminus) region of yeast hexokinase. An essential serine residue implicated in the binding of Glc to the yeast enzyme is also conserved in Peptide III from rat brain hexokinase. These results provide strong support for the view that the "catalytic domain" at the C-terminus of the mammalian Type I hexokinase shares a common ancestry with yeast hexokinase. Peptide II appears to be nonspecifically labeled by GlcNBrAc since labeling is insensitive to the presence of protective ligands such as Glc or GlcNAc; the sequence of Peptide II shows no detectable homology with the yeast isozymes.

Acetylglucosamine↗
PubMed1995

A method of directed random mutagenesis of the yeast chromosome shows that the iso-1-cytochrome c heme ligand His18 is essential.

A method to perform site-directed random mutagenesis directly in the yeast chromosomal DNA at the iso-1-cytochrome c-encoding gene locus (CYC1) is described. To test the effectiveness of the random mutagenesis procedure, the heme ligand His18 was mutated to Ala (H18A), rendering cytochrome c (Cyc) nonfunctional. Random mutagenesis was performed by transforming yeast cells with a synthetic oligodeoxyribonucleotide (oligo) that randomizes the codon for His18. The transformed cells were then selected for reversion to a functional Cyc on selective media. Ten functional mutants were recovered, all of which had integrated the synthetic oligo. Sequencing showed that five of the recovered mutants carried the His codon, CAU, and five mutants contained the His codon, CAC. Because Arg had previously been found as a heme ligand, this mutant was produced by standard techniques and integrated into the yeast chromosome. These yeast did not produce a holo cytochrome c that was detectable by low-temperature spectroscopy. To develop a selection for nonfunctional Cyc, competent yeast (which lack the ability to synthesize tryptophan) were cotransformed with a plasmid carrying the TRP1 gene and the random oligo, and were plated on media lacking tryptophan. Of the 1200 colonies that grew, 120 tested negative for the integration of the random oligo, demonstrating that this particular selection for nonfunctional protein is not feasible. A method is thus described for directed, random mutagenesis directly in the yeast chromosome that can be used to probe structure/function relationships in Cyc. Only His can act as a heme ligand at position 18, using the functional selection described here.

Base Sequence↗
PubMed1995

Genetically engineered yeast cells and their applications.

The first generation of yeast expression systems relies on inducible expression cassettes borne by multicopy plasmids for production of unmodified human P450s and on the endogenous NADPH-P450 reductase to support activities. A second generation of engineered yeast involved targeted genomic modifications allowing overexpression of the yeast reductase and coexpression of human cytochrome b5 and of a phase II enzyme such as epoxide hydrolase. These features allow improved P450 turnover numbers and simulation of some phase I-phase II couplings. In the third generation, the human reductase was substituted for the yeast reductase by genome engineering. Simultaneously, induction procedures were optimized to reach high P450 specific contents. Dramatic improvements (1000-fold) of yeast-expressed P450 activities have thus been obtained. To get more insight into complex metabolic events, such as that of a typical pollutant: benzo[a]pyrene, an approach was designed which involves a complementary use of yeast expression and computer simulations.

Benzo(a)pyrene↗
PubMed2004

Genetic aspects of targeted insertion mutagenesis in yeasts.

Targeted insertion mutagenesis is a main molecular tool of yeast science initially applied in Saccharomyces cerevisiae. The method was extended to fission yeast Schizosaccharomyces pombe and to "non-conventional" yeast species, which show specific properties of special interest to both basic and applied research. Consequently, the behaviour of such non-Saccharomyces yeasts is reviewed against the background of the knowledge of targeted insertion mutagenesis in S. cerevisiae. Data of homologous integration efficiencies obtained with circular, ends-in or ends-out vectors in several yeasts are compared. We follow details of targeted insertion mutagenesis in order to recognize possible rate-limiting steps. The route of the vector to the target and possible mechanisms of its integration into chromosomal genes are considered. Specific features of some yeast species are discussed. In addition, similar approaches based on homologous recombination that have been established for the mitochondrial genome of S. cerevisiae are described.

Gene Expression Regulation, Fungal↗
PubMed2005

Dissemination and survival of commercial wine yeast in the vineyard: a large-scale, three-years study.

The use of commercial wine yeast strains as starters has been extensively generalised over the past two decades. In this study, a large-scale sampling plan was devised over a period of three years in six different vineyards to evaluate the dynamics and survival of industrial yeast strains in the vineyard. A total of 198 grape samples were collected at various distances from the wineries, before and after harvest, and yeast strains isolated after spontaneous fermentation were subsequently identified by molecular methods. Among 3780 yeast strains identified, 296 isolates had a genetic profile identical to that of commercial yeast strains. For a large majority (94%), these strains were recovered at very close proximity to the winery (10-200 m). Commercial strains were mostly found in the post-harvest samples, reflecting immediate dissemination. Analysis of population variations from year to year indicated that permanent implantation of commercial strains in the vineyard did not occur, but instead that these strains were subject to natural fluctuations of periodical appearance/disappearance like autochthonous strains. Our data show that dissemination of commercial yeast in the vineyard is restricted to short distances and limited periods of time and is largely favoured by the presence of water run-off.

DNA Fingerprinting↗
PubMed2006

Isolation of epiphytic yeasts with potential for biocontrol of Aspergillus carbonarius and A. niger on grape.

Antagonistic yeasts were isolated from the epiphytic flora associated with grape berries cv. Negroamaro and identified at species level using molecular methods. A total of 144 yeast isolates were tested in a preliminary screening on agar to select isolates showing a killer activity against Aspergillus carbonarius and A. niger, the main species responsible for the accumulation of ochratoxin A in grape. Twenty-eight yeast isolates were selected for their inhibitory effects on the above fungal species and assayed by an in vitro nutritional competition test for their antagonistic capacity towards three selected ochratoxigenic strains. Six yeast isolates belonging to five species, namely 2 isolates of Issatchenkia orientalis and one each of Metschnikowia pulcherrima, Kluyveromyces thermotolerans, Issatchenkia terricola and Candida incommunis, were finally selected and screened on wounded grape berries for their ability to inhibit infection by ochratoxigenic moulds. With the exception of the K. thermotolerans isolate, when inoculated at 10(9) CFU/wound, the other five challenger yeasts reduced the A. carbonarius and A. niger colonization on grape berry (P<0.05). In particular, the best antagonistic activity was shown by the two I. orientalis isolates. Results suggest that antagonist yeasts with the potential to control A. carbonarius and A. niger on grape can be found among the microflora associated with the berries.

Antibiosis↗
PubMed2006

Yeasts isolated from three varieties of grapes cultivated in different locations of the Dolenjska vine-growing region, Slovenia.

The number and diversity of yeasts on grape berry surfaces are influenced by several factors, such as grape variety, degree of grape maturity at harvest, climatological conditions, geographic location, physical damage of grapes, the intensity of pest management etc. Cvicek is a typical Slovene wine, which has obtained a special protection under the Slovene Wine Law for its geographical origin. This blended red wine is produced from different grape varieties (Vitis vinifera L.), mostly from red grapes of Zametovka and Modra frankinja and from white grapes of Kraljevina. The aim of this study was to evaluate the impact of geographical locations in the Dolenjska vine-growing region and to obtain precise information about the influence of different grape varieties on the composition of yeast community on grape berries. The restriction fragment length polymorphism of PCR-amplified fragments from the rDNA gene cluster (PCR RFLP of rDNA) has been used for the differentiation of yeast species. The standard identification procedure has been performed on representative strains that shared identical RFLP profiles. The number of yeasts and yeast species isolated varied according to different grape varieties, Zametovka, Modra frankinja and Kraljevina (V. vinifera L.) and according to different sampling location. On the surface of grape berries 13 different yeast species have been identified. Saccharomyces cerevisiae has not been found.

Cluster Analysis↗
PubMed2005

Yeast signaling pathways in the oxidative stress response.

Oxidative stress that generates the reactive oxygen species (ROS) is one of the major causes of DNA damage and mutations. The "DNA damage checkpoint" that arrests cell cycle and repairs damaged DNA has been a focus of recent studies, and the genetically amenable model systems provided by yeasts have been playing a leading role in the eukaryotic checkpoint research. However, means to eliminate ROS are likely to be as important as the DNA repair mechanisms in order to suppress mutations in the chromosomal DNA, and yeasts also serve as excellent models to understand how eukaryotes combat oxidative stress. In this article, we present an overview of the signaling pathways that sense oxidative stress and induce expression of various anti-oxidant genes in the budding yeast Saccharomyces cerevisiae, the fission yeast Schizosaccharomyces pombe and the pathogenic yeast Candida albicans. Three conserved signaling modules have been identified in the oxidative stress response of these diverse yeast species: the stress-responsive MAP kinase cascade, the multistep phosphorelay and the AP-1-like transcription factor. The structure and function of these signaling modules are discussed.

Mitogen-Activated Protein Kinases↗