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PubMed1972

Prevalence and species distribution of yeast in mammary glands of dairy cows in Minnesota.

A study of the prevalence of yeast-like fungi in the mammary glands of dairy cattle was conducted in Minnesota. Quarter samples from 6,020 cows were cultured for yeast. Growth of organisms was obtained from 3.2% of the quarter milk samples. The rate of yeast infection for Minnesota dairy cattle in this study was 2.0%. The majority of the yeast isolated belonged to one of four species of the Candida genus. Candida krusei, Candida parakrusei, Candida guilliermundi, and Candida tropicalis, comprised 89% of the yeasts isolated. All of these species have been reported to cause clinical mastitis (1, 7, 9, 10, 12, 13, 15, 16). It would appear that yeast-like fungi are of sufficient prevalence in mammary glands that yeast infection would be considered in the differential diagnosis in cases of clinical mastitis.

Animals↗
PubMed1980

Purification and characterization of two forms of DNA-dependent ATPase from yeast.

Two forms of DNA-dependent ATPase activity have been purified from yeast extracts. The two ATPases differ from each other in chromatographic properties and heat stabilities but have similar molecular weight and reaction properties. DNA-dependent ATPase I has been purified to near homogeneity, while DNA-dependent ATPase II is only partially purified. The two ATPases from yeast are related structurally since antiserum raised against ATPase I cross-react against ATPase II. Yeast DNA-dependent ATPase I has a native molecular weight of about 68,000 and consists of a single polypeptide chain. ATPase II also sediments on sucrose gradient as a 68,000-dalton protein. Both yeast DNA-dependent ATPases hydrolyze dNTPs and rNTPs to their corresponding nucleoside diphosphates and orthophosphate, but dATP and ATP are preferred substrates. In addition to nucleoside triphosphates, both enzymes require a divalent cation and a polynucleotide for activity. Single-stranded DNAs and polydeoxynucleotides are the most effective co-substrates for yeast DNA-dependent ATPases. Addition of yeast DNA-dependent ATPases to DNA synthesis system containing yeast DNA polymerases does not significantly stimulate the rate of DNA synthesis.

Adenosine Triphosphatases↗
PubMed1980

Isolation and characterization of the yeast 3-phosphoglycerokinase gene (PGK) by an immunological screening technique.

An immunological screening technique has been used for the detection of a specific antigen-producing clone in a bank of bacterial colonies containing hybrid plasmids. This technique involves covalent attachment of antiserum to cyanogen bromide-activated paper discs, contact of this paper with lysed colonies on agar plates, and finally detection of the bound antigen with 125I-labeled antibody. Using this method, we have identified an Escherichia coli colony, containing a yeast DNA insert in plasmid ColE1, that produces antigen which combines with antibody directed against purified yeast 3-phosphoglycerate kinase. The hybrid plasmid (pYe57E2) obtained by this procedure has been shown by both biochemical and genetic methods to contain the structural gene PGK for yeast 3-phosphoglycerate kinase. The location of the PGK structural gene on pYe56E2 was determined by immunological screening of E. coli colonies bearing plasmids containing various reconstructions of the original yeast DNA insert. Examination of the expression of the cloned yeast PGK gene in both E. coli and yeast has shown that functional enzyme is synthesized from the cloned gene in yeast, but not in E. coli.

Cloning, Molecular↗
PubMed1982

Selection of the nuclear gene for the mitochondrial adenine nucleotide translocator by genetic complementation of the op1 mutation in yeast.

Oxidative phosphorylation 1 (OP1), a nuclear gene of yeast Saccharomyces cerevisiae which is required for the expression of a functional mitochondria, has been isolated on a recombinant plasmid. The gene was selected from a recombinant plasmid pool which contained wild type yeast genomic DNA by transformation of the yeast nuclear mutant (op1) followed by a two-stage screening procedure. A recombinant plasmid containing a 2.6 kilobase Bam HI fragment of genomic yeast DNA inserted in either orientation into the single Bam HI site of yeast vector YEp 13 could complement the op1 mutation. Analysis of the gene product of this inserted DNA by three independent methods, 1) in vivo expression in Escherichia coli maxicells, 2) cell-free translation of plasmid selected RNA, and 3) expression analysis in yeast, revealed that its gene product is a protein of Mr = 30,000-32,000, which cross-reacts with specific anti-serum to the adenine nucleotide translocator of the mitochondrial inner membrane. The selection procedure is efficient and can be used for the isolation of any defined yeast nuclear gene which participates in mitochondrial development.

Cell Nucleus↗
PubMed1983

A guanine nucleotide-sensitive adenylate cyclase in the yeast Saccharomyces cerevisiae.

Adenylate cyclase in particulate extracts of Saccharomyces cerevisiae utilized either MnATP or MgATP as substrate. A mutation in the CYR1 gene, which codes for the catalytic unit of yeast adenylate cyclase (Matsumoto, K., Uno, I., and Ishikawa, T. (1983) Cell 32, 417-423), eliminated utilization of both MgATP and MnATP, indicating that a single enzyme was responsible for both activities. GTP and guanylyl-5'-imidodiphosphate stimulated yeast adenylate cyclase, while a GDP analog, guanosine-5'-O-(2-thiodiphosphate), competitively inhibited this stimulation. Thermal inactivation studies distinguished putative guanine-nucleotide regulatory protein (N) from the catalytic unit (C) of yeast adenylate cyclase. Yeast N, which conferred guanine nucleotide regulation and the ability to utilize MgATP on yeast C, was quickly inactivated by incubation of particulate extracts at 30 degrees C. In contrast, yeast C, which apparently utilized MnATP as substrate in the absence of a functional N protein, resisted inactivation at 30 degrees C. These observations suggested that physically distinct protein components mediated the catalytic activity of yeast adenylate cyclase and its regulation by guanine nucleotides. These findings indicate a striking homology between the adenylate cyclase systems of S. cerevisiae and those of vertebrate cells.

Adenylyl Cyclases↗
PubMed1995

Study of Fc gamma murine macrophage receptors (Fc gamma R) in the internalization of Histoplasma capsulatum yeasts.

Reports about Fc gamma R involvement in the phagocytosis of Histoplasma capsulatum yeast are contradictory. Fungal cells were incubated with anti-Histoplasma murine IgG or normal IgG as control. The opsonized yeasts were adjusted and spread on a J774.2 macrophage cell line monolayer. Yeast cells were allowed to attach to the monolayers at 4 degrees C for 1 h prior to initiating the internalization step of the phagocytic process, by shifting the cells to 37 degrees C. The participation of Fc gamma R in the internalization of yeast was monitored by radioiodination labelling of the macrophage surface proteins, and rosette-forming cells for erythrocytes coated with antibodies (RFC-EA). Results showed decreased [125I]-incorporation on the macrophage surface proteins at 15 min post-anti-Histoplasma IgG opsonized yeast infection. The same was observed when high and low virulent H. capsulatum strains were used. A decrease of RFC percentage was also observed at 15 min after IgG opsonized yeast phagocytosis. Results support the disappearance of Fc gamma R at 15 min from the surface of the macrophage that had ingested anti-Histoplasma IgG opsonized yeasts. The recovery of [125I]-counts and the RFC response at a longer time of phagocytosis suggest a possible Fc gamma R recycling mechanism.

Animals↗
PubMed1994

Purified yeast translational initiation factor eIF-3 is an RNA-binding protein complex that contains the PRT1 protein.

Eukaryotic initiation factor-3 (eIF-3) plays a pivotal role in the initiation phase of protein synthesis where it promotes dissociation of 80 S ribosomes into subunits, stabilizes methionyl-tRNAi binding to 40 S ribosomal subunits, and is required for mRNA binding. Mammalian eIF-3 is comprised of eight subunits, but no mammalian cDNA encoding these proteins has been cloned and sequenced, nor has the corresponding factor been characterized in yeast. Since many initiation factors are strongly conserved between mammalian and yeast systems, we employed a mammalian assay for initiation, the synthesis of methionyl-puromycin, to detect eIF-3 activity in yeast subcellular fractions. Yeast eIF-3 was purified from the high salt wash of ribosomes by Superose 6 molecular sieve and MonoS ion exchange chromatography. Yeast eIF-3 contains eight subunits with masses of 16, 21, 29, 33, 39, 62, 90, and 135 kilodaltons all of which coelute with an apparent mass of 550 kilodaltons from the Superose 6 column. Immunoblotting shows that the 90-kDa subunit corresponds to the product of the PRT1 gene whose mutant form, prt1-1, exhibits destabilization of methionyl-tRNAi binding to 40 S ribosomal subunits. eIF-3, and specifically the 62-kDa subunit, bind to RNA. These biochemical approaches to defining yeast eIF-3 complement genetic methods so far used in characterizing the initiation factors and provide another route to defining the yeast translational machinery.

Binding Sites↗
PubMed1994

The rectal carriage of yeast in patients with vaginal candidiasis.

Reinfection from the lower gastrointestinal tract is a possible source of recurrent vulvo-vaginal candidiasis. A prospective study to assess the prevalence of yeast carriage in various orifices (including the rectum) in controls and patients, and the relationship to acute vaginitis, was conducted. Cultures for yeast were obtained from the mouth, rectum, vulva, and vagina every 1-2 months for 1 y from the patients. The prevalence of yeast carriage in healthy controls was 3/37 (8.1%) from the vulva, vagina, and rectum, and 4/37 (10.8%) from the mouth. In patients, yeast carriage during episodes of vaginitis was: from the vagina, 190/193 (98.4%); from the vulva, 107/193 (55.4%); from the rectum, 93/193 (48.2%); and from the mouth, 52/193 (26.9%). During visits without vaginitis, yeast carriage was lower: in the rectum, 59/587 (10.1%); in the vulva, 53/459 (11.6%); in the vagina, 77/587 (13.1%); and in the mouth, 89/587 (15.2%). Yeast in the lower bowel during symptomatic vaginitis is higher (p = 0.0001) than in controls, but not significantly greater during asymptomatic periods. Recurrence of Candida vaginitis is not dependent on yeast reservoir in the lower gut between symptomatic episodes.

Administration, Intravaginal↗
PubMed1994

Molecular cloning and characterization of yeast rho GDP dissociation inhibitor.

We have previously isolated rho GDP dissociation inhibitor (rho DGI) from bovine brain and characterized it. Bovine rho GDI is a protein of a M(r) of 23,421 with 204 amino acids. rho GDI inhibits the GDP/GTP exchange reaction of post-translationally lipid-modified small GTP-binding proteins (G proteins) of the rho family, including the rho, rac, and cdc42 subfamilies, and keeps them in the GDP-bound inactive form. In the present study, we first purified rho GDI from the cytosol fraction of the yeast Saccharomyces cerevisiae and isolated its gene. Yeast rho GDI gene had an open reading frame without introns encoding a protein of a M(r) of 23,138 with 202 amino acids. Yeast rho GDI protein was 36% identical with bovine rho GDI. Yeast rho GDI expressed in Escherichia coli was active not only on yeast rho1 but also on mammalian rho family members which were post-translationally modified. Disruption of rho GDI did not induce apparent phenotypes, whereas overexpression of yeast or bovine rho GDI resulted in the inhibition of cell growth. These results indicate that rho GDI exists and regulates the function of the rho family members in yeast.

Amino Acid Sequence↗
PubMed1994

Analysis of yeast DNA topoisomerase II mutants resistant to the antitumor drug amsacrine.

Site-directed mutagenesis of regions within a plasmid-borne yeast TOP2 gene encoding DNA topoisomerase II and hydroxylamine mutagenesis of the entire plasmid were carried out, and the mutagenized plasmid DNA pools were used separately to transform yeast with a temperature-sensitive top2-4 mutation in the chromosomal TOP2 locus. By selecting transformants that grow in the presence of the antitumor drug amsacrine at 35 degrees C, a nonpermissive temperature for the top2-4 allele, plasmid-borne top2 mutants expressing amsacrine-resistant and physiologically functional DNA topoisomerase II were readily obtained. The causality between amsacrine resistance and the presence of these mutations in yeast DNA topoisomerase II has been firmly established, and this causality in turn shows that, in yeast at least, DNA topoisomerase II is the only significant cellular target of amsacrine. Three classes of such mutants have been identified: one involves single or multiple changes in a sequence PLRGK-MLN located at positions 474-481 of yeast DNA topoisomerase II, a highly conserved motif in all type II DNA topoisomerases; a second involving a single mutation changing Ala642 to threonine or glycine; and a third involving deletions of portions of the carboxy-terminal domain of the yeast enzyme. The nature of drug resistance of these different classes of mutants is discussed. The approaches used in this work should be readily applicable to yeast cells expressing heterologous DNA topoisomerases such as human DNA topoisomerase II alpha. Other DNA topoisomerase II-targeting drugs can also be studied in such a system.

Alleles↗
PubMed1993

Mutagenesis of the fourth calcium-binding domain of yeast calmodulin.

The fourth calcium-binding domain (domain IV) of the yeast (Saccharomyces cerevisiae) calmodulin is unable to bind Ca2+ (Matsuura, I., Ishihara, K., Nakai, Y., Yazawa, M., Toda, H., and Yagi, K. (1991) J. Biochem. (Tokyo) 109, 190-197). The functional significance of Ca2+ binding to domain IV was investigated by site-directed mutagenesis or recombinant DNA techniques. A recognition site for the restriction enzyme ClaI was introduced at the homologous position of Ile130 in the nucleotide sequence of chicken and yeast calmodulin cDNA, and chimeric proteins of the yeast and the vertebrate calmodulin were prepared. One of the resulting mutants named C4Y consisted of Ala1-Ile130 of chicken calmodulin and Asp131-Lys148 of yeast calmodulin. The mutant C4Y showed the yeast-type feature, and its enzyme activation profiles were similar to those of yeast calmodulin. A single substitution of Glu for Gln140 was carried out in the mutant C4Y. The resulting mutant (C4Y140E) bound 4 mol of Ca2+ and showed the vertebrate-type enzyme activation. Therefore, the alterations of 3 residues in the Ca(2+)-binding loop of the yeast-type domain IV, Ser129-->Asp, insertion of Ile130, and Gln140-->Glu, were enough for the recovery of Ca2+ binding and enzyme activation. Ca2+ binding to domain IV may induce the active conformation of the C-terminal half-molecular domain.

Amino Acid Sequence↗
PubMed1995

Yeasts: from genetics to biotechnology.

Yeasts have been known and used in food and alcoholic fermentations ever since the Neolithic Age. In more recent times, on the basis of their peculiar features and history, yeasts have become very important experimental models in both microbiological and genetic research, as well as the main characters in many fermentative production processes. In the last 40 years, advances in molecular biology and genetic engineering have made possible not only the genetic selection of organisms, but also the genetic modification of some of them, especially the simplest of them, such as bacteria and yeasts. These discoveries have led to the availability of new yeast strains fit to fulfill requests of industrial production and fermentation. Moreover, genetically modified and transformed yeasts have been constructed that are able to produce large amounts of biologically active proteins and enzymes. Thus, recombinant yeasts make it easier to produce drugs, biologically active products, diagnostics, and vaccines, by inexpensive and relatively simple techniques. Yeasts are going to become more and more important in the "biotechnological revolution" by virtue of both their features and their very long and safe use in human nutrition and industry.

Biotechnology↗
PubMed1995

Yeast communities in a natural tequila fermentation.

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

Alcoholic Beverages↗
PubMed1962

Action of deflocculating agents on Saccharomyces cerevisiae Class III brewer's yeast.

Earlier work with a fluorescent aid indicated that flocculent brewer's yeast may have more surface lipids than nonflocculent types. Organic solvents were checked against flocculent Gilliland yeasts. It was found that those reagents which affect "free" lipids had no dispersive action, and those which remove "bound" fats had a powerful dispersive action against such yeasts. There was no indication that such an action could be correlated with other physical properties of the solvents. The uranyl ion is known for its ability to complex with phospholipids, and it was found to have a powerful dispersive action on Gilliland yeasts. Its effect was compared with that of glucose in its dispersion of yeast flocs, and possible cell "sites" were suggested. This, along with other work, suggests the possibility that lipids are directly or indirectly involved in yeast flocculation.

Alcohols↗
PubMed1998

The structure and function of yeast xylose (aldose) reductases.

Yeast xylose (aldose) reductases are members of the aldo-keto reductase family of enzymes which are widely distributed in a variety of other organisms. In yeasts, these enzymes catalyse the first step of xylose metabolism where xylose is converted to xylitol. In the past 16 years, xylose reductases from yeasts able to ferment or utilize xylose have been isolated and studied mainly because of their importance in xylose bioconversions. In recent years, genes encoding xylose reductases from several yeasts have been cloned and sequenced. A comparison of the primary sequences of yeast xylose reductases with the much better characterized human aldose reductase and human aldehyde reductase reveals that the yeast enzymes are hybrids between aldo-keto reductases and the short chain dehydrogenases/reductases families of enzymes. Why this is so and its evolutionary significance is presently not known. This short review will critically examine the structure and function information that can be gleaned from the sequence comparison. Several interesting questions arise from the sequence comparison and these can provide fruitful areas for further investigations.

Aldehyde Reductase↗
PubMed1999

An inverse correlation between stress resistance and stuck fermentations in wine yeasts. A molecular study.

During alcoholic fermentations yeast cells are subjected to several stress conditions and, therefore, yeasts have developed molecular mechanisms in order to resist this adverse situation. The mechanisms involved in stress response have been studied in Saccharomyces cerevisiae laboratory strains. However a better understanding of these mechanisms in wine yeasts could open the possibility to improve the fermentation process. In this work an analysis of the stress response in three wine yeasts has been carried out by studying the expression of several representative genes under several stress conditions which occur during fermentation. We propose a simplified method to study how these stress conditions affect the viability of yeast cells. Using this approach an inverse correlation between stress-resistance and stuck fermentations has been found. We also have preliminary data about the use of the HSP12 gene as a molecular marker for stress-resistance in wine yeasts.

Bacterial Proteins↗
PubMed1975

Biological value of the biomass and protein isolates from different yeasts.

The microbiological analysis with the test-organism Tetrahymena pyriformis W can be used successfully to measure the relative nutritive value of the biomass and protein isolates from different yeasts for screening the groups of micro-organisms to choose those of the desired quality. In general, this method is rapid, comparatively cheap and gives the possibility to test large numbers of samples simultaneously. According to the literature and our own results, the relative nutritive value, the percentage of absorbed "N", retained by test-organism and used for its growth and multiplication expressed as cell count and given in relation to a standard protein (casein) is generally in a good agreement with results obtained with animals. This microbiological method is promising for investigating the influence of certain technological operations on the quality of protein. The investigation has been performed by the use of Baker's yeast Saccharomyces cerevisiae, of fodder yeast Candida, grown on oil hydrocarbons and on wood hydrolysates, yeasts Hansenula and Mycoderma, grown on a medium containing ethanol as the sole carbon source. The best results were obtained with the yeast grown on the ethanol-containing medium. The biological value of the biomass of yeast Hansenula is 91% and of protein isolate 96% as related to casein as the standard protein.

Amino Acids↗
PubMed2006

A simplified technique for evaluating the adherence of yeasts to human vaginal epithelial cells.

Thousands of women all over the world annually suffer of vulvovaginal candidiasis (VVC), an infection caused by yeasts, which mainly affect the mucosa of the vulva and vagina. The adherence of the yeasts to the mucosae is an essential step for colonization and predisposes the start of the infectious process. In this study, a technique capable of evaluating the adhesion of yeasts to human vaginal epithelial cells (HVEC) was employed. Twenty-five vaginal yeast isolates (10 Candida albicans, nine C. glabrata, two C. parapsilosis, one C. tropicalis, two Saccharomyces cerevisiae, and one Trichosporon sp.) were evaluated. A suspension of each yeast was co-incubated with HVEC obtained from a healthy donor in the ovulatory phase. After 1 hr, smears were made, stained with crystal violet and Papanicolaou, and the number of yeasts that adhered to 600 HVEC was evaluated. The adhesion of C. albicans was significantly greater than that of the other species and occurred mainly in the intermediate HVEC, rather than the superficial. In addition, the proposed technique, easy to execute and of low cost showed to be reproducible and enables the determination of the adherence capacity of different isolates, whose adhesion was confirmed by scanning electron microscopy.

Cell Adhesion↗