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1

Mating type switching in the tetrapolar basidiomycete Agrocybe aegerita.  

PubMed

The study of fruiting in the basidiomycete Agrocybe aegerita has shown that some haploid homokaryotic strains can spontaneously switch their mating specificities at the two unlinked A and B mating type factors. This event causes the dikaryotisation of primary homokaryons without plasmogamy and leads to the differentiation of sporulating fruit-bodies (pseudo-homokaryotic fruiting). For each mating type factor, the genetic analyses have revealed that: (1) parental and switched mating types segregate meiotically as Mendelian markers, (2) a total of six switched mating type factors (two parental and four nonparental) were obtained from a wild strain, (3) most of the nonparental factors have specificities differing from those of a large series of wild factors, (4) strains with the same expressed mating type can generate different specificities, (5) switching is always restricted to the same mating type in a homokaryon, (6) nonparental types can switch again, and (7) meiosis fixes the specificities to which switching can occur. This suggests, for the first time in filamentous fungi, the existence of a mechanism analogous to the mating type switching in yeasts. We hypothese that both A and B mating type regions in A. aegerita are constituted of three loci, one specialized in expression and two other carrying silent information. Mating type switching in homokaryotic strains would occur by copy transposition of silent A and B information into the expression loci. Moreover, we propose that during meiosis the silent loci are substituted by copies of the expressed loci. PMID:1644274

Labarère, J; Noël, T

1992-06-01

2

Inversion of the chromosomal region between two mating type loci switches the mating type in Hansenula polymorpha.  

PubMed

Yeast mating type is determined by the genotype at the mating type locus (MAT). In homothallic (self-fertile) Saccharomycotina such as Saccharomyces cerevisiae and Kluveromyces lactis, high-efficiency switching between a and ? mating types enables mating. Two silent mating type cassettes, in addition to an active MAT locus, are essential components of the mating type switching mechanism. In this study, we investigated the structure and functions of mating type genes in H. polymorpha (also designated as Ogataea polymorpha). The H. polymorpha genome was found to harbor two MAT loci, MAT1 and MAT2, that are ?18 kb apart on the same chromosome. MAT1-encoded ?1 specifies ? cell identity, whereas none of the mating type genes were required for a identity and mating. MAT1-encoded ?2 and MAT2-encoded a1 were, however, essential for meiosis. When present in the location next to SLA2 and SUI1 genes, MAT1 or MAT2 was transcriptionally active, while the other was repressed. An inversion of the MAT intervening region was induced by nutrient limitation, resulting in the swapping of the chromosomal locations of two MAT loci, and hence switching of mating type identity. Inversion-deficient mutants exhibited severe defects only in mating with each other, suggesting that this inversion is the mechanism of mating type switching and homothallism. This chromosomal inversion-based mechanism represents a novel form of mating type switching that requires only two MAT loci. PMID:25412462

Maekawa, Hiromi; Kaneko, Yoshinobu

2014-11-01

3

Mating-type switching by chromosomal inversion in methylotrophic yeasts suggests an origin for the three-locus Saccharomyces cerevisiae system.  

PubMed

Saccharomyces cerevisiae has a complex system for switching the mating type of haploid cells, requiring the genome to have three mating-type (MAT)-like loci and a mechanism for silencing two of them. How this system originated is unknown, because the three-locus system is present throughout the family Saccharomycetaceae, whereas species in the sister Candida clade have only one locus and do not switch. Here we show that yeasts in a third clade, the methylotrophs, have a simpler two-locus switching system based on reversible inversion of a section of chromosome with MATa genes at one end and MATalpha genes at the other end. In Hansenula polymorpha the 19-kb invertible region lies beside a centromere so that, depending on the orientation, either MATa or MATalpha is silenced by centromeric chromatin. In Pichia pastoris, the orientation of a 138-kb invertible region puts either MATa or MATalpha beside a telomere and represses transcription of MATa2 or MATalpha2. Both species are homothallic, and inversion of their MAT regions can be induced by crossing two strains of the same mating type. The three-locus system of S. cerevisiae, which uses a nonconservative mechanism to replace DNA at MAT, likely evolved from a conservative two-locus system that swapped genes between expression and nonexpression sites by inversion. The increasing complexity of the switching apparatus, with three loci, donor bias, and cell lineage tracking, can be explained by continuous selection to increase sporulation ability in young colonies. Our results provide an evolutionary context for the diversity of switching and silencing mechanisms. PMID:25349420

Hanson, Sara J; Byrne, Kevin P; Wolfe, Kenneth H

2014-11-11

4

Mating-Type Genes and MAT Switching in Saccharomyces cerevisiae  

PubMed Central

Mating type in Saccharomyces cerevisiae is determined by two nonhomologous alleles, MATa and MAT?. These sequences encode regulators of the two different haploid mating types and of the diploids formed by their conjugation. Analysis of the MATa1, MAT?1, and MAT?2 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, HML? 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

Haber, James E.

2012-01-01

5

RAS/Cyclic AMP and Transcription Factor Msn2 Regulate Mating and Mating-Type Switching in the Yeast Kluyveromyces lactis ?  

PubMed Central

In response to harsh environmental conditions, ascomycetes produce stress-resistant spores to promote survival. As sporulation requires a diploid DNA content, species with a haploid lifestyle, such as Kluyveromyces lactis, first induce mating in response to stress. In K. lactis, mating and mating-type switching are induced by the DNA-binding protein Mts1. Mts1 expression is known to be upregulated by nutrient limitation, but the mechanism is unknown. We show that a ras2 mutation results in a hyperswitching phenotype. In contrast, strains lacking the phosphodiesterase Pde2 had lower switching rates compared to that of the wild type (WT). As Ras2 promotes cyclic AMP (cAMP) production and Pde2 degrades cAMP, these data suggest that low cAMP levels induce switching. Because the MTS1 regulatory region contains several Msn2 binding sites and Msn2 is a transcription factor that is activated by low cAMP levels, we investigated if Msn2 regulates MTS1 transcription. Consistently with this idea, an msn2 mutant strain displayed lower switching rates than the WT strain. The transcription of MTS1 is highly induced in the ras2 mutant strain. In contrast, an msn2 ras2 double mutant strain displays WT levels of the MTS1 transcript, showing that Msn2 is a critical inducer of MTS1 transcription. Strains lacking Msn2 and Pde2 also exhibit mating defects that can be complemented by the ectopic expression of Mts1. Finally, we show that MTS1 is subjected to negative autoregulation, presumably adding robustness to the mating and switching responses. We suggest a model in which Ras2/cAMP/Msn2 mediates the stress-induced mating and mating-type switching responses in K. lactis. PMID:21890818

Barsoum, E.; Rajaei, N.; Åström, S. U.

2011-01-01

6

Four mating-type genes control sexual differentiation in the fission yeast.  

PubMed Central

The mating-type region of fission yeast consists of three components, mat1, mat2-P and mat3-M, each separated by 15 kb. Cell-type is determined by the alternate allele present at mat1, either P in an h+ or M in an h- cell. mat2-P and mat3-M serve as donors of information that is transposed to mat1 during a switch of mating type. We have determined the nucleotide sequence of each component of mat. The P and M specific regions are 1104 and 1128 bp, respectively, and bounded by sequences common to each mating-type cassette (H1; 59 bp and H2; 135 bp). A third sequence is present at mat2-P and mat3-M but absent at mat1 (H3; 57 bp), and may be involved in transcriptional repression of these cassettes. mat1-P and mat1-M each encode two genes (Pc; 118 amino acids, Pi; 159 amino acids, Mc; 181 amino acids and Mi; 42 amino acids). Introduction of opal or frame-shift mutations into the open-reading-frame of each gene revealed that Pc and Mc are necessary and sufficient for mating and confer an h+ or h- mating type respectively. All four genes are required for meiotic competence in an h+/h- diploid. The transcription of each mat gene is strongly influenced by nutritional conditions and full induction was observed only in nitrogen-free medium. The predicted product of the Pi gene contains a region of homology with the homeobox sequence, suggesting that this gene encodes a DNA binding protein that directly regulates the expression of other genes. Images PMID:2900761

Kelly, M; Burke, J; Smith, M; Klar, A; Beach, D

1988-01-01

7

Electrofusion of haploid Saccharomyces yeast cells of identical mating type  

Microsoft Academic Search

Yeast protoplasts from the haploid strains 21 a and 111a were exposed to an inhomogeneous alternating field (about 1 kV\\/cm, 2 MHz). Due to dielectrophoretic aggregation two or more cells with close membrane contact are formed between the electrodes. Cell fusion was observed by application of two field pulses (11 kV\\/cm, 7 µs duration) applied at an interval of 1

H. J. Halfmann; C. C. Emeis; U. Zimmermann

1983-01-01

8

Identification of Mating Type Genes in the Bipolar Basidiomycetous Yeast Rhodosporidium toruloides: First Insight into the MAT Locus Structure of the Sporidiobolales? †  

PubMed Central

Rhodosporidium toruloides is a heterothallic, bipolar, red yeast that belongs to the Sporidiobolales, an order within a major lineage of basidiomycetes, the Pucciniomycotina. In contrast to other basidiomycetes, considerably less is known about the nature of the mating type (MAT) loci that control sexual reproduction in this lineage. Three genes (RHA1, RHA2, and RHA3) encoding precursors of the MAT A1 pheromone (rhodotorucine A) were previously identified and formed the basis for a genome walking approach that led to the identification of additional MAT genes in complementary mating strains of R. toruloides. Two mating type-specific alleles encoding a p21-activated kinase (PAK; Ste20 homolog) were found between the RHA2 and RHA3 genes, and identification in MAT A2 strains of a gene encoding a presumptive pheromone precursor enabled prediction of the structure of rhodotorucine a. In addition, a putative pheromone receptor gene (STE3 homolog) was identified upstream of RHA1. Analyses of genomic data from two closely related species, Sporobolomyces roseus and Sporidiobolus salmonicolor, identified syntenic regions that contain homologs of all the above-mentioned genes. Notably, six novel pheromone precursor genes were uncovered, which encoded, similarly to the RHA genes, multiple tandem copies of the peptide moiety. This suggests that this structure, which is unique among fungal lipopeptide pheromones, seems to be prevalent in red yeasts. Species comparisons provided evidence for a large, multigenic MAT locus structure in the Sporidiobolales, but no putative homeodomain transcription factor genes (which are present in all basidiomycetous MAT loci characterized thus far) could be found in any of the three species in the vicinity of the MAT genes identified. PMID:18408057

Coelho, Marco A.; Rosa, André; Rodrigues, Nádia; Fonseca, Álvaro; Gonçalves, Paula

2008-01-01

9

Basidiomycete Mating Type Genes and Pheromone Signaling?  

PubMed Central

The genome sequences of the basidiomycete Agaricomycetes species Coprinopsis cinerea, Laccaria bicolor, Schizophyllum commune, Phanerochaete chrysosporium, and Postia placenta, as well as of Cryptococcus neoformans and Ustilago maydis, are now publicly available. Out of these fungi, C. cinerea, S. commune, and U. maydis, together with the budding yeast Saccharomyces cerevisiae, have been investigated for years genetically and molecularly for signaling in sexual reproduction. The comparison of the structure and organization of mating type genes in fungal genomes reveals an amazing conservation of genes regulating the sexual reproduction throughout the fungal kingdom. In agaricomycetes, two mating type loci, A, coding for homeodomain type transcription factors, and B, encoding a pheromone/receptor system, regulate the four typical mating interactions of tetrapolar species. Evidence for both A and B mating type genes can also be identified in basidiomycetes with bipolar systems, where only two mating interactions are seen. In some of these fungi, the B locus has lost its self/nonself discrimination ability and thus its specificity while retaining the other regulatory functions in development. In silico analyses now also permit the identification of putative components of the pheromone-dependent signaling pathways. Induction of these signaling cascades leads to development of dikaryotic mycelia, fruiting body formation, and meiotic spore production. In pheromone-dependent signaling, the role of heterotrimeric G proteins, components of a mitogen-activated protein kinase (MAPK) cascade, and cyclic AMP-dependent pathways can now be defined. Additionally, the pheromone-dependent signaling through monomeric, small GTPases potentially involved in creating the polarized cytoskeleton for reciprocal nuclear exchange and migration during mating is predicted. PMID:20190072

Raudaskoski, Marjatta; Kothe, Erika

2010-01-01

10

Control of yeast cell types by mobile genes: A test  

PubMed Central

The yeast Saccharomyces cerevisiae changes cell types by switching the alleles of the mating type locus (MAT) from a to ? and vice versa. In the cassette model, these switches—e.g., from a to ?—occur when a replica of silent ? information (an ? “cassette”) replaces the resident a cassette at the mating type locus and is thereby expressed. We have identified a mutation in the locus postulated to be the silent ? information (HML?) and find that a mutation is introduced into the mating type locus as a result of interconversion: HML?-MAT? cells switch to MATa and then to MAT?-. The MAT?- mutation leads to defective mating and behaves like some previously identified MAT?- mutations. These observations satisfy the prediction of the cassette and controlling element models that genetic information is transmitted from HML? to the mating type locus. PMID:14627013

Kushner, Peter J.; Blair, Lindley C.; Herskowitz, Ira

1979-01-01

11

Selective Gene Expression in Multigene Families from Yeast to Mammals  

NSDL National Science Digital Library

Cell identity is the direct consequence of the genes expressed. This STKE Review highlights the diverse mechanisms that cells use to achieve exclusive gene expression. The details of the molecular mechanism underlying yeast mating-type switching are compared and contrasted with the mechanisms involved in immunoglobulin gene expression and odorant receptor gene expression in mammals.

Jacob Z. Dalgaard (Marie Curie Research Institute; REV)

2004-10-26

12

Recombination Hotspots Flank the Cryptococcus Mating-Type Locus: Implications for the Evolution of a Fungal Sex Chromosome  

PubMed Central

Recombination increases dramatically during meiosis to promote genetic exchange and generate recombinant progeny. Interestingly, meiotic recombination is unevenly distributed throughout genomes, and, as a consequence, genetic and physical map distances do not have a simple linear relationship. Recombination hotspots and coldspots have been described in many organisms and often reflect global features of chromosome structure. In particular, recombination frequencies are often distorted within or outside sex-determining regions of the genome. Here, we report that recombination is elevated adjacent to the mating-type locus (MAT) in the pathogenic basidiomycete Cryptococcus neoformans. Among fungi, C. neoformans has an unusually large MAT locus, and recombination is suppressed between the two >100-kilobase mating-type specific alleles. When genetic markers were introduced at defined physical distances from MAT, we found the meiotic recombination frequency to be ~20% between MAT and a flanking marker at 5, 10, 50, or 100 kilobases from the right border. As a result, the physical/genetic map ratio in the regions adjacent to MAT is distorted ~10- to 50-fold compared to the genome-wide average. Moreover, recombination frequently occurred on both sides of MAT and negative interference between crossovers was observed. MAT heterozygosity was not required for enhanced recombination, implying that this process is not due to a physical distortion from the two non-paired alleles and could also occur during same-sex mating. Sequence analysis revealed a correlation between high G + C content and these hotspot regions. We hypothesize that the presence of recombinational activators may have driven several key events during the assembly and reshaping of the MAT locus and may have played similar roles in the origins of both metabolic and biosynthetic gene clusters. Our findings suggest that during meiosis the MAT locus may be exchanged onto different genetic backgrounds and therefore have broad evolutionary implications with respect to mating-type switching in both model and pathogenic yeasts. PMID:17083277

Hsueh, Yen-Ping; Idnurm, Alexander; Heitman, Joseph

2006-01-01

13

Sequence diversity of mating-type genes in Phaeosphaeria avenaria.  

PubMed

Phaeosphaeria avenaria, one of the causal agents of stagonospora leaf blotch diseases in cereals, is composed of two subspecies, P. avenaria f. sp. triticea (Pat) and P. avenaria f. sp. avenaria (Paa). The Pat subspecies was grouped into Pat1-Pat3, based on restriction fragment length polymorphism (RFLP) and ribosomal DNA (rDNA) internal transcribed spacer (ITS) sequences in previous studies. Mating-type genes and their potential use in phylogeny and molecular classification were studied by DNA hybridization and PCR amplification. The majority of Pat1 isolates reported to be homothallic and producing sexual reproduction structures on cultural media had only the MAT1-1 gene. Minor sequence variations were found in the conserved region of MAT1-1 gene in Pat1 isolates. However, both mating-type genes, MAT1-1 and MAT1-2, were identified in P. avenaria isolates represented by ATCC12277 from oats (Paa) and the Pat2 isolates from foxtail barley ( Hordeum jubatum L.). Cluster analyses based on mating-type gene conserved regions revealed that cereal Phaeosphaeria is not phylogenetically closely related to other ascomycetes, including Mycosphaerella graminicola (anamorph Septoria tritici). The sequence diversity of mating-type genes in Pat and Paa supports our previous phylogenetic relationship and molecular classification based on RFLP fingerprinting and rDNA ITS sequences. PMID:12695852

Ueng, Peter P; Dai, Qun; Cui, Kai-rong; Czembor, Pawe? C; Cunfer, Barry M; Tsang, H; Arseniuk, Edward; Bergstrom, Gary C

2003-05-01

14

Evolutionary Strata in a Small Mating-Type-Specific Region of the Smut Fungus Microbotryum violaceum  

PubMed Central

DNA sequence analysis and genetic mapping of loci from mating-type-specific chromosomes of the smut fungus Microbotryum violaceum demonstrated that the nonrecombining mating-type-specific region in this species comprises ?25% (?1 Mb) of the chromosome length. Divergence between homologous mating-type-linked genes in this region varies between 0 and 8.6%, resembling the evolutionary strata of vertebrate and plant sex chromosomes. PMID:19448270

Votintseva, Antonina A; Filatov, Dmitry A.

2009-01-01

15

Evolutionary strata in a small mating-type-specific region of the smut fungus Microbotryum violaceum.  

PubMed

DNA sequence analysis and genetic mapping of loci from mating-type-specific chromosomes of the smut fungus Microbotryum violaceum demonstrated that the nonrecombining mating-type-specific region in this species comprises approximately 25% ( approximately 1 Mb) of the chromosome length. Divergence between homologous mating-type-linked genes in this region varies between 0 and 8.6%, resembling the evolutionary strata of vertebrate and plant sex chromosomes. PMID:19448270

Votintseva, Antonina A; Filatov, Dmitry A

2009-08-01

16

Genes Controlling Mating-Type Specificity in PARAMECIUM CAUDATUM: Three Loci Revealed by Intersyngenic Crosses  

PubMed Central

In mating interactions in Paramecium caudatum, initial mating agglutination is strictly mating-type specific, but subsequent conjugating pair formation is not mating-type specific. Using this nonspecificity of pair formation, intersyngenic (intersibling species) pairs were induced by mixing four mating types of two different syngens. To distinguish intersyngenic pairs from intrasyngenic ones, the behavioral marker CNR (Takahashi 1979) was mainly used. Clones of intersyngenic hybrids showed high fertility and thus made feasible a genetic analysis of syngenic specificity of mating type. The syngenic specificities of E (even) mating types were found to be controlled by co-dominant multiple alleles at the Mt locus, and those of O (odd) mating types by interactions of co-dominant multiple alleles at two loci, MA and MB. Clones of heterozygotes express dual mating types. Mt is epistatic to MA and MB, and thus O mating types can be expressed only in the recessive homozygote (mt/mt) at the Mt locus. In addition, at least one allele each at the MA and MB loci must have a common syngen specificity for the expression of O types. Thus, when MA is homozygous for one syngen and MB is homozygous for another syngen, no mating type is expressed. PMID:17246132

Tsukii, Yuuji; Hiwatashi, Koichi

1983-01-01

17

Lsd1 and Lsd2 control programmed replication fork pauses and imprinting in fission yeast  

PubMed Central

In the fission yeast Schizosaccharomyces pombe a chromosomal imprinting event controls the asymmetric pattern of mating-type switching. The orientation of DNA replication at the mating-type locus is instrumental in this process. However, the factors leading to imprinting are not fully identified and the mechanism is poorly understood. Here we show that the replication fork pause at the mat1 locus (MPS1), essential for imprint formation, depends on the lysine specific demethylase, Lsd1. We demonstrate that either Lsd1 or Lsd2 amine oxidase activity is required for these processes, working upstream of the imprinting factors Swi1 and Swi3 (homologs of mammalian Timeless and Tipin, respectively). We also show that the Lsd1/2 complex controls the replication fork terminators, within the rDNA repeats. These findings reveal a novel role for the Lsd1/2 demethylases in controlling polar replication fork progression, imprint formation and subsequent asymmetric cell divisions. PMID:23260662

Holmes, Allyson; Roseaulin, Laura; Schurra, Catherine; Waxin, Herve; Lambert, Sarah; Zaratiegui, Mikel; Martienssen, Robert A.; Arcangioli, Benoit

2014-01-01

18

Sexual reproduction between partners of the same mating type in Cryptococcus neoformans  

Microsoft Academic Search

Cryptococcus neoformans is a globally distributed human fungal pathogen that causes life-threatening meningoencephalitis in immunocompromised patients. It has a defined sexual cycle involving haploid cells of alpha and a mating types, yet the vast majority of environmental and clinical isolates are alpha (ref. 3). Sexual recombination is normally expected to occur between isolates of opposite mating type in organisms with

Xiaorong Lin; Christina M. Hull; Joseph Heitman

2005-01-01

19

Mating type gene analysis in apparently asexual Cercospora species is suggestive of cryptic sex.  

PubMed

The genus Cercospora consists of numerous important, apparently asexual plant pathogens. We designed degenerate primers from homologous sequences in related species to amplify part of the C. apii, C. apiicola, C. beticola, C. zeae-maydis and C. zeina mating type genes. Chromosome walking was used to determine the full length mating type genes of these species. Primers were developed to amplify and sequence homologous portions of the mating type genes of additional species. Phylogenetic analyses of these sequences revealed little variation among members of the C. apii complex, whereas C. zeae-maydis and C. zeina were found to be dissimilar. The presence of both mating types in approximately even proportions in C. beticola, C. zeae-maydis and C. zeina populations, in contrast to single mating types in C. apii (MAT1) and C. apiicola (MAT2), suggests that a sexual cycle may be active in some of these species. PMID:16839791

Groenewald, Marizeth; Groenewald, Johannes Z; Harrington, Thomas C; Abeln, Edwin C A; Crous, Pedro W

2006-12-01

20

Development of SCAR markers to determine the mating types of Lepista nuda protoplast monokaryons.  

PubMed

Lepista nuda (Bull. ex Fr.) Cooke belongs to Tricholomataceae and is an edible fungus with both economic and medical value. Mycelia were isolated from the fruiting bodies of L. nuda and were used to prepare the protoplast monokaryons. One hundred and fifteen monokaryons were obtained and their mating types were determined using somatic incompatibility tests. Protoplast monokaryons segregated into either the A1B1 or the A2B2 mating types. Inter-simple sequence repeats and sequence-related amplified polymorphism fingerprinting were used to analyse the mating types of these protoplast monokaryons and 16 sequence-characterised amplified region primers were developed to efficiently differentiate between the monokaryon mating types. Multiplex PCR analyses were also established. The data presented here outline a method for the precise and rapid identification of protoplast monokaryon mating types, which has the promise to shorten the period required for conventional crossbreeding. PMID:24352297

Li, Dengjin; Liu, Yu; Wang, Peng; Ma, Yuanwei; Wang, Shouxian; Zhao, Shuang; Xu, Feng

2014-04-01

21

Domesticated transposase Kat1 and its fossil imprints induce sexual differentiation in yeast.  

PubMed

Transposable elements (TEs) have had a major influence on shaping both prokaryotic and eukaryotic genomes, largely through stochastic events following random or near-random insertions. In the mammalian immune system, the recombination activation genes1/2 (Rag1/2) recombinase has evolved from a transposase gene, demonstrating that TEs can be domesticated by the host. In this study, we uncovered a domesticated transposase, Kluyveromyces lactis hobo/Activator/Tam3 (hAT) transposase 1 (Kat1), operating at the fossil imprints of an ancient transposon, that catalyzes the differentiation of cell type. Kat1 induces mating-type switching from mating type a (MATa) to MAT? in the yeast K. lactis. Kat1 activates switching by introducing two hairpin-capped DNA double-strand breaks (DSBs) in the MATa1-MATa2 intergenic region, as we demonstrate both in vivo and in vitro. The DSBs stimulate homologous recombination with the cryptic hidden MAT left alpha (HML?) locus resulting in a switch of the cell type. The sites where Kat1 acts in the MATa locus most likely are ancient remnants of terminal inverted repeats from a long-lost TE. The KAT1 gene is annotated as a pseudogene because it contains two overlapping ORFs. We demonstrate that translation of full-length Kat1 requires a programmed -1 frameshift. The frameshift limited Kat1 activity, because restoring the zero frame causes switching to the MAT? genotype. Kat1 also was transcriptionally activated by nutrient limitation via the transcription factor mating type switch 1 (Mts1). A phylogenetic analysis indicated that KAT1 was domesticated specifically in the Kluyveromyces clade of the budding yeasts. We conclude that Kat1 is a highly regulated transposase-derived endonuclease vital for sexual differentiation. PMID:25313032

Rajaei, Naghmeh; Chiruvella, Kishore K; Lin, Feng; Aström, Stefan U

2014-10-28

22

High-Resolution Structural Analysis of Chromatin at Specific Loci: Saccharomyces cerevisiae Silent Mating-Type Locus HMRa  

PubMed Central

Genetic and biochemical evidence implicates chromatin structure in the silencing of the two quiescent mating-type loci near the telomeres of chromosome III in yeast. With high-resolution micrococcal nuclease mapping, we show that the HMRa locus has 12 precisely positioned nucleosomes spanning the distance between the E and I silencer elements. The nucleosomes are arranged in pairs with very short linkers; the pairs are separated from one another by longer linkers of ?20 bp. Both the basic amino-terminal region of histone H4 and the silent information regulator protein Sir3p are necessary for the organized repressive chromatin structure of the silent locus. Compared to HMRa, only small differences in the availability of the TATA box are present for the promoter in the cassette at the active MATa locus. Features of the chromatin structure of this silent locus compared to the previously studied HML? locus suggest differences in the mechanisms of silencing and may relate to donor selection during mating-type interconversion. PMID:10567520

Ravindra, Anish; Weiss, Kerstin; Simpson, Robert T.

1999-01-01

23

Evidence of Recombination in Mixed-Mating-Type and ?-Only Populations of Cryptococcus gattii Sourced from Single Eucalyptus Tree Hollows?  

PubMed Central

Disease caused by the pathogenic yeast Cryptococcus gattii begins with the inhalation of an infectious propagule. As C. gattii is heavily encapsulated, this propagule is most likely to be a basidiospore. However, most C. gattii strains are infertile in laboratory crosses, and population studies indicate that recombination and dispersal are very restricted. In addition, strains of the ? mating type predominate, which would not be expected in a mating population. C. gattii comprises four genetically distinct molecular genotypes, designated VGI to VGIV. C. gattii molecular type VGI has a strong association with Eucalyptus camaldulensis and can be found in high numbers in E. camaldulensis hollows. Previous work on isolates obtained from E. camaldulensis suggested that environmental populations of C. gattii are highly fragmented, have limited ability to disperse, and are confined to individual tree hollows. In the current study, we examined large numbers of isolates from three separate hollows for evidence of recombination. In two hollows, the ? and a mating types were present in approximately equal numbers. The third hollow had ? cells only and was from a region where a isolates have never been found. Statistical analysis of multilocus genotypes revealed recombining subpopulations in the three Eucalyptus hollows. Recombination was equally present in the ?-a and ?-only populations. This is consistent with recent studies that have found evidence suggestive of ?-? mating in C. gattii and Cryptococcus neoformans and raises the possibility this may be a widespread phenomenon, allowing these fungi to recombine despite a paucity of a mating partners. PMID:18281600

Saul, Nathan; Krockenberger, Mark; Carter, Dee

2008-01-01

24

Tuber melanosporum: mating type distribution in a natural plantation and dynamics of strains of different mating types on the roots of nursery-inoculated host plants.  

PubMed

• In light of the recent finding that Tuber melanosporum, the ectomycorrhizal ascomycete that produces the most highly prized black truffles, is a heterothallic species, we monitored the spatial distribution of strains with opposite mating types (MAT) in a natural truffle ground and followed strain dynamics in artificially inoculated host plants grown under controlled conditions. • In a natural truffle ground, ectomycorrhizas (ECMs), soil samples and fruit bodies were sampled and genotyped to determine mating types. Simple sequence repeat (SSR) markers were also used to fingerprint ECMs and fruit bodies. The ECMs from nursery-inoculated host plants were analysed for mating type at 6 months and 19 months post-inoculation. • In open-field conditions, all ECMs from the same sampling site showed an identical mating type and an identical haploid genotype, based on SSR analysis. Interestingly, the gleba of fruit bodies always demonstrated the same genotype as the surrounding ECMs. Although root tips from nursery-grown plants initially developed ECMs of both mating types, a dominance of ECMs of the same MAT were found after several months. • The present study deepens our understanding of the vegetative and sexual propagation modes of T. melanosporum. These results are highly relevant for truffle cultivation. PMID:20964691

Rubini, Andrea; Belfiori, Beatrice; Riccioni, Claudia; Arcioni, Sergio; Martin, Francis; Paolocci, Francesco

2011-02-01

25

Pseudohomothallism and evolution of the mating-type chromosome in Neurospora tetrasperma  

SciTech Connect

Ascospores of Neurospora tetrasperma normally contain nuclei of both mating-type idiomorphs (a and A), resulting in self-fertile heterokaryons (a type of sexual reproduction termed pseudohomothallism). Occasional homokaryotic self-sterile strains (either a or A) behave as heterothallics and, in principal, provide N. tetrasperma to assess levels of intrastrain heterokaryosis (heterozygosity). The unexpected result was the mating-type chromosome and autosomes exhibited very different patterns of evolution, apparently because of suppressed recombination between mating-type chromosomes. Analysis of sequences on the mating-type chromosomes of wild-collected self-fertile strains revealed high levels of genetic variability between sibling A and a nuclei. In contrast, sequences on autosomes of sibling A and a nuclei exhibited nearly complete homogeneity. Conservation of distinct haplotype combinations on A and a mating-type chromosomes in strains from diverse locations further suggested an absence of recombination over substantial periods of evolutionary time. The suppression of recombination of the N. tetrasperma mating-type chromosome, expected to ensure a high frequency of self fertility, presents an interesting parallel with, and possible model for studying aspects of, the evolution of mammalian sex chromosomes. 39 refs., 5 figs., 1 tab.

Merino, S.T.; Nelson, M.A.; Natvig, D.O. [Univ. of New Mexico, Albuquerque, NM (United States)] [and others

1996-06-01

26

The Mutator Gene Swi8 Effects Specific Mutations in the Mating-Type Region of Schizosaccharomyces Pombe  

PubMed Central

The swi8(+) gene of Schizosaccharomyces pombe appears to be involved in the termination step of copy synthesis during mating-type (MT) switching. Mutations in swi8 confer a general mutator phenotype and, in particular, generate specific mutations in the MT region. Sequencing of the MT cassettes of the h(90) swi8-137 mutant revealed three altered sites. One is situated at the switching (smt) signal adjacent to the H1 homology box of the expression locus mat1:1. It reduces the rate of MT switching. The alteration at the smt signal arose frequently in other h(90) swi8 strains and is probably caused by gene conversion in which the sequence adjacent to the H1 box of mat2:2 is used as template. This change might be generated during the process of MT switching when hybrid DNA formation is anomalously extended into the more heterologous region flanking the H1 homology box. In addition to the gene conversion at mat1:1, two mutations were found in the H3 homology boxes of the silent cassettes mat2:2 and mat3:3. PMID:7851760

Fleck, O.; Rudolph, C.; Albrecht, A.; Lorentz, A.; Schar, P.; Schmidt, H.

1994-01-01

27

Sex-Determination System in the Diploid Yeast Zygosaccharomyces sapae  

PubMed Central

Sexual reproduction and breeding systems are driving forces for genetic diversity. The mating-type (MAT) locus represents a mutation and chromosome rearrangement hotspot in yeasts. Zygosaccharomyces rouxii complex yeasts are naturally faced with hostile low water activity (aw) environments and are characterized by gene copy number variation, genome instability, and aneuploidy/allodiploidy. Here, we investigated sex-determination system in Zygosaccharomyces sapae diploid strain ABT301T, a member of the Z. rouxii complex. We cloned three divergent mating type-like (MTL) ?-idiomorph sequences and designated them as ZsMTL? copies 1, 2, and 3. They encode homologs of Z. rouxii CBS 732T MAT?2 (amino acid sequence identities spanning from 67.0 to 99.5%) and MAT?1 (identity range 81.5–99.5%). ABT301T possesses two divergent HO genes encoding distinct endonucleases 100% and 92.3% identical to Z. rouxii HO. Cloning of MATa-idiomorph resulted in a single ZsMTLa locus encoding two Z. rouxii-like proteins MATa1 and MATa2. To assign the cloned ZsMTL? and ZsMTLa idiomorphs as MAT, HML, and HMR cassettes, we analyzed their flanking regions. Three ZsMTL? loci exhibited the DIC1-MAT-SLA2 gene order canonical for MAT expression loci. Furthermore, four putative HML cassettes were identified, two containing the ZsMTL? copy 1 and the remaining harboring ZsMTL? copies 2 and 3. Finally, the ZsMTLa locus was 3?-flanked by SLA2, suggesting the status of MAT expression locus. In conclusion, Z. sapae ABT301T displays an a??? genotype missing of the HMR silent cassette. Our results demonstrated that mating-type switching is a hypermutagenic process in Z. rouxii complex that generates genetic diversity de novo. This error-prone mechanism could be suitable to generate progenies more rapidly adaptable to hostile environments. PMID:24939186

Solieri, Lisa; Dakal, Tikam Chand; Giudici, Paolo; Cassanelli, Stefano

2014-01-01

28

Evolution of Sexes from an Ancestral Mating-Type Specification Pathway  

PubMed Central

Male and female sexes have evolved repeatedly in eukaryotes but the origins of dimorphic sexes and their relationship to mating types in unicellular species are not understood. Volvocine algae include isogamous species such as Chlamydomonas reinhardtii, with two equal-sized mating types, and oogamous multicellular species such as Volvox carteri with sperm-producing males and egg-producing females. Theoretical work predicts genetic linkage of a gamete cell-size regulatory gene(s) to an ancestral mating-type locus as a possible step in the evolution of dimorphic gametes, but this idea has not been tested. Here we show that, contrary to predictions, a single conserved mating locus (MT) gene in volvocine algae—MID, which encodes a RWP-RK domain transcription factor—evolved from its ancestral role in C. reinhardtii as a mating-type specifier, to become a determinant of sperm and egg development in V. carteri. Transgenic female V. carteri expressing male MID produced functional sperm packets during sexual development. Transgenic male V. carteri with RNA interference (RNAi)-mediated knockdowns of VcMID produced functional eggs, or self-fertile hermaphrodites. Post-transcriptional controls were found to regulate cell-type–limited expression and nuclear localization of VcMid protein that restricted its activity to nuclei of developing male germ cells and sperm. Crosses with sex-reversed strains uncoupled sex determination from sex chromosome identity and revealed gender-specific roles for male and female mating locus genes in sexual development, gamete fitness and reproductive success. Our data show genetic continuity between the mating-type specification and sex determination pathways of volvocine algae, and reveal evidence for gender-specific adaptations in the male and female mating locus haplotypes of Volvox. These findings will enable a deeper understanding of how a master regulator of mating-type determination in an ancestral unicellular species was reprogrammed to control sexually dimorphic gamete development in a multicellular descendant. PMID:25003332

Geng, Sa; De Hoff, Peter; Umen, James G.

2014-01-01

29

Transcription of Two Long Noncoding RNAs Mediates Mating-Type Control of Gametogenesis in Budding Yeast  

E-print Network

The cell-fate decision leading to gametogenesis is essential for sexual reproduction. In S. cerevisiae, only diploid MATa/? but not haploid MATa or MAT? cells undergo gametogenesis, known as sporulation. We find that ...

van Werven, Folkert J.

30

Environmental Induction of White–Opaque Switching in Candida albicans  

PubMed Central

Candida albicans strains that are homozygous at the mating type locus (MTLa or MTL?) can spontaneously switch at a low frequency from the normal yeast cell morphology (white) to an elongated cell type (opaque), which is the mating-competent form of the fungus. The ability to switch reversibly between these two cell types also contributes to the pathogenicity of C. albicans, as white and opaque cells are differently adapted to specific host niches. We found that in strain WO-1, a strain in which genomic alterations have occurred, but not in other tested strains, switching from the white to the opaque phase can also be induced by environmental conditions. Transient incubation of white cells under anaerobic conditions programmed the cells to switch en masse to the opaque phase. The anaerobic induction of white–opaque switching was controlled by the transcription factor CZF1, which in heterozygous MTLa/? cells regulates filamentous growth under embedded, hypoxic conditions. Intriguingly, passage of white cells of strain WO-1 through the mouse intestine, a host niche in which the cells are likely to be exposed to anaerobic conditions, resulted in a strongly increased frequency of switching to the opaque phase. These results demonstrate that white–opaque switching is not only a spontaneous process but, in combination with genomic alterations, can also be induced by environmental signals, suggesting that switching and mating of C. albicans may occur with high efficiency in appropriate niches within its human host. PMID:18551173

Ramírez-Zavala, Bernardo; Reuß, Oliver; Park, Yang-Nim; Ohlsen, Knut; Morschhäuser, Joachim

2008-01-01

31

Phylogenetic and structural analyses of the mating-type loci in Clavicipitaceae.  

PubMed

Entomopathogens and other econutritional fungi belonging to Clavicipitaceae were phylogenetically analyzed on the basis of the 18S rRNA gene and mating-type genes (MAT1-1-1 and MAT1-2-1). The phylogenies of the mating-type genes yielded better resolutions than that of 18S rRNA gene. Entomopathogens (Cordyceps bassiana, Cordyceps brongniartii, Cordyceps militaris, Cordyceps sinclairii, Cordyceps takaomontana, Isaria cateniannulata, Isaria farinosa, Isaria fumosorosea, Isaria javanica, Lecanicillium muscarium and Torrubiella flava) were considered as a phylogenetically defined group, and were closely related to mycopathogens (Lecanicillium psalliotae and Verticillium fungicola). They located at more descendant positions in the mating-type trees than other fungi, and lacked the mating-type gene MAT1-1-3. The deletion of MAT1-1-3 was supposed to have occurred once in Clavicipitaceae, and a good indication for the evolution of Clavicipitaceae. Other entomopathogens (Cordyceps cylindrica, Cordyceps subsessilis, Metarhizium anisopliae and Nomuraea rileyi) and pathogens of plants, nematodes and slime molds, were relatively related to each other, and possessed MAT1-1-3, but were supposed to be heterogeneous. Root-associated fungi did not form any clade with other species. PMID:17064371

Yokoyama, Eiji; Arakawa, Masao; Yamagishi, Kenzo; Hara, Akira

2006-11-01

32

Asexual Cephalosporin C Producer Acremonium chrysogenum Carries a Functional Mating Type Locus  

Microsoft Academic Search

Acremonium chrysogenum, the fungal producer of the pharmaceutically relevant -lactam antibiotic cepha- losporin C, is classified as asexual because no direct observation of mating or meiosis has yet been reported. To assess the potential of A. chrysogenum for sexual reproduction, we screened an expressed sequence tag library from A. chrysogenum for the expression of mating type (MAT) genes, which are

Stefanie Poggeler; Birgit Hoff; Ulrich Kuck

2008-01-01

33

Extensive Divergence Between Mating-Type Chromosomes of the Anther-Smut Fungus  

PubMed Central

Genomic regions that determine mating compatibility are subject to distinct evolutionary forces that can lead to a cessation of meiotic recombination and the accumulation of structural changes between members of the homologous chromosome pair. The relatively recent discovery of dimorphic mating-type chromosomes in fungi can aid the understanding of sex chromosome evolution that is common to dioecious plants and animals. For the anther-smut fungus, Microbotryum lychnidis-dioicae (= M. violaceum isolated from Silene latifolia), the extent of recombination cessation on the dimorphic mating-type chromosomes has been conflictingly reported. Comparison of restriction digest optical maps for the two mating-type chromosomes shows that divergence extends over 90% of the chromosome lengths, flanked at either end by two pseudoautosomal regions. Evidence to support the expansion of recombination cessation in stages from the mating-type locus toward the pseudoautosomal regions was not found, but evidence of such expansion could be obscured by ongoing processes that affect genome structure. This study encourages the comparison of forces that may drive large-scale recombination suppression in fungi and other eukaryotes characterized by dimorphic chromosome pairs associated with sexual life cycles. PMID:23150606

Hood, Michael E.; Petit, Elsa; Giraud, Tatiana

2013-01-01

34

Extensive divergence between mating-type chromosomes of the anther-smut fungus.  

PubMed

Genomic regions that determine mating compatibility are subject to distinct evolutionary forces that can lead to a cessation of meiotic recombination and the accumulation of structural changes between members of the homologous chromosome pair. The relatively recent discovery of dimorphic mating-type chromosomes in fungi can aid the understanding of sex chromosome evolution that is common to dioecious plants and animals. For the anther-smut fungus, Microbotryum lychnidis-dioicae (= M. violaceum isolated from Silene latifolia), the extent of recombination cessation on the dimorphic mating-type chromosomes has been conflictingly reported. Comparison of restriction digest optical maps for the two mating-type chromosomes shows that divergence extends over 90% of the chromosome lengths, flanked at either end by two pseudoautosomal regions. Evidence to support the expansion of recombination cessation in stages from the mating-type locus toward the pseudoautosomal regions was not found, but evidence of such expansion could be obscured by ongoing processes that affect genome structure. This study encourages the comparison of forces that may drive large-scale recombination suppression in fungi and other eukaryotes characterized by dimorphic chromosome pairs associated with sexual life cycles. PMID:23150606

Hood, Michael E; Petit, Elsa; Giraud, Tatiana

2013-01-01

35

Scanning electron microscopy as a tool for the analysis of colony architecture produced by phenotypic switching of a human pathogenic yeast Candida tropicalis  

NASA Astrophysics Data System (ADS)

Candida tropicalis has been identified as one of the most prevalent pathogenic yeast species of the Candida-non-albicans group. Phenotypic switching is a biological phenomenon related to the occurrence of spontaneous emergence of colonies with different morphologies that provides variability within colonizing populations in order to adapt to different environments. Currently, studies of the microstructure of switching variant colonies are not subject of extensive research. SEM analysis was used to verify the architecture of whole Candida colonies. The strain 49/07 exhibited a hemispherical shape character, while the strain 335/07 showed a volcano shape with mycelated-edge colony. The ring switch variant is characterized by a highly wrinkled centre and an irregular periphery. The rough phenotype exhibited a three-dimensional architecture and was characterized by the presence of deep central and peripheral depressions areas. The ultrastructural analysis also allowed the observation of the arrangement of individual cells within the colonies. The whole smooth colony consisted entirely of yeast cells. Differently, aerial filaments were found all around the colony periphery of the volcano shape colony. For this colony type the mycelated-edge consisted mainly of hyphae, although yeast cells are also seen. The ring and rough colonies phenotypes comprised mainly yeast cells with the presence of extracellular material connecting neighbouring cells. This study has shown that SEM can be used effectively to examine the microarchitecture of colonies morphotypes of the yeast C. tropicalis and further our understanding of switching event in this pathogen.

Furlaneto, M. C.; Andrade, C. G. T. J.; Aragão, P. H. A.; França, E. J. G.; Moralez, A. T. P.; Ferreira, L. C. S.

2012-07-01

36

Mating-type genes for basidiomycete strain improvement in mushroom farming  

Microsoft Academic Search

Mushroom production is dependent on the quality of the spawn used to inoculate the cultures. In order to produce high-quality spawn, breeding programs for strains resistant to certain diseases and able to form high-quality fruit bodies under standard growth conditions are necessary. The investigation of the molecular basis for mating provides access to the use of mating-type genes in order

E. Kothe

2001-01-01

37

Identity and conservation of mating type genes in geographically diverse isolates of Phaeosphaeria nodorum.  

PubMed

Mating type idiomorphs (MAT1-1 and MAT1-2) were identified from the heterothallic loculoascomycete Phaeosphaeria nodorum (wheat biotype) using DNA from a pair of isolates from Poland and Georgia, USA that are known to mate. MAT predicted proteins of P. nodorum are similar in sequence and in phylogenetic relationship to those described for other loculoascomycetes such as Cochliobolus spp., Alternaria alternata, and Didymella zeae-maydis. The organization of the MAT locus of the P. nodorum differs from these species in that its idiomorph begins within an adjacent upstream conserved ORF of unknown function. MAT-specific primers were used to identify isolates of both mating types in field populations, demonstrating that an absence of either mating type is not the reason that the teleomorph has not been found in New York. Portions of MAT1-1 and MAT1-2 were sequenced from geographically diverse isolates, including those from regions where the teleomorph has been reported. MAT was highly conserved and no significant differences in sequence were found. PMID:12948511

Bennett, R S; Yun, S-H; Lee, T Y; Turgeon, B G; Arseniuk, E; Cunfer, B M; Bergstrom, G C

2003-10-01

38

Asexual Cephalosporin C Producer Acremonium chrysogenum Carries a Functional Mating Type Locus?  

PubMed Central

Acremonium chrysogenum, the fungal producer of the pharmaceutically relevant ?-lactam antibiotic cephalosporin C, is classified as asexual because no direct observation of mating or meiosis has yet been reported. To assess the potential of A. chrysogenum for sexual reproduction, we screened an expressed sequence tag library from A. chrysogenum for the expression of mating type (MAT) genes, which are the key regulators of sexual reproduction. We identified two putative mating type genes that are homologues of the ?-box domain gene, MAT1-1-1 and MAT1-1-2, encoding an HPG domain protein defined by the presence of the three invariant amino acids histidine, proline, and glycine. In addition, cDNAs encoding a putative pheromone receptor and pheromone-processing enzymes, as well as components of a pheromone response pathway, were found. Moreover, the entire A. chrysogenum MAT1-1 (AcMAT1-1) gene and regions flanking the MAT region were obtained from a genomic cosmid library, and sequence analysis revealed that in addition to AcMAT1-1-1 and AcMAT1-1-2, the AcMAT1-1 locus comprises a third mating type gene, AcMAT1-1-3, encoding a high-mobility-group domain protein. The ?-box domain sequence of AcMAT1-1-1 was used to determine the phylogenetic relationships of A. chrysogenum to other ascomycetes. To determine the functionality of the AcMAT1-1 locus, the entire MAT locus was transferred into a MAT deletion strain of the heterothallic ascomycete Podospora anserina (the Pa?MAT strain). After fertilization with a P. anserina MAT1-2 (MAT+) strain, the corresponding transformants developed fruiting bodies with mature ascospores. Thus, the results of our functional analysis of the AcMAT1-1 locus provide strong evidence to hypothesize a sexual cycle in A. chrysogenum. PMID:18689517

Pöggeler, Stefanie; Hoff, Birgit; Kück, Ulrich

2008-01-01

39

Characterization of the mating-type genes in Leptographium procerum and Leptographium profanum.  

PubMed

Leptographium procerum and the closely related species Leptographium profanum, are ascomycetes associated with root-infesting beetles on pines and hardwood trees, respectively. Both species occur in North America where they are apparently native. L. procerum has also been found in Europe, China New Zealand, and South Africa where it has most probably been introduced. As is true for many other Leptographium species, sexual states have never been observed in L. procerum or L. profanum. The objectives of this study were to clone and characterize the mating type loci of these fungi, and to develop markers to determine the mating types of individual isolates. To achieve this, a partial sequence of MAT1-2-1 was amplified using degenerate primers targeting the high mobility group (HMG) sequence. A complete MAT1-2 idiomorph of L. profanum was subsequently obtained by screening a genomic library using the HMG sequence as a probe. Long range PCR was used to amplify the complete MAT1-1 idiomorph of L. profanum and both the MAT1-1 and MAT1-2 idiomorphs of L. procerum. Characterization of the MAT idiomorphs suggests that the MAT genes are fully functional and that individuals of both these species are self-sterile in nature with a heterothallic mating system. Mating type markers were developed and tested on a population of L. procerum isolates from the USA, the assumed center of origin for this species. The results suggest that cryptic sexual reproduction is occurring or has recently taken place within this population. PMID:23809651

Duong, Tuan A; de Beer, Z Wilhelm; Wingfield, Brenda D; Wingfield, Michael J

2013-06-01

40

Presence and Functionality of Mating Type Genes in the Supposedly Asexual Filamentous Fungus Aspergillus oryzae  

PubMed Central

The potential for sexual reproduction in Aspergillus oryzae was assessed by investigating the presence and functionality of MAT genes. Previous genome studies had identified a MAT1-1 gene in the reference strain RIB40. We now report the existence of a complementary MAT1-2 gene and the sequencing of an idiomorphic region from A. oryzae strain AO6. This allowed the development of a PCR diagnostic assay, which detected isolates of the MAT1-1 and MAT1-2 genotypes among 180 strains assayed, including industrial tane-koji isolates. Strains used for sake and miso production showed a near-1:1 ratio of the MAT1-1 and MAT1-2 mating types, whereas strains used for soy sauce production showed a significant bias toward the MAT1-2 mating type. MAT1-1 and MAT1-2 isogenic strains were then created by genetic manipulation of the resident idiomorph, and gene expression was compared by DNA microarray and quantitative real-time PCR (qRT-PCR) methodologies under conditions in which MAT genes were expressed. Thirty-three genes were found to be upregulated more than 10-fold in either the MAT1-1 host strain or the MAT1-2 gene replacement strain relative to each other, showing that both the MAT1-1 and MAT1-2 genes functionally regulate gene expression in A. oryzae in a mating type-dependent manner, the first such report for a supposedly asexual fungus. MAT1-1 expression specifically upregulated an ?-pheromone precursor gene, but the functions of most of the genes affected were unknown. The results are consistent with a heterothallic breeding system in A. oryzae, and prospects for the discovery of a sexual cycle are discussed. PMID:22327593

Wada, Ryuta; Maruyama, Jun-ichi; Yamaguchi, Haruka; Yamamoto, Nanase; Wagu, Yutaka; Paoletti, Mathieu; Archer, David B.; Dyer, Paul S.

2012-01-01

41

Environmental and Genetic Determinants of Colony Morphology in Yeast  

PubMed Central

Nutrient stresses trigger a variety of developmental switches in the budding yeast Saccharomyces cerevisiae. One of the least understood of such responses is the development of complex colony morphology, characterized by intricate, organized, and strain-specific patterns of colony growth and architecture. The genetic bases of this phenotype and the key environmental signals involved in its induction have heretofore remained poorly understood. By surveying multiple strain backgrounds and a large number of growth conditions, we show that limitation for fermentable carbon sources coupled with a rich nitrogen source is the primary trigger for the colony morphology response in budding yeast. Using knockout mutants and transposon-mediated mutagenesis, we demonstrate that two key signaling networks regulating this response are the filamentous growth MAP kinase cascade and the Ras-cAMP-PKA pathway. We further show synergistic epistasis between Rim15, a kinase involved in integration of nutrient signals, and other genes in these pathways. Ploidy, mating-type, and genotype-by-environment interactions also appear to play a role in the controlling colony morphology. Our study highlights the high degree of network reuse in this model eukaryote; yeast use the same core signaling pathways in multiple contexts to integrate information about environmental and physiological states and generate diverse developmental outputs. PMID:20107600

Granek, Joshua A.; Magwene, Paul M.

2010-01-01

42

Characterisation of the mating-type locus in the genus Xanthoria (lichen-forming ascomycetes, Lecanoromycetes).  

PubMed

Conserved regions of mating-type genes were amplified in four representatives of the genus Xanthoria (X. parietina, X. polycarpa, X. flammea, and X. elegans) using PCR-based methods. The complete MAT locus, containing one ORF (MAT1-2-1) coding for a truncated HMG-box protein, and two partial flanking genes, were cloned by screening a genomic lambda phage library of the homothallic X. parietina. The flanking genes, a homologue of SLA2 of Saccharomyces cerevisiae and a DNA lyase gene, served to amplify the two idiomorphs of the X. polycarpa MAT locus. Each idiomorph contains a single gene: MAT1-2-1 codes for a HMG-box protein, MAT1-1-1 encodes an alpha domain protein. The occurrence of mating-type genes in eight single spore isolates derived from one ascus was studied with a PCR assay. In the homothallic X. parietina a HMG fragment, but no alpha box fragment was found in all isolates, whereas in X. elegans, another homothallic species, all tested isolates contained a fragment of both idiomorphs. Conversely, isolates of the heterothallic X. polycarpa contained either a HMG or an alpha box fragment, but never both. PMID:16266815

Scherrer, Sandra; Zippler, Undine; Honegger, Rosmarie

2005-12-01

43

Isolation and characterisation of the mating-type (MAT) locus from Rhynchosporium secalis.  

PubMed

The mating-type ( MAT) genes from Rhynchosporium secalis were isolated using PCR-based methods. Characterisation of the MAT idiomorphs suggests that R. secalis is closely related to the discomycetes Pyrenopeziza brassicae and Tapesia yallundae in terms of sequence and MAT locus gene composition. The MAT1-2 idiomorph contains a single gene encoding a protein with a high-mobility group (HMG) DNA-binding domain. The MAT1-1 idiomorph contains two genes, one encoding a protein with a HMG domain and the other encoding an alpha box domain. A second, previously undescribed, intron was identified within the P. brassicae MAT1-2-1 gene. Two introns were also present in the corresponding gene in R. secalis and this showed the similarity between these genes at the discomycete MAT1-2 locus. Using PCR, we identified isolates of both mating types from barley crops in different parts of the UK and showed that the composition of the MAT idiomorphs is conserved in these isolates. These findings support the hypothesis that R. secalis is a heterothallic discomycete which has an as yet unidentified teleomorph. PMID:14517690

Foster, Simon J; Fitt, Bruce D L

2003-12-01

44

Further evidence for sexual reproduction in Rhynchosporium secalis based on distribution and frequency of mating-type alleles.  

PubMed

Rhynchosporium secalis, the causal agent of scald on barley, is thought to be exclusively asexual because no teleomorph has been found. Partial sequences of the HMG-box and alpha-domain of Rhynchosporium secalis isolates were identified and used to develop a PCR assay for the mating-type locus. PCR amplification of only one of these two domains was possible in each strain, suggesting that R. secalis has a MAT organization that is similar to other known heterothallic fungi. A multiplex PCR with primers amplifying either a MAT1-1- or MAT1-2-specific amplicon was used to determine the distribution of mating types in several R. secalis populations. In total, 1101 isolates from Australia, Switzerland, Ethiopia, Scandinavia, California, and South Africa were included in the analysis. Mating types occurred in equal frequencies for most of these populations, suggesting frequency-dependent selection consistent with sexual reproduction. In addition, both mating types were frequently found occupying the same lesion or leaf, providing opportunities for isolates of opposite mating type to interact and reproduce sexually. We propose that R. secalis should be considered a sexual pathogen, although the sexual cycle may occur infrequently in some populations. PMID:14516764

Linde, Celeste C; Zala, Marcello; Ceccarelli, Sara; McDonald, Bruce A

2003-11-01

45

Global changes in gene expression associated with phenotypic switching of wild yeast  

PubMed Central

Background Saccharomyces cerevisiae strains isolated from natural settings form structured biofilm colonies that are equipped with intricate protective mechanisms. These wild strains are able to reprogram themselves with a certain frequency during cultivation in plentiful laboratory conditions. The resulting domesticated strains switch off certain protective mechanisms and form smooth colonies that resemble those of common laboratory strains. Results Here, we show that domestication can be reversed when a domesticated strain is challenged by various adverse conditions; the resulting feral strain restores its ability to form structured biofilm colonies. Phenotypic, microscopic and transcriptomic analyses show that phenotypic transition is a complex process that affects various aspects of feral strain physiology; it leads to a phenotype that resembles the original wild strain in some aspects and the domesticated derivative in others. We specify the genetic determinants that are likely involved in the formation of a structured biofilm colonies. In addition to FLO11, these determinants include genes that affect the cell wall and membrane composition. We also identify changes occurring during phenotypic transitions that affect other properties of phenotypic strain-variants, such as resistance to the impact of environmental stress. Here we document the regulatory role of the histone deacetylase Hda1p in developing such a resistance. Conclusions We provide detailed analysis of transcriptomic and phenotypic modulations of three related S. cerevisiae strains that arose by phenotypic switching under diverse environmental conditions. We identify changes specifically related to a strain’s ability to create complex structured colonies; we also show that other changes, such as genome rearrangement(s), are unrelated to this ability. Finally, we identify the importance of histone deacetylase Hda1p in strain resistance to stresses. PMID:24533484

2014-01-01

46

Mycological Society of America The Distribution of Mating-Type Bias in Natural Populations of the Anther-Smut Ustilago  

E-print Network

Mycological Society of America The Distribution of Mating-Type Bias in Natural Populations - Jun., 1998), pp. 372-381 Published by: Mycological Society of America Stable URL: http@jstor.org. . Mycological Society of America is collaborating with JSTOR to digitize, preserve and extend access

Antonovics, Janis

47

Analysis of Mycosphaerella Graminicola from California, Indiana, Kansas and North Dakota with Mating Type and SSR Markers  

Technology Transfer Automated Retrieval System (TEKTRAN)

Septoria tritici blotch, caused by Mycosphaerella graminicola, is one of the most important foliar diseases of wheat. Genetic diversity of 333 isolates of M. graminicola collected from spring (California, North Dakota) and winter wheat (Indiana, Kansas) was analyzed for mating type and 17 SSR marker...

48

Connections between RNA splicing and DNA intron mobility in yeast mitochondria: RNA maturase and DNA endonuclease switching experiments.  

PubMed Central

The intron-encoded proteins bI4 RNA maturase and aI4 DNA endonuclease can be faithfully expressed in yeast cytoplasm from engineered forms of their mitochondrial coding sequences. In this work we studied the relationships between these two activities associated with two homologous intron-encoded proteins: the bI4 RNA maturase encoded in the fourth intron of the cytochrome b gene and the aI4 DNA endonuclease (I-SceII) encoded in the fourth intron of the gene coding for the subunit I of cytochrome oxidase. Taking advantage of both the high recombinogenic properties of yeast and the similarities between the two genes, we constructed in vivo a family of hybrid genes carrying parts of both RNA maturase and DNA endonuclease coding sequences. The presence of a sequence coding for a mitochondrial targeting peptide upstream from these hybrid genes allowed us to study the properties of their translation products within the mitochondria in vivo. We thus could analyze the ability of the recombinant proteins to complement RNA maturase deficiencies in different strains. Many combinations of the two parental intronic sequences were found in the recombinants. Their structural and functional analysis revealed the following features. (i) The N-terminal half of the bI4 RNA maturase could be replaced in total by its equivalent from the aI4 DNA endonuclease without affecting the RNA maturase activity. In contrast, replacing the C-terminal half of the bI4 RNA maturase with its equivalent from the aI4 DNA endonuclease led to a very weak RNA maturase activity, indicating that this region is more differentiated and linked to the maturase activity. (ii) None of the hybrid proteins carrying an RNA maturase activity kept the DNA endonuclease activity, suggesting that the latter requires the integrity of the aI4 protein. These observations are interesting because the aI4 DNA endonuclease is known to promote the propagation, at the DNA level, of the aI4 intron, whereas the bI4 RNA maturase, which is required for the splicing of its coding intron, also controls the splicing process of the aI4 intron. We propose a scenario for the evolution of these intronic proteins that relies on a switch from DNA endonuclease to RNA maturase activity. Images PMID:1310149

Goguel, V; Delahodde, A; Jacq, C

1992-01-01

49

DNA polymorphism in recombining and non-recombining mating-type-specific loci of the smut fungus Microbotryum.  

PubMed

The population-genetic processes leading to the genetic degeneration of non-recombining regions have mainly been studied in animal and plant sex chromosomes. Here, we report population genetic analysis of the processes in the non-recombining mating-type-specific regions of the smut fungus Microbotryum violaceum. M. violaceum has A1 and A2 mating types, determined by mating-type-specific 'sex chromosomes' that contain 1-2?Mb long non-recombining regions. If genetic degeneration were occurring, then one would expect reduced DNA polymorphism in the non-recombining regions of this fungus. The analysis of DNA diversity among 19 M. violaceum strains, collected across Europe from Silene latifolia flowers, revealed that (i) DNA polymorphism is relatively low in all 20 studied loci (??0.15%), (ii) it is not significantly different between the two mating-type-specific chromosomes nor between the non-recombining and recombining regions, (iii) there is substantial population structure in M. violaceum populations, which resembles that of its host species, S. latifolia, and (iv) there is significant linkage disequilibrium, suggesting that widespread selfing in this species results in a reduction of the effective recombination rate across the genome. We hypothesise that selfing-related reduction of recombination across the M. violaceum genome negates the difference in the level of DNA polymorphism between the recombining and non-recombining regions, and may possibly lead to similar levels of genetic degeneration in the mating-type-specific regions of the non-recombining 'sex chromosomes' and elsewhere in the genome. PMID:21081967

Votintseva, A A; Filatov, D A

2011-06-01

50

DNA polymorphism in recombining and non-recombing mating-type-specific loci of the smut fungus Microbotryum  

PubMed Central

The population-genetic processes leading to the genetic degeneration of non-recombining regions have mainly been studied in animal and plant sex chromosomes. Here, we report population genetic analysis of the processes in the non-recombining mating-type-specific regions of the smut fungus Microbotryum violaceum. M. violaceum has A1 and A2 mating types, determined by mating-type-specific ‘sex chromosomes' that contain 1–2?Mb long non-recombining regions. If genetic degeneration were occurring, then one would expect reduced DNA polymorphism in the non-recombining regions of this fungus. The analysis of DNA diversity among 19 M. violaceum strains, collected across Europe from Silene latifolia flowers, revealed that (i) DNA polymorphism is relatively low in all 20 studied loci (??0.15%), (ii) it is not significantly different between the two mating-type-specific chromosomes nor between the non-recombining and recombining regions, (iii) there is substantial population structure in M. violaceum populations, which resembles that of its host species, S. latifolia, and (iv) there is significant linkage disequilibrium, suggesting that widespread selfing in this species results in a reduction of the effective recombination rate across the genome. We hypothesise that selfing-related reduction of recombination across the M. violaceum genome negates the difference in the level of DNA polymorphism between the recombining and non-recombining regions, and may possibly lead to similar levels of genetic degeneration in the mating-type-specific regions of the non-recombining ‘sex chromosomes' and elsewhere in the genome. PMID:21081967

Votintseva, A A; Filatov, D A

2011-01-01

51

The Distribution of Mating-Type Bias in Natural Populations of the Anther-Smut Ustilago violacea on Silene alba in Virginia  

E-print Network

Complete individual-wide mating-type bias (retrieval of sporidia of only one mating type from germinated teliospores of one fungal individual) was observed to be a common and widespread feature of the anther-smut fungus, Ustilago violacea, collected...

Oudemans, Peter V.; Alexander, Helen M.; Antonovics, Janice; Altizer, S.; Thrall, Peter H.; Rose, L.

1998-05-01

52

Genetically Engineered Transvestites Reveal Novel Mating Genes in Budding Yeast  

PubMed Central

Haploid budding yeast has two mating types, defined by the alleles of the MAT locus, MATa and MAT?. Two haploid cells of opposite mating types mate by signaling to each other using reciprocal pheromones and receptors, polarizing and growing toward each other, and eventually fusing to form a single diploid cell. The pheromones and receptors are necessary and sufficient to define a mating type, but other mating-type-specific proteins make mating more efficient. We examined the role of these proteins by genetically engineering “transvestite” cells that swap the pheromone, pheromone receptor, and pheromone processing factors of one mating type for another. These cells mate with each other, but their mating is inefficient. By characterizing their mating defects and examining their transcriptomes, we found Afb1 (a-factor barrier), a novel MAT?-specific protein that interferes with a-factor, the pheromone secreted by MATa cells. Strong pheromone secretion is essential for efficient mating, and the weak mating of transvestites can be improved by boosting their pheromone production. Synthetic biology can characterize the factors that control efficiency in biological processes. In yeast, selection for increased mating efficiency is likely to have continually boosted pheromone levels and the ability to discriminate between partners who make more and less pheromone. This discrimination comes at a cost: weak mating in situations where all potential partners make less pheromone. PMID:24121774

Huberman, Lori B.; Murray, Andrew W.

2013-01-01

53

Activation of the Cph1-Dependent MAP Kinase Signaling Pathway Induces White-Opaque Switching in Candida albicans  

PubMed Central

Depending on the environmental conditions, the pathogenic yeast Candida albicans can undergo different developmental programs, which are controlled by dedicated transcription factors and upstream signaling pathways. C. albicans strains that are homozygous at the mating type locus can switch from the normal yeast form (white) to an elongated cell type (opaque), which is the mating-competent form of this fungus. Both white and opaque cells use the Ste11-Hst7-Cek1/Cek2 MAP kinase signaling pathway to react to the presence of mating pheromone. However, while opaque cells employ the transcription factor Cph1 to induce the mating response, white cells recruit a different downstream transcription factor, Tec1, to promote the formation of a biofilm that facilitates mating of opaque cells in the population. The switch from the white to the opaque cell form is itself induced by environmental signals that result in the upregulation of the transcription factor Wor1, the master regulator of white-opaque switching. To get insight into the upstream signaling pathways controlling the switch, we expressed all C. albicans protein kinases from a tetracycline-inducible promoter in a switching-competent strain. Screening of this library of strains showed that a hyperactive form of Ste11 lacking its N-terminal domain (Ste11?N467) efficiently stimulated white cells to switch to the opaque phase, a behavior that did not occur in response to pheromone. Ste11?N467-induced switching specifically required the downstream MAP kinase Cek1 and its target transcription factor Cph1, but not Cek2 and Tec1, and forced expression of Cph1 also promoted white-opaque switching in a Wor1-dependent manner. Therefore, depending on the activation mechanism, components of the pheromone-responsive MAP kinase pathway can be reconnected to stimulate an alternative developmental program, switching of white cells to the mating-competent opaque phase. PMID:24130492

Ramírez-Zavala, Bernardo; Weyler, Michael; Gildor, Tsvia; Schmauch, Christian; Kornitzer, Daniel; Arkowitz, Robert; Morschhäuser, Joachim

2013-01-01

54

Genetic structure of the mating-type locus of Chlamydomonas reinhardtii.  

PubMed

Portions of the cloned mating-type (MT) loci (mt(+) and mt(-)) of Chlamydomonas reinhardtii, defined as the approximately 1-Mb domains of linkage group VI that are under recombinational suppression, were subjected to Northern analysis to elucidate their coding capacity. The four central rearranged segments of the loci were found to contain both housekeeping genes (expressed during several life-cycle stages) and mating-related genes, while the sequences unique to mt(+) or mt(-) carried genes expressed only in the gametic or zygotic phases of the life cycle. One of these genes, Mtd1, is a candidate participant in gametic cell fusion; two others, Mta1 and Ezy2, are candidate participants in the uniparental inheritance of chloroplast DNA. The identified housekeeping genes include Pdk, encoding pyruvate dehydrogenase kinase, and GdcH, encoding glycine decarboxylase complex subunit H. Unusual genetic configurations include three genes whose sequences overlap, one gene that has inserted into the coding region of another, several genes that have been inactivated by rearrangements in the region, and genes that have undergone tandem duplication. This report extends our original conclusion that the MT locus has incurred high levels of mutational change. PMID:11805055

Ferris, Patrick J; Armbrust, E Virginia; Goodenough, Ursula W

2002-01-01

55

Detection of resistance to fungicides, mating types and fitness of Phytophthora infestans in Hebei, China.  

PubMed

In vitro, isolates resistant to metalaxyl (M) and oxadixyl (O) of Phytophthora infestans were 11.2% of 62 isolates from potato and tomato in Hebei Province, mean resistance factor was 15,022 fold and 24,733 fold, respectively, no isolates resistant either to cymoxanil (C) or to dimethomorph (D) were detected. On the other hand, in vivo, isolates resistant to M and O were 29.0% and 32.7%, respectively, among 217 isolates from potato plants in Weichang and Chongli, Hebei, only one isolate resistant to M and O was found among 88 isolates from tomato plants in Xushui, Hebei. Among 73 isolates from potato in Weichang and Chongli, 6 isolates with A2 mating type were 8.2%, 3 A2 isolates resistant to metalaxyl and oxadixyl. 3 A2 isolates were 6.8% of 44 isolates from tomato in Xushui. Cross resistance in Phytophthora infestans was confirmed between M and O, but no cross resistance between C or D and M or O. The field isolates resistant to M and O were outstandingly fitter than sensitive or intermediate ones, mainly due to stronger sporulation capacity of the field isolates. PMID:12701437

Wang, Wen-Qiao; Ma, Zhi-Qiang; Han, Xiu-Ying; Zhang, Xiao-Feng; Chen, Shu-Long

2002-01-01

56

Genetic basis of self-incompatibility in the lichen-forming fungus Lobaria pulmonaria and skewed frequency distribution of mating-type idiomorphs: implications for conservation.  

PubMed

Fungal populations that reproduce sexually are likely to be genetically more diverse and have a higher adaptive potential than asexually reproducing populations. Mating systems of fungal species can be self-incompatible, requiring the presence of isolates of different mating-type genes for sexual reproduction to occur, or self-compatible, requiring only one. Understanding the distribution of mating-type genes in populations can help to assess the potential of self-incompatible species to reproduce sexually. In the locally threatened epiphytic lichen-forming fungus Lobaria pulmonaria (L.) Hoffm., low frequency of sexual reproduction is likely to limit the potential of populations to adapt to changing environmental conditions. Our study provides direct evidence of self-incompatibility (heterothallism) in L. pulmonaria. It can thus be hypothesized that sexual reproduction in small populations might be limited by an unbalanced distribution of mating-type genes. We therefore assessed neutral genetic diversity (using microsatellites) and mating-type ratio in 27 lichen populations (933 individuals). We found significant differences in the frequency of the two mating types in 13 populations, indicating a lower likelihood of sexual reproduction in these populations. This suggests that conservation translocation activities aiming at maximizing genetic heterogeneity in threatened and declining populations should take into account not only presence of fruiting bodies in transplanted individuals, but also the identity and balanced representation of mating-type genes. PMID:23236495

Singh, Garima; Dal Grande, Francesco; Cornejo, Carolina; Schmitt, Imke; Scheidegger, Christoph

2012-01-01

57

Genetic Basis of Self-Incompatibility in the Lichen-Forming Fungus Lobaria pulmonaria and Skewed Frequency Distribution of Mating-Type Idiomorphs: Implications for Conservation  

PubMed Central

Fungal populations that reproduce sexually are likely to be genetically more diverse and have a higher adaptive potential than asexually reproducing populations. Mating systems of fungal species can be self-incompatible, requiring the presence of isolates of different mating-type genes for sexual reproduction to occur, or self-compatible, requiring only one. Understanding the distribution of mating-type genes in populations can help to assess the potential of self-incompatible species to reproduce sexually. In the locally threatened epiphytic lichen-forming fungus Lobaria pulmonaria (L.) Hoffm., low frequency of sexual reproduction is likely to limit the potential of populations to adapt to changing environmental conditions. Our study provides direct evidence of self-incompatibility (heterothallism) in L. pulmonaria. It can thus be hypothesized that sexual reproduction in small populations might be limited by an unbalanced distribution of mating-type genes. We therefore assessed neutral genetic diversity (using microsatellites) and mating-type ratio in 27 lichen populations (933 individuals). We found significant differences in the frequency of the two mating types in 13 populations, indicating a lower likelihood of sexual reproduction in these populations. This suggests that conservation translocation activities aiming at maximizing genetic heterogeneity in threatened and declining populations should take into account not only presence of fruiting bodies in transplanted individuals, but also the identity and balanced representation of mating-type genes. PMID:23236495

Singh, Garima; Dal Grande, Francesco; Cornejo, Carolina; Schmitt, Imke; Scheidegger, Christoph

2012-01-01

58

Systematic Definition of Protein Constituents along the Major Polarization Axis Reveals an Adaptive Reuse of the Polarization Machinery in Pheromone-Treated Budding Yeast  

Microsoft Academic Search

Polarizing cells extensively restructure cellular components in a spatially and temporally coupled manner along the major axis of cellular extension. Budding yeast are a useful model of polarized growth, helping to define many molecular components of this conserved process. Besides budding, yeast cells also differentiate upon treatment with pheromone from the opposite mating type, forming a mating projection (the 'shmoo')

Rammohan Narayanaswamy; Emily K. Moradi; Wei Niu; G. Traver Hart; Matthew Davis; Kriston L. McGary; Andrew D. Ellington; Edward M. Marcotte

2009-01-01

59

Mating type locus of Chinese black truffles reveals heterothallism and the presence of cryptic species within the T. indicum species complex.  

PubMed

Tuber spp. are filamentous ascomycetes which establish symbiosis with the roots of trees and shrub species. By virtue of this symbiosis they produce hypogeous ascocarps, known as truffles. Filamentous ascomycetes can reproduce by homothallism or heterothallism depending on the structure and organization of their mating type locus. The first mating type locus in a truffle species has been recently characterized in Tuber melanosporum and it has been shown that this fungus, endemic in Europe, is heterothallic. The availability of sequence information for T. melanosporum mating type genes is seminal to cloning their orthologs from other Tuber species and assessing their reproductive mode. Here we report on the organization of the mating type region in T. indicum, the black truffle species present in Asia, which is the closest relative to T. melanosporum and is characterized by an high level of morphological and genetic variability. The present study shows that T. indicum is also heterothallic. Examination of Asiatic black truffles belonging to different genetic classes, sorted according to the sequence polymorphism of the internal transcribed spacer rDNA region, has revealed sequence variations and rearrangements in both coding and non-coding regions of the mating type locus, to suggest the existence of cryptic species within the T. indicum complex. The presence of transposable elements within or linked to the mating type region suggests a role of these elements in generating the genotypic diversity present among T. indicum strains. Overall, comparative analyses of the mating type locus have thus allowed us to tackle taxonomical and phylogenetic issues within black truffles and make inferences about the evolution of T. melanosporum-T. indicum lineage. Our results are not only of fundamental but also of applied relevance as T. indicum produces edible fruit bodies that are imported also into Europe and thus may represent a biological threat for T. melanosporum. PMID:24358175

Belfiori, Beatrice; Riccioni, Claudia; Paolocci, Francesco; Rubini, Andrea

2013-01-01

60

Mating Type Locus of Chinese Black Truffles Reveals Heterothallism and the Presence of Cryptic Species within the T. indicum Species Complex  

PubMed Central

Tuber spp. are filamentous ascomycetes which establish symbiosis with the roots of trees and shrub species. By virtue of this symbiosis they produce hypogeous ascocarps, known as truffles. Filamentous ascomycetes can reproduce by homothallism or heterothallism depending on the structure and organization of their mating type locus. The first mating type locus in a truffle species has been recently characterized in Tuber melanosporum and it has been shown that this fungus, endemic in Europe, is heterothallic. The availability of sequence information for T. melanosporum mating type genes is seminal to cloning their orthologs from other Tuber species and assessing their reproductive mode. Here we report on the organization of the mating type region in T. indicum, the black truffle species present in Asia, which is the closest relative to T. melanosporum and is characterized by an high level of morphological and genetic variability. The present study shows that T. indicum is also heterothallic. Examination of Asiatic black truffles belonging to different genetic classes, sorted according to the sequence polymorphism of the internal transcribed spacer rDNA region, has revealed sequence variations and rearrangements in both coding and non-coding regions of the mating type locus, to suggest the existence of cryptic species within the T. indicum complex. The presence of transposable elements within or linked to the mating type region suggests a role of these elements in generating the genotypic diversity present among T. indicum strains. Overall, comparative analyses of the mating type locus have thus allowed us to tackle taxonomical and phylogenetic issues within black truffles and make inferences about the evolution of T. melanosporum-T. indicum lineage. Our results are not only of fundamental but also of applied relevance as T. indicum produces edible fruit bodies that are imported also into Europe and thus may represent a biological threat for T. melanosporum. PMID:24358175

Belfiori, Beatrice; Riccioni, Claudia; Paolocci, Francesco; Rubini, Andrea

2013-01-01

61

Sexual reproduction and mating-type–mediated strain development in the penicillin-producing fungus Penicillium chrysogenum  

PubMed Central

Penicillium chrysogenum is a filamentous fungus of major medical and historical importance, being the original and present-day industrial source of the antibiotic penicillin. The species has been considered asexual for more than 100 y, and despite concerted efforts, it has not been possible to induce sexual reproduction, which has prevented sexual crosses being used for strain improvement. However, using knowledge of mating-type (MAT) gene organization, we now describe conditions under which a sexual cycle can be induced leading to production of meiotic ascospores. Evidence of recombination was obtained using both molecular and phenotypic markers. The identified heterothallic sexual cycle was used for strain development purposes, generating offspring with novel combinations of traits relevant to penicillin production. Furthermore, the MAT1-1–1 mating-type gene, known primarily for a role in governing sexual identity, was also found to control transcription of a wide range of genes with biotechnological relevance including those regulating penicillin production, hyphal morphology, and conidial formation. These discoveries of a sexual cycle and MAT gene function are likely to be of broad relevance for manipulation of other asexual fungi of economic importance. PMID:23307807

Böhm, Julia; Hoff, Birgit; O’Gorman, Céline M.; Wolfers, Simon; Klix, Volker; Binger, Danielle; Zadra, Ivo; Kürnsteiner, Hubert; Pöggeler, Stefanie; Dyer, Paul S.; Kück, Ulrich

2013-01-01

62

Cloning of mating-type gene MAT1-1 from the caterpillar medicinal mushroom, Cordyceps militaris (Ascomycetes) using TAIL-PCR technology.  

PubMed

Cordyceps militaris and Ophiocordyceps sinensis (syn. Cordyceps sinensis), 2 well-known traditional Chinese medicines, contain the same bioactive components and share a similar developmental process. In this study, one C. militaris strain preserved in our laboratory was proven to be a MAT1 mating-type strain using a polymerase chain reaction-based mating-type assay. A 5000-bp nucleotide sequence of the mating-type MAT1-1 from C. militaris was amplified by thermal asymmetric interlaced polymerase chain reaction, but genes within the mating-type MAT1-2 remain undetectable. Sequence analysis shows that the mating-type gene MAT1-1 idiomorph contains 2 genes, MAT1-1-1 and MAT1-1-2. The MAT1-1-1 gene consists of 1480-bp nucleotides that encode 456 amino acids and contain the conserved a-box domain interrupted by 2 introns; the MAT1-1-2 gene consists of 1066 nucleotides that encode 377 amino acids interrupted by one intron. The intervening distance between MAT1-1-1 and MAT1-1-2 is 778 bp. The C. militaris MAT1-1 idiomorph organization is the same as that of Cordyceps takaomontana. The MAT1-1 mating-type idiomorph of both Cordyceps species lacks the MAT1-1-3 gene, which is typically present in Pyrenomycetes. These studies provide some insights for further study of the morphological development of C. militaris and will eventually benefit the domestication of O. sinensis. PMID:25271980

Cong, Wei-Ran; Gong, Zhen-Hua; Shi, Dan-Dan; Guo, Hui; Zhou, Xuanwei

2014-01-01

63

The Yeast Deletion Collection: A Decade of Functional Genomics  

PubMed Central

The yeast deletion collections comprise >21,000 mutant strains that carry precise start-to-stop deletions of ?6000 open reading frames. This collection includes heterozygous and homozygous diploids, and haploids of both MATa and MAT? mating types. The yeast deletion collection, or yeast knockout (YKO) set, represents the first and only complete, systematically constructed deletion collection available for any organism. Conceived during the Saccharomyces cerevisiae sequencing project, work on the project began in 1998 and was completed in 2002. The YKO strains have been used in numerous laboratories in >1000 genome-wide screens. This landmark genome project has inspired development of numerous genome-wide technologies in organisms from yeast to man. Notable spinoff technologies include synthetic genetic array and HIPHOP chemogenomics. In this retrospective, we briefly describe the yeast deletion project and some of its most noteworthy biological contributions and the impact that these collections have had on the yeast research community and on genomics in general. PMID:24939991

Giaever, Guri; Nislow, Corey

2014-01-01

64

Maintenance of Sex-Related Genes and the Co-Occurrence of Both Mating Types in Verticillium dahliae  

PubMed Central

Verticillium dahliae is a cosmopolitan, soilborne fungus that causes a significant wilt disease on a wide variety of plant hosts including economically important crops, ornamentals, and timber species. Clonal expansion through asexual reproduction plays a vital role in recurring plant epidemics caused by this pathogen. The recent discovery of recombination between clonal lineages and preliminary investigations of the meiotic gene inventory of V. dahliae suggest that cryptic sex appears to be rare in this species. Here we expanded on previous findings on the sexual nature of V. dahliae. Only 1% of isolates in a global collection of 1120 phytopathogenic V. dahliae isolates contained the MAT1-1 idiomorph, whereas 99% contained MAT1-2. Nine unique multilocus microsatellite types comprised isolates of both mating types, eight of which were collected from the same substrate at the same time. Orthologs of 88 previously characterized sex-related genes from fungal model systems in the Ascoymycota were identified in the genome of V. dahliae, out of 93 genes investigated. Results of RT-PCR experiments using both mating types revealed that 10 arbitrarily chosen sex-related genes, including MAT1-1-1 and MAT1-2-1, were constitutively expressed in V. dahliae cultures grown under laboratory conditions. Ratios of non-synonymous (amino-acid altering) to synonymous (silent) substitutions in V. dahliae MAT1-1-1 and MAT1-2-1 sequences were indistinguishable from the ratios observed in the MAT genes of sexual fungi in the Pezizomycotina. Patterns consistent with strong purifying selection were also observed in 18 other arbitrarily chosen V. dahliae sex-related genes, relative to the patterns in orthologs from fungi with known sexual stages. This study builds upon recent findings from other laboratories and mounts further evidence for an ancestral or cryptic sexual stage in V. dahliae. PMID:25383550

Hu, Xiaoping; Inderbitzin, Patrik; Subbarao, Krishna V.

2014-01-01

65

Single Cell Visualization of Yeast Gene Expression Shows Correlation of Epigenetic Switching between Multiple Heterochromatic Regions through Multiple Generations  

PubMed Central

Differences in gene expression between individual cells can be mediated by epigenetic regulation; thus, methods that enable detailed analyses of single cells are crucial to understanding this phenomenon. In this study, genomic silencing regions of Saccharomyces cerevisiae that are subject to epigenetic regulation, including the HMR, HML, and telomere regions, were investigated using a newly developed single cell analysis method. This method uses fluorescently labeled proteins to track changes in gene expression over multiple generations of a single cell. Epigenetic control of gene expression differed depending on the specific silencing region at which the reporter gene was inserted. Correlations between gene expression at the HMR-left and HMR-right regions, as well as the HMR-right and HML-right regions, were observed in the single-cell level; however, no such correlations involving the telomere region were observed. Deletion of the histone acetyltransferase GCN5 gene from a yeast strain carrying a fluorescent reporter gene at the HMR-left region reduced the frequency of changes in gene expression over a generation. The results presented here suggest that epigenetic control within an individual cell is reversible and can be achieved via regulation of histone acetyltransferase activity. PMID:23843746

Mano, Yasunobu; Kobayashi, Tetsuya J.; Nakayama, Jun-ichi; Uchida, Hiroyuki; Oki, Masaya

2013-01-01

66

Commercial Fungicide Formulations Induce In Vitro Oospore Formation and Phenotypic Change in Mating Type in Phytophthora infestans.  

PubMed

ABSTRACT A wide range of commercially formulated fungicides cause in vitro effects on mating behavior in specific isolates of Phytophthora infestans, the causal agent of late blight of potato and tomato. Four isolates of P. infestans representing each of the four common US genotypes, US-1, US-6, US-7, and US-8 and varying in their sensitivity to metalaxyl, were exposed to a variety of fungicides used to control late blight in petri dish assays at concentrations ranging from 1 to 100 mug a.i./ml. Exposure of each of these normally heterothallic single mating type isolates of P. infestans to 9 of the 11 commercial fungicide formulations tested resulted in the formation of oospores after 2 to 4 weeks. The highest numbers of oospores were formed on media amended with Ridomil 2E (metalaxyl) and Ridomil Gold EC (mefenoxam) at 0.1 to 10 mug a.i./ml, averaging as many as 471 and 450 oospores per petri dish, respectively. Several other fungicides including Maneb, Manzate (Mancozeb), Curzate (cymoxanil + mancozeb), and Acrobat MZ (dimethomorph + mancozeb) also induced oospore formation, producing from 0 to 200 oospores per plate at fungicide concentrations from 0.1 to 10 mug a.i./ml. The metalaxyl resistant isolates formed oospores in response to the fungicides more often than the metalaxyl sensitive isolates. No oospores were formed on media amended with Bravo (chlorothalonil) or Tattoo C (chlorothalonil + propamocarb HCl) and these compounds completely suppressed growth of the isolates at 0.1 and 1 mug a.i./ml. Three metalaxyl resistant A2 isolates mated with both A1 and A2 isolates after exposure to the fungicides Ridomil 2E and Ridomil Gold EC. Alterations in mating type expression were also observed in a metalaxyl sensitive A1 isolate after exposure to Benlate (benomyl). Copious amounts of chemicals are applied annually to potato and tomato production areas to control late blight. Our results indicate that a wide range of chemically diverse fungicides can induce normally heterothallic metalaxyl resistant isolates of P. infestans to form oospores in vitro after short exposures to the fungicides. PMID:18944421

Groves, C T; Ristaino, J B

2000-11-01

67

Diversity of the Lactic Acid Bacterium and Yeast Microbiota in the Switch from Firm- to Liquid-Sourdough Fermentation  

PubMed Central

Four traditional type I sourdoughs were comparatively propagated (28 days) under firm (dough yield, 160) and liquid (dough yield, 280) conditions to mimic the alternative technology options frequently used for making baked goods. After 28 days of propagation, liquid sourdoughs had the lowest pH and total titratable acidity (TTA), the lowest concentrations of lactic and acetic acids and free amino acids, and the most stable density of presumptive lactic acid bacteria. The cell density of yeasts was the highest in liquid sourdoughs. Liquid sourdoughs showed simplified microbial diversity and harbored a low number of strains, which were persistent. Lactobacillus plantarum dominated firm sourdoughs over time. Leuconostoc lactis and Lactobacillus brevis dominated only some firm sourdoughs, and Lactobacillus sanfranciscensis persisted for some time only in some firm sourdoughs. Leuconostoc citreum persisted in all firm and liquid sourdoughs, and it was the only species detected in liquid sourdoughs at all times; it was flanked by Leuconostoc mesenteroides in some sourdoughs. Saccharomyces cerevisiae, Candida humilis, Saccharomyces servazzii, Saccharomyces bayanus-Kazachstania sp., and Torulaspora delbrueckii were variously identified in firm and liquid sourdoughs. A total of 197 volatile components were identified through purge and trap–/solid-phase microextraction–gas chromatography-mass spectrometry (PT–/SPME–GC-MS). Aldehydes, several alcohols, and some esters were at the highest levels in liquid sourdoughs. Firm sourdoughs mainly contained ethyl acetate, acetic acid, some sulfur compounds, and terpenes. The use of liquid fermentation would change the main microbial and biochemical features of traditional baked goods, which have been manufactured under firm conditions for a long time. PMID:24632249

Di Cagno, Raffaella; Pontonio, Erica; Buchin, Solange; De Angelis, Maria; Lattanzi, Anna; Valerio, Francesca; Calasso, Maria

2014-01-01

68

Structure and function of the mating-type locus in the homothallic ascomycete, Didymella zeae-maydis.  

PubMed

Homothallic Didymella zeae-maydis undergoes sexual reproduction by selfing. Sequence analysis of the mating type (MAT) locus from this fungus revealed that MAT carries both MAT1-1-1 and MAT1-2-1 genes found in heterothallic Dothideomycetes, separated by ?1.0 kb of noncoding DNA. To understand the mechanistic basis of homothallism in D. zeae-maydis, each of the MAT genes was deleted and the effects on selfing and on ability to cross in a heterothallic manner were determined. The strain carrying an intact MAT1-1-1 but defective MAT1-2-1 gene (MAT1-1-1;?MAT1-2-1) was self-sterile, however strains carrying an intact MAT1-2-1 but defective MAT1-1-1 gene (?MAT1-1-1;MAT1-2-1), when selfed, showed delayed production of a few ascospores. Attempts to cross the two MAT deletion strains yielded fewer ?MAT1-1-1;MAT1-2-1 than MAT1-1-1;?MAT1-2-1 progeny and very few ascospores overall compared to WT selfs. This study demonstrates that, as in the other homothallic Dothideomycetes, both MAT genes are required for full fertility, but that, in contrast to other cases, the presence of a single MAT1-2-1 gene can induce homothallism, albeit inefficiently, in D. zeae-maydis. PMID:24385359

Yun, Sung-Hwan; Yoder, Olen C; Turgeon, B Gillian

2013-12-01

69

A fungal mating type protein that regulates sexual and asexual development contains a POU-related domain.  

PubMed

The A mating type factor of the fungus Coprinus cinereus regulates essential steps in sexual development. Here we describe features of one of the four specificity genes of the A42 factor. By transformation we show that the gene regulates not only sexual development but also asexual sporulation. DNA sequence analysis shows that the gene beta 1-1, encodes a protein with a DNA binding motif and is thus likely to be a transcription factor. The DNA binding domain is an unusual homeodomain with D replacing the normally invariant N in the recognition helix and apparent absence of helix II. The homeodomain is linked to a helical region related to the POUs domain, which is part of a bipartite DNA binding domain of certain animal transcription factors. Like POU factors, the beta 1-1 protein has regions rich in serine, threonine and proline which are possible transactivation domains. Putative dimerization domains and sites for post-translational modification are described. PMID:1582410

Tymon, A M; Kües, U; Richardson, W V; Casselton, L A

1992-05-01

70

Degeneration in Codon Usage within the Region of Suppressed Recombination in the Mating-Type Chromosomes of Neurospora tetrasperma ? †  

PubMed Central

The origin and early evolution of sex chromosomes are currently poorly understood. The Neurospora tetrasperma mating-type (mat) chromosomes have recently emerged as a model system for the study of early sex chromosome evolution, since they contain a young (<6 million years ago [Mya]), large (>6.6-Mb) region of suppressed recombination. Here we examined preferred-codon usage in 290 genes (121,831 codon positions) in order to test for early signs of genomic degeneration in N. tetrasperma mat chromosomes. We report several key findings about codon usage in the region of recombination suppression, including the following: (i) this region has been subjected to marked and largely independent degeneration among gene alleles; (ii) the level of degeneration is magnified over longer periods of recombination suppression; and (iii) both mat a and mat A chromosomes have been subjected to deterioration. The frequency of shifts from preferred codons to nonpreferred codons is greater for shorter genes than for longer genes, suggesting that short genes play an especially significant role in early sex chromosome evolution. Furthermore, we show that these degenerative changes in codon usage are best explained by altered selection efficiency in the recombinationally suppressed region. These findings demonstrate that the fungus N. tetrasperma provides an effective system for the study of degenerative genomic changes in young regions of recombination suppression in sex-regulating chromosomes. PMID:21335530

Whittle, C. A.; Sun, Y.; Johannesson, H.

2011-01-01

71

The RAD7 and RAD16 genes, which are essential for pyrimidine dimer removal from the silent mating type loci, are also required for repair of the nontranscribed strand of an active gene in Saccharomyces cerevisiae.  

PubMed Central

The rad16 mutant of Saccharomyces cerevisiae was previously shown to be impaired in removal of UV-induced pyrimidine dimers from the silent mating-type loci (D. D. Bang, R. A. Verhage, N. Goosen, J. Brouwer, and P. van de Putte, Nucleic Acids Res. 20:3925-3931, 1992). Here we show that rad7 as well as rad7 rad16 double mutants have the same repair phenotype, indicating that the RAD7 and RAD16 gene products might operate in the same nucleotide excision repair subpathway. Dimer removal from the genome overall is essentially incomplete in these mutants, leaving about 20 to 30% of the DNA unrepaired. Repair analysis of the transcribed RPB2 gene shows that the nontranscribed strand is not repaired at all in rad7 and rad16 mutants, whereas the transcribed strand is repaired in these mutants at a fast rate similar to that in RAD+ cells. When the results obtained with the RPB2 gene can be generalized, the RAD7 and RAD16 proteins not only are essential for repair of silenced regions but also function in repair of nontranscribed strands of active genes in S. cerevisiae. The phenotype of rad7 and rad16 mutants closely resembles that of human xeroderma pigmentosum complementation group C (XP-C) cells, suggesting that RAD7 and RAD16 in S. cerevisiae function in the same pathway as the XPC gene in human cells. RAD4, which on the basis of sequence homology has been proposed to be the yeast XPC counterpart, seems to be involved in repair of both inactive and active yeast DNA, challenging the hypothesis that RAD4 and XPC are functional homologs. Images PMID:8065346

Verhage, R; Zeeman, A M; de Groot, N; Gleig, F; Bang, D D; van de Putte, P; Brouwer, J

1994-01-01

72

Fine-scale spatial genetic structure of the black truffle (Tuber melanosporum) investigated with neutral microsatellites and functional mating type genes.  

PubMed

The genetic structure of ectomycorrhizal (ECM) fungal populations results from both vegetative and sexual propagation. In this study, we have analysed the spatial genetic structure of Tuber melanosporum populations, a heterothallic ascomycete that produces edible fruit bodies. Ectomycorrhizas from oaks and hazels from two orchards were mapped and genotyped using simple sequence repeat markers and the mating type locus. The distribution of the two T. melanosporum mating types was also monitored in the soil. In one orchard, the genetic profiles of the ascocarps were compared with those of the underlying mycorrhizas. A pronounced spatial genetic structure was found. The maximum genet sizes were 2.35 and 4.70 m in the two orchards, with most manifesting a size < 1 m. Few genets persisted throughout two seasons. A nonrandom distribution pattern of the T. melanosporum was observed, resulting in field patches colonized by genets that shared the same mating types. Our findings suggest that competition occurs between genets and provide basic information on T. melanosporum propagation patterns that are relevant for the management of productive truffle orchards. PMID:23574460

Murat, Claude; Rubini, Andrea; Riccioni, Claudia; De la Varga, Herminia; Akroume, Emila; Belfiori, Beatrice; Guaragno, Marco; Le Tacon, François; Robin, Christophe; Halkett, Fabien; Martin, Francis; Paolocci, Francesco

2013-07-01

73

Impact of the competition between mating types on the cultivation of Tuber melanosporum: Romeo and Juliet and the matter of space and time.  

PubMed

Major breakthroughs in our understanding of the life cycles of the symbiotic ascomycetes belonging to the genus Tuber have occurred over the last several years. A number of Tuber species produce edible fruiting bodies, known as truffles, that are marketed worldwide. A better understanding of the basic biological characteristics of Tuber spp. is likely to have tremendous practical relevance for their cultivation. Tuber melanosporum produces the most valuable black truffles and its genome has been recently sequenced. This species is now serving as a model for studying the biology of truffles. Here, we review recent progress in the understanding of sexual reproduction modalities in T. melanosporum. The practical relevance of these findings is outlined. In particular, the discoveries that T. melanosporum is heterothallic and that strains of different mating types compete to persist on the roots of host plants suggest that the spatial and temporal distributional patterns of strains of different mating types are key determinants of truffle fructification. The spatial segregation of the two mating types in areas where T. melanosporum occurs likely limits truffle production. Thus, host plant inoculation techniques and agronomic practices that might be pursued to manage T. melanosporum orchards with a balanced presence of the two mating partners are described. PMID:24384788

Rubini, Andrea; Riccioni, Claudia; Belfiori, Beatrice; Paolocci, Francesco

2014-04-01

74

Steps in Assembly of Silent Chromatin in Yeast: Sir3Independent Binding of a Sir2\\/Sir4 Complex to Silencers and Role for Sir2Dependent Deacetylation  

Microsoft Academic Search

Transcriptional silencing at the budding yeast silent mating type (HM) loci and telomeric DNA regions requires Sir2, a conserved NAD-dependent histone deacetylase, Sir3, Sir4, histones H3 and H4, and several DNA-binding proteins. Silencing at the yeast ribosomal DNA (rDNA) repeats requires a complex containing Sir2, Net1, and Cdc14. Here we show that the native Sir2\\/Sir4 complex is composed solely of

Georg J. Hoppe; Jason C. Tanny; Adam D. Rudner; Scott A. Gerber; Sherwin Danaie; Steven P. Gygi; Danesh Moazed

2002-01-01

75

Chromosomal Inheritance of Epigenetic States in Fission Yeast During Mitosis and Meiosis  

Microsoft Academic Search

Inheritance of the active and inactive states of gene expression by individual cells is crucial for development. In fission yeast, mating-type region consists of three loci called mat1, mat2, and mat3. Transcriptionally silent mat2 and mat3 loci are separated by a 15 kb interval, designated the K-region, and serve as donors of information for transcriptionally active mat1 interconversion. In a

Shiv I. S. Grewal; Amar J. S. Klar

1996-01-01

76

Fission Yeast Pxd1 Promotes Proper DNA Repair by Activating Rad16XPF and Inhibiting Dna2  

PubMed Central

Structure-specific nucleases play crucial roles in many DNA repair pathways. They must be precisely controlled to ensure optimal repair outcomes; however, mechanisms of their regulation are not fully understood. Here, we report a fission yeast protein, Pxd1, that binds to and regulates two structure-specific nucleases: Rad16XPF-Swi10ERCC1 and Dna2-Cdc24. Strikingly, Pxd1 influences the activities of these two nucleases in opposite ways: It activates the 3? endonuclease activity of Rad16-Swi10 but inhibits the RPA-mediated activation of the 5? endonuclease activity of Dna2. Pxd1 is required for Rad16-Swi10 to function in single-strand annealing, mating-type switching, and the removal of Top1-DNA adducts. Meanwhile, Pxd1 attenuates DNA end resection mediated by the Rqh1-Dna2 pathway. Disabling the Dna2-inhibitory activity of Pxd1 results in enhanced use of a break-distal repeat sequence in single-strand annealing and a greater loss of genetic information. We propose that Pxd1 promotes proper DNA repair by differentially regulating two structure-specific nucleases. PMID:25203555

Zhang, Jia-Min; Liu, Xiao-Man; Ding, Yue-He; Xiong, Liang-Yao; Ren, Jing-Yi; Zhou, Zhi-Xiong; Wang, Hai-Tao; Zhang, Mei-Jun; Yu, Yang; Dong, Meng-Qiu; Du, Li-Lin

2014-01-01

77

Genetic Diversity and Mating Type Distribution of Tuber melanosporum and Their Significance to Truffle Cultivation in Artificially Planted Truffiéres in Australia  

PubMed Central

Tuber melanosporum is a truffle native to Europe and is cultivated in countries such as Australia for the gastronomic market, where production yields are often lower than expected. We assessed the genetic diversity of T. melanosporum with six microsatellite loci to assess the effect of genetic drift on truffle yield in Australia. Genetic diversity as assessed on 210 ascocarps revealed a higher allelic diversity compared to previous studies from Europe, suggesting a possible genetic expansion and/or multiple and diverse source populations for inoculum. The results also suggest that the single sequence repeat diversity of locus ME2 is adaptive and that, for example, the probability of replication errors is increased for this locus. Loss of genetic diversity in Australian populations is therefore not a likely factor in limiting ascocarp production. A survey of nursery seedlings and trees inoculated with T. melanosporum revealed that <70% of seedlings and host trees were colonized with T. melanosporum and that some trees had been contaminated by Tuber brumale, presumably during the inoculation process. Mating type (MAT1-1-1 and MAT1-2-1) analyses on seedling and four- to ten-year-old host trees found that 100% of seedlings but only approximately half of host trees had both mating types present. Furthermore, MAT1-1-1 was detected significantly more commonly than MAT1-2-1 in established trees, suggesting a competitive advantage for MAT1-1-1 strains. This study clearly shows that there are more factors involved in ascocarp production than just the presence of both mating types on host trees. PMID:22773652

Selmes, H.

2012-01-01

78

Genetic diversity and mating type distribution of Tuber melanosporum and their significance to truffle cultivation in artificially planted truffieres in Australia.  

PubMed

Tuber melanosporum is a truffle native to Europe and is cultivated in countries such as Australia for the gastronomic market, where production yields are often lower than expected. We assessed the genetic diversity of T. melanosporum with six microsatellite loci to assess the effect of genetic drift on truffle yield in Australia. Genetic diversity as assessed on 210 ascocarps revealed a higher allelic diversity compared to previous studies from Europe, suggesting a possible genetic expansion and/or multiple and diverse source populations for inoculum. The results also suggest that the single sequence repeat diversity of locus ME2 is adaptive and that, for example, the probability of replication errors is increased for this locus. Loss of genetic diversity in Australian populations is therefore not a likely factor in limiting ascocarp production. A survey of nursery seedlings and trees inoculated with T. melanosporum revealed that <70% of seedlings and host trees were colonized with T. melanosporum and that some trees had been contaminated by Tuber brumale, presumably during the inoculation process. Mating type (MAT1-1-1 and MAT1-2-1) analyses on seedling and four- to ten-year-old host trees found that 100% of seedlings but only approximately half of host trees had both mating types present. Furthermore, MAT1-1-1 was detected significantly more commonly than MAT1-2-1 in established trees, suggesting a competitive advantage for MAT1-1-1 strains. This study clearly shows that there are more factors involved in ascocarp production than just the presence of both mating types on host trees. PMID:22773652

Linde, C C; Selmes, H

2012-09-01

79

Tracing the Origin of the Fungal ?1 Domain Places Its Ancestor in the HMG-Box Superfamily: Implication for Fungal Mating-Type Evolution  

PubMed Central

Background Fungal mating types in self-incompatible Pezizomycotina are specified by one of two alternate sequences occupying the same locus on corresponding chromosomes. One sequence is characterized by a gene encoding an HMG protein, while the hallmark of the other is a gene encoding a protein with an ?1 domain showing similarity to the Mat?1p protein of Saccharomyces cerevisiae. DNA-binding HMG proteins are ubiquitous and well characterized. In contrast, ?1 domain proteins have limited distribution and their evolutionary origin is obscure, precluding a complete understanding of mating-type evolution in Ascomycota. Although much work has focused on the role of the S. cerevisiae Mat?1p protein as a transcription factor, it has not yet been placed in any of the large families of sequence-specific DNA-binding proteins. Methodology/Principal Findings We present sequence comparisons, phylogenetic analyses, and in silico predictions of secondary and tertiary structures, which support our hypothesis that the ?1 domain is related to the HMG domain. We have also characterized a new conserved motif in ?1 proteins of Pezizomycotina. This motif is immediately adjacent to and downstream of the ?1 domain and consists of a core sequence Y-[LMIF]-x(3)-G-[WL] embedded in a larger conserved motif. Conclusions/Significance Our data suggest that extant ?1-box genes originated from an ancestral HMG gene, which confirms the current model of mating-type evolution within the fungal kingdom. We propose to incorporate ?1 proteins in a new subclass of HMG proteins termed MAT?_HMG. PMID:21170349

van Tilbeurgh, Herman; Ripoll, Daniel R.; Dixelius, Christina; Turgeon, B. Gillian; Debuchy, Robert

2010-01-01

80

Size and competitive mating success in the yeast Saccharomyces cerevisiae  

PubMed Central

In unicellular organisms like yeast, mating with the right partner is critical to future fitness because each individual can only mate once. Because cell size is important for viability, mating with a partner of the right size could be a significant advantage. To investigate this idea, we manipulated the size of unmated yeast cells and showed that their viability depended on environmental conditions; large cells do better on rich medium and small cells do better on poor medium. We also found that the fitness of offspring is determined by the size of their parents. Finally, we demonstrated that when a focal cell of one mating type was placed with a large and a small cell of the opposite mating type, it was more likely to mate with the cell that was closer to the optimum size for growth in a given environment. This pattern was not generated by differences in passive mating efficiency of large and small cells across environments but by competitive mating behavior, mate preference, or both. We conclude that the most likely mechanism underlying this interesting behavior is that yeast cells compete for mates by producing pheromone signals advertising their viability, and cells with the opportunity to choose prefer to mate with stronger signalers because such matings produce more viable offspring. PMID:24616602

2014-01-01

81

The Nuclease Activity of Mre11 Is Required for Meiosis but Not for Mating Type Switching, End Joining, or Telomere Maintenance  

Microsoft Academic Search

The Saccharomyces cerevisiae MRE11 gene is required for the repair of ionizing radiation-induced DNA damage and for the initiation of meiotic recombination. Sequence analysis has revealed homology between Mre11 and SbcD, the catalytic subunit of an Escherichia coli enzyme with endo- and exonuclease activity, SbcCD. In this study, the purified Mre11 protein was found to have single-stranded endonuclease activity. This

SYLVIE MOREAU; JOHN R. FERGUSON; LORRAINE S. SYMINGTON

82

Grapevine MATE-Type Proteins Act as Vacuolar H+-Dependent Acylated Anthocyanin Transporters1[W][OA  

PubMed Central

In grapevine (Vitis vinifera), anthocyanins are responsible for most of the red, blue, and purple pigmentation found in the skin of berries. In cells, anthocyanins are synthesized in the cytoplasm and accumulated into the vacuole. However, little is known about the transport of these compounds through the tonoplast. Recently, the sequencing of the grapevine genome allowed us to identify genes encoding proteins with high sequence similarity to the Multidrug And Toxic Extrusion (MATE) family. Among them, we selected two genes as anthocyanin transporter candidates and named them anthoMATE1 (AM1) and AM3. The expression of both genes was mainly fruit specific and concomitant with the accumulation of anthocyanin pigment. Subcellular localization assays in grapevine hairy roots stably transformed with AM1? or AM3?green fluorescent protein fusion protein revealed that AM1 and AM3 are primarily localized to the tonoplast. Yeast vesicles expressing anthoMATEs transported acylated anthocyanins in the presence of MgATP. Inhibitor studies demonstrated that AM1 and AM3 proteins act in vitro as vacuolar H+-dependent acylated anthocyanin transporters. By contrast, under our experimental conditions, anthoMATEs could not transport malvidin 3-O-glucoside or cyanidin 3-O-glucoside, suggesting that the acyl conjugation was essential for the uptake. Taken together, these results provide evidence that in vitro the two grapevine AM1 and AM3 proteins mediate specifically acylated anthocyanin transport. PMID:19297587

Gomez, Camila; Terrier, Nancy; Torregrosa, Laurent; Vialet, Sandrine; Fournier-Level, Alexandre; Verriès, Clotilde; Souquet, Jean-Marc; Mazauric, Jean-Paul; Klein, Markus; Cheynier, Véronique; Ageorges, Agnès

2009-01-01

83

Isolation of the MAT1-1 mating type idiomorph and evidence for selfing in the Chinese medicinal fungus Ophiocordyceps sinensis.  

PubMed

Ophiocordyceps sinensis is one of the most valued medicinal fungi in China. Research on the mating system and sexual development is vitally important to this endangered species. Previous efforts devoted to investigate the mating type (MAT) locus of O. sinensis, however, resulted in an incomplete understanding. In this study, the MAT1-1 locus of O. sinensis was investigated. The conserved ?-box and HMG-box regions of the MAT1-1-1 and MAT1-1-3 genes, respectively, and a conserved region of the DNA lyase gene were successfully amplified using degenerate PCR. A combination of TAIL-PCR and long-range PCR were used to connect these genes and obtain the sequence of the MAT1-1 locus. Screening of 22 single spore isolates by PCR demonstrated that both the MAT1-1-1 and MAT1-2-1 genes cooccurred within the same isolate. Additionally, both MAT1-1-1 and MAT1-2-1 are expressed in vegetative mycelia, providing evidence that O. sinensis is likely capable of selfing. DAPI (4,6-diamidino-2-phenylindole) staining of ascospores and hyphae showed that a majority of hyphal compartments are binucleate, suggesting that O. sinensis may be pseudohomothallic. Analyses of sequence diversity showed lower levels of genetic diversity in MAT1-1-1 compared to MAT1-2-1, indicating the possibility that different selective pressures act on the two MAT idiomorphs. The MAT1-1-1 sequences of O. sinensis and Tolypocladium inflatum cluster as a monophyletic group consistent with phylogenetic classification of Ophiocordycipitaceae. Comparison of the structure of the MAT1-1 locus across hypocrealean taxa showed that O. sinensis contains all three mating type genes (MAT1-1-1, MAT1-1-2, and MAT1-1-3) and supported previous observations that of the four families in Hypocreales, MAT1-1-3 has undergone a lineage specific loss only in some members of the Cordycipitaceae. PMID:24012300

Bushley, Kathryn E; Li, Yi; Wang, Wen-Jing; Wang, Xiao-Liang; Jiao, Lei; Spatafora, Joseph W; Yao, Yi-Jian

2013-09-01

84

RNA Methylation by the MIS Complex Regulates a Cell Fate Decision in Yeast  

E-print Network

For the yeast Saccharomyces cerevisiae, nutrient limitation is a key developmental signal causing diploid cells to switch from yeast-form budding to either foraging pseudohyphal (PH) growth or meiosis and sporulation. ...

Agarwala, Sundeep

85

SIR Functions Are Required for the Toleration of an Unrepaired Double-Strand Break in a Dispensable Yeast Chromosome  

PubMed Central

Unrepaired DNA double-strand breaks (DSBs) typically result in G2 arrest. Cell cycle progression can resume following repair of the DSBs or through adaptation to the checkpoint, even if the damage remains unrepaired. We developed a screen for factors in the yeast Saccharomyces cerevisiae that affect checkpoint control and/or viability in response to a single, unrepairable DSB that is induced by HO endonuclease in a dispensable yeast artificial chromosome containing human DNA. SIR2, -3, or -4 mutants exhibit a prolonged, RAD9-dependent G2 arrest in response to the unrepairable DSB followed by a slow adaptation to the persistent break, leading to division and rearrest in the next G2. There are a small number of additional cycles before permanent arrest as microcolonies. Thus, SIR genes, which repress silent mating type gene expression, are required for the adaptation and the prevention of indirect lethality resulting from an unrepairable DSB in nonessential DNA. Rapid adaptation to the G2 checkpoint and high viability were restored in sir? strains containing additional deletions of the silent mating type loci HML and HMR, suggesting that genes under mating type control can reduce the toleration of a single DSB. However, coexpression of MATa1 and MAT?2 in Sir+ haploid cells did not lead to lethality from the HO-induced DSB, suggesting that toleration of an unrepaired DSB requires more than one Sir+ function. PMID:11463819

Bennett, Craig B.; Snipe, Joyce R.; Westmoreland, James W.; Resnick, Michael A.

2001-01-01

86

DNA Sequence Characterization and Molecular Evolution of MAT1 and MAT2 Mating-Type Loci of the Self-Compatible Ascomycete Mold Neosartorya fischeri?  

PubMed Central

Degenerate PCR and chromosome-walking approaches were used to identify mating-type (MAT) genes and flanking regions from the homothallic (sexually self-fertile) euascomycete fungus Neosartorya fischeri, a close relative of the opportunistic human pathogen Aspergillus fumigatus. Both putative alpha- and high-mobility-group-domain MAT genes were found within the same genome, providing a functional explanation for self-fertility. However, unlike those in many homothallic euascomycetes (Pezizomycotina), the genes were not found adjacent to each other and were termed MAT1 and MAT2 to recognize the presence of distinct loci. Complete copies of putative APN1 (DNA lyase) and SLA2 (cytoskeleton assembly control) genes were found bordering the MAT1 locus. Partial copies of APN1 and SLA2 were also found bordering the MAT2 locus, but these copies bore the genetic hallmarks of pseudogenes. Genome comparisons revealed synteny over at least 23,300 bp between the N. fischeri MAT1 region and the A. fumigatus MAT locus region, but no such long-range conservation in the N. fischeri MAT2 region was evident. The sequence upstream of MAT2 contained numerous candidate transposase genes. These results demonstrate a novel means involving the segmental translocation of a chromosomal region by which the ability to undergo self-fertilization may be acquired. The results are also discussed in relation to their significance in indicating that heterothallism may be ancestral within the Aspergillus section Fumigati. PMID:17384199

Rydholm, C.; Dyer, P. S.; Lutzoni, F.

2007-01-01

87

Evidence of the accumulation of allele-specific non-synonymous substitutions in the young region of recombination suppression within the mating-type chromosomes of Neurospora tetrasperma  

PubMed Central

Currently, little is known about the origin and early evolution of sex chromosomes. This is largely due to the fact that ancient non-recombining sex chromosomes are highly degenerated, and thus provide little information about the early genomic events in their evolution. The Neurospora tetrasperma mating-type (mat) chromosomes contain a young (<6 Mya) and large region (>6.6?Mb) of suppressed recombination, thereby providing a model system to study early stages of sex chromosome evolution. Here, we examined alleles of 207 genes located on the N. tetrasperma mat a and mat A chromosomes to test for signs of genomic alterations at the protein level in the young region of recombination suppression. We report that the N. tetrasperma mat a and mat A chromosomes have each independently accumulated allele-specific non-synonymous codon substitutions in a time-dependent, and gene-specific manner in the recombinationally suppressed region. In addition, examination of the ratio (?) of non-synonymous substitutions (dN) to synonymous substitutions (dS) using maximum likelihood analyses, indicates that such changes are associated with relaxed purifying selection, a finding consistent with genomic degeneration. We also reveal that sex specific biases in mutation rates or selection pressures are not necessary for genomic alterations in sex chromosomes, and that recombination suppression in itself is sufficient to explain these results. The present findings extend our current understanding of genomic events associated within the young region of recombination suppression in these fungal sex-regulating chromosomes. PMID:21386869

Whittle, C A; Johannesson, H

2011-01-01

88

Genomes of Ashbya Fungi Isolated from Insects Reveal Four Mating-Type Loci, Numerous Translocations, Lack of Transposons, and Distinct Gene Duplications  

PubMed Central

The filamentous fungus Ashbya gossypii is a cotton pathogen transmitted by insects. It is readily grown and manipulated in the laboratory and is commercially exploited as a natural overproducer of vitamin B2. Our previous genome analysis of A. gossypii isolate ATCC10895, collected in Trinidad nearly 100 years ago, revealed extensive synteny with the Saccharomyces cerevisiae genome, leading us to use it as a model organism to understand the evolution of filamentous growth. To further develop Ashbya as a model system, we have investigated the ecological niche of A. gossypii and isolated additional strains and a sibling species, both useful in comparative analysis. We isolated fungi morphologically similar to A. gossypii from different plant-feeding insects of the suborder Heteroptera, generated a phylogenetic tree based on rDNA-ITS sequences, and performed high coverage short read sequencing with one A. gossypii isolate from Florida, a new species, Ashbya aceri, isolated in North Carolina, and a genetically marked derivative of ATCC10895 intensively used for functional studies. In contrast to S. cerevisiae, all strains carry four not three mating type loci, adding a new puzzle in the evolution of Ashbya species. Another surprise was the genome identity of 99.9% between the Florida strain and ATCC10895, isolated in Trinidad. The A. aceri and A. gossypii genomes show conserved gene orders rearranged by eight translocations, 90% overall sequence identity, and fewer tandem duplications in the A. aceri genome. Both species lack transposable elements. Finally, our work identifies plant-feeding insects of the suborder Heteroptera as the most likely natural reservoir of Ashbya, and that infection of cotton and other plants may be incidental to the growth of the fungus in its insect host. PMID:23749448

Dietrich, Fred S.; Voegeli, Sylvia; Kuo, Sidney; Philippsen, Peter

2013-01-01

89

Alternative mating type configurations (a/? versus a/a or ?/?) of Candida albicans result in alternative biofilms regulated by different pathways.  

PubMed

Similar multicellular structures can evolve within the same organism that may have different evolutionary histories, be controlled by different regulatory pathways, and play similar but nonidentical roles. In the human fungal pathogen Candida albicans, a quite extraordinary example of this has occurred. Depending upon the configuration of the mating type locus (a/? versus a/a or ?/?), C. albicans forms alternative biofilms that appear similar morphologically, but exhibit dramatically different characteristics and are regulated by distinctly different signal transduction pathways. Biofilms formed by a/? cells are impermeable to molecules in the size range of 300 Da to 140 kDa, are poorly penetrated by human polymorphonuclear leukocytes (PMNs), and are resistant to antifungals. In contrast, a/a or ?/? biofilms are permeable to molecules in this size range, are readily penetrated by PMNs, and are susceptible to antifungals. By mutational analyses, a/? biofilms are demonstrated to be regulated by the Ras1/cAMP pathway that includes Ras1?Cdc35?cAMP(Pde2-|)?Tpk2(Tpk1)?Efg1?Tec1?Bcr1, and a/a biofilms by the MAP kinase pathway that includes Mf??Ste2? (Ste4, Ste18, Cag1)?Ste11?Hst7?Cek2(Cek1)?Tec1. These observations suggest the hypothesis that while the upstream portion of the newly evolved pathway regulating a/a and ?/? cell biofilms was derived intact from the upstream portion of the conserved pheromone-regulated pathway for mating, the downstream portion was derived through modification of the downstream portion of the conserved pathway for a/? biofilm formation. C. albicans therefore forms two alternative biofilms depending upon mating configuration. PMID:21829325

Yi, Song; Sahni, Nidhi; Daniels, Karla J; Lu, Kevin L; Srikantha, Thyagarajan; Huang, Guanghua; Garnaas, Adam M; Soll, David R

2011-08-01

90

Alternative Mating Type Configurations (a/? versus a/a or ?/?) of Candida albicans Result in Alternative Biofilms Regulated by Different Pathways  

PubMed Central

Similar multicellular structures can evolve within the same organism that may have different evolutionary histories, be controlled by different regulatory pathways, and play similar but nonidentical roles. In the human fungal pathogen Candida albicans, a quite extraordinary example of this has occurred. Depending upon the configuration of the mating type locus (a/? versus a/a or ?/?), C. albicans forms alternative biofilms that appear similar morphologically, but exhibit dramatically different characteristics and are regulated by distinctly different signal transduction pathways. Biofilms formed by a/? cells are impermeable to molecules in the size range of 300 Da to 140 kDa, are poorly penetrated by human polymorphonuclear leukocytes (PMNs), and are resistant to antifungals. In contrast, a/a or ?/? biofilms are permeable to molecules in this size range, are readily penetrated by PMNs, and are susceptible to antifungals. By mutational analyses, a/? biofilms are demonstrated to be regulated by the Ras1/cAMP pathway that includes Ras1?Cdc35?cAMP(Pde2—|)?Tpk2(Tpk1)?Efg1?Tec1?Bcr1, and a/a biofilms by the MAP kinase pathway that includes Mf??Ste2? (Ste4, Ste18, Cag1)?Ste11?Hst7?Cek2(Cek1)?Tec1. These observations suggest the hypothesis that while the upstream portion of the newly evolved pathway regulating a/a and ?/? cell biofilms was derived intact from the upstream portion of the conserved pheromone-regulated pathway for mating, the downstream portion was derived through modification of the downstream portion of the conserved pathway for a/? biofilm formation. C. albicans therefore forms two alternative biofilms depending upon mating configuration. PMID:21829325

Srikantha, Thyagarajan; Huang, Guanghua; Garnaas, Adam M.; Soll, David R.

2011-01-01

91

Yeast Infections  

MedlinePLUS

Candida is the scientific name for yeast. It is a fungus that lives almost everywhere, including in ... infection that causes white patches in your mouth Candida esophagitis is thrush that spreads to your esophagus, ...

92

Rare-Cell Fusion Events between Diploid and Haploid Strains of the Sexually Agglutinative Yeast HANSENULA WINGEI  

PubMed Central

Diploids of the yeast Hansenula wingei are nonagglutinative and do not form zygotes in mixed cultures with either sexually agglutinative haploid mating type. However, a low frequency of diploid x haploid cell fusions (about 10-3) is detectable by prototrophic selection. This frequency of rare diploid x haploid matings is not increased after the diploid culture is induced for sexual agglutination. Therefore, we conclude that genes that repress mating are different from those that repress sexual agglutination.——Six prototrophs isolated from one diploid x haploid cross had an average DNA value (µg DNA per 108 cells) of 6.19, compared to 2.53 and 4.35 for the haploid and diploid strains, respectively. Four prototrophs were clearly cell-fusion products because they contained genes from both the diploid and the haploid partners. However, genetic analysis of the prototrophs yielded results inconsistent with triploid meiosis; all six isolates yielded a 2:2 segregation for the mating-type alleles and linked genes.——Mitotic segregation of monosomic (2n-1) cells lacking one homolog of the chromosome carrying the mating-type locus is proposed to explain the rare production of sexually active cells in the diploid cultures. Fusion between such monosomic cells and normal haploids is thought to have produced 3n-1 cells, disomic for the chromosome carrying the mating-type locus. We conclude that in the diploid strain we studied, the physiological mechanisms repressing sexual agglutination and conjugation function efficiently, but events occuring during mitosis lead to a low frequency of genetically altered cells in the population. PMID:17248985

Crandall, Marjorie; Caulton, Joan H.

1979-01-01

93

Rare-Cell Fusion Events between Diploid and Haploid Strains of the Sexually Agglutinative Yeast HANSENULA WINGEI.  

PubMed

Diploids of the yeast Hansenula wingei are nonagglutinative and do not form zygotes in mixed cultures with either sexually agglutinative haploid mating type. However, a low frequency of diploid x haploid cell fusions (about 10(-3)) is detectable by prototrophic selection. This frequency of rare diploid x haploid matings is not increased after the diploid culture is induced for sexual agglutination. Therefore, we conclude that genes that repress mating are different from those that repress sexual agglutination.--Six prototrophs isolated from one diploid x haploid cross had an average DNA value (microg DNA per 10(8) cells) of 6.19, compared to 2.53 and 4.35 for the haploid and diploid strains, respectively. Four prototrophs were clearly cell-fusion products because they contained genes from both the diploid and the haploid partners. However, genetic analysis of the prototrophs yielded results inconsistent with triploid meiosis; all six isolates yielded a 2:2 segregation for the mating-type alleles and linked genes.--Mitotic segregation of monosomic (2n-1) cells lacking one homolog of the chromosome carrying the mating-type locus is proposed to explain the rare production of sexually active cells in the diploid cultures. Fusion between such monosomic cells and normal haploids is thought to have produced 3n-1 cells, disomic for the chromosome carrying the mating-type locus. We conclude that in the diploid strain we studied, the physiological mechanisms repressing sexual agglutination and conjugation function efficiently, but events occuring during mitosis lead to a low frequency of genetically altered cells in the population. PMID:17248985

Crandall, M; Caulton, J H

1979-12-01

94

Effect of fungicides on epiphytic yeasts associated with strawberry  

PubMed Central

We studied the effect of two commonly used fungicides on the epiphytic yeast community of strawberry. Greenhouse and field experiments were conducted applying Switch (cyprodinil plus fludioxonil) or Signum (boscalid plus pyraclostrobin) to strawberry plants. Yeasts on leaves and fruits were assessed on treated and untreated plants at several time points via plating and denaturing gradient gel electrophoresis (DGGE) analysis. The yeast counts on plates of the treated plants were similar to the control plants. Unripe fruits had 10 times larger yeast concentrations than ripe fruits or leaves. Some dominant yeast types were isolated and in vitro tests showed that they were at least 10 times less sensitive to Switch and Signum as compared with two important fungal strawberry pathogens Botrytis cinerea and Colletotrichum acutatum, which are the targets for the fungicide control. DGGE analysis showed that the applied fungicides had no effect on the composition of the yeast communities, while the growing system, strawberry tissue, and sampling time did affect the yeast communities. The yeast species most commonly identified were Cryptococcus, Rhodotorula, and Sporobolomyces. These results point toward the potential applicability of natural occurring yeast antagonists into an integrated disease control strategy for strawberry diseases.

Debode, Jane; Van Hemelrijck, Wendy; Creemers, Piet; Maes, Martine

2013-01-01

95

Electric Switches  

NSDL National Science Digital Library

In this activity, learners incorporate a simple switch into a battery/bulb circuit. Learners will use their knowledge of circuits to design and make their own switches using common materials. Learners will also identify switches found in common appliances.
Note: This activity is designed to be done under the supervision of an educator familiar with electrical and electronic concepts.

2014-05-22

96

A Feast for Yeast  

NSDL National Science Digital Library

In this activity on page 6 of the PDF, learners investigate yeast. Learners prepare an experiment to observe what yeast cells like to eat. Learners feed the yeast cells various ingredients in plain bread--water, flour, sugar, and salt--to discover yeast's favorite food.

Society, American C.

2000-01-01

97

Yeast-Air Balloons  

NSDL National Science Digital Library

In this activity, learners make a yeast-air balloon to get a better idea of what yeast can do. Learners discover that the purpose of leaveners like yeast is to produce the gas that makes bread rise. Learners discover that as yeast feeds on sugar, it produces carbon dioxide which slowly fills the balloon.

The Exploratorium

2012-03-10

98

Ethernet Switching  

NSDL National Science Digital Library

Created by Tony Castro of the Information and Communications Technologies Center (ICT), this simulation demonstrates ethernet switching. The animation depicts three separate local area networks connecting to an ethernet hub. The animation also includes descriptive text. This resource would be a helpful addition to any course on information and communications technologies as it allows students to see exactly how ethernet switching works.

Castro, Tony

2012-10-25

99

Switching Amplifiers  

NSDL National Science Digital Library

Created by Work-Ready Electronics, a project of the Advanced Technological Education, this module walks visitors through switching amplifiers. The site content is divided up into four sections: Switching Amplifiers Introduction, Class D Switching Amplifiers, Switching RF Power Amplifiers, and Troubleshooting. There is a quiz for each section to test what students learned in the module in the Knowledge Probe section, and the Learning Resources section contains four activities to help cement student understanding. There are also further resources - both print and Web based - for more information and two Questor games, a Flash quiz that reiterates the material covered. The Notebook function allows visitors to take notes and review them at any time. This is an excellent resource students and educators in electronics technician programs to introduce and explore switching amplifiers.

100

Yeast Education Network  

NSDL National Science Digital Library

The Yeast Education Network provides a variety of resources to facilitate use of the budding yeast Saccharomyces cerevisiae in undergraduate science curricula. Laboratory, classroom, and computer-based activities can be used with college and advanced high school students.

101

Gene Switches  

NSDL National Science Digital Library

In this activity, learners explore how genetic switches function and the role of genetic switches in the process of evolution. To make these concepts less abstract and more understandable, learners first view a series of video clips and animations from the HHMI DVD (or online) "Evolution: Constant Change and Common Threads." Then, learners construct a model of a gene switch using craft materials or FridgiGears (magnetic gears). This activity can be done as a demonstration, a student inquiry activity, or a combination of the two.

2013-07-30

102

Evidence for maintenance of sex determinants but not of sexual stages in red yeasts, a group of early diverged basidiomycetes  

PubMed Central

Background The red yeasts are an early diverged group of basidiomycetes comprising sexual and asexual species. Sexuality is based on two compatible mating types and sexual identity is determined by MAT loci that encode homeodomain transcription factors, peptide pheromones and their receptors. The objective of the present study was to investigate the presence and integrity of MAT genes throughout the phylogenetic diversity of red yeasts belonging to the order Sporidiobolales. Results We surveyed 18 sexual heterothallic and self-fertile species and 16 asexual species. Functional pheromone receptor homologues (STE3.A1 and STE3.A2) were found in multiple isolates of most of the sexual and asexual species. For each of the two mating types, sequence comparisons with whole-genome data indicated that synteny tended to be conserved along the pheromone receptor region. For the homeodomain transcription factor, likelihood methods suggested that diversifying selection acting on the self/non-self recognition region promotes diversity in sexual species, while rapid evolution seems to be due to relaxed selection in asexual strains. Conclusions The majority of both sexual and asexual species of red yeasts have functional pheromone receptors and homeodomain homologues. This and the frequent existence of asexual strains within sexual species, makes the separation between sexual and asexual species imprecise. Events of loss of sexuality seem to be recent and frequent, but not uniformly distributed within the Sporidiobolales. Loss of sex could promote speciation by fostering the emergence of asexual lineages from an ancestral sexual stock, but does not seem to contribute to the generation of exclusively asexual lineages that persist for a long time. PMID:21880139

2011-01-01

103

Acceleration switch  

DOEpatents

The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

Abbin, Jr., Joseph P. (Albuquerque, NM); Devaney, Howard F. (Cedar Crest, NM); Hake, Lewis W. (Albuquerque, NM)

1982-08-17

104

Nucleosome Switches  

NASA Astrophysics Data System (ADS)

We present a statistical-mechanical model for the positioning of nucleosomes along genomic DNA molecules as a function of the strength of the binding potential and the chemical potential of the nucleosomes. We show that a significant section of the DNA is composed of two-level nucleosome switching regions where the nucleosome distribution undergoes a localized, first-order transition. The location of the nucleosome switches shows a strong correlation with the location of gene-regulation regions.

Schwab, David J.; Bruinsma, Robijn F.; Rudnick, Joseph; Widom, Jonathan

2008-06-01

105

Fisetin up-regulates the expression of adiponectin in 3T3-L1 adipocytes via the activation of silent mating type information regulation 2 homologue 1 (SIRT1)-deacetylase and peroxisome proliferator-activated receptors (PPARs).  

PubMed

Adiponectin, an adipokine, has been described as showing physiological benefits against obesity-related malfunctions and vascular dysfunction. Several natural compounds that promote the expression and secretion of adipokines in adipocytes could be useful for treating metabolic disorders. This study investigated the effect of fisetin, a dietary flavonoid, on the regulation of adiponectin in adipocytes using 3T3-L1 preadipocytes. The expression and secretion of adiponectin increased in 3T3-L1 cells upon treatment with fisetin in a dose-dependent manner. Fisetin-induced adiponectin secretion was inhibited by peroxisome proliferator-activated receptor (PPAR) antagonists. It was also revealed that fisetin increased the activities of PPARs and silent mating type information regulation 2 homologue 1 (SIRT1) in a dose-dependent manner. Furthermore, the up-regulation of adiponectin and the activation of PPARs induced by fisetin were prevented by a SIRT1 inhibitor. Fisetin also promoted deacetylation of PPAR ? coactivator 1 (PGC-1) and its interaction with PPARs. SIRT knockdown by siRNA significantly decreased both adiponectin production and PPARs-PGC-1 interaction. These results provide evidence that fisetin promotes the gene expression of adiponectin through the activation of SIRT1 and PPARs in adipocytes. PMID:25286082

Jin, Taewon; Kim, Oh Yoen; Shin, Min-Jeong; Choi, Eun Young; Lee, Sung Sook; Han, Ye Sun; Chung, Ji Hyung

2014-10-29

106

Identification and characterization of genes and mutants for an N-terminal acetyltransferase from yeast.  

PubMed

A gene from Saccharomyces cerevisiae has been mapped, cloned, sequenced and shown to encode a catalytic subunit of an N-terminal acetyltransferase. Regions of this gene, NAT1, and the chloramphenicol acetyltransferase genes of bacteria have limited but significant homology. A nat1 null mutant is viable but exhibits a variety of phenotypes, including reduced acetyltransferase activity, derepression of a silent mating type locus (HML) and failure to enter G0. All these phenotypes are identical to those of a previously characterized mutant, ard1. NAT1 and ARD1 are distinct genes that encode proteins with no obvious similarity. Concomitant overexpression of both NAT1 and ARD1 in yeast causes a 20-fold increase in acetyltransferase activity in vitro, whereas overexpression of either NAT1 or ARD1 alone does not raise activity over basal levels. A functional iso-1-cytochrome c protein, which is N-terminally acetylated in a NAT1 strain, is not acetylated in an isogenic nat1 mutant. At least 20 other yeast proteins, including histone H2B, are not N-terminally acetylated in either nat1 or ard1 mutants. These results suggest that NAT1 and ARD1 proteins function together to catalyze the N-terminal acetylation of a subset of yeast proteins. PMID:2551674

Mullen, J R; Kayne, P S; Moerschell, R P; Tsunasawa, S; Gribskov, M; Colavito-Shepanski, M; Grunstein, M; Sherman, F; Sternglanz, R

1989-07-01

107

Population Growth in Yeasts  

NSDL National Science Digital Library

This lesson is the second of two that explore cellular respiration and population growth in yeasts. In the first lesson, students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures. Based on questions that arose during the first lesson and its associated activity, students in this lesson work in small groups to design experiments that determine how environmental factors affect yeast population growth.

Engineering K-Phd Program

108

Optical switch  

DOEpatents

An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching. 3 figs.

Reedy, R.P.

1987-11-10

109

Optical switch  

DOEpatents

An optical switching device (10) is provided whereby light from a first glass fiber (16) or a second glass fiber (14) may be selectively transmitted into a third glass fiber (18). Each glass fiber is provided with a focusing and collimating lens system (26, 28, 30). In one mode of operation, light from the first glass fiber (16) is reflected by a planar mirror (36) into the third glass fiber (18). In another mode of operation, light from the second glass fiber (14) passes directly into the third glass fiber (18). The planar mirror (36) is attached to a rotatable table (32) which is rotated to provide the optical switching.

Reedy, Robert P. (Livermore, CA)

1987-01-01

110

Optical switch  

DOEpatents

An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching.

Reedy, R.P.

1985-01-18

111

Yeasts: Neglected Pathogens  

Microsoft Academic Search

Background: Current research on Crohn’s disease (CD) concerns molecular events related to loss of tolerance to microbes that could trigger or maintain inflammation in genetically susceptible individuals. CD is also associated with antimicrobial antibodies, including the antibodies we described against yeast oligomannosides (ASCA). This prompted us to investigate a role for another yeast, Candida albicans, a very common commensal of

Daniel Poulain; Boualem Sendid; Annie Standaert-Vitse; Chantal Fradin; Thierry Jouault; Samir Jawhara; Jean-Frederic Colombel

2009-01-01

112

Moonlighting Proteins in Yeasts  

PubMed Central

Proteins able to participate in unrelated biological processes have been grouped under the generic name of moonlighting proteins. Work with different yeast species has uncovered a great number of moonlighting proteins and shown their importance for adequate functioning of the yeast cell. Moonlighting activities in yeasts include such diverse functions as control of gene expression, organelle assembly, and modification of the activity of metabolic pathways. In this review, we consider several well-studied moonlighting proteins in different yeast species, paying attention to the experimental approaches used to identify them and the evidence that supports their participation in the unexpected function. Usually, moonlighting activities have been uncovered unexpectedly, and up to now, no satisfactory way to predict moonlighting activities has been found. Among the well-characterized moonlighting proteins in yeasts, enzymes from the glycolytic pathway appear to be prominent. For some cases, it is shown that despite close phylogenetic relationships, moonlighting activities are not necessarily conserved among yeast species. Organisms may utilize moonlighting to add a new layer of regulation to conventional regulatory networks. The existence of this type of proteins in yeasts should be taken into account when designing mutant screens or in attempts to model or modify yeast metabolism. PMID:18322039

Gancedo, Carlos; Flores, Carmen-Lisset

2008-01-01

113

Alcoholic Fermentation in Yeast  

NSDL National Science Digital Library

Students learn about the basics of aerobic cellular respiration and alcoholic fermentation and design and carry out experiments to test how variables such as sugar concentration influence the rate of alcoholic fermentation in yeast. In an optional extension activity students can use their yeast mixture to make a small roll of bread.

Ingrid Waldron

114

Prions in Yeast  

PubMed Central

The concept of a prion as an infectious self-propagating protein isoform was initially proposed to explain certain mammalian diseases. It is now clear that yeast also has heritable elements transmitted via protein. Indeed, the “protein only” model of prion transmission was first proven using a yeast prion. Typically, known prions are ordered cross-? aggregates (amyloids). Recently, there has been an explosion in the number of recognized prions in yeast. Yeast continues to lead the way in understanding cellular control of prion propagation, prion structure, mechanisms of de novo prion formation, specificity of prion transmission, and the biological roles of prions. This review summarizes what has been learned from yeast prions. PMID:22879407

Liebman, Susan W.; Chernoff, Yury O.

2012-01-01

115

Yeast Alive! Watch Yeast Live and Breathe  

NSDL National Science Digital Library

This lesson for Grades 6-8 explores the chemical reaction that happens when yeast makes bread rise. The process, called fermentation, occurs when tiny living organisms (yeast) feed on the sugars in flour dough, expelling carbon dioxide as they go. It promotes understanding of how enzymes can cause chemical reactions. This resource combines a 4-minute video of the process plus a hands-on lab that allows students to see the effects of fermentation within a typical 40-45 minute middle school class period.

2011-08-19

116

Silencing Motifs in the Clr2 Protein from Fission Yeast, Schizosaccharomyces pombe  

PubMed Central

The fission yeast, Schizosaccharomyces pombe, is a well-established model for heterochromatin formation, but the exact sequence of events for initiation remains to be elucidated. The essential factors involved include RNA transcribed from repeated sequences together with the methyltransferase Clr4. In addition, histone deacetylases, like Clr3, found in the SHREC complex are also necessary for transcriptional silencing. Clr2 is another crucial factor required for heterochromatin formation found in the SHREC complex. The function of Clr2 has been difficult to establish due to the lack of conserved domains or homology to proteins of known molecular function. Using a bioinformatics approach, three conserved motifs in Clr2 were identified, which contained amino acids important for transcriptional repression. Analysis of clr2 mutant strains revealed a major role for Clr2 in mating-type and rDNA silencing, and weaker effects on centromeric silencing. The effect on mating-type silencing showed variegation in several of the strains with mutated versions of Clr2 indicating an establishment or maintenance defect. Moreover, the critical amino acids in Clr2 were also necessary for transcriptional repression in a minimal system, by the tethering of Clr4 upstream of a reporter gene, inserted into the euchromatic part of the genome. Finally, in silico modeling suggested that the mutations in Clr2 cause disruption of secondary structures in the Clr2 protein. Identification of these critical amino acids in the protein provides a useful tool to explore the molecular mechanism behind the role of Clr2 in heterochromatin formation. PMID:24475199

Steinhauf, Daniel; Maksimov, Vladimir; Kristell, Carolina; Olsson, Ida; Linder, Tomas; Kossida, Sophia; Bongcam-Rudloff, Erik; Bjerling, Pernilla

2014-01-01

117

RNAi in Budding Yeast  

E-print Network

RNA interference (RNAi), a gene-silencing pathway triggered by double-stranded RNA, is conserved in diverse eukaryotic species but has been lost in the model budding yeast Saccharomyces cerevisiae. Here, we show that RNAi ...

Drinnenberg, Ines A.

118

Vaginal Yeast Infection  

MedlinePLUS

... caused by an overgrowth of a fungus called Candida albicans in the vagina. Candida is yeast, which is a type of fungus. ... small numbers, and symptoms only appear with overgrowth. Candida can multiply when an imbalance occurs, such as ...

119

Yeast infections (image)  

MedlinePLUS

Yeast infections may follow a course of antibiotics that were prescribed for another purpose. The antibiotics change the normal "balance" between organisms in the vagina by suppressing the growth of protective bacteria that normally have an antifungal effect.

120

Prion Switching in Response to Environmental Jens Tyedmers1[  

E-print Network

Prion Switching in Response to Environmental Stress Jens Tyedmers1[ , Maria Lucia Madariaga1, might provide such a mechanism. In yeast, the prion [PSIþ ] exposes a large array of previously hidden genes were particularly prominent. Furthermore, prion induction increased by as much as 60-fold when

Lindquist, Susan

121

Nitrile Metabolizing Yeasts  

NASA Astrophysics Data System (ADS)

Nitriles and amides are widely distributed in the biotic and abiotic components of our ecosystem. Nitrile form an important group of organic compounds which find their applications in the synthesis of a large number of compounds used as/in pharmaceutical, cosmetics, plastics, dyes, etc>. Nitriles are mainly hydro-lyzed to corresponding amide/acid in organic chemistry. Industrial and agricultural activities have also lead to release of nitriles and amides into the environment and some of them pose threat to human health. Biocatalysis and biotransformations are increasingly replacing chemical routes of synthesis in organic chemistry as a part of ‘green chemistry’. Nitrile metabolizing organisms or enzymes thus has assumed greater significance in all these years to convert nitriles to amides/ acids. The nitrile metabolizing enzymes are widely present in bacteria, fungi and yeasts. Yeasts metabolize nitriles through nitrilase and/or nitrile hydratase and amidase enzymes. Only few yeasts have been reported to possess aldoxime dehydratase. More than sixty nitrile metabolizing yeast strains have been hither to isolated from cyanide treatment bioreactor, fermented foods and soil. Most of the yeasts contain nitrile hydratase-amidase system for metabolizing nitriles. Transformations of nitriles to amides/acids have been carried out with free and immobilized yeast cells. The nitrilases of Torulopsis candida>and Exophiala oligosperma>R1 are enantioselec-tive and regiospecific respectively. Geotrichum>sp. JR1 grows in the presence of 2M acetonitrile and may have potential for application in bioremediation of nitrile contaminated soil/water. The nitrilase of E. oligosperma>R1 being active at low pH (3-6) has shown promise for the hydroxy acids. Immobilized yeast cells hydrolyze some additional nitriles in comparison to free cells. It is expected that more focus in future will be on purification, characterization, cloning, expression and immobilization of nitrile metabolizing enzymes of yeasts.

Bhalla, Tek Chand; Sharma, Monica; Sharma, Nitya Nand

122

Yeast expression platforms  

Microsoft Academic Search

Yeasts provide attractive expression platforms. They combine ease of genetic manipulations and the option for a simple fermentation\\u000a design of a microbial organism with the capabilities of an eukaryotic organism to secrete and to modify a protein according\\u000a to a general eukaryotic scheme. For platform applications, a range of yeast species has been developed during the last decades.\\u000a We present

Erik Böer; Gerhard Steinborn; Gotthard Kunze; Gerd Gellissen

2007-01-01

123

Forces in yeast flocculation  

NASA Astrophysics Data System (ADS)

In the baker's yeast Saccharomyces cerevisiae, cell-cell adhesion (``flocculation'') is conferred by a family of lectin-like proteins known as the flocculin (Flo) proteins. Knowledge of the adhesive and mechanical properties of flocculins is important for understanding the mechanisms of yeast adhesion, and may help controlling yeast behaviour in biotechnology. We use single-molecule and single-cell atomic force microscopy (AFM) to explore the nanoscale forces engaged in yeast flocculation, focusing on the role of Flo1 as a prototype of flocculins. Using AFM tips labelled with mannose, we detect single flocculins on Flo1-expressing cells, showing they are widely exposed on the cell surface. When subjected to force, individual Flo1 proteins display two distinct force responses, i.e. weak lectin binding forces and strong unfolding forces reflecting the force-induced extension of hydrophobic tandem repeats. We demonstrate that cell-cell adhesion bonds also involve multiple weak lectin interactions together with strong unfolding forces, both associated with Flo1 molecules. Single-molecule and single-cell data correlate with microscale cell adhesion behaviour, suggesting strongly that Flo1 mechanics is critical for yeast flocculation. These results favour a model in which not only weak lectin-sugar interactions are involved in yeast flocculation but also strong hydrophobic interactions resulting from protein unfolding.

El-Kirat-Chatel, Sofiane; Beaussart, Audrey; Vincent, Stéphane P.; Abellán Flos, Marta; Hols, Pascal; Lipke, Peter N.; Dufrêne, Yves F.

2015-01-01

124

Forces in yeast flocculation.  

PubMed

In the baker's yeast Saccharomyces cerevisiae, cell-cell adhesion ("flocculation") is conferred by a family of lectin-like proteins known as the flocculin (Flo) proteins. Knowledge of the adhesive and mechanical properties of flocculins is important for understanding the mechanisms of yeast adhesion, and may help controlling yeast behaviour in biotechnology. We use single-molecule and single-cell atomic force microscopy (AFM) to explore the nanoscale forces engaged in yeast flocculation, focusing on the role of Flo1 as a prototype of flocculins. Using AFM tips labelled with mannose, we detect single flocculins on Flo1-expressing cells, showing they are widely exposed on the cell surface. When subjected to force, individual Flo1 proteins display two distinct force responses, i.e. weak lectin binding forces and strong unfolding forces reflecting the force-induced extension of hydrophobic tandem repeats. We demonstrate that cell-cell adhesion bonds also involve multiple weak lectin interactions together with strong unfolding forces, both associated with Flo1 molecules. Single-molecule and single-cell data correlate with microscale cell adhesion behaviour, suggesting strongly that Flo1 mechanics is critical for yeast flocculation. These results favour a model in which not only weak lectin-sugar interactions are involved in yeast flocculation but also strong hydrophobic interactions resulting from protein unfolding. PMID:25515338

El-Kirat-Chatel, Sofiane; Beaussart, Audrey; Vincent, Stéphane P; Abellán Flos, Marta; Hols, Pascal; Lipke, Peter N; Dufrêne, Yves F

2015-01-22

125

Yeast killer toxins and dimorphism.  

PubMed Central

The differential action of four selected yeast killer toxins on the mycelial and yeast forms of four isolates of the dimorphic fungus Sporothrix schenckii was comparatively evaluated. The results confirmed that the yeast killer phenomenon is present among hyphomycetes and yeasts and that both morphological forms of S. schenckii are susceptible to the action of the same yeast killer toxin. Quantitative differences in the response to the killer action of the mycelial and yeast forms in individual strains were also observed. To avoid retroconversion of the dimorphic forms, we used a modification of the conventional killer system. Images PMID:2754015

Polonelli, L; Conti, S; Campani, L; Morace, G; Fanti, F

1989-01-01

126

21 CFR 172.896 - Dried yeasts.  

Code of Federal Regulations, 2010 CFR

...172.896 Dried yeasts. Dried yeast (Saccharomyces cerevisiae and Saccharomyces fragilis ) and dried torula yeast (Candida utilis ) may be safely used in food provided the total folic acid content of the yeast does not exceed 0.04 milligram...

2010-04-01

127

Oxygen requirements of yeasts.  

PubMed

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 max, 0.03 and 0.05 h-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. PMID:2082825

Visser, W; Scheffers, W A; Batenburg-van der Vegte, W H; van Dijken, J P

1990-12-01

128

Oxygen requirements of yeasts.  

PubMed Central

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 max, 0.03 and 0.05 h-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. Images PMID:2082825

Visser, W; Scheffers, W A; Batenburg-van der Vegte, W H; van Dijken, J P

1990-01-01

129

Mapping Yeast Transcriptional Networks  

PubMed Central

The term “transcriptional network” refers to the mechanism(s) that underlies coordinated expression of genes, typically involving transcription factors (TFs) binding to the promoters of multiple genes, and individual genes controlled by multiple TFs. A multitude of studies in the last two decades have aimed to map and characterize transcriptional networks in the yeast Saccharomyces cerevisiae. We review the methodologies and accomplishments of these studies, as well as challenges we now face. For most yeast TFs, data have been collected on their sequence preferences, in vivo promoter occupancy, and gene expression profiles in deletion mutants. These systematic studies have led to the identification of new regulators of numerous cellular functions and shed light on the overall organization of yeast gene regulation. However, many yeast TFs appear to be inactive under standard laboratory growth conditions, and many of the available data were collected using techniques that have since been improved. Perhaps as a consequence, comprehensive and accurate mapping among TF sequence preferences, promoter binding, and gene expression remains an open challenge. We propose that the time is ripe for renewed systematic efforts toward a complete mapping of yeast transcriptional regulatory mechanisms. PMID:24018767

Hughes, Timothy R.; de Boer, Carl G.

2013-01-01

130

Ancient Evolutionary Trade-Offs between Yeast Ploidy States  

PubMed Central

The number of chromosome sets contained within the nucleus of eukaryotic organisms is a fundamental yet evolutionarily poorly characterized genetic variable of life. Here, we mapped the impact of ploidy on the mitotic fitness of baker's yeast and its never domesticated relative Saccharomyces paradoxus across wide swaths of their natural genotypic and phenotypic space. Surprisingly, environment-specific influences of ploidy on reproduction were found to be the rule rather than the exception. These ploidy–environment interactions were well conserved across the 2 billion generations separating the two species, suggesting that they are the products of strong selection. Previous hypotheses of generalizable advantages of haploidy or diploidy in ecological contexts imposing nutrient restriction, toxin exposure, and elevated mutational loads were rejected in favor of more fine-grained models of the interplay between ecology and ploidy. On a molecular level, cell size and mating type locus composition had equal, but limited, explanatory power, each explaining 12.5%–17% of ploidy–environment interactions. The mechanism of the cell size–based superior reproductive efficiency of haploids during Li+ exposure was traced to the Li+ exporter ENA. Removal of the Ena transporters, forcing dependence on the Nha1 extrusion system, completely altered the effects of ploidy on Li+ tolerance and evoked a strong diploid superiority, demonstrating how genetic variation at a single locus can completely reverse the relative merits of haploidy and diploidy. Taken together, our findings unmasked a dynamic interplay between ploidy and ecology that was of unpredicted evolutionary importance and had multiple molecular roots. PMID:23555297

Zörgö, Enikö; Chwialkowska, Karolina; Gjuvsland, Arne B.; Garré, Elena; Sunnerhagen, Per; Liti, Gianni; Blomberg, Anders; Omholt, Stig W.; Warringer, Jonas

2013-01-01

131

Extremely conserved histone H4 N terminus is dispensable for growth but essential for repressing the silent mating loci in yeast.  

PubMed

Yeast histone H4 function was probed in vivo by deleting segments of this extremely conserved 102 amino acid protein. Deletions in the hydrophobic core of H4 are lethal and block chromosomal segregation. In contrast, deletions at the hydrophilic N terminus (residues 4-28) and C terminus (residues 100-102) are viable. However, N-terminal deletion alters normal chromatin structure and lengthens the cell cycle, especially G2. Surprisingly, removal of the H4 N terminus also derepresses the silent mating type loci, HML alpha and HMRa, disrupting mating. This activation is specific since other regulated genes (GAL10, PHO5, CUP1) are repressed and induced normally in these cells. Deletions of the hydrophilic N termini of H2A or H2B do not show this effect on mating. These experiments allow us to define a unique H4 function that is not shared by other histones (H2A and H2B). PMID:3048701

Kayne, P S; Kim, U J; Han, M; Mullen, J R; Yoshizaki, F; Grunstein, M

1988-10-01

132

Vaginal Yeast Infections (For Parents)  

MedlinePLUS

... a common infection caused by a yeast called candida albicans (a type of fungus). Yeast infections usually ... the vagina, it is known as vulvovaginal candidiasis . Candida can overgrow for many reasons. Stress, pregnancy, and ...

133

Virtual Yeast Cell  

NSDL National Science Digital Library

Learning about the various parts of a cell can be tricky business, but this virtual yeast cell offered by The University of Nottingham will come in handy for biology students and science instructors. This learning resource was created to help students in the brewing science program learn about yeast cytology, though just about anyone with an interest in cells will learn something from visiting the site. After entering the interactive cell, visitors can click on different parts of the cell (such as the cytoplasm or the nucleus) in order to learn more about the importance of each one. Visitors should remember that they can also download the virtual yeast cell and use it in the classroom or just with a group of friends.

134

Yeast killer systems.  

PubMed Central

The killer phenomenon in yeasts has been revealed to be a multicentric model for molecular biologists, virologists, phytopathologists, epidemiologists, industrial and medical microbiologists, mycologists, and pharmacologists. The surprisingly widespread occurrence of the killer phenomenon among taxonomically unrelated microorganisms, including prokaryotic and eukaryotic pathogens, has engendered a new interest in its biological significance as well as its theoretical and practical applications. The search for therapeutic opportunities by using yeast killer systems has conceptually opened new avenues for the prevention and control of life-threatening fungal diseases through the idiotypic network that is apparently exploited by the immune system in the course of natural infections. In this review, the biology, ecology, epidemiology, therapeutics, serology, and idiotypy of yeast killer systems are discussed. PMID:9227858

Magliani, W; Conti, S; Gerloni, M; Bertolotti, D; Polonelli, L

1997-01-01

135

Latching relay switch assembly  

DOEpatents

A latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes at least one permanent magnet and at least one electromagnet. The respective sections are, generally, arranged in separate locations or cavities in the assembly. The switch is latched by a permanent magnet assembly and selectively switched by an overriding electromagnetic assembly.

Duimstra, Frederick A. (Anaheim Hills, CA)

1991-01-01

136

Genetics of Yeasts  

NASA Astrophysics Data System (ADS)

The use of yeasts in biotechnology processes dates back to ancient days. Before 7000 BC, beer was produced in Sumeria. Wine was made in Assyria in 3500 BC, and ancient Rome had over 250 bakeries, which were making leavened bread by 100 BC. And milk has been made into Kefyr and Koumiss in Asia for many centuries (Demain, Phaff, & Kurtzman, 1999). However, the importance of yeast in the food and beverage industries was only realized about 1860, when their role in food manufacturing became evident.

Querol, Amparo; Fernández-Espinar, M. Teresa; Belloch, Carmela

137

Radiation hard vacuum switch  

DOEpatents

A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction.

Boettcher, Gordon E. (Albuquerque, NM)

1990-01-01

138

L-arabinose fermenting yeast  

DOEpatents

An L-arabinose utilizing yeast strain is provided for the production of ethanol by introducing and expressing bacterial araA, araB and araD genes. L-arabinose transporters are also introduced into the yeast to enhance the uptake of arabinose. The yeast carries additional genomic mutations enabling it to consume L-arabinose, even as the only carbon source, and to produce ethanol. A yeast strain engineered to metabolize arabinose through a novel pathway is also disclosed. Methods of producing ethanol include utilizing these modified yeast strains.

Zhang, Min; Singh, Arjun; Suominen, Pirkko; Knoshaug, Eric; Franden, Mary Ann; Jarvis, Eric

2013-02-12

139

L-arabinose fermenting yeast  

DOEpatents

An L-arabinose utilizing yeast strain is provided for the production of ethanol by introducing and expressing bacterial araA, araB and araD genes. L-arabinose transporters are also introduced into the yeast to enhance the uptake of arabinose. The yeast carries additional genomic mutations enabling it to consume L-arabinose, even as the only carbon source, and to produce ethanol. A yeast strain engineered to metabolize arabinose through a novel pathway is also disclosed. Methods of producing ethanol include utilizing these modified yeast strains.

Zhang, Min; Singh, Arjun; Suominen, Pirkko; Knoshaug, Eric; Franden, Mary Ann; Jarvis, Eric

2014-09-23

140

Vaginal Yeast Infections  

MedlinePLUS

... rash on the penis if they have unprotected sex with an infected woman. If this happens to your partner, he should see a doctor. Men who haven’t been circumcised are at higher risk. Lesbians may be at risk for spreading yeast infections ...

141

Yeast DNA Extraction  

NSDL National Science Digital Library

This laboratory exercise is designed to show learners how DNA can easily be extracted from yeast using simple materials. Use this experiment to supplement any unit on genetics and to demonstrate how scientists study DNA. Adult supervision is recommended. This resource guide includes tips and suggestions for instructors as well as other DNA extraction experiments and a chart for learners to answer questions.

Lana Hays

2009-01-01

142

Microencapsulation in yeast cells.  

PubMed

A method for encapsulating high concentrations of essential oils into bakers' yeast (Saccharomyces cerevisiae) is described. The process involves mixing an aqueous suspension of yeast and an essential oil, which allows the oil to pass freely through the cell wall and membrane and remain passively within the cell. Oil droplets sequestered within the cell were clearly visible using confocal microscopy. Transmission electron microscopy demonstrated that the cell wall and membrane remain intact during the process. Cells quickly lost viability during the process and it appeared unnecessary for the cells to be viable for the process to occur. Encapsulated oil was recovered from the cells using a water/ethanol extraction procedure and analysed by gas chromatography. No significant differences were noted between encapsulated and unencapsulated oil profiles. The rate of permeation of oil into the yeast cells was found to increase significantly at higher temperatures due to the phase transition of the lipid membrane. The rates at which different essential oils permeated the cell varied considerably due to variations in terpene chemistry. The encapsulation of straight chain hydrocarbons highlighted the effects of molecular size, shape and the presence of hydroxl groups on the process. The process occurs by passive diffusion as a result of hydrophobic flavour components partitioning into the cell membrane and intracellular lipid. This paper briefly reviews the patented literature and reports some of the initial observations of the transport mechanisms involved during the accumulation of essential oils by yeast cells. PMID:9818954

Bishop, J R; Nelson, G; Lamb, J

1998-01-01

143

RF MEMS switches and switch circuits  

Microsoft Academic Search

MEMS switches are devices that use mechanical movement to achieve a short circuit or an open circuit in the RF transmission line. RF MEMS switches are the specific micromechanical switches that are designed to operate at RF-to-millimeter-wave frequencies (0.1 to 100 GHz). The forces required for the mechanical movement can be obtained using electrostatic, magnetostatic, piezoelectric, or thermal designs. To

G. M. Rebeiz; J. B. Muldavin

2001-01-01

144

Nanoelectromechanical contact switches.  

PubMed

Nanoelectromechanical (NEM) switches are similar to conventional semiconductor switches in that they can be used as relays, transistors, logic devices and sensors. However, the operating principles of NEM switches and semiconductor switches are fundamentally different. These differences give NEM switches an advantage over semiconductor switches in some applications--for example, NEM switches perform much better in extreme environments--but semiconductor switches benefit from a much superior manufacturing infrastructure. Here we review the potential of NEM-switch technologies to complement or selectively replace conventional complementary metal-oxide semiconductor technology, and identify the challenges involved in the large-scale manufacture of a representative set of NEM-based devices. PMID:22543427

Loh, Owen Y; Espinosa, Horacio D

2012-05-01

145

Differential arrival of leading and lagging strand DNA polymerases at fission yeast telomeres  

E-print Network

Differential arrival of leading and lagging strand DNA polymerases at fission yeast telomeres of Medicine, Philadelphia, PA, USA To maintain genomic integrity, telomeres must undergo switches from a protected state to an accessible state that allows telomerase recruitment. To better understand how telomere

Nakamura, Toru M.

146

Extracellular Polysaccharides Produced by Yeasts and Yeast-Like Fungi  

NASA Astrophysics Data System (ADS)

Several yeasts and yeast-like fungi are known to produce extracellular polysaccharides. Most of these contain D-mannose, either alone or in combination with other sugars or phosphate. A large chemical and structural variability is found between yeast species and even among different strains. The types of polymers that are synthesized can be chemically characterized as mannans, glucans, phosphoman-nans, galactomannans, glucomannans and glucuronoxylomannans. Despite these differences, almost all of the yeast exopolysaccharides display some sort of biological activity. Some of them have already applications in chemistry, pharmacy, cosmetics or as probiotic. Furthermore, some yeast exopolysaccharides, such as pullulan, exhibit specific physico-chemical and rheological properties, making them useful in a wide range of technical applications. A survey is given here of the production, the characteristics and the application potential of currently well studied yeast extracellular polysaccharides.

van Bogaert, Inge N. A.; de Maeseneire, Sofie L.; Vandamme, Erick J.

147

Identification of silencer binding proteins from yeast: possible roles in SIR control and DNA replication  

PubMed Central

The `silent' yeast mating-type loci (HML and HMR) are repressed by sequences (HMLE and HMRE) located over 1 kb from their promoters which have properties opposite those of enhancers, and are called `silencers'. Both silencers contain autonomously replicating sequences (ARS). Silencer activity requires four trans-acting genes called SIR (silent information regulator). We have identified two DNA binding factors, SBF-B and SBF-E, which bind to known regulatory elements at HMRE. SBF-B binds to a region involved in both the silencer and ARS functions of HMRE, but does not bind to HMLE. This factor also binds to the unlinked ARS1 element. SBF-E recognizes a sequence found at both silencers. These results suggest that the two silencers may be composed of different combinations of regulatory elements at least one of which is common to both. Neither factor appears to be a SIR gene product. Hence the SIR proteins may not directly interact with the silencer control sites. ImagesFig. 2.Fig. 3.Fig. 4.Fig. 5.Fig. 6.Fig. 7. PMID:15981337

Shore, David; Stillman, David J.; Brand, Andrea H.; Nasmyth, Kim A.

1987-01-01

148

Mammalian Homology to Yeast  

NSDL National Science Digital Library

This site allows researchers to retrieve a yeast-against-mammal Basic Local Alignment Search Tool (BLAST) report by entering a gene or ORF name into a search function. The supporting data were first summarized in a recent Science article which is provided via a link to the journal (Science, 22 July 1997; Issue 277: p.1259). Steve Chervitz of Stanford University maintains this site.

1997-01-01

149

Yeast Colony Embedding Method  

PubMed Central

Patterning of different cell types in embryos is a key mechanism in metazoan development. Communities of microorganisms, such as colonies and biofilms also display patterns of cell types. For example, in the yeast S. cerevisiae, sporulated cells and pseudohyphal cells are not uniformly distributed in colonies. The functional importance of patterning and the molecular mechanisms that underlie these patterns are still poorly understood. One challenge with respect to investigating patterns of cell types in fungal colonies is that unlike metazoan tissue, cells in colonies are relatively weakly attached to one another. In particular, fungal colonies do not contain the same extensive level of extracellular matrix found in most tissues . Here we report on a method for embedding and sectioning yeast colonies that reveals the interior patterns of cell types in these colonies. The method can be used to prepare thick sections (0.5 ?) useful for light microscopy and thin sections (0.1 ?) suitable for transmission electron microscopy. Asci and pseudohyphal cells can easily be distinguished from ovoid yeast cells by light microscopy , while the interior structure of these cells can be visualized by EM. The method is based on surrounding colonies with agar, infiltrating them with Spurr's medium, and then sectioning. Colonies with a diameter in the range of 1-2 mm are suitable for this protocol. In addition to visualizing the interior of colonies, the method allows visualization of the region of the colony that invades the underlying agar. PMID:21445054

Piccirillo, Sarah; Honigberg, Saul M.

2011-01-01

150

Genome evolution in yeasts.  

PubMed

Identifying the mechanisms of eukaryotic genome evolution by comparative genomics is often complicated by the multiplicity of events that have taken place throughout the history of individual lineages, leaving only distorted and superimposed traces in the genome of each living organism. The hemiascomycete yeasts, with their compact genomes, similar lifestyle and distinct sexual and physiological properties, provide a unique opportunity to explore such mechanisms. We present here the complete, assembled genome sequences of four yeast species, selected to represent a broad evolutionary range within a single eukaryotic phylum, that after analysis proved to be molecularly as diverse as the entire phylum of chordates. A total of approximately 24,200 novel genes were identified, the translation products of which were classified together with Saccharomyces cerevisiae proteins into about 4,700 families, forming the basis for interspecific comparisons. Analysis of chromosome maps and genome redundancies reveal that the different yeast lineages have evolved through a marked interplay between several distinct molecular mechanisms, including tandem gene repeat formation, segmental duplication, a massive genome duplication and extensive gene loss. PMID:15229592

Dujon, Bernard; Sherman, David; Fischer, Gilles; Durrens, Pascal; Casaregola, Serge; Lafontaine, Ingrid; De Montigny, Jacky; Marck, Christian; Neuvéglise, Cécile; Talla, Emmanuel; Goffard, Nicolas; Frangeul, Lionel; Aigle, Michel; Anthouard, Véronique; Babour, Anna; Barbe, Valérie; Barnay, Stéphanie; Blanchin, Sylvie; Beckerich, Jean-Marie; Beyne, Emmanuelle; Bleykasten, Claudine; Boisramé, Anita; Boyer, Jeanne; Cattolico, Laurence; Confanioleri, Fabrice; De Daruvar, Antoine; Despons, Laurence; Fabre, Emmanuelle; Fairhead, Cécile; Ferry-Dumazet, Hélène; Groppi, Alexis; Hantraye, Florence; Hennequin, Christophe; Jauniaux, Nicolas; Joyet, Philippe; Kachouri, Rym; Kerrest, Alix; Koszul, Romain; Lemaire, Marc; Lesur, Isabelle; Ma, Laurence; Muller, Héloïse; Nicaud, Jean-Marc; Nikolski, Macha; Oztas, Sophie; Ozier-Kalogeropoulos, Odile; Pellenz, Stefan; Potier, Serge; Richard, Guy-Franck; Straub, Marie-Laure; Suleau, Audrey; Swennen, Dominique; Tekaia, Fredj; Wésolowski-Louvel, Micheline; Westhof, Eric; Wirth, Bénédicte; Zeniou-Meyer, Maria; Zivanovic, Ivan; Bolotin-Fukuhara, Monique; Thierry, Agnès; Bouchier, Christiane; Caudron, Bernard; Scarpelli, Claude; Gaillardin, Claude; Weissenbach, Jean; Wincker, Patrick; Souciet, Jean-Luc

2004-07-01

151

Tapping into yeast diversity.  

PubMed

Domesticated organisms demonstrate our capacity to influence wild species but also provide us with the opportunity to understand rapid evolution in the context of substantially altered environments and novel selective pressures. Recent advances in genetics and genomics have brought unprecedented insights into the domestication of many organisms and have opened new avenues for further improvements to be made. Yet, our ability to engineer biological systems is not without limits; genetic manipulation is often quite difficult. The budding yeast, Saccharomyces cerevisiae, is not only one of the most powerful model organisms, but is also the premier producer of fermented foods and beverages around the globe. As a model system, it entertains a hefty workforce dedicated to deciphering its genome and the function it encodes at a rich mechanistic level. As a producer, it is used to make leavened bread, and dozens of different alcoholic beverages, such as beer and wine. Yet, applying the awesome power of yeast genetics to understanding its origins and evolution requires some knowledge of its wild ancestors and the environments from which they were derived. A number of surprisingly diverse lineages of S. cerevisiae from both primeval and secondary forests in China have been discovered by Wang and his colleagues. These lineages substantially expand our knowledge of wild yeast diversity and will be a boon to elucidating the ecology, evolution and domestication of this academic and industrial workhorse. PMID:23281494

Fay, Justin C

2012-11-01

152

Automatic thermal switches  

NASA Technical Reports Server (NTRS)

Two automatic switches control heat flow from one thermally conductive plate to another. One switch permits heat flow to outside; other limits heat flow. In one switch, heat on conductive plate activates piston that forces saddle against plate. Heat carriers then conduct heat to second plate that radiates it away. After temperature is first plate drops, piston contracts and spring breaks thermal contact with plate. In second switch, action is reversed.

Cunningham, J. W.; Wing, L. D.

1980-01-01

153

Remote switch actuator  

DOEpatents

The invention provides a device and method for actuating electrical switches remotely. The device is removably attached to the switch and is actuated through the transfer of a user's force. The user is able to remain physically removed from the switch site obviating need for protective equipment. The device and method allow rapid, safe actuation of high-voltage or high-current carrying electrical switches or circuit breakers.

Haas, Edwin Gerard; Beauman, Ronald; Palo, Jr., Stefan

2013-01-29

154

Triggered plasma opening switch  

DOEpatents

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open the switch.

Mendel, Clifford W. (Albuquerque, NM)

1988-01-01

155

ENERGY LOSSES IN SWITCHES  

Microsoft Academic Search

The authors experiments show energy losses between 2 and 10 times that of the resistive time predictions. The experiments used hydrogen, helium, air, nitrogen, SFâ polyethylene, and water for the switching dielectric. Previously underestimated switch losses have caused over predicting the accelerator outputs. Accurate estimation of these losses is now necessary for new high-efficiency pulsed power devices where the switching

T. H. Martin; J. F. Seamen; D. O. Jobe

1993-01-01

156

Autoregulation of convergent RNAi genes in fission yeast  

PubMed Central

RNAi plays a central role in the regulation of eukaryotic genes. In Schizosaccharomyces pombe fission yeast, RNAi involves the formation of siRNA from dsRNA that acts to establish and maintain heterochromatin over centromeres, telomeres, and mating loci. We showed previously that transient heterochromatin also forms over S. pombe convergent genes (CGs). Remarkably, most RNAi genes are themselves convergent. We demonstrate here that transient heterochromatin formed by the RNAi pathway over RNAi CGs leads to their autoregulation in G1–S. Furthermore, the switching of RNAi gene orientation from convergent to tandem causes loss of their G1–S down-regulation. Surprisingly, yeast mutants with tandemized dcr1, ago1, or clr4 genes display aberrant centromeric heterochromatin, which results in abnormal cell morphology. Our results emphasize the significance of gene orientation for correct RNAi gene expression, and suggest a role for cell cycle-dependent formation of RNAi CG heterochromatin in cellular integrity. PMID:21357674

Gullerova, Monika; Moazed, Danesh; Proudfoot, Nick J.

2011-01-01

157

Production of Food Grade Yeasts  

Microsoft Academic Search

Summary Yeasts have been known to humans for thousands of years as they have been used in traditional fermentation processes like wine, beer and bread making. Today, yeasts are also used as alternative sources of high nutritional value proteins, enzymes and vitamins, and have numerous applications in the health food industry as food additives, conditioners and flavouring agents, for the

Argyro Bekatorou; Costas Psarianos; Athanasios A. Koutinas

2006-01-01

158

Red yeast rice for dysipidemia.  

PubMed

Red yeast rice is an ancient Chinese food product that contains monacolins, chemical substances that are similar to statins in their mechanisms of action and lipid lowering properties. Several studies have found red yeast rice to be moderately effective at improving the lipid profile, particularly for lowering the low-density lipoprotein cholesterol levels. One large randomized controlled study from China found that red yeast rice significantly improved risk of major adverse cardiovascular events and overall survival in patients following myocardial infarction. Thus, red yeast rice is a potentially useful over-the-counter cholesterol-lowering agent. However, many red yeast rice formulations are non-standardized and unregulated food supplements, and there is a need for further research and regulation of production. PMID:24003656

Shamim, Shariq; Al Badarin, Firas J; DiNicolantonio, James J; Lavie, Carl J; O'Keefe, James H

2013-01-01

159

Effective switching frequency multiplier inverter  

DOEpatents

A switching frequency multiplier inverter for low inductance machines that uses parallel connection of switches and each switch is independently controlled according to a pulse width modulation scheme. The effective switching frequency is multiplied by the number of switches connected in parallel while each individual switch operates within its limit of switching frequency. This technique can also be used for other power converters such as DC/DC, AC/DC converters.

Su, Gui-Jia (Oak Ridge, TN); Peng, Fang Z. (Okemos, MI)

2007-08-07

160

Agriculturally important yeasts: Biological control of field and postharvest diseases using yeast antagonists, and yeasts as pathogens of plants  

Technology Transfer Automated Retrieval System (TEKTRAN)

Two important agricultural aspects of yeasts, control of plant diseases through application of yeasts as the control agent, and yeasts that are plant pathogens are reviewed. Yeasts as biocontrol organisms are presented first, followed by a discussion of some of the more common plant pathogenic yeas...

161

Forward-Reverse Switch  

NSDL National Science Digital Library

In this activity, learners build a switch to turn electrical circuits on and off. Learners can connect their switches to other projects they want to power and swing the popsicle stick around to control the direction of movement of the connected devices. Use this activity to introduce learners to concepts related to electrical circuits, switches, and polarity. Note: this activity requires the use of a drill, which is not included in the cost of materials.

Workshop, Fresno C.

2012-01-01

162

A nonlinear resonant switch  

Microsoft Academic Search

A resonant switch is introduced that uses linear tank elements. Zero-current switching is obtained even through the peak transistor voltage and current stresses can approach those of an equivalent ideal pulsewidth-modulated converter. Reduced switching loss without a substantial increase in conduction loss is therefore possible. An approximate analysis is outlined, and transistor peak-voltage and current stresses are shown to be

R. W. Erickson; A. F. Hernandez; A. F. Witulski; R. Xu

1989-01-01

163

Reusable fast opening switch  

DOEpatents

A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and insulating states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

Van Devender, John P. (Albuquerque, NM); Emin, David (Albuquerque, NM)

1986-01-01

164

Reusable fast opening switch  

DOEpatents

A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and metallic states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

Van Devender, J.P.; Emin, D.

1983-12-21

165

30 GHz tuned MEMS switches  

Microsoft Academic Search

This paper demonstrates the use of resonant tuning in high-isolation reflective MEMS electrostatic switches. Tuned switches can achieve higher isolation and a lower pulldown voltage than a comparable single element switch. An equivalent circuit model was developed for individual shunt capacitive membrane switches and then implemented in tuned circuits. The novel cross switch was developed on a high resistivity silicon.

Jeremy B. Muldavin; Gabriel M. Rebeiz

1999-01-01

166

Yeasts from the leaves of pasture plants  

Microsoft Academic Search

The yeast population upon the leaves of pasture plants in New Zealand has been investigated in relation to season, soil yeast flora, and incidence of facial eczema toxin in autumn pasture. Leaf yeasts were shown to be taxonomically distinct from soil yeasts and to vary with season but not to vary with the localities sampled. During most of the year

M. E. di Menna

1959-01-01

167

Yeasts: From genetics to biotechnology  

SciTech Connect

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 {open_quotes}biotechnological revolution{close_quotes} by virtue of both their features and their very long and safe use in human nutrition and industry. 175 refs., 4 figs., 6 tabs.

Russo, S.; Poli, G. [Univ. of Milan (Italy); Siman-Tov, R.B. [Univ. of Jerusalem, Rehovot (Israel)

1995-12-31

168

Interaction Between Yeasts and Zinc  

NASA Astrophysics Data System (ADS)

Zinc is an essential trace element in biological systems. For example, it acts as a cellular membrane stabiliser, plays a critical role in gene expression and genome modification and activates nearly 300 enzymes, including alcohol dehydrogenase. The present chapter will be focused on the influence of zinc on cell physiology of industrial yeast strains of Saccharomyces cerevisiae, with special regard to the uptake and subsequent utilisation of this metal. Zinc uptake by yeast is metabolism-dependent, with most of the available zinc translocated very quickly into the vacuole. At cell division, zinc is distributed from mother to daughter cells and this effectively lowers the individual cellular zinc concentration, which may become zinc depleted at the onset of the fermentation. Zinc influences yeast fermentative performance and examples will be provided relating to brewing and wine fermentations. Industrial yeasts are subjected to several stresses that may impair fermentation performance. Such stresses may also impact on yeast cell zinc homeostasis. This chapter will discuss the practical implications for the correct management of zinc bioavailability for yeast-based biotechnologies aimed at improving yeast growth, viability, fermentation performance and resistance to environmental stresses

Nicola, Raffaele De; Walker, Graeme

169

Lager yeast comes of age.  

PubMed

Alcoholic fermentations have accompanied human civilizations throughout our history. Lager yeasts have a several-century-long tradition of providing fresh beer with clean taste. The yeast strains used for lager beer fermentation have long been recognized as hybrids between two Saccharomyces species. We summarize the initial findings on this hybrid nature, the genomics/transcriptomics of lager yeasts, and established targets of strain improvements. Next-generation sequencing has provided fast access to yeast genomes. Its use in population genomics has uncovered many more hybridization events within Saccharomyces species, so that lager yeast hybrids are no longer the exception from the rule. These findings have led us to propose network evolution within Saccharomyces species. This "web of life" recognizes the ability of closely related species to exchange DNA and thus drain from a combined gene pool rather than be limited to a gene pool restricted by speciation. Within the domesticated lager yeasts, two groups, the Saaz and Frohberg groups, can be distinguished based on fermentation characteristics. Recent evidence suggests that these groups share an evolutionary history. We thus propose to refer to the Saaz group as Saccharomyces carlsbergensis and to the Frohberg group as Saccharomyces pastorianus based on their distinct genomes. New insight into the hybrid nature of lager yeast will provide novel directions for future strain improvement. PMID:25084862

Wendland, Jürgen

2014-10-01

170

Marine yeast isolation and industrial application.  

PubMed

Over the last century, terrestrial yeasts have been widely used in various industries, such as baking, brewing, wine, bioethanol and pharmaceutical protein production. However, only little attention has been given to marine yeasts. Recent research showed that marine yeasts have several unique and promising features over the terrestrial yeasts, for example higher osmosis tolerance, higher special chemical productivity and production of industrial enzymes. These indicate that marine yeasts have great potential to be applied in various industries. This review gathers the most recent techniques used for marine yeast isolation as well as the latest applications of marine yeast in bioethanol, pharmaceutical and enzyme production fields. PMID:24738708

Zaky, Abdelrahman Saleh; Tucker, Gregory A; Daw, Zakaria Yehia; Du, Chenyu

2014-09-01

171

Marine yeast isolation and industrial application  

PubMed Central

Over the last century, terrestrial yeasts have been widely used in various industries, such as baking, brewing, wine, bioethanol and pharmaceutical protein production. However, only little attention has been given to marine yeasts. Recent research showed that marine yeasts have several unique and promising features over the terrestrial yeasts, for example higher osmosis tolerance, higher special chemical productivity and production of industrial enzymes. These indicate that marine yeasts have great potential to be applied in various industries. This review gathers the most recent techniques used for marine yeast isolation as well as the latest applications of marine yeast in bioethanol, pharmaceutical and enzyme production fields. PMID:24738708

Zaky, Abdelrahman Saleh; Tucker, Gregory A; Daw, Zakaria Yehia; Du, Chenyu

2014-01-01

172

Medicinal yeast extracts.  

PubMed

Alcoholic extracts of bakers' yeast (Saccharomyces cerevisiae) have been used for over 60 years in over-the-counter medications for the treatment of hemorrhoids, burns, and wounds. Although previous studies suggested that small peptides were responsible for the medical observations, the peptides were never resolved into separate fractions and identified. In the present report, a protein fraction was prepared by RPC18 chromatography of the extract which enhances wound closure in both diabetic and non-diabetic littermates. The peptides are active in nanomolar amounts and are 600 times more active than the initial extract. SDS-PAGE and N-terminal amino acid sequencing identified 4 polypeptides in the extract. Three of the proteins were small molecular weight stress-associated proteins: copper, zinc superoxide-dismutase, ubiquitin, and glucose lipid regulated protein (HSP 12). The fourth protein, acyl-CoA binding protein II, has not been previously associated with stress proteins. PMID:10547066

Schlemm, D J; Crowe, M J; McNeill, R B; Stanley, A E; Keller, S J

1999-09-01

173

Yeast Breads: Made at Home.  

E-print Network

of ' oven to give crustiness. Makes 2 dozen large rolls. 1 Crusty water rolls. TOMATO CHEESE ROLLS 314 cup lukewarm tomato juice 1 package yeast or 1 .yeast cake 1 tablespoon sugar 1 teaspoon salt 3 tablespoons .melted butter or margarine 2114 CUPS... flour Add yeast and sugar to lukewarm tomato juice and Irt $tdnd until dissolved. Add salt and fat. Add half the fln~lr and beat until smooth. Add remaining flour Place in greased bowl and brush with melted fat. Cover 2nd let rise until doubled...

Cox, Maeona; Harris, Jimmie Nell; Reasonover, Frances; Mason, Lousie

1957-01-01

174

Transcription mediated insulation and interference direct gene cluster expression switches.  

PubMed

In yeast, many tandemly arranged genes show peak expression in different phases of the metabolic cycle (YMC) or in different carbon sources, indicative of regulation by a bi-modal switch, but it is not clear how these switches are controlled. Using native elongating transcript analysis (NET-seq), we show that transcription itself is a component of bi-modal switches, facilitating reciprocal expression in gene clusters. HMS2, encoding a growth-regulated transcription factor, switches between sense- or antisense-dominant states that also coordinate up- and down-regulation of transcription at neighbouring genes. Engineering HMS2 reveals alternative mono-, di- or tri-cistronic and antisense transcription units (TUs), using different promoter and terminator combinations, that underlie state-switching. Promoters or terminators are excluded from functional TUs by read-through transcriptional interference, while antisense TUs insulate downstream genes from interference. We propose that the balance of transcriptional insulation and interference at gene clusters facilitates gene expression switches during intracellular and extracellular environmental change. PMID:25407679

Nguyen, Tania; Fischl, Harry; Howe, Françoise S; Woloszczuk, Ronja; Serra Barros, Ana; Xu, Zhenyu; Brown, David; Murray, Struan C; Haenni, Simon; Halstead, James M; O'Connor, Leigh; Shipkovenska, Gergana; Steinmetz, Lars M; Mellor, Jane

2014-01-01

175

The Electrical Switch  

NSDL National Science Digital Library

This activity is inquiry-based in that students will perform the activity before they formally learn about how a switch works. They will use a multimeter to discover the different settings on a triple-throw switch. The teacher should show the students how

Horton, Michael

2009-05-30

176

Closing photoconductive semiconductor switches  

Microsoft Academic Search

One of the most important limitations of Photoconductive Semiconductor Switches (PCSS) for pulsed power applications is the high laser powers required to activate the switches. In this paper, we discuss recent developments on two different aspects of GaAs PCSS that result in reductions in laser power by a factor of nearly 1000. The advantages of using GaAs over Si are

G. M. Loubriel; F. J. Zutavern; H. P. Hjalmarson; M. W. O'Malley

1989-01-01

177

The Yeast Sphingolipid Signaling Landscape  

PubMed Central

Sphingolipids are recognized as signaling mediators in a growing number of pathways, and represent potential targets to address many diseases. The study of sphingolipid signaling in yeast has created a number of breakthroughs in the field, and has the potential to lead future advances. The aim of this article is to provide an inclusive view of two major frontiers in yeast sphingolipid signaling. In the first section, several key studies in the field of sphingolipidomics are consolidated to create a yeast sphingolipidome that ranks nearly all known sphingolipid species by their level in a resting yeast cell. The second section presents an overview of most known phenotypes identified for sphingolipid gene mutants, presented with the intention of illuminating not yet discovered connections outside and inside of the field. PMID:24220500

Montefusco, David J.; Matmati, Nabil

2014-01-01

178

Yeast Breads: Made at Home.  

E-print Network

/4 cup lukewarm tomato juice I 1 package or cake yeast 1 tablespoon sugar 1 teaspoon salt 3 tablespoons melted butter or margarine 21/4 CUPS flour Add penst and sugar to lukewarm tomato juice and tomato juice I 1 package or cake yeast 1 tablespoon sugar 1 teaspoon salt 3 tablespoons melted butter or margarine 21/4 CUPS flour Add penst and sugar to lukewarm tomato juice and

Reasonover, Frances

1971-01-01

179

Molecular Genetic Analysis in Yeast  

NSDL National Science Digital Library

The four exercises presented here use basic and advanced procedures of recombinant DNA technology to perform molecular genetic analysis in the yeast Saccharomyces cerevisiae. Their fulluse is intended for a senior-level molecular genetics (or similar) course; however, Experiments 1, 2, and 4 are appropriate for lower-level courses. It is expected that the instructor will have some familiarity with the concepts and terminology of recombinant DNA technology and with yeast genetics.

Daniel D. Burke (Seton Hall University; )

1989-06-06

180

Yeast and cancer cells – common principles in lipid metabolism  

PubMed Central

One of the paradigms in cancer pathogenesis is the requirement of a cell to undergo transformation from respiration to aerobic glycolysis – the Warburg effect – to become malignant. The demands of a rapidly proliferating cell for carbon metabolites for the synthesis of biomass, energy and redox equivalents, are fundamentally different from the requirements of a differentiated, quiescent cell, but it remains open whether this metabolic switch is a cause or a consequence of malignant transformation. One of the major requirements is the synthesis of lipids for membrane formation to allow for cell proliferation, cell cycle progression and cytokinesis. Enzymes involved in lipid metabolism were indeed found to play a major role in cancer cell proliferation, and most of these enzymes are conserved in the yeast, Saccharomyces cerevisiae. Most notably, cancer cell physiology and metabolic fluxes are very similar to those in the fermenting and rapidly proliferating yeast. Both types of cells display highly active pathways for the synthesis of fatty acids and their incorporation into complex lipids, and imbalances in synthesis or turnover of lipids affect growth and viability of both yeast and cancer cells. Thus, understanding lipid metabolism in S. cerevisiae during cell cycle progression and cell proliferation may complement recent efforts to understand the importance and fundamental regulatory mechanisms of these pathways in cancer. PMID:22989772

Natter, Klaus; Kohlwein, Sepp D.

2013-01-01

181

Metabolic regulation of yeast  

NASA Astrophysics Data System (ADS)

Metabolic regulation which is based on endogeneous and exogeneous process variables which may act constantly or time dependently on the living cell is discussed. The observed phenomena of the regulation are the result of physical, chemical, and biological parameters. These parameters are identified. Ethanol is accumulated as an intermediate product and the synthesis of biomass is reduced. This regulatory effect of glucose is used for the aerobic production of ethanol. Very high production rates are thereby obtained. Understanding of the regulation mechanism of the glucose effect has improved. In addition to catabolite repression, several other mechanisms of enzyme regulation have been described, that are mostly governed by exogeneous factors. Glucose also affects the control of respiration in a third class of yeasts which are unable to make use of ethanol as a substrate for growth. This is due to the lack of any anaplerotic activity. As a consequence, diauxic growth behavior is reduced to a one-stage growth with a drastically reduced cell yield. The pulse chemostat technique, a systematic approach for medium design is developed and medium supplements that are essential for metabolic control are identified.

Fiechter, A.

1982-12-01

182

Synthetic Yeast Cooperation  

NASA Astrophysics Data System (ADS)

Cooperation is wide-spread and has been postulated to drive major transitions in evolution. However, Darwinian selection favors ``cheaters'' that consume benefits without paying a fair cost. How did cooperation evolve against the threat of cheaters? To investigate the evolutionary trajectories of cooperation, we created a genetically tractable system that can be observed as it evolves from inception. The system consists of two engineered yeast strains -- a red-fluorescent strain that requires adenine and releases lysine and a yellow-fluorescent strain that requires lysine and releases adenine. Cells that consume but not supply metabolites would be cheaters. From the properties of two cooperating strains, we calculated and experimentally verified the minimal initial cell densities required for the viability of the cooperative system in the absence of exogenously added adenine and lysine. Strikingly, evolved cooperative systems were viable at 100-fold lower initial cell densities than their ancestors. We are investigating the nature and diversity of pro-cooperation changes, the dynamics of cooperator-cheater cocultures, and the effects of spatial environment on cooperation and cheating.

Shou, Wenying; Burton, Justin

2010-03-01

183

Telecommunications: Switches and Hubs  

NSDL National Science Digital Library

We all know how important computers are in our every day communication, but do you know how the computer in your office transfers information between the others? This online slideshow provided by Wisc-Online and the National Science Foundation explains the difference between a switch and a hub and the reasons to use them. For example, with helpful animations and a personalized speed, one can learn that hubs often cause broadcast collisions and are less efficient than switches when trying to send information quickly among networked computers. This is great for students and teachers introducing switches and hubs to their telecommunications repertoire.

Bartelt, Terry L.

2009-10-07

184

Photoconductive switch package  

DOEpatents

A photoconductive switch is formed of a substrate that has a central portion of SiC or other photoconductive material and an outer portion of cvd-diamond or other suitable material surrounding the central portion. Conducting electrodes are formed on opposed sides of the substrate, with the electrodes extending beyond the central portion and the edges of the electrodes lying over the outer portion. Thus any high electric fields produced at the edges of the electrodes lie outside of and do not affect the central portion, which is the active switching element. Light is transmitted through the outer portion to the central portion to actuate the switch.

Ca[rasp, George J

2013-10-22

185

Switching to Iloperidone.  

PubMed

Objective: To describe secondary analyses from a 12-week, randomized, open-label trial where adult schizophrenia outpatients receiving risperidone, olanzapine, or aripiprazole were switched to iloperidone. Methods: Patients switched to iloperidone were randomized into 2 groups - one group where the dose of the antecedent antipsychotic was titrated downwards and discontinued by 2 weeks, and the other group where the antecedent antipsychotic was abruptly stopped. A total of 500 patients were randomized and received open-label iloperidone (gradual switch, n=240; immediate switch, n=260), with 175, 155, and 170 patients switched from risperidone, olanzapine, and aripiprazole, respectively. All patients were titrated on iloperidone to an initial target dose of 12 mg/day (6 mg twice a day) by Day 4 after which iloperidone could be flexibly dosed between 12 to 24 mg/day (6 to 12 mg twice a day), as per clinical judgment (median dose at study end was 16 mg/day). Adaptations of the Clinical Global Impression-Severity (CGI-S) scale were used to evaluate clinical changes that occurred from baseline over 12 weeks of treatment, providing data on efficacy (E-CGI-S) and safety (ST-CGI-S), as well as on an integrated measure of severity (I-CGI-S) and change (I-CGI-C). Other assessments included the reporting of adverse events (AEs), study discontinuation, body weight, and metabolic variables. Results:Improvement was steady throughout the study for both gradual- and immediate-switch groups starting at Week 1 and continuing through Week 12. Discontinuations due to AEs in the first 2 weeks of treatment were higher for the immediate-switch group compared with the gradual-switch group (10.8% vs. 5.4%, NNT 19, 95% CI 10-151). Fewer patients in the gradual- switch group experienced dizziness as an AE, whereas a higher percentage of patients in the immediate-switch group exhibited earlier onset of a therapeutic response within the first 2 weeks; both groups were comparable thereafter with low rates of dizziness and similar efficacy outcomes. Conclusions: Switching to iloperidone can be accomplished either with a gradual crossover or immediate discontinuation of the prior antipsychotic; however, the immediate-switch method is associated with greater proportion of initial dizziness. The observed outcomes are consistent with what has been previously reported regarding iloperidone's favorable akathisia/EPS profile and modest impact on somnolence/sedation, body weight, and metabolic variables.. PMID:25367165

Citrome, Leslie; Weiden, Peter J; Gus, Alva; Glick, Ira D; Jackson, Richard; Mattingly, Greg; Kianifard, Farid; Meng, Xiangyi; Winseck, Adam

2014-11-01

186

Plasmonic enhanced ultrafast switch.  

SciTech Connect

Ultrafast electronic switches fabricated from defective material have been used for several decades in order to produce picosecond electrical transients and TeraHertz radiation. Due to the ultrashort recombination time in the photoconductor materials used, these switches are inefficient and are ultimately limited by the amount of optical power that can be applied to the switch before self-destruction. The goal of this work is to create ultrafast (sub-picosecond response) photoconductive switches on GaAs that are enhanced through plasmonic coupling structures. Here, the plasmonic coupler primarily plays the role of being a radiation condenser which will cause carriers to be generated adjacent to metallic electrodes where they can more efficiently be collected.

Subramania,Ganapathi Subramanian; Reno, John Louis; Passmore, Brandon Scott; Harris, Tom.; Shaner, Eric Arthur; Barrick, Todd A.

2009-09-01

187

Basics of Safety Switches  

NSDL National Science Digital Library

This course is one of the quickStep series offered by Siemens in Safety Switches. These are FREE on-line industrial knowledge building tutorials. quickSTEPs are a great start for industry novices moving into technical jobs or staff in operational support rolls. They can also be very effectively used as out of class assignments for review or to build fundamental skills. Each course includes: an online tutorial organized as a number of units, lessons with self check quiz questions, a glossary of terms, a self-check final exam with scoring, an extensive downloadable PDF study guide. This course offers: current protection, fuses, enclosures, switch design, switch terminology, safety switches, a final exam, a glossary and a 72 page study guide.

188

An optical switch  

DOEpatents

The invention is a gas mixture for a diffuse discharge switch having an electron attaching gas wherein electron attachment is brought about by indirect excitation of molecules to long live states by exposure to laser light. 3 figs.

Christophorou, L.G.; Hunter, S.R.

1987-04-30

189

A yeast-based rapid prototype platform for gene control elements in mammalian cells.  

PubMed

Programming genetic circuits in mammalian cells requires flexible, tunable, and user-tailored gene-control systems. However, most existing control systems are either mechanistically specific for microbial organisms or must be laboriously re-engineered to function in mammalian cells. Here, we demonstrate a ribozyme-based device platform that can be directly transported from yeast to mammalian cells in a "plug-and-play" manner. Ribozyme switches previously prototyped in yeast are shown to regulate gene expression in a predictable, ligand-responsive manner in human HEK 293, HeLa, and U2OS cell lines without any change to device sequence nor further optimization. The ribozyme-based devices, which exhibit activation ratios comparable to the best RNA-based regulatory devices demonstrated in mammalian cells to-date, retain their prescribed functions (ON or OFF switch), tunability of regulatory stringency, and responsiveness to different small-molecule inputs in mammalian hosts. Furthermore, we observe strong correlations of device performance between yeast and all mammalian cell lines tested (R(2) ?= 0.63-0.97). Our unique device architecture can therefore act as a rapid prototyping platform (RPP) based on a yeast chassis, providing a well-developed and genetically tractable system that supports rapid and high-throughput screens for generating gene-controllers with a broad range of functions in mammalian cells. This platform will accelerate development of mammalian gene-controllers for diverse applications, including cell-based therapeutics and cell-fate reprogramming. PMID:23184812

Wei, Kathy Y; Chen, Yvonne Y; Smolke, Christina D

2013-04-01

190

Nuclear Transport of Yeast Proteasomes  

PubMed Central

Proteasomes are conserved protease complexes enriched in the nuclei of dividing yeast cells, a major site for protein degradation. If yeast cells do not proliferate and transit to quiescence, metabolic changes result in the dissociation of proteasomes into proteolytic core and regulatory complexes and their sequestration into motile cytosolic proteasome storage granuli. These granuli rapidly clear with the resumption of growth, releasing the stored proteasomes, which relocalize back to the nucleus to promote cell cycle progression. Here, I report on three models of how proteasomes are transported from the cytoplasm into the nucleus of yeast cells. The first model applies for dividing yeast and is based on the canonical pathway using classical nuclear localization sequences of proteasomal subcomplexes and the classical import receptor importin/karyopherin ??. The second model applies for quiescent yeast cells, which resume growth and use Blm10, a HEAT-like repeat protein structurally related to karyopherin ?, for nuclear import of proteasome core particles. In the third model, the fully-assembled proteasome is imported into the nucleus. Our still marginal knowledge about proteasome dynamics will inspire the discussion on how protein degradation by proteasomes may be regulated in different cellular compartments of dividing and quiescent eukaryotic cells. PMID:25333764

Enenkel, Cordula

2014-01-01

191

uv preilluminated gas switches  

Microsoft Academic Search

We have designed, built, and characterized uv preilluminated gas switches for a trigger circuit and a low inductance discharge circuit. These switches have been incorporated into a 54 x 76 x 150 cm pulser module to produce a 1 Ma output current rising at 5 x 10¹² amps\\/sec with 1 ns jitter. Twenty such modules will be used on the

L. P. Bradley; E. L. Orham; I. F. Stowers; J. R. Braucht

1980-01-01

192

Cygnus Water Switch Jitter  

SciTech Connect

The Cygnus Dual Beam Radiographic Facility consists of two identical radiographic sources - Cygnus 1 and Cygnus 2. Each source has the following x-ray output: 1-mm diameter spot size, 4 rad at 1 m, 50-ns Full Width Half Max. The diode pulse has the following electrical specifications: 2.25 MV, 60 kA, 60 ns. This Radiographic Facility is located in an underground tunnel test area at the Nevada Test Site (NTS). The sources were developed to produce high-resolution images on subcritical tests which are performed at NTS. Subcritical tests are single-shot, high-value events. For this application, it is desirable to maintain a high level of reproducibility in source output. The major components of the Cygnus machines are: Marx generator, water-filled pulse–forming line (PFL), water-filled coaxial transmission line, three-cell inductive voltage adder, and rod-pinch diode. A primary source of fluctuation in Cygnus shot-to-shot performance is jitter in breakdown of the main PFL switch, which is a “self-break” switch. The PFL switch breakdown time determines the peak PFL charging voltage, which ultimately affects the diode pulse. Therefore, PFL switch jitter contributes to shot-to-shot variation in source endpoint energy and dose. In this paper we will present PFL switch jitter analysis for both Cygnus machines and give the correlation with diode performance. For this analysis the PFL switch on each machine was maintained at a single gap setting which has been used for the majority of shots at NTS. In addition to this analysis, PFL switch performance for different switch gap settings taken recently will be examined. Lastly, implications of source jitter for radiographic diagnosis of subcritical shots will be discussed.

Charles V. Mitton, George D. Corrow, Mark D. Hansen, David J. Henderson, et al.

2008-03-01

193

A radiation hard vacuum switch  

DOEpatents

A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction. 3 figs.

Boettcher, G.E.

1988-07-19

194

APPENDIX 4LGrowth and Manipulation of Yeast PREPARATION OF SELECTED YEAST MEDIA  

E-print Network

APPENDIX 4LGrowth and Manipulation of Yeast PREPARATION OF SELECTED YEAST MEDIA Like Escherichia media of consistently high quality is essential for the genetic manipulation of yeast. Autoclaving coli, yeast can be grown in either liquid media or on the surface of (or embedded in) solid agar plates

Winston, Fred

195

The intronome of budding yeasts.  

PubMed

Whatever their abundance in genomes, spliceosomal introns are the signature of eukaryotic genes. The sequence of Saccharomyces cerevisiae, achieved fifteen years ago, revealed that this yeast has very few introns, but conserved intron boundaries typical for an intron definition mechanism. With the improvement and the development of new sequencing technologies, yeast genomes have been extensively sequenced during the last decade. We took advantage of this plethora of data to compile and assess the intron content of the protein-coding genes of 13 genomes representative of the evolution of hemiascomycetous yeasts. We first observed that intron paucity is a general rule and that the fastest evolving genomes tend to lose their introns more rapidly (e.g. S. cerevisiae versus Yarrowia lipolytica). Noticeable differences were also confirmed for 5' splice sites and branch point sites (BP) as well as for the relative position of the BP. These changes seemed to be correlated with the lineage specific evolution of splicing factors. PMID:21819948

Neuvéglise, Cécile; Marck, Christian; Gaillardin, Claude

2011-01-01

196

Cdc42 Oscillations in Yeasts  

NSDL National Science Digital Library

A fundamental problem in cell biology is how cells define one or several discrete sites of polarity. Through mechanisms involving positive and negative feedback, the small Rho-family guanosine triphosphatase Cdc42 breaks symmetry in round budding yeast cells to define a single site of polarized cell growth. However, it is not clear how cells can define multiple sites of polarization concurrently. We discuss a study in which rod-shaped fission yeast cells, which naturally polarize growth at their two cell ends, exhibited oscillations of Cdc42 activity between these sites. We compare these findings with similar oscillatory behavior of Cdc42 detected in budding yeast cells and discuss the possible mechanism and functional outputs of these oscillations.

Felipe O. Bendezu (Switzerland;University of Lausanne REV); Sophie G. Martin (Switzerland;University of Lausanne REV)

2012-12-04

197

The protein sequence and some intron positions are conserved between the switching gene swi10 of Schizosaccharomyces pombe and the human excision repair gene ERCC1.  

PubMed

The switching gene swi10+ has a function in mating-type switching as well as in the repair of radiation damages. We have cloned the genomic swi10+ gene by functional complementation of the switching defect of the swi10-154 mutant. The swi10+ gene is not essential for viability. The DNA sequence revealed an open reading frame of 759 nucleotides interrupted by three introns of 127, 52 and 60 bp, respectively. The positions of intron I as well as of intron III of swi10 are evolutionary conserved in comparison to the introns III and IV of the human ERCC1 gene. The analysis of cDNA clones isolated by PCR amplification confirmed the structure of the swi10 gene. The putative Swi10 protein has homologies to the human and mouse ERCC1 protein, to Rad10 of Saccharomyces cerevisiae and to parts of UvrA and UvrC of E. coli. All these proteins are essential components for excision repair of damaged DNA. The Swi10 protein contains a putative DNA binding domain previously found in other proteins. Northern blot experiments and the analyses of cDNA clones indicate that intron I of the swi10 gene is not efficiently spliced. PMID:1475195

Rödel, C; Kirchhoff, S; Schmidt, H

1992-12-11

198

Oily yeasts as oleaginous cell factories  

Microsoft Academic Search

Oily yeasts have been described to be able to accumulate lipids up to 20% of their cellular dry weight. These yeasts represent\\u000a a minor proportion of the total yeast population, and only 5% of them have been reported as able to accumulate more than 25%\\u000a of lipids. The oily yeast genera include Yarrowia, Candida, Rhodotorula, Rhodosporidium, Cryptococcus, Trichosporon, and Lipomyces.

Jose Manuel Ageitos; Juan Andres Vallejo; Patricia Veiga-Crespo; Tomas G. Villa

2011-01-01

199

Chromatin and Transcription in Yeast  

PubMed Central

Understanding the mechanisms by which chromatin structure controls eukaryotic transcription has been an intense area of investigation for the past 25 years. Many of the key discoveries that created the foundation for this field came from studies of Saccharomyces cerevisiae, including the discovery of the role of chromatin in transcriptional silencing, as well as the discovery of chromatin-remodeling factors and histone modification activities. Since that time, studies in yeast have continued to contribute in leading ways. This review article summarizes the large body of yeast studies in this field. PMID:22345607

Rando, Oliver J.; Winston, Fred

2012-01-01

200

Spatial control of mitotic commitment in fission yeast.  

PubMed

The activation of the Cdk1 (cyclin-dependent kinase 1)-cyclin B complex to promote commitment to mitosis is controlled by the phosphorylation status of the Cdk1 catalytic subunit. Cdk1 phosphorylation by Wee1 kinases blocks activation until Cdc25 (cell division cycle 25) phosphatases remove this phosphate to drive division. Feedback inhibition of Wee1 and promotion of Cdc25 activities by the newly activated Cdk1-cyclin B complexes ensure that the transition from interphase to mitosis is a rapid and complete bi-stable switch. Although this level of molecular understanding of the mitotic commitment switch has been clear for over two decades, it is still unclear how the switch is engaged to promote division at the right time for a particular context. We discuss recent work in fission yeast that shows how the spatial organization of signalling networks, in particular events on the centrosome equivalent, the spindle pole body, plays a key role in ensuring that the timing of cell division is coupled to environmental cues. PMID:24256289

Hagan, Iain M; Grallert, Agnes

2013-12-01

201

Yeast: A Research Organism for Teaching Genetics.  

ERIC Educational Resources Information Center

Explains why laboratory strains of bakers yeast, Saccharomyces cerevisiae, are particularly suited for classroom science activities. Describes the sexual life cycle of yeast and the genetic system with visible mutations. Presents an overview of activities that can be done with yeast and gives a source for teachers to obtain more information. (PR)

Manney, Thomas R.; Manney, Monta L.

1992-01-01

202

Energy losses in switches  

SciTech Connect

The authors experiments show energy losses between 2 and 10 times that of the resistive time predictions. The experiments used hydrogen, helium, air, nitrogen, SF{sub 6} polyethylene, and water for the switching dielectric. Previously underestimated switch losses have caused over predicting the accelerator outputs. Accurate estimation of these losses is now necessary for new high-efficiency pulsed power devices where the switching losses constitute the major portion of the total energy loss. They found that the switch energy losses scale as (V{sub peak}I{sub peak}){sup 1.1846}. When using this scaling, the energy losses in any of the tested dielectrics are almost the same. This relationship is valid for several orders of magnitude and suggested a theoretical basis for these results. Currents up to .65 MA, with voltages to 3 MV were applied to various gaps during these experiments. The authors data and the developed theory indicates that the switch power loss continues for a much longer time than the resistive time, with peak power loss generally occurring at peak current in a ranging discharge instead of the early current time. All of the experiments were circuit code modeled after developing a new switch loss version based on the theory. The circuit code predicts switch energy loss and peak currents as a function of time. During analysis of the data they noticed slight constant offsets between the theory and data that depended on the dielectric. They modified the plasma conductivity for each tested dielectric to lessen this offset.

Martin, T.H.; Seamen, J.F.; Jobe, D.O.

1993-07-01

203

Optical Packet Switching  

NASA Astrophysics Data System (ADS)

This chapter provides an outline of the main concepts and issues related to optical packet switching (OPS). The basic network functions required by this paradigm are discussed and references to past and current research on the topic are provided. Optical packet switching is a transport technique that assumes information to be organized in packets formed by a payload and a header both encoded as optical signals. The payload is transferred through the network without any optical to electronic conversion. The header is processed in the early phase in the electronic domain. Optical packet switching may be considered as a long-term and more flexible alternative to the circuit-switched optical networks currently being deployed by operators. This innovative paradigm aims at optimizing the utilization of the dense wavelength division multiplexing (DWDM) channels by means of fast and highly dynamic resource allocation, overcoming the inefficiency typical of the circuit transfer modes. Traditionally, packet transfer modes have proved to be very flexible by nature, with respect to bandwidth exploitation. In fact, link capacity is shared in time by means of statistical multiplexing, while contentions occurring at each node are solved by storing packets as long as the required resources become available again. Therefore, network links are in general used more efficiently in OPS than in circuit-switching.

Raffaelli, Carla; Aleksic, Slavisa; Callegati, Franco; Cerroni, Walter; Maier, Guido; Pattavina, Achille; Savi, Michele

204

Thermionic gas switch  

DOEpatents

The present invention is directed to an improved temperature responsive thermionic gas switch utilizing a hollow cathode and a folded emitter surface area. The folded emitter surface area of the thermionic switch substantially increases the on/off ratio by changing the conduction surface area involved in the two modes thereof. The improved switch of this invention provides an on/off ratio of 450:1 compared to the 10:1 ratio of the prior known thermionic switch, while providing for adjusting the on current. In the improved switch of this invention the conduction area is made small in the off mode, while in the on mode the conduction area is made large. This is achieved by utilizing a folded hollow cathode configuration and utilizing a folded emitter surface area, and by making the dimensions of the folds small enough so that a space charge will develop in the convolutions of the folds and suppress unignited current, thus limiting the current carrying surface in the off mode.

Hatch, G.L.; Brummond, W.A.; Barrus, D.M.

1984-04-05

205

Dynamic switch matrix for the TDMA satellite switching system  

NASA Technical Reports Server (NTRS)

Future high capacity satellite communication systems require signal processing on board satellites. The on-board signal processing includes switching of RF signals between multiple antennas to provide interconnection between the uplink and downlink beams. This paper describes the development of a dynamic switch matrix for a TDMA satellite switching system to be used in the next generation communications satellites. In this paper, a dynamic switch matrix, which includes the microwave switch matrix, the distribution control unit and the timing source, will be described. Several different microwave switch matrix architectures and switching devices were evaluated and compared. A unique coupler crossbar switch matrix architecture with dual-gate field effect transistor as switching element was developed. Experimental results of both microwave switch matrix (MSM) and distribution control unit (DCU) are presented. These test results verify the MSM with coupler crossbar architecture and dual-gate FET as switching element will meet the future SS-TDMA system requirements. Finally, the reliability of the dynamic switch matrix is addressed. The analysis shows reliability of 0.9981 for 7 year space operation can be achieved for the designed dynamic switch matrix.

Ho, P. T.; Wisniewski, J. H.; Pelose, J. R.; Perasso, H. M.

1982-01-01

206

Dynamic switch matrix for the TDMA satellite switching system  

NASA Astrophysics Data System (ADS)

Future high capacity satellite communication systems require signal processing on board satellites. The on-board signal processing includes switching of RF signals between multiple antennas to provide interconnection between the uplink and downlink beams. This paper describes the development of a dynamic switch matrix for a TDMA satellite switching system to be used in the next generation communications satellites. In this paper, a dynamic switch matrix, which includes the microwave switch matrix, the distribution control unit and the timing source, will be described. Several different microwave switch matrix architectures and switching devices were evaluated and compared. A unique coupler crossbar switch matrix architecture with dual-gate field effect transistor as switching element was developed. Experimental results of both microwave switch matrix (MSM) and distribution control unit (DCU) are presented. These test results verify the MSM with coupler crossbar architecture and dual-gate FET as switching element will meet the future SS-TDMA system requirements. Finally, the reliability of the dynamic switch matrix is addressed. The analysis shows reliability of 0.9981 for 7 year space operation can be achieved for the designed dynamic switch matrix.

Ho, P. T.; Wisniewski, J. H.; Pelose, J. R.; Perasso, H. M.

207

Grape seed procyanidin B2 ameliorates mitochondrial dysfunction and inhibits apoptosis via the AMP-activated protein kinase-silent mating type information regulation 2 homologue 1-PPAR? co-activator-1? axis in rat mesangial cells under high-dose glucosamine.  

PubMed

Grape seed procyanidin B2 (GSPB2), an antioxidative and anti-inflammatory polyphenol in grape seed, has been found to have protective effects on diabetic nephropathy. Based on its favourable biological activities, in the present study, we aimed to investigate whether GSPB2 could inhibit apoptosis in rat mesangial cells treated with glucosamine (GlcN) under high-dose conditions. The results showed that the administration of GSPB2 (10 ?g/ml) significantly increased the viability of mesangial cells treated with GlcN at a dose of 15 mm. We found that GSPB2 inhibited apoptosis in mesangial cells using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphates (dUTP) nick-end labelling staining and flow cytometry technique (P< 0·05 for both). GSPB2 treatment also suppressed oxidative stress by elevating the activity of glutathione peroxidase (P< 0·05) and superoxide dismutase (P< 0·01), as well as prevented cellular damage. GSPB2 enhanced the mRNA expression of nuclear respiratory factor 1, mitochondrial transcription factor A and mitochondrial DNA copy number in mesangial cells as determined by real-time PCR (P< 0·05 for each). Finally, GSPB2 treatment activated the protein expression of PPAR? co-activator-1? (PGC-1?), silent mating type information regulation 2 homologue 1 (SIRT1) and AMP-activated protein kinase (AMPK) in mesangial cells. These findings suggest that GSPB2 markedly ameliorates mitochondrial dysfunction and inhibits apoptosis in rat mesangial cells treated with high-dose GlcN. This protective effect could be, at least in part, due to the activation of the AMPK-SIRT1-PGC-1? axis. PMID:25404010

Bao, Lei; Cai, Xiaxia; Zhang, Zhaofeng; Li, Yong

2014-11-18

208

Optimal switching using coherent control  

NASA Astrophysics Data System (ADS)

We introduce a general framework for the analysis of coherent control in coupled optical cavity-waveguide systems. Within this framework, we use an analytically solvable model, which is validated by independent numerical calculations, to investigate switching in a micro cavity and demonstrate that the switching time, in general, is not limited by the cavity lifetime. Therefore, the total energy required for switching is a more relevant figure of merit than the switching speed, and for a particular two-pulse switching scheme we use calculus of variations to optimize the switching in terms of input energy.

Trøst Kristensen, Philip; Heuck, Mikkel; Mørk, Jesper

2013-01-01

209

Recombinant protein production in yeasts.  

PubMed

Recombinant protein production is a multibillion-dollar market. The development of a new product begins with the choice of a production host. While one single perfect host for every protein does not exist, several expression systems ranging from bacterial hosts to mammalian cells have been established. Among them, yeast cell factories combine the advantages of being single cells, such as fast growth and easy genetic manipulation, as well as eukaryotic features including a secretory pathway leading to correct protein processing and post-translational modifications. In this respect, especially the engineering of yeast glycosylation to produce glycoproteins of human-like glycan structures is of great interest. Additionally, different attempts of cellular engineering as well as the design of different production processes that are leading to improved productivities are presented. With the advent of cheaper next-generation sequencing techniques, systems biotechnology approaches focusing on genome scale analyses will advance and accelerate yeast cell factories and thus recombinant protein production processes in the near future. In this review we summarize advantages and limitations of the main and most promising yeast hosts, including Saccharomyces cerevisiae, Pichia pastoris, and Hansenula polymorpha as those presently used in large scale production of heterologous proteins. PMID:22160907

Mattanovich, Diethard; Branduardi, Paola; Dato, Laura; Gasser, Brigitte; Sauer, Michael; Porro, Danilo

2012-01-01

210

Microfabricated triggered vacuum switch  

DOEpatents

A microfabricated vacuum switch is disclosed which includes a substrate upon which an anode, cathode and trigger electrode are located. A cover is sealed over the substrate under vacuum to complete the vacuum switch. In some embodiments of the present invention, a metal cover can be used in place of the trigger electrode on the substrate. Materials used for the vacuum switch are compatible with high vacuum, relatively high temperature processing. These materials include molybdenum, niobium, copper, tungsten, aluminum and alloys thereof for the anode and cathode. Carbon in the form of graphitic carbon, a diamond-like material, or carbon nanotubes can be used in the trigger electrode. Channels can be optionally formed in the substrate to mitigate against surface breakdown.

Roesler, Alexander W. (Tijeras, NM); Schare, Joshua M. (Albuquerque, NM); Bunch, Kyle (Albuquerque, NM)

2010-05-11

211

Main electrical switch banks, plant switch house, looking to the ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Main electrical switch banks, plant switch house, looking to the North - Bureau of Mines Metallurgical Research Laboratory, Original Building, Date Street north of U.S. Highway 93, Boulder City, Clark County, NV

212

43. OBLIQUE VIEW, GREEN SWITCH TOWER, COS COB, SHOWING SWITCH ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

43. OBLIQUE VIEW, GREEN SWITCH TOWER, COS COB, SHOWING SWITCH LEVER ASSEMBLAGE AND DISPLAY BOARD - New York, New Haven & Hartford Railroad, Automatic Signalization System, Long Island Sound shoreline between Stamford & New Haven, Stamford, Fairfield County, CT

213

Yeast DEL assay detects clastogens.  

PubMed

Chromosomal rearrangements, including DNA deletions are involved in carcinogenesis. The deletion (DEL) assay scoring for DNA deletions in the yeast Saccharomyces cerevisiae is able to detect a wide range of carcinogens. Among approximately 60 compounds of known carcinogenic activity, the DEL assay detected 86% correctly whereas the Ames Salmonella assay detected only 30% correctly [R.J. Brennan, R.H. Schiestl, Detecting carcinogens with the yeast DEL assay, Methods Mol. Biol. 262 (2004) 111-124]. Since the DEL assay is highly inducible by DNA double strand breaks, this study examined the utility of the DEL assay for detecting clastogens. Ten model compounds, with varied mechanisms of genotoxicity, were examined for their effect on the frequency of DNA deletions with the DEL assay. The compounds tested were: actinomycin D, camptothecin, methotrexate and 5-fluorodeoxyuridine, which are anticancer agents, noscapine and furosemide are therapeutics, acridine, methyl acrylate and resorcinol are industrial chemicals and diazinon is an insecticide. The in vitro micronucleus assay (IVMN) in CHO cells, a commonly used tool for detection of clastogens, was performed on the same compounds and the results of the two assays were compared. The results of our study show that there is 70% concordance in the presence of metabolic activation (rat liver S9) and 80% concordance in the absence of metabolic activation between the DEL assay and the standard in vitro micronucleus assay. The lack of cytotoxicity observed for four of the ten compounds examined indicates limited diffusion of lipophilic compounds across the yeast cell wall. Thus, the development of a more permeable yeast tester strain is expected to greatly improve concordance of the DEL assay with the IVMN assay. The yeast DEL assay is inexpensive, amenable to automation and requires less expertise to perform than the IVMN. Thus, it has a strong potential as a robust, fast and economical screen for detecting clastogens in vitro. PMID:15781217

Kirpnick, Zhanna; Homiski, Michael; Rubitski, Elizabeth; Repnevskaya, Marina; Howlett, Niall; Aubrecht, Jiri; Schiestl, Robert H

2005-04-01

214

Occurrence and Growth of Yeasts in Yogurts  

PubMed Central

Yogurts purchased from retail outlets were examined for the presence of yeasts by being plated onto oxytetracycline malt extract agar. Of the 128 samples examined, 45% exhibited yeast counts above 103 cells per g. A total of 73 yeast strains were isolated and identified as belonging to the genera Torulopsis, Kluyveromyces, Saccharomyces, Candida, Rhodotorula, Pichia, Debaryomyces, and Sporobolomyces. Torulopsis candida and Kluyveromyces fragilis were the most frequently isolated species, followed by Saccharomyces cerevisiae, Rhodotorula rubra, Kluyveromyces lactis, and Torulopsis versatilis. The growth of yeasts in yogurts was related to the ability of the yeasts to grow at refrigeration temperatures, to ferment lactose and sucrose, and to hydrolyze milk casein. Most yeast isolates grew in the presence of 100 ?g of sorbate and benzoate preservatives per ml. Higher yeast counts from yogurts were obtained when the yogurts were plated onto oxytetracycline malt extract agar than when they were plated onto acidified malt extract agar. PMID:16345853

Suriyarachchi, V. R.; Fleet, G. H.

1981-01-01

215

Plasma erosion opening switch  

NASA Astrophysics Data System (ADS)

The plasma erosion opening switch (PEOS) can conduct high current (approx. MA), open quickly ( 10 ns), and withstand high voltage (approx. MV). This switching technique has been used in inductive energy storage experiments and can be used with existing generators for pulse compression, voltage multiplication and power multiplication. The PEOS is used routinely for other types of power conditioning including prepulse suppression, pulse sharpening and multimodule jitter reduction. The PEOS work to data is reviewed. It reviews basic physics principles of the PEOS and outlines the operational limits of a system that employs a PEOS. Examples of present applications of the PEOS are also discussed.

Commisso, R. J.; Cooperstein, G.; Meger, R. A.; Neri, J. M.; Ottinger, P. F.; Weber, B. V.

1985-05-01

216

A nanophotonic switching cell  

NASA Astrophysics Data System (ADS)

We present a nanophotonic/nanometric switching cell to operate in the infrared and terahertz frequency range of telecommunications. This switching cell is based on a directional coupler made of two graphene nanoribbons separated in the vertical direction, which are embedded in a hexagonal boron nitride substrate. Theoretical analysis revealed that a graphene based nanophotonics coupler, initially working in the bar state (or cross state), can be brought into the cross state (or bar state), by modifying the graphene sheet chemical potential via the gate voltage. The analytical results are confirmed by the finite element method simulations and numerical analysis scripts.

Wirth L, A.; Sombra, A. S. B.

2014-10-01

217

How Switches Increase Speed  

NSDL National Science Digital Library

This brief interactive activity, by the Electromechanical Digital Library and Wisconsin Technical College System faculty, explains clearly the reasons to use switches in place of hubs when using an LAN. The animations and corresponding explanations are helpful as the user clicks through each slide at his or her own pace. Animations can be viewed again and navigation is simple. At the end, review questions test the userâ??s knowledge. This is a good resource for students and teachers alike to familiarize themselves with switches in this fast-paced technological world.

Bartelt, Terry L. M.

218

49 CFR 236.6 - Hand-operated switch equipped with switch circuit controller.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Hand-operated switch equipped with switch...Instructions: All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped...

2011-10-01

219

49 CFR 236.6 - Hand-operated switch equipped with switch circuit controller.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Hand-operated switch equipped with switch...Instructions: All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped...

2012-10-01

220

49 CFR 236.6 - Hand-operated switch equipped with switch circuit controller.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Hand-operated switch equipped with switch...Instructions: All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped...

2010-10-01

221

49 CFR 236.6 - Hand-operated switch equipped with switch circuit controller.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Hand-operated switch equipped with switch...Instructions: All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped...

2013-10-01

222

Coherence Switching in a Four-Level System: Quantum Switching  

NASA Astrophysics Data System (ADS)

Dark resonance switching among three-laser interactions in a four-level system is observed by using an enhanced nondegenerate four-wave mixing technique. This coherence switching mechanism is based on simultaneous suppression and enhancement of two-photon absorption and has a novel application to high-speed optical switches.

Ham, Byoung S.; Hemmer, Philip R.

2000-05-01

223

Solid-state RF switch  

NASA Technical Reports Server (NTRS)

Consisting of NAND gates, switch can be expanded to multipole input and can switch at frequencies up to 30MHz. Device uses digital integrated circuits to provide isolation between inputs and between input and output ports.

Hanna, M. F.; Detweiler, H. K.

1977-01-01

224

Transparent electrode for optical switch  

DOEpatents

The invention relates generally to optical switches and techniques for applying a voltage to an electro-optical crystal, and more particularly, to transparent electodes for an optical switch. System architectures for very large inertial confinement fusion (ICF) lasers require active optical elements with apertures on the order of one meter. Large aperture optical switches are needed for isolation of stages, switch-out from regenerative amplifier cavities and protection from target retroreflections.

Goldhar, J.; Henesian, M.A.

1984-10-19

225

Kiowa Creek Switching Station  

SciTech Connect

The Western Area Power Administration (Western) proposes to construct, operate, and maintain a new Kiowa Creek Switching Station near Orchard in Morgan County, Colorado. Kiowa Creek Switching Station would consist of a fenced area of approximately 300 by 300 feet and contain various electrical equipment typical for a switching station. As part of this new construction, approximately one mile of an existing 115-kilovolt (kV) transmission line will be removed and replaced with a double circuit overhead line. The project will also include a short (one-third mile) realignment of an existing line to permit connection with the new switching station. In accordance with the Council on Environmental Quality (CEQ) regulations for implementing the procedural provisions of the National Environmental Policy Act of 1969 (NEPA), 40 CFR Parts 1500--1508, the Department of Energy (DOE) has determined that an environmental impact statement (EIS) is not required for the proposed project. This determination is based on the information contained in this environmental assessment (EA) prepared by Western. The EA identifies and evaluates the environmental and socioeconomic effects of the proposed action, and concludes that the advance impacts on the human environment resulting from the proposed project would not be significant. 8 refs., 3 figs., 1 tab.

Not Available

1990-03-01

226

Multipath star switch controller  

NASA Technical Reports Server (NTRS)

Device concept permits parallel computers to scan several commonnetwork-connected data stations at maximum rate. Sequencers leap-frog to bypass ports already being serviced by another computer. Two-path system for 16-port star switch controller is cost effective if added bandwidth or increased reliability is desired. Triple-path system would be cost effective for 32-port controller.

Anderson, T. O.

1980-01-01

227

Photonic MEMS switch applications  

NASA Astrophysics Data System (ADS)

As carriers and service providers continue their quest for profitable network solutions, they have shifted their focus from raw bandwidth to rapid provisioning, delivery and management of revenue generating services. Inherently transparent to data rate the transmission wavelength and data format, MEMS add scalability, reliability, low power and compact size providing flexible solutions to the management and/or fiber channels in long haul, metro, and access networks. MEMS based photonic switches have gone from the lab to commercial availability and are now currently in carrier trials and volume production. 2D MEMS switches offer low up-front deployment costs while remaining scalable to large arrays. They allow for transparent, native protocol transmission. 2D switches enable rapid service turn-up and management for many existing and emerging revenue rich services such as storage connectivity, optical Ethernet, wavelength leasing and optical VPN. As the network services evolve, the larger 3D MEMS switches, which provide greater scalability and flexibility, will become economically viable to serve the ever-increasing needs.

Husain, Anis

2001-07-01

228

Molecular Rotors as Switches  

PubMed Central

The use of a functional molecular unit acting as a state variable provides an attractive alternative for the next generations of nanoscale electronics. It may help overcome the limits of conventional MOSFETd due to their potential scalability, low-cost, low variability, and highly integratable characteristics as well as the capability to exploit bottom-up self-assembly processes. This bottom-up construction and the operation of nanoscale machines/devices, in which the molecular motion can be controlled to perform functions, have been studied for their functionalities. Being triggered by external stimuli such as light, electricity or chemical reagents, these devices have shown various functions including those of diodes, rectifiers, memories, resonant tunnel junctions and single settable molecular switches that can be electronically configured for logic gates. Molecule-specific electronic switching has also been reported for several of these device structures, including nanopores containing oligo(phenylene ethynylene) monolayers, and planar junctions incorporating rotaxane and catenane monolayers for the construction and operation of complex molecular machines. A specific electrically driven surface mounted molecular rotor is described in detail in this review. The rotor is comprised of a monolayer of redox-active ligated copper compounds sandwiched between a gold electrode and a highly-doped P+ Si. This electrically driven sandwich-type monolayer molecular rotor device showed an on/off ratio of approximately 104, a read window of about 2.5 V, and a retention time of greater than 104 s. The rotation speed of this type of molecular rotor has been reported to be in the picosecond timescale, which provides a potential of high switching speed applications. Current-voltage spectroscopy (I-V) revealed a temperature-dependent negative differential resistance (NDR) associated with the device. The analysis of the device I–V characteristics suggests the source of the observed switching effects to be the result of the redox-induced ligand rotation around the copper metal center and this attribution of switching is consistent with the observed temperature dependence of the switching behavior as well as the proposed energy diagram of the device. The observed resistance switching shows the potential for future non-volatile memories and logic devices applications. This review will discuss the progress and provide a perspective of molecular motion for nanoelectronics and other applications.

Xue, Mei; Wang, Kang L.

2012-01-01

229

A RAILROAD SWITCHING YARD CONTROLLER  

E-print Network

A RAILROAD SWITCHING YARD CONTROLLER: DIGITAL ELECTRONICS AS AN EDUCATIONAL TOOL I. Program. Funding: NSF, DOE, CPS (~$45K / yr.) A Sample Lesson: Train Switching Yard Design #12;BUILDING A RAILROAD is then applied to building a railroad switching yard controller. STEP 1: Base 10 numbers, Base 2, TRUE or FALSE 1

Reed, Dale F.

230

Illuminated push-button switch  

NASA Technical Reports Server (NTRS)

An illuminated push-button switch is described. It is characterized by the fact that is consists of a switch group, an operator button opening and closing the switch group, and a light-emitting element which illuminates the face of the operator button.

Iwagiri, T.

1983-01-01

231

Heterothallism in Saccharomyces cerevisiae isolates from nature: effect of HO locus on the mode of reproduction  

PubMed Central

Understanding the evolution of sex and recombination, key factors in the evolution of life, is a major challenge in biology. Studies of reproduction strategies of natural populations are important to complement the theoretical and experimental models. Fungi with both sexual and asexual life cycles are an interesting system for understanding the evolution of sex. In a study of natural populations of yeast Saccharomyces cerevisiae, we found that the isolates are heterothallic, meaning their mating type is stable, while the general belief is that natural S. cerevisiae strains are homothallic (can undergo mating-type switching). Mating-type switching is a gene-conversion process initiated by a site-specific endonuclease HO; this process can be followed by mother–daughter mating. Heterothallic yeast can mate with unrelated haploids (amphimixis), or undergo mating between spores from the same tetrad (intratetrad mating, or automixis), but cannot undergo mother–daughter mating as homothallic yeasts can. Sequence analysis of HO gene in a panel of natural S. cerevisiae isolates revealed multiple mutations. Good correspondence was found in the comparison of population structure characterized using 19 microsatellite markers spread over eight chromosomes and the HO sequence. Experiments that tested whether the mating-type switching pathway upstream and downstream of HO is functional, together with the detected HO mutations, strongly suggest that loss of function of HO is the cause of heterothallism. Furthermore, our results support the hypothesis that clonal reproduction and intratetrad mating may predominate in natural yeast populations, while mother–daughter mating might not be as significant as was considered. PMID:20002587

EZOV, TAL KATZ; CHANG, SHANG-LIN; FRENKEL, ZE’EV; SEGRÈ, AYELLET V.; BAHALUL, MORAN; MURRAY, ANDREW W.; LEU, JUN-YI; KOROL, ABRAHAM; KASHI, YECHEZKEL

2014-01-01

232

High gain GaAs photoconductive semiconductor switches: Switch longevity  

SciTech Connect

Optically activated, high gain GaAs switches are being tested for many different pulsed power applications that require long lifetime (longevity). The switches have p and n contact metallization (with intentional or unintentional dopants) configured in such a way as to produce p-i-n or n-i-n switches. The longevity of the switches is determined by circuit parameters and by the ability of the contacts to resist erosion. This paper will describe how the switches performed in test-beds designed to measure switch longevity. The best longevity was achieved with switches made with diffused contacts, achieving over 50 million pulses at 10 A and over 2 million pulses at 80 A.

Loubriel, G.M.; Zutavern, F.J.; Mar, A. [and others

1998-07-01

233

Original article Effect of a viable yeast culture on digestibility  

E-print Network

with 5 g yeast supplement (Saccharomyces cerevisiae, Biosafe) per day in a latin square design. Diets by yeast treatment. Supplementation of yeast in- creased acetate: propionate ratio, butyrate, isoacids, p number in the rumen fluid rapidly declined when dietary yeast was ceased. Further- more, yeast cells

Boyer, Edmond

234

Sequence specificity and fidelity of prion transmission in yeast.  

PubMed

Amyloid formation is a widespread feature of various proteins. It is associated with both important diseases (including infectious mammalian prions) and biologically positive functions, and provides a basis for structural "templating" and protein-based epigenetic inheritance (for example, in the case of yeast prions). Amyloid templating is characterized by a high level of sequence specificity and conformational fidelity. Even slight variations in sequence may produce a strong barrier for prion transmission. Yeast models provide useful insight into a mechanism of amyloid specificity and fidelity. Accumulating evidence indicates that cross-species prion transmission is controlled by the identity of short sequences (specificity stretches) rather than by the overall level of sequence identity. Location of the specificity stretches determines the location and/or size of the cross-? amyloid region that controls patterns of prion variants. In some cases of cross-species prion transmission, fidelity of variant reproduction is impaired, leading to the formation of new structural variants. We propose that such a variant switch may occur due to choice of the alternatively located secondary specificity stretches, when interaction between the primary stretches is impaired due to sequence divergence. PMID:21439395

Bruce, Kathryn L; Chernoff, Yury O

2011-07-01

235

Symmetric cell division in pseudohyphae of the yeast Saccharomyces cerevisiae.  

PubMed Central

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

Kron, S J; Styles, C A; Fink, G R

1994-01-01

236

Plasma Opening Switch Synchronization Facility  

NASA Astrophysics Data System (ADS)

The Baikal program provides a superpower generator creation which uses a plasma opening switch for output pulse production. The MOL facility is being developed within the frames of this program to test main units and systems of the planned generator at 4-6 MV, 3 MA and 100 ns. The MOL facility is planned to use 7 parallel plasma opening switch modules placed in the relatively compact vacuum chamber of 140 cm diameter. This aims at solving two main technical issued: plasma opening switch module development with external applied magnetic field and plasma switch modules synchronization. The paper describes plasma switch module design and low inductance load synchronization experimental tests results.

Altuhov, Aleksey A.; Blinov, Petr I.; Dolgachev, Georgi I.; Maslennikov, Dmitry D.; Khodeev, Ivan A.

2002-12-01

237

Sterols in yeast subcellular fractions.  

PubMed

Yeast is the most primitive organism synthesizing substantial amounts of sterols. Because of this eucaryotic organism's versatility in growth conditions, ease of culture, well-defined genetic mechanism, and characteristic subcellar architecture, it is readily applied to studies of the role of sterols in the general economy of the cell. Sterols exist in two major forms, as the free sterol, or esterified with long chain fatty acids. The importance of sterols for this organism can be demonstrated using a naturally occurring antimycotic azasterol. This agent inhibits yeast growth. Three effects are seen on sterol synthesis: inhibition of the enzymes delta14-reductase, sterol methyltransferase, and methylene reductase. Cells cultured on respiratory substrates are more sensitive to inhibition than are cells growing on glucose. We have demonstrated a relationship between respiratory competency and sterol biosynthesis in this organism. Many mutants altered in sterol synthesis are respirationally defective and must grow fermentatively. One clone has temperature conditional respiration. Experiments with purified mitochondria, prepared from this mutant and its isogenic wildtype, show that the mutant organism is able to respire at the higher temperature but lacks the ability to couple respiration to phosphorylation. No similar loss is seen in the wild-type clones. Data are given which support the proposal that, for inclusion in mitochondrial structures, yeast cells may discriminate among sterols available from the total sterol pool in favor of ergosterol. PMID:364234

Parks, L W; McLean-Bowen, C; Taylor, F R; Hough, S

1978-10-01

238

Pheromone Signaling Pathways in Yeast  

NSDL National Science Digital Library

The actions of many extracellular stimuli are elicited by complexes of cell surface receptors, heterotrimeric guanine nucleotide–binding proteins (G proteins), and mitogen-activated protein kinase (MAPK) complexes. Analysis of haploid yeast cells and their response to peptide mating pheromones has produced important advances in the understanding of G protein and MAPK signaling mechanisms. Many of the components, their interrelationships, and their regulators were first identified in yeast. Examples include definitive demonstration of a positive signaling role for G protein βγ subunits, the discovery of a three-tiered structure of the MAPK module, development of the concept of a kinase-scaffold protein, and the discovery of the first regulator of G protein signaling protein. New and powerful genomic, proteomic, and computational approaches available in yeast are beginning to uncover new pathway components and interactions and have revealed their presence in unexpected locations within the cell. This updated Connections Map in the Database of Cell Signaling includes several major revisions to this prototypical signal response pathway.

Henrik G. Dohlman (University of North Carolina;Department of Biochemistry and Biophysics REV); Janna E. Slessareva (University of North Carolina;Department of Biochemistry and Biophysics REV)

2006-12-05

239

Biopharmaceutical discovery and production in yeast.  

PubMed

The selection of an expression platform for recombinant biopharmaceuticals is often centered upon suitable product titers and critical quality attributes, including post-translational modifications. Although notable differences between microbial, yeast, plant, and mammalian host systems exist, recent advances have greatly mitigated any inherent liabilities of yeasts. Yeast expression platforms are important to both the supply of marketed biopharmaceuticals and the pipelines of novel therapeutics. In this review, recent advances in yeast-based expression of biopharmaceuticals will be discussed. The advantages of using glycoengineered yeast as a production host and in the discovery space will be illustrated. These advancements, in turn, are transforming yeast platforms from simple production systems to key technological assets in the discovery and selection of biopharmaceutical lead candidates. PMID:25014890

Meehl, Michael A; Stadheim, Terrance A

2014-12-01

240

Yeasts Diversity in Fermented Foods and Beverages  

NASA Astrophysics Data System (ADS)

People across the world have learnt to culture and use the essential microorganisms for production of fermented foods and alcoholic beverages. A fermented food is produced either spontaneously or by adding mixed/pure starter culture(s). Yeasts are among the essential functional microorganisms encountered in many fermented foods, and are commercially used in production of baker's yeast, breads, wine, beer, cheese, etc. In Asia, moulds are predominant followed by amylolytic and alcohol-producing yeasts in the fermentation processes, whereas in Africa, Europe, Australia and America, fermented products are prepared exclusively using bacteria or bacteria-yeasts mixed cultures. This chapter would focus on the varieties of fermented foods and alcoholic beverages produced by yeasts, their microbiology and role in food fermentation, widely used commercial starters (pilot production, molecular aspects), production technology of some common commercial fermented foods and alcoholic beverages, toxicity and food safety using yeasts cultures and socio-economy

Tamang, Jyoti Prakash; Fleet, Graham H.

241

Assembly of eukaryotic algal chromosomes in yeast  

PubMed Central

Background Synthetic genomic approaches offer unique opportunities to use powerful yeast and Escherichia coli genetic systems to assemble and modify chromosome-sized molecules before returning the modified DNA to the target host. For example, the entire 1 Mb Mycoplasma mycoides chromosome can be stably maintained and manipulated in yeast before being transplanted back into recipient cells. We have previously demonstrated that cloning in yeast of large (>?~?150 kb), high G?+?C (55%) prokaryotic DNA fragments was improved by addition of yeast replication origins every ~100 kb. Conversely, low G?+?C DNA is stable (up to at least 1.8 Mb) without adding supplemental yeast origins. It has not been previously tested whether addition of yeast replication origins similarly improves the yeast-based cloning of large (>150 kb) eukaryotic DNA with moderate G?+?C content. The model diatom Phaeodactylum tricornutum has an average G?+?C content of 48% and a 27.4 Mb genome sequence that has been assembled into chromosome-sized scaffolds making it an ideal test case for assembly and maintenance of eukaryotic chromosomes in yeast. Results We present a modified chromosome assembly technique in which eukaryotic chromosomes as large as ~500 kb can be assembled from cloned ~100 kb fragments. We used this technique to clone fragments spanning P. tricornutum chromosomes 25 and 26 and to assemble these fragments into single, chromosome-sized molecules. We found that addition of yeast replication origins improved the cloning, assembly, and maintenance of the large chromosomes in yeast. Furthermore, purification of the fragments to be assembled by electroelution greatly increased assembly efficiency. Conclusions Entire eukaryotic chromosomes can be successfully cloned, maintained, and manipulated in yeast. These results highlight the improvement in assembly and maintenance afforded by including yeast replication origins in eukaryotic DNA with moderate G?+?C content (48%). They also highlight the increased efficiency of assembly that can be achieved by purifying fragments before assembly. PMID:24325901

2013-01-01

242

Breaking an Epigenetic Chromatin Switch: Curious Features of Hysteresis in Saccharomyces cerevisiae Telomeric Silencing  

PubMed Central

In addition to gene network switches, local epigenetic modifications to DNA and histones play an important role in all-or-none cellular decision-making. Here, we study the dynamical design of a well-characterized epigenetic chromatin switch: the yeast SIR system, in order to understand the origin of the stability of epigenetic states. We study hysteresis in this system by perturbing it with a histone deacetylase inhibitor. We find that SIR silencing has many characteristics of a non-linear bistable system, as observed in conventional genetic switches, which are based on activities of a few promoters affecting each other through the abundance of their gene products. Quite remarkably, our experiments in yeast telomeric silencing show a very distinctive pattern when it comes to the transition from bistability to monostability. In particular, the loss of the stable silenced state, upon increasing the inhibitor concentration, does not seem to show the expected saddle node behavior, instead looking like a supercritical pitchfork bifurcation. In other words, the ‘off’ state merges with the ‘on’ state at a threshold concentration leading to a single state, as opposed to the two states remaining distinct up to the threshold and exhibiting a discontinuous jump from the ‘off’ to the ‘on’ state. We argue that this is an inevitable consequence of silenced and active regions coexisting with dynamic domain boundaries. The experimental observations in our study therefore have broad implications for the understanding of chromatin silencing in yeast and beyond. PMID:25536038

Nagaraj, Vijayalakshmi H.; Mukhopadhyay, Swagatam; Dayarian, Adel; Sengupta, Anirvan M.

2014-01-01

243

Plasma opening switch  

DOEpatents

A command triggered plasma opening switch assembly using an amplification stage. The assembly surrounds a coaxial transmission line and has a main plasma opening switch (POS) close to the load and a trigger POS upstream from the main POS. The trigger POS establishes two different current pathways through the assembly depended on whether it has received a trigger current pulse. The initial pathway has both POS's with plasma between their anodes and cathodes to form a short across the transmission line and isolating the load. The final current pathway is formed when the trigger POS receives a trigger current pulse which energizes its fast coil to push the conductive plasma out from between its anode and cathode, allowing the main transmission line current to pass to the fast coil of the main POS, thus pushing its plasma out the way so as to establish a direct current pathway to the load.

Savage, Mark E. (Albuquerque, NM); Mendel, Jr., Clifford W. (Albuquerque, NM)

2001-01-01

244

Switching Power Supplies  

NSDL National Science Digital Library

Created by Work-Ready Electronics, a project of the Advanced Technological Education program, this module walks visitors through the basics of switching power supplies. The content of the site is divided into four areas: SMPS Basics and Switching Regulators; DC-DC Converters: Charge Pumps, Forwards Converters and Flyback Converters; Inverters, UPS and Hysteresis Curve, and SMPS: Advantages, Disadvantages and Troubleshooting. There is a quiz for each area in the Knowledge Probe area, and the Learning Resources section contains five activities to help cement student understanding. There are also further resources - both print and Web based - for more information and two Questors, a Flash trivia game. The Notebook function allows visitors to take notes and review them at any time. This is an excellent resource students and educators in electronics technician programs.

245

The quantum cryptographic switch  

NASA Astrophysics Data System (ADS)

We illustrate the principle of a cryptographic switch for a quantum scenario, in which a third party (Charlie) can control to a continuously varying degree the amount of information the receiver (Bob) receives, after the sender (Alice) has sent her information through a quantum channel. Suppose Charlie transmits a Bell state to Alice and Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit information corresponding to the choice of the Bell state is made available by Charlie to Bob can the latter recover Alice's information. By varying the amount of information Charlie gives, he can continuously alter the information recovered by Bob. The performance of the protocol as subjected to the squeezed generalized amplitude damping channel is considered. We also present a number of practical situations where a cryptographic switch would be of use.

Srinatha, N.; Omkar, S.; Srikanth, R.; Banerjee, Subhashish; Pathak, Anirban

2014-01-01

246

Evaluation of Automated Yeast Identification System  

NASA Technical Reports Server (NTRS)

One hundred and nine teleomorphic and anamorphic yeast isolates representing approximately 30 taxa were used to evaluate the accuracy of the Biolog yeast identification system. Isolates derived from nomenclatural types, environmental, and clinica isolates of known identity were tested in the Biolog system. Of the isolates tested, 81 were in the Biolog database. The system correctly identified 40, incorrectly identified 29, and was unable to identify 12. Of the 28 isolates not in the database, 18 were given names, whereas 10 were not. The Biolog yeast identification system is inadequate for the identification of yeasts originating from the environment during space program activities.

McGinnis, M. R.

1996-01-01

247

Role of glucose signaling in yeast metabolism  

SciTech Connect

The conversion of glucose to ethanol and carbon dioxide by yeast was the first biochemical pathway to be studied in detail. The initial observation that this process is catalyzed by an extract of yeast led to the discovery of enzymes and coenzymes and laid the foundation for modern biochemistry. In this article, knowledge concerning the relation between uptake of and signaling by glucose in the yeast Saccharomyces cerevisiae is reviewed and compared to the analogous process in prokaryotes. It is concluded that (much) more fundamental knowledge concerning these processes is required before rational redesign of metabolic fluxes from glucose in yeast can be achieved.

Dam, K. van [Univ. of Amsterdam (Netherlands). E.C. Slater Inst.

1996-10-05

248

Prevention of Yeast Spoilage in Feed and Food by the Yeast Mycocin HMK  

Microsoft Academic Search

The yeast Williopsis mrakii produces a mycocin or yeast killer toxin designated HMK; this toxin exhibits high thermal stability, high pH stability, and a broad spectrum of activity against other yeasts. We describe con- struction of a synthetic gene for mycocin HMK and heterologous expression of this toxin in Aspergillus niger. Mycocin HMK was fused to a glucoamylase protein carrier,

K. F. Lowes; C. A. Shearman; J. Payne; D. MacKenzie; D. B. Archer; R. J. Merry; M. J. Gasson

2000-01-01

249

INDISIM-YEAST, an individual-based model to study yeast population in batch cultures  

Microsoft Academic Search

INDISIM-YEAST, an individual-based simulator, models the evolution of a yeast population by setting up rules of behaviour for each individual cell according to their own biological rules and characteristics. It takes into account the uptake, metabolism, budding reproduction and viability of the yeast cells, over a period of time in the bulk of a liquid medium, occupying a three dimensional

Marta Ginovart; Joan Xifré; Daniel López; Moises Silbert

250

CREE: Making the Switch  

SciTech Connect

CREE, with the help of ARPA-E funding, has developed a Silicon Carbide (SIC) transistor which can be used to create solid state transformers capable of meeting the unique needs of the emerging smart grid. SIC transistors are different from common silicon computer chips in that they handle grid scale voltages with ease and their high frequency switching is well suited to the intermittent nature of renewable energy generation.

Grider, David; Palmer, John

2014-03-06

251

The Acetate Switch  

PubMed Central

To succeed, many cells must alternate between life-styles that permit rapid growth in the presence of abundant nutrients and ones that enhance survival in the absence of those nutrients. One such change in life-style, the “acetate switch,” occurs as cells deplete their environment of acetate-producing carbon sources and begin to rely on their ability to scavenge for acetate. This review explains why, when, and how cells excrete or dissimilate acetate. The central components of the “switch” (phosphotransacetylase [PTA], acetate kinase [ACK], and AMP-forming acetyl coenzyme A synthetase [AMP-ACS]) and the behavior of cells that lack these components are introduced. Acetyl phosphate (acetyl?P), the high-energy intermediate of acetate dissimilation, is discussed, and conditions that influence its intracellular concentration are described. Evidence is provided that acetyl?P influences cellular processes from organelle biogenesis to cell cycle regulation and from biofilm development to pathogenesis. The merits of each mechanism proposed to explain the interaction of acetyl?P with two-component signal transduction pathways are addressed. A short list of enzymes that generate acetyl?P by PTA-ACKA-independent mechanisms is introduced and discussed briefly. Attention is then directed to the mechanisms used by cells to “flip the switch,” the induction and activation of the acetate-scavenging AMP-ACS. First, evidence is presented that nucleoid proteins orchestrate a progression of distinct nucleoprotein complexes to ensure proper transcription of its gene. Next, the way in which cells regulate AMP-ACS activity through reversible acetylation is described. Finally, the “acetate switch” as it exists in selected eubacteria, archaea, and eukaryotes, including humans, is described. PMID:15755952

Wolfe, Alan J.

2005-01-01

252

Ultrafast gas switching experiments  

SciTech Connect

We describe recent experiments which studied the physics of ultrafast gas breakdown under the extreme overvoltages which occur when a high pressure gas switch is pulse charged to hundreds of kV in 1 ns or less. The highly overvolted peaking gaps produce powerful electromagnetic pulses with risetimes < 100 ps which can be used for ultrawideband radar systems, particle accelerators, laser drivers, bioelectromagnetic studies, electromagnetic effects testing, and for basic studies of gas breakdown physics. We have produced and accurately measured pulses with 50 to 100 ps risetimes to peak levels of 75 to 160 kV at pulse repetition frequencies (PRF) to I kHz. A unique gas switch was developed to hold off hundreds of kV with parasitic inductance less than I nH. An advanced diagnostic system using Fourier compensation was developed to measure single-shot risetimes below 35 ps. The complete apparatus is described and wave forms are presented. The measured data are compared with a theoretical model which predicts key features including dependence on gas species and pressure. We have applied this technology to practical systems driving ultrawideband radiating antennas and bounded wave simulators. For example, we have developed a thyristor/pulse transformer based system using a highly overvolted cable switch. This pulser driving a Sandia- designed TEM cell, provides an ultra wideband impulse with < 200 ps risetime to the test object at a PRF > 1 kHz at > 100 kV/m E field.

Frost, C.A.; Martin, T.H.; Patterson, P.E.; Rinehart, L.F.; Rohwein, G.J.; Roose, L.D.; Aurand, J.F.; Buttram, M.T.

1996-11-01

253

Ultrafast gas switching experiments  

SciTech Connect

We describe recent experiments which studied the physics of ultrafast gas breakdown under the extreme overvoltages which occur when a high pressure gas switch is pulse charged to hundreds of kV in 1 ns or less. The highly overvolted peaking gaps produce powerful electromagnetic pulses with risetimes < 100 ps which can be used for ultrawideband radar systems, particle accelerators, laser drivers, bioelectromagnetic studies, electromagnetic effects testing, and for basic studies of gas breakdown physics. We have produced and accurately measured pulses with 50 to 100 ps risetimes to peak levels of 75 to 160 kV at pulse repetition frequencies (PRF) to 1 kHz. A unique gas switch was developed to hold off hundreds of kV with parasitic inductance less than 1 nH. An advanced diagnostic system using Fourier compensation was developed to measure single-shot risetimes below 35 ps. The complete apparatus is described and waveforms are presented. The measured data are compared with a theoretical model which predicts key features including dependence on gas species and technology to practical systems antennas and bounded wave developed a thyristor/pulse transformer based system using a highly overvolted cable switch. This pulser driving a Sandia-designed TEM cell, provides an ultra wideband impulse with < 200 ps risetime to the test object at a PRF > Khz at > 100 kV/m E field.

Frost, C.A.; Martin, T.H.; Patterson, P.E.; Rinehart, L.F.; Rohwein, G.J.; Roose, L.D.; Aurand, J.F.; Buttram, M.T.

1993-08-01

254

Cygnus Diverter Switch Analysis  

SciTech Connect

The Cygnus Dual Beam Radiographic Facility consists of two 2.25-MV, 60-kA, 50-ns x-ray sources fielded in an underground laboratory at the Nevada Test Site. The tests performed in this laboratory involve study of the dynamic properties of plutonium and are called subcritical experiments. From end-to-end, the Cygnus machines utilize the following components: Marx generator, water-filled pulse-forming line (PFL), waterfilled coaxial transmission line (WTL), 3-cell inductive voltage adder (IVA), and rod-pinch diode. The upstream WTL interface to the PFL is via a radial insulator with coaxial geometry. The downstream WTL terminates in a manifold where the center conductor splits into three lines which individually connect to each of the IVA cell inputs. There is an impedance mismatch at this juncture. It is a concern that a reflected pulse due to anomalous behavior in the IVA or diode might initiate breakdown upon arrival at the upstream PFL/WTL insulator. Therefore near the beginning of the WTL a radial diverter switch is installed to protect the insulator from over voltage and breakdown. The diverter has adjustable gap spacing, and an in-line aqueous-solution (sodium thiosulfate) resistor array for energy dissipation. There are capacitive voltage probes at both ends of the WTL and on the diverter switch. These voltage signals will be analyzed to determine diverter performance. Using this analysis the usefulness of the diverter switch will be evaluated.

G. Corrow, M. Hansen, D. Henderson, C. Mitton et al.

2008-02-01

255

Ferroelectric switching of elastin  

PubMed Central

Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 ?C/cm2, whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications. PMID:24958890

Liu, Yuanming; Cai, Hong-Ling; Zelisko, Matthew; Wang, Yunjie; Sun, Jinglan; Yan, Fei; Ma, Feiyue; Wang, Peiqi; Chen, Qian Nataly; Zheng, Hairong; Meng, Xiangjian; Sharma, Pradeep; Zhang, Yanhang; Li, Jiangyu

2014-01-01

256

Photoconductive semiconductor switches: Laser Q-switch trigger and switch-trigger laser integration  

SciTech Connect

This report provides a summary of the Pulser In a Chip 9000-Discretionary LDRD. The program began in January of 1997 and concluded in September of 1997. The over-arching goal of this LDRD is to study whether laser diode triggered photoconductive semiconductor switches (PCSS) can be used to activate electro-optic devices such as Q-switches and Pockels cells and to study possible laser diode/switch integration. The PCSS switches we used were high gain GaAs switches because they can be triggered with small amounts of laser light. The specific goals of the LDRD were to demonstrate: (1) that small laser diode arrays that are potential candidates for laser-switch integration will indeed trigger the PCSS switch, and (2) that high gain GaAs switches can be used to trigger optical Q-switches in lasers such as the lasers to be used in the X-1 Advanced Radiation Source and the laser used for direct optical initiation (DOI) of explosives. The technology developed with this LDRD is now the prime candidate for triggering the Q switch in the multiple lasers in the laser trigger system of the X-1 Advanced Radiation Source and may be utilized in other accelerators. As part of the LDRD we developed a commercial supplier. To study laser/switch integration we tested triggering the high gain GaAs switches with: edge emitting laser diodes, vertical cavity surface emitting lasers (VCSELs), and transverse junction stripe (TJS) lasers. The first two types of lasers (edge emitting and VCSELs) did activate the PCSS but are harder to integrate with the PCSS for a compact package. The US lasers, while easier to integrate with the switch, did not trigger the PCSS at the US laser power levels we used. The PCSS was used to activate the Q-switch of the compact laser to be used in the X-1 Advanced Radiation Source.

Loubriel, G.M.; Mar, A.; Hamil, R.A.; Zutavern, F.J.; Helgeson, W.D.

1997-12-01

257

Drosophila Regulate Yeast Density and Increase Yeast Community Similarity in a Natural Substrate  

PubMed Central

Drosophila melanogaster adults and larvae, but especially larvae, had profound effects on the densities and community structure of yeasts that developed in banana fruits. Pieces of fruit exposed to adult female flies previously fed fly-conditioned bananas developed higher yeast densities than pieces of the same fruits that were not exposed to flies, supporting previous suggestions that adult Drosophila vector yeasts to new substrates. However, larvae alone had dramatic effects on yeast density and species composition. When yeast densities were compared in pieces of the same fruits assigned to different treatments, fruits that developed low yeast densities in the absence of flies developed significantly higher yeast densities when exposed to larvae. Across all of the fruits, larvae regulated yeast densities within narrow limits, as compared to a much wider range of yeast densities that developed in pieces of the same fruits not exposed to flies. Larvae also affected yeast species composition, dramatically reducing species diversity across fruits, reducing variation in yeast communities from one fruit to the next (beta diversity), and encouraging the consistent development of a yeast community composed of three species of yeast (Candida californica, C. zemplinina, and Pichia kluvyeri), all of which were palatable to larvae. Larvae excreted viable cells of these three yeast species in their fecal pools, and discouraged the growth of filamentous fungi, processes which may have contributed to their effects on the yeast communities in banana fruits. These and other findings suggest that D. melanogaster adults and their larval offspring together engage in ‘niche construction’, facilitating a predictable microbial environment in the fruit substrates in which the larvae live and develop. PMID:22860093

Stamps, Judy A.; Yang, Louie H.; Morales, Vanessa M.; Boundy-Mills, Kyria L.

2012-01-01

258

Unisexual and Heterosexual Meiotic Reproduction Generate Aneuploidy and Phenotypic Diversity De Novo in the Yeast Cryptococcus neoformans  

PubMed Central

Aneuploidy is known to be deleterious and underlies several common human diseases, including cancer and genetic disorders such as trisomy 21 in Down's syndrome. In contrast, aneuploidy can also be advantageous and in fungi confers antifungal drug resistance and enables rapid adaptive evolution. We report here that sexual reproduction generates phenotypic and genotypic diversity in the human pathogenic yeast Cryptococcus neoformans, which is globally distributed and commonly infects individuals with compromised immunity, such as HIV/AIDS patients, causing life-threatening meningoencephalitis. C. neoformans has a defined a-? opposite sexual cycle; however, >99% of isolates are of the ? mating type. Interestingly, ? cells can undergo ?-? unisexual reproduction, even involving genotypically identical cells. A central question is: Why would cells mate with themselves given that sex is costly and typically serves to admix preexisting genetic diversity from genetically divergent parents? In this study, we demonstrate that ?-? unisexual reproduction frequently generates phenotypic diversity, and the majority of these variant progeny are aneuploid. Aneuploidy is responsible for the observed phenotypic changes, as chromosome loss restoring euploidy results in a wild-type phenotype. Other genetic changes, including diploidization, chromosome length polymorphisms, SNPs, and indels, were also generated. Phenotypic/genotypic changes were not observed following asexual mitotic reproduction. Aneuploidy was also detected in progeny from a-? opposite-sex congenic mating; thus, both homothallic and heterothallic sexual reproduction can generate phenotypic diversity de novo. Our study suggests that the ability to undergo unisexual reproduction may be an evolutionary strategy for eukaryotic microbial pathogens, enabling de novo genotypic and phenotypic plasticity and facilitating rapid adaptation to novel environments. PMID:24058295

Li, Wenjun; Floyd-Averette, Anna; Mieczkowski, Piotr; Dietrich, Fred S.; Heitman, Joseph

2013-01-01

259

High power switching with a V/n oil switch  

NASA Astrophysics Data System (ADS)

Accurate switching is necessary to get reproducible pulses with minimal jitter from pulse power equipment. On a 10 MV pulse power machine, Aurora, we have improved the triggering of the oil closing switch in various ways. These include suppressing fast current oscillations during capacitive charging of the switch electrodes, using a faster trigger pulse that acts only during a fraction of the switch closure time, and localization of the arc. With additional use of the machine's symmetry the output pulses are now reproducible to better than 2% over the entire pulse shape, and the jitter is reduced about twofold, to 5 ns.

Pereira, N. R.; Gondarenko, N. A.

1996-01-01

260

Multi-Port RF MEMS Switches and Switch Matrices.  

E-print Network

??Microwave and millimeter wave switch matrices are essential components in telecommunication systems. These matrices enhance satellite capacity by providing full and flexible interconnectivity between the… (more)

Daneshmand, Mojgan

2006-01-01

261

YMDB: the Yeast Metabolome Database.  

PubMed

The Yeast Metabolome Database (YMDB, http://www.ymdb.ca) is a richly annotated 'metabolomic' database containing detailed information about the metabolome of Saccharomyces cerevisiae. Modeled closely after the Human Metabolome Database, the YMDB contains >2000 metabolites with links to 995 different genes/proteins, including enzymes and transporters. The information in YMDB has been gathered from hundreds of books, journal articles and electronic databases. In addition to its comprehensive literature-derived data, the YMDB also contains an extensive collection of experimental intracellular and extracellular metabolite concentration data compiled from detailed Mass Spectrometry (MS) and Nuclear Magnetic Resonance (NMR) metabolomic analyses performed in our lab. This is further supplemented with thousands of NMR and MS spectra collected on pure, reference yeast metabolites. Each metabolite entry in the YMDB contains an average of 80 separate data fields including comprehensive compound description, names and synonyms, structural information, physico-chemical data, reference NMR and MS spectra, intracellular/extracellular concentrations, growth conditions and substrates, pathway information, enzyme data, gene/protein sequence data, as well as numerous hyperlinks to images, references and other public databases. Extensive searching, relational querying and data browsing tools are also provided that support text, chemical structure, spectral, molecular weight and gene/protein sequence queries. Because of S. cervesiae's importance as a model organism for biologists and as a biofactory for industry, we believe this kind of database could have considerable appeal not only to metabolomics researchers, but also to yeast biologists, systems biologists, the industrial fermentation industry, as well as the beer, wine and spirit industry. PMID:22064855

Jewison, Timothy; Knox, Craig; Neveu, Vanessa; Djoumbou, Yannick; Guo, An Chi; Lee, Jacqueline; Liu, Philip; Mandal, Rupasri; Krishnamurthy, Ram; Sinelnikov, Igor; Wilson, Michael; Wishart, David S

2012-01-01

262

Engineering the Substrate Specificity of the DhbE Adenylation Domain by Yeast Cell Surface Display  

PubMed Central

SUMMARY The adenylation (A) domains of nonribosomal peptide synthetases (NRPSs) activate aryl acids or amino acids to launch their transfer through the NRPS assembly line for the biosynthesis of many medicinally important natural products. In order to expand the substrate pool of NRPSs, we developed a method based on yeast cell surface display to engineer the substrate specificities of the A-domains. We acquired A-domain mutants of DhbE that have 11- and 6-fold increases in kcat/Km with nonnative substrates 3-hydroxybenzoic acid and 2-aminobenzoic acid, respectively and corresponding 3- and 33-fold decreases in kcat/Km values with the native substrate 2,3-dihydroxybenzoic acid, resulting in a dramatic switch in substrate specificity of up to 200-fold. Our study demonstrates that yeast display can be used as a high throughput selection platform to reprogram the “nonribosomal code” of A-domains. PMID:23352143

Zhang, Keya; Nelson, Kathryn M.; Bhuripanyo, Karan; Grimes, Kimberly D.; Zhao, Bo; Aldrich, Courtney C.; Yin, Jun

2013-01-01

263

Prevention of Yeast Spoilage in Feed and Food by the Yeast Mycocin HMK  

PubMed Central

The yeast Williopsis mrakii produces a mycocin or yeast killer toxin designated HMK; this toxin exhibits high thermal stability, high pH stability, and a broad spectrum of activity against other yeasts. We describe construction of a synthetic gene for mycocin HMK and heterologous expression of this toxin in Aspergillus niger. Mycocin HMK was fused to a glucoamylase protein carrier, which resulted in secretion of biologically active mycocin into the culture media. A partial purification protocol was developed, and a comparison with native W. mrakii mycocin showed that the heterologously expressed mycocin had similar physiological properties and an almost identical spectrum of biological activity against a number of yeasts isolated from silage and yoghurt. Two food and feed production systems prone to yeast spoilage were used as models to assess the ability of mycocin HMK to act as a biocontrol agent. The onset of aerobic spoilage in mature maize silage was delayed by application of A. niger mycocin HMK on opening because the toxin inhibited growth of the indigenous spoilage yeasts. This helped maintain both higher lactic acid levels and a lower pH. In yoghurt spiked with dairy spoilage yeasts, A. niger mycocin HMK was active at all of the storage temperatures tested at which yeast growth occurred, and there was no resurgence of resistant yeasts. The higher the yeast growth rate, the more effective the killing action of the mycocin. Thus, mycocin HMK has potential applications in controlling both silage spoilage and yoghurt spoilage caused by yeasts. PMID:10698773

Lowes, K. F.; Shearman, C. A.; Payne, J.; MacKenzie, D.; Archer, D. B.; Merry, R. J.; Gasson, M. J.

2000-01-01

264

Growth requirements of san francisco sour dough yeasts and bakers' yeast.  

PubMed

The growth requirements of several yeasts isolated from San Francisco sour dough mother sponges were compared with those of bakers' yeast. The sour dough yeasts studied were one strain of Saccharomyces uvarum, one strain of S. inusitatus, and four strains of S. exiguus. S. inusitatus was the only yeast found to have an amino acid requirement, namely, methionine. All of the yeasts had an absolute requirement for pantothenic acid and a partial requirement for biotin. Inositol was stimulatory to all except bakers' yeast. All strains of S. exiguus required niacin and thiamine. Interestingly, S. inusitatus, the only yeast that required methionine, also needed folic acid. For optimal growth of S. exiguus in a molasses medium, supplementation with thiamine was required. PMID:16345154

Henry, N

1976-03-01

265

Switched Ethernet for factory communication  

Microsoft Academic Search

Focuses on the special requirements of the control-level within factory communication systems to transmit real-time data via a switched Ethernet network. A performance evaluation of switched Ethernet is presented by providing simulation results. The simulations study the influence of different network topologies as well as the scheduling algorithms first-come-first-served and priority queuing within devices and intermediate systems, like switches. Furthermore

E. Jasperneite; Peter Neumann

2001-01-01

266

Yeast flora of grape berries during ripening  

Microsoft Academic Search

The yeast flora associated with the surface of grapes during ripening was studied with regard to different sectors of the grape skin and the position in the bunch by means of traditional as well as more vigorous preisolation and precounting treatments. The yeast number per square centimeter of skin increases with ripening and is highest in the area immediately surrounding

Gianfranco Rosini; Federico Federici; Alessandro Martini

1982-01-01

267

Fermentation studies using Saccharomyces diastaticus yeast strains  

SciTech Connect

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).

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

1981-01-01

268

Yeast: An Experimental Organism for Modern Biology.  

ERIC Educational Resources Information Center

Discusses the applicability and advantages of using yeasts as popular and ideal model systems for studying and understanding eukaryotic biology at the cellular and molecular levels. Cites experimental tractability and the cooperative tradition of the research community of yeast biologists as reasons for this success. (RT)

Botstein, David; Fink, Gerald R.

1988-01-01

269

The wine and beer yeast Dekkera bruxellensis  

PubMed Central

Recently, the non-conventional yeast Dekkera bruxellensis has been gaining more and more attention in the food industry and academic research. This yeast species is a distant relative of Saccharomyces cerevisiae and is especially known for two important characteristics: on the one hand, it is considered to be one of the main spoilage organisms in the wine and bioethanol industry; on the other hand, it is 'indispensable' as a contributor to the flavour profile of Belgium lambic and gueuze beers. Additionally, it adds to the characteristic aromatic properties of some red wines. Recently this yeast has also become a model for the study of yeast evolution. In this review we focus on the recently developed molecular and genetic tools, such as complete genome sequencing and transformation, to study and manipulate this yeast. We also focus on the areas that are particularly well explored in this yeast, such as the synthesis of off-flavours, yeast detection methods, carbon metabolism and evolutionary history. © 2014 The Authors. Yeast published by John Wiley & Sons, Ltd. PMID:24932634

Schifferdecker, Anna Judith; Dashko, Sofia; Ishchuk, Olena P; Piškur, Jure

2014-01-01

270

The yeast expression system for recombinant glycosyltransferases  

Microsoft Academic Search

Glycosyltransferases are increasingly being used for in vitro synthesis of oligosaccharides. Since these enzymes are difficult to purify from natural sources, expression systems for soluble forms of the recombinant enzymes have been developed. This review focuses on the current state of development of yeast expression systems. Two yeast species have mainly been used, i.e. Saccharomyces cerevisiae and Pichia pastoris. Safety

Martine Malissard; Steffen Zeng; Eric G. Berger

1999-01-01

271

Production of serpins using yeast expression systems  

Microsoft Academic Search

Serpins occupy a unique niche in the field of biology. As more of them are discovered, the need to produce sufficient quantities of each to aid experimental and therapeutic research increases. Yeast expression systems are well suited for the production of recombinant serpins. The genetics of many yeast species is well understood and readily manipulated to induce the targeted over-production

Philip A. Pemberton; Phillip I. Bird

2004-01-01

272

YEAST MEIOSIS Sister kinetochores are mechanically  

E-print Network

YEAST MEIOSIS Sister kinetochores are mechanically fused during meiosis I in yeast Krishna K Production of healthy gametes requires a reductional meiosis I division in which replicated sister chromatids comigrate, rather than separate as in mitosis or meiosis II. Fusion of sister kinetochores during meiosis I

Asbury, Chip

273

Chronological aging leads to apoptosis in yeast  

Microsoft Academic Search

uring the past years, yeast has been successfully established as a model to study mechanisms of apoptotic regulation. However, the beneficial effects of such a cell suicide program for a unicellular organism remained obscure. Here, we demonstrate that chronologi- cally aged yeast cultures die exhibiting typical markers of apoptosis, accumulate oxygen radicals, and show caspase activation. Age-induced cell death is

Eva Herker; Helmut Jungwirth; Katharina A. Lehmann; Corinna Maldener; Kai-Uwe Fröhlich; Silke Wissing; Sabrina Büttner; Markus Fehr; Stephan Sigrist; Frank Madeo

2004-01-01

274

Definition, classification and nomenclature of the yeasts  

Technology Transfer Automated Retrieval System (TEKTRAN)

This submission includes sections for the Preface, Use of this Book, Table of Contents and a chapter entitled Definition, classification and nomenclature of the yeasts, which are to be published in The Yeasts, A Taxonomic Study, 5th edition. This book has been prepared by a team of international ex...

275

Enological functions of parietal yeast mannoproteins.  

PubMed

Parietal yeast mannoproteins play a very important role in the overall vinification process. Their production and release, both during winemaking and aging on lees, depends on the specific yeast strain and the nutritional conditions. The following enological functions of parietal yeast mannoproteins have been described: (a) adsorption of ochratoxin A; (b) combination with phenolic compounds; (c) increased growth of malolactic bacteria; (d) inhibition of tartrate salt crystallization; (e) interaction with flor wines; (f) prevention of haze; (g) reinforcement of aromatic components; (h) wine enrichment during aging on fine lees; (i) yeast flocculation and autolysis in sparkling wines. Further discoveries related to their enological functions are foreseeable. Yeast-derived mannoproteins may well induce chemical, sensorial and health benefits, thus greatly improving wine quality. PMID:16622788

Caridi, Andrea

2006-01-01

276

Composite Thermal Switch  

NASA Technical Reports Server (NTRS)

Lithium primary and lithium ion secondary batteries provide high specific energy and energy density. The use of these batteries also helps to reduce launch weight. Both primary and secondary cells can be packaged as high-rate cells, which can present a threat to crew and equipment in the event of external or internal short circuits. Overheating of the cell interior from high current flows induced by short circuits can result in exothermic reactions in lithium primary cells and fully charged lithium ion secondary cells. Venting of the cell case, ejection of cell components, and fire have been reported in both types of cells, resulting from abuse, cell imperfections, or faulty electronic control design. A switch has been developed that consists of a thin layer of composite material made from nanoscale particles of nickel and Teflon that conducts electrons at room temperature and switches to an insulator at an elevated temperature, thus interrupting current flow to prevent thermal runaway caused by internal short circuits. The material is placed within the cell, as a thin layer incorporated within the anode and/or the cathode, to control excess currents from metal-to-metal or metal-to-carbon shorts that might result from cell crush or a manufacturing defect. The safety of high-rate cells is thus improved, preventing serious injury to personnel and sensitive equipment located near the battery. The use of recently available nanoscale particles of nickel and Teflon permits an improved, homogeneous material with the potential to be fine-tuned to a unique switch temperature, sufficiently below the onset of a catastrophic chemical reaction. The smaller particles also permit the formation of a thinner control film layer (<50 m), which can be incorporated into commercial high-rate lithium primary and secondary cells. The innovation permits incorporation in current lithium and lithium-ion cell designs with a minimal impact on cell weight and volume. The composite thermal switch (CTS(TradeMark)) coating can be incorporated in either the anode or cathode or both. The coating can be applied in a variety of different processes that permits incorporation in the cell and electrode manufacturing processes. The CTS responds quickly and halts current flow in the hottest parts of the cell first. The coating can be applied to metal foil and supplied as a cell component onto which the active electrode materials are coated.

McDonald, Robert; Brawn, Shelly; Harrison, Katherine; O'Toole, Shannon; Moeller, Michael

2011-01-01

277

Power transistor switching characterization  

NASA Technical Reports Server (NTRS)

The switching properties of power transistors are investigated. The devices studied were housed in IO-3 cases and were of an n(+)-p-n(-)-n(+) vertical dopant structure. The effects of the magnitude of the reverse-base current and temperature on the reverse-bias second breakdown characteristics are discussed. Brief discussions of device degradation due to second breakdown and of a constant voltage turn-off circuit are included. A description of a vacuum tube voltage clamp circuit which reduces clamped collector voltage overshoot is given.

Blackburn, D. L.

1981-01-01

278

Hybrid switch for resonant power converters  

DOEpatents

A hybrid switch comprising two semiconductor switches connected in parallel but having different voltage drop characteristics as a function of current facilitates attainment of zero voltage switching and reduces conduction losses to complement reduction of switching losses achieved through zero voltage switching in power converters such as high-current inverters.

Lai, Jih-Sheng; Yu, Wensong

2014-09-09

279

Solid State Spark Gap Replacement Switches  

Microsoft Academic Search

Improvements in solid state high voltage switching technology now makes it feasible to replace triggered spark gap switches, used in many medical and commercial applications to switch tens of kilovolts and thousands of amperes, with compact solid state switches. The solid state switch we have developed is triggered by a single 10 V isolated trigger pulse to only one stage

S. C. Glidden; H. D. Sanders

2005-01-01

280

LCT protective dump-switch tests  

SciTech Connect

Each of the six coils in the Large Coil Task (LCT) has a separate power supply, dump resistor, and switching circuit. Each switching circuit contains five switches, two of which are redundant. The three remaining switches perform separate duties in an emergency dump situation. These three switches were tested to determine their ability to meet the LCT conditions.

Parsons, W.M.

1981-01-01

281

Growing yeast into cylindrical colonies.  

PubMed

Microorganisms often form complex multicellular assemblies such as biofilms and colonies. Understanding the interplay between assembly expansion, metabolic yield, and nutrient diffusion within a freely growing colony remains a challenge. Most available data on microorganisms are from planktonic cultures, due to the lack of experimental tools to control the growth of multicellular assemblies. Here, we propose a method to constrain the growth of yeast colonies into simple geometric shapes such as cylinders. To this end, we designed a simple, versatile culture system to control the location of nutrient delivery below a growing colony. Under such culture conditions, yeast colonies grow vertically and only at the locations where nutrients are delivered. Colonies increase in height at a steady growth rate that is inversely proportional to the cylinder radius. We show that the vertical growth rate of cylindrical colonies is not defined by the single-cell division rate, but rather by the colony metabolic yield. This contrasts with cells in liquid culture, in which the single-cell division rate is the only parameter that defines the population growth rate. This method also provides a direct, simple method to estimate the metabolic yield of a colony. Our study further demonstrates the importance of the shape of colonies on setting their expansion. We anticipate that our approach will be a starting point for elaborate studies of the population dynamics, evolution, and ecology of microbial colonies in complex landscapes. PMID:24853750

Vulin, Clément; Di Meglio, Jean-Marc; Lindner, Ariel B; Daerr, Adrian; Murray, Andrew; Hersen, Pascal

2014-05-20

282

Exact emulation of an output queueing switch by a combined input output queueing switch  

Microsoft Academic Search

Combined input-output queueing switches (CIOQ) have better scaling properties than output queueing (OQ) switches. However, a CIOQ switch may have lower switch throughput and, more importantly, it is difficult to control delay in a CIOQ switch due to the existence of multiple queueing points. In this paper, we study the following problem: can a CIOQ switch be designed to behave

Ion Stoica; Hui Zhang

1998-01-01

283

Heat pipe thermal switch  

NASA Technical Reports Server (NTRS)

A thermal switch for controlling the dissipation of heat between a body is described. The thermal switch is comprised of a flexible bellows defining an expansible vapor chamber for a working fluid located between an evaporation and condensation chamber. Inside the bellows is located a coiled retaining spring and four axial metal mesh wicks, two of which have their central portions located inside of the spring while the other two have their central portions located between the spring and the side wall of the bellows. The wicks are terminated and are attached to the inner surfaces of the outer end walls of evaporation and condensation chambers respectively located adjacent to the heat source and heat sink. The inner surfaces of the end walls furthermore include grooves to provide flow channels of the working fluid to and from the wick ends. The evaporation and condensation chambers are connected by turnbuckles and tension springs to provide a set point adjustment for setting the gap between an interface plate on the condensation chamber and the heat sink.

Wolf, D. A. (inventor)

1983-01-01

284

A high capacity satellite switched TDMA microwave switch matrix  

NASA Technical Reports Server (NTRS)

A description is given of the conceptual design of a high-capacity satellite switched-time division multiple access (SS-TDMA) microwave switch matrix fabricated with GaAs monolithic microwave integrated circuits (MMICs), including integration of both microwave and control logic circuits into the monolithic design. The technology required for a 30/20 GHz communications system includes an on-board SS-TDMA switch matrix. A conceptual design study that has been completed for a wideband, high-capacity (typically 100 x 100) channel switch matrix using technology anticipated for 1987 is described, noting that the study resulted in a switch matrix design concept using a coupled crossbar architecture implemented with MMIC. The design involves basic building block MMIC, permitting flexible growth and efficient wraparound redundancy to increase reliability.

Cory, B. J.; Berkowitz, M.

1981-01-01

285

Transcriptional regulation and chromatin remodeling mechanisms at PHO5  

E-print Network

in nucleosome remodeling. The most widely studied complex is the Swi-Snf complex in yeast, named for its role in mating- type switching as well as sucrose fermentation (reviewed in Martens and Winston, 2003). Defects in the human Swi-Snf complex are linked... with permission from Archana Dhasarathy. 12 An earlier study showed that yeast genes could be classified into three distinct classes based on their requirement for the chromatin remodelers Swi- Snf and SAGA: 1) those genes which require both Swi-Snf...

Carvin, Christopher Dumas

2005-08-29

286

Robust adaptive control of switched systems  

E-print Network

In this thesis, robust adaptive controllers are developed for classes of switched nonlinear systems. Switched systems are those governed by differential equations, which undergo vector field switching due to sudden changes ...

El-Rifai, Khalid, 1979-

2007-01-01

287

14 CFR 25.1145 - Ignition switches.  

Code of Federal Regulations, 2010 CFR

... 1 2010-01-01 2010-01-01 false Ignition switches. 25.1145 Section 25.1145 ...Powerplant Controls and Accessories § 25.1145 Ignition switches. (a) Ignition switches must control each engine ignition...

2010-01-01

288

14 CFR 23.1145 - Ignition switches.  

Code of Federal Regulations, 2010 CFR

... 1 2010-01-01 2010-01-01 false Ignition switches. 23.1145 Section 23.1145 ...Powerplant Controls and Accessories § 23.1145 Ignition switches. (a) Ignition switches must control and shut off each...

2010-01-01

289

14 CFR 29.1145 - Ignition switches.  

Code of Federal Regulations, 2010 CFR

... 1 2010-01-01 2010-01-01 false Ignition switches. 29.1145 Section 29.1145 ...Powerplant Controls and Accessories § 29.1145 Ignition switches. (a) Ignition switches must control each ignition circuit...

2010-01-01

290

Performance evaluation of transoceanic switching  

Microsoft Academic Search

The method of synchronous digital hierarchy self-healing ring (SDH SHR) in submarine operation is being developed to improve the reliability of international submarine optical communications. Transoceanic switching is applied in SDH SHR because of the unique features of an international optical submarine cable network: longer distance, submarine environment and fewer terminal stations. We study the system performance of transoceanic switching.

Du Yingzi; Hao Weimin

1998-01-01

291

Corona in switching power supplies  

Microsoft Academic Search

Design literature for dealing with corona in switching power supplies for aircraft or in lamp ballasts does not contain the effects of the switching frequency on corona inception or extinguish voltages. Test data is presented showing these effects. Design techniques for corona are also discussed

A. Brockschmidt

1997-01-01

292

Audio Switch SpeakersAvotec  

E-print Network

Control Monitor Keyboard & Mouse Audio Switch Control SpeakersAvotec USB HUB USB HUB USB CAT5FORP USB Ext Stim PC Stim Mac Laptop Audio RCA RCA USB CAT5 FORPUSB Ext Video K&M Video Video Speakers Avotec Projector Video Switch VGA RCA RCA 3T Audio and Visual Stimulus Setup DVD Drive K&MSiemens RCA

Walker, Matthew P.

293

Biosorption of mercury on magnetically modified yeast cells  

Microsoft Academic Search

Brewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water based magnetic fluid stabilized perchloric acid. The magnetically modified yeast cells were characterized by scanning electron microscopy (SEM) and electron spin resonance (ESR). Hg2+ biosorption-desorption properties of magnetically modified yeast cells from synthetic solutions were utilized in batch system. The biosorption process was fast; 80% of

Handan Yavuz; Adil Denizli; Hakan Güngüne?; Mirka Safarikova; Ivo Safarik

2006-01-01

294

Copper Biosorption on Magnetically Modified Yeast Cells Under Magnetic Field  

Microsoft Academic Search

Brewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water-based magnetic fluid stabilized perchloric acid. The magnetically modified yeast cells were characterized by scanning electron microscopy (SEM). Cu biosorption properties of magnetically modified yeast cells from synthetic solutions were utilized in a continuous magnetic system. The Cu ion-binding capacity decreased drastically with the increase of the

Lokman Uzun; Necdet Sa?lam; Mirka Safarikova; Ivo Safarik; Adil Denizli

2011-01-01

295

The genetics of aging in the yeast Saccharomyces cerevisiae  

Microsoft Academic Search

The yeastSaccharomyces cerevisiae possesses a finite life span similar in many attributes and implications to that of higher eukaryotes. Here, the measure of the life span is the number of generations or divisions the yeast cell has undergone. The yeast cell is the organism, simplifying many aspects of aging research. Most importantly, the genetics of yeast is highly-developed and readily

S. Michal Jazwinski

1993-01-01

296

A Caspase-Related Protease Regulates Apoptosis in Yeast  

Microsoft Academic Search

Yeast can undergo cell death accompanied by cellular markers of apoptosis. However, orthologs of classical mammalian apoptosis regulators appeared to be missing from the yeast genome, challenging a common mechanism of yeast and mammalian apoptosis. Here we investigate Yor197w, a yeast protein with structural homology to mammalian caspases, and demonstrate caspase-like processing of the protein. Hydrogen peroxide treatment induces apoptosis

Frank Madeo; Eva Herker; Corinna Maldener; Silke Wissing; Stephan Lächelt; Mark Herlan; Markus Fehr; Kirsten Lauber; Stephan J Sigrist; Sebastian Wesselborg; Kai-Uwe Fröhlich

2002-01-01

297

The wine and beer yeast Dekkera bruxellensis.  

PubMed

Recently, the non-conventional yeast Dekkera bruxellensis has been gaining more and more attention in the food industry and academic research. This yeast species is a distant relative of Saccharomyces cerevisiae and is especially known for two important characteristics: on the one hand, it is considered to be one of the main spoilage organisms in the wine and bioethanol industry; on the other hand, it is 'indispensable' as a contributor to the flavour profile of Belgium lambic and gueuze beers. Additionally, it adds to the characteristic aromatic properties of some red wines. Recently this yeast has also become a model for the study of yeast evolution. In this review we focus on the recently developed molecular and genetic tools, such as complete genome sequencing and transformation, to study and manipulate this yeast. We also focus on the areas that are particularly well explored in this yeast, such as the synthesis of off-flavours, yeast detection methods, carbon metabolism and evolutionary history. PMID:24932634

Schifferdecker, Anna Judith; Dashko, Sofia; Ishchuk, Olena P; Piškur, Jure

2014-09-01

298

Accelerating Yeast Prion Biology using Droplet Microfluidics  

NASA Astrophysics Data System (ADS)

Prions are infectious proteins in a misfolded form, that can induce normal proteins to take the misfolded state. Yeast prions are relevant, as a model of human prion diseases, and interesting from an evolutionary standpoint. Prions may also be a form of epigenetic inheritance, which allow yeast to adapt to stressful conditions at rates exceeding those of random mutations and propagate that adaptation to their offspring. Encapsulation of yeast in droplet microfluidic devices enables high-throughput measurements with single cell resolution, which would not be feasible using bulk methods. Millions of populations of yeast can be screened to obtain reliable measurements of prion induction and loss rates. The population dynamics of clonal yeast, when a fraction of the cells are prion expressing, can be elucidated. Furthermore, the mechanism by which certain strains of bacteria induce yeast to express prions in the wild can be deduced. Integrating the disparate fields of prion biology and droplet microfluidics reveals a more complete picture of how prions may be more than just diseases and play a functional role in yeast.

Ung, Lloyd; Rotem, Assaf; Jarosz, Daniel; Datta, Manoshi; Lindquist, Susan; Weitz, David

2012-02-01

299

Sonic crystal acoustic switch device.  

PubMed

This study reports a wave-controlled sonic crystal switch device that exhibits a destructive interference-based wave to wave reverse switching effect. By applying control waves, this acoustic device, composed of a two-dimensional square lattice sonic crystal block, reduces acoustic wave transmission from input to output. The finite difference time domain simulation and experimental results confirm the wave-to-wave reverse switching effect at the peak frequencies of the second band. The proposed sonic crystal switch prototype provides a contrast rate of 86% at 11.3 kHz frequency. This wave-to-wave switching effect is useful for controlling wave propagation for smart structure applications. PMID:23742444

Alagoz, Serkan; Alagoz, Baris Baykant

2013-06-01

300

Optical Tweezing of Yeast Cells  

NASA Astrophysics Data System (ADS)

Optical Tweezers is a powerful technique that aids in understanding and applying the unique principles of photonics, optical physics, and basic cell biology. The experiments presented involve using HeNe lasers (632.8 nm) to trap spherical and ovular shaped objects in a solution. Polystyrene spheres, six micrometers in diameter, were trapped and moved with the laser to calibrate our system. The spheres were submerged in a Sodium Phosphate buffer solution to prevent sticking. Saccharomyces cerevisae, better known as yeast, was grown in a glucose rich environment to reach sizes of four to nine micrometers. Our optical tweezers captured and moved these cells under the operators command. A two laser system was utilized to control two cells simultaneously and attempt the splitting of cells. )

Gilroy, Kyle; Ochoa, Romulo

2010-02-01

301

Optimized scalable network switch  

DOEpatents

In a massively parallel computing system having a plurality of nodes configured in m multi-dimensions, each node including a computing device, a method for routing packets towards their destination nodes is provided which includes generating at least one of a 2m plurality of compact bit vectors containing information derived from downstream nodes. A multilevel arbitration process in which downstream information stored in the compact vectors, such as link status information and fullness of downstream buffers, is used to determine a preferred direction and virtual channel for packet transmission. Preferred direction ranges are encoded and virtual channels are selected by examining the plurality of compact bit vectors. This dynamic routing method eliminates the necessity of routing tables, thus enhancing scalability of the switch.

Blumrich, Matthias A. (Ridgefield, CT); Chen, Dong (Croton on Hudson, NY); Coteus, Paul W. (Yorktown Heights, NY)

2010-02-23

302

''Smart'' watchdog safety switch  

DOEpatents

A method and apparatus for monitoring a process having a periodic output so that the process equipment is not damaged in the event of a controller failure, comprising a low-pass and peak clipping filter, an event detector that generates an event pulse for each valid change in magnitude of the filtered periodic output, a timing pulse generator, a counter that increments upon receipt of any timing pulse and resets to zero on receipt of any event pulse, an alarm that alerts when the count reaches some preselected total count, and a set of relays that opens to stop power to process equipment. An interface module can be added to allow the switch to accept a variety of periodic output signals. 21 figures.

Kronberg, J.W.

1991-10-01

303

"Smart" watchdog safety switch  

DOEpatents

A method and apparatus for monitoring a process having a periodic output so that the process equipment is not damaged in the event of a controller failure, comprising a low-pass and peak clipping filter, an event detector that generates an event pulse for each valid change in magnitude of the filtered periodic output, a timing pulse generator, a counter that increments upon receipt of any timing pulse and resets to zero on receipt of any event pulse, an alarm that alerts when the count reaches some preselected total count, and a set of relays that opens to stop power to process equipment. An interface module can be added to allow the switch to accept a variety of periodic output signals.

Kronberg, James W. (353 Church Rd., Beech Island, SC 29842)

1991-01-01

304

Optimized scalable network switch  

DOEpatents

In a massively parallel computing system having a plurality of nodes configured in m multi-dimensions, each node including a computing device, a method for routing packets towards their destination nodes is provided which includes generating at least one of a 2m plurality of compact bit vectors containing information derived from downstream nodes. A multilevel arbitration process in which downstream information stored in the compact vectors, such as link status information and fullness of downstream buffers, is used to determine a preferred direction and virtual channel for packet transmission. Preferred direction ranges are encoded and virtual channels are selected by examining the plurality of compact bit vectors. This dynamic routing method eliminates the necessity of routing tables, thus enhancing scalability of the switch.

Blumrich, Matthias A. (Ridgefield, CT); Chen, Dong (Croton On Hudson, NY); Coteus, Paul W. (Yorktown Heights, NY); Gara, Alan G. (Mount Kisco, NY); Giampapa, Mark E. (Irvington, NY); Heidelberger, Philip (Cortlandt Manor, NY); Steinmacher-Burow, Burkhard D. (Mount Kisco, NY); Takken, Todd E. (Mount Kisco, NY); Vranas, Pavlos M. (Bedford Hills, NY)

2007-12-04

305

Yeast and yeast-like diversity in the southernmost glacier of Europe (Calderone Glacier, Apennines, Italy).  

PubMed

The present study reports the characterization of psychrophilic yeast and yeast-like diversity in cold habitats (superficial and deep sediments, ice cores and meltwaters) of the Calderone Glacier (Italy), which is the southernmost glacier in Europe. After incubation at 4 and 20 degrees C, sediments contained about 10(2)-10(3) CFU of yeasts g(-1). The number of viable yeast cells in ice and meltwaters was several orders of magnitude lower. The concomitant presence of viable bacteria and filamentous fungi has also been observed. In all, 257 yeast strains were isolated and identified by 26S rRNA gene D1/D2 and internal transcribed spacers (1 and 2) sequencing as belonging to 28 ascomycetous and basidiomycetous species of 11 genera (Candida, Cystofilobasidium, Cryptococcus, Dioszegia, Erythrobasidium, Guehomyces, Mastigobasidium, Mrakia, Mrakiella, Rhodotorula and Sporobolomyces). Among them, the species Cryptococcus gastricus accounted for almost 40% of the total isolates. In addition, 12 strains were identified as belonging to the yeast-like species Aureobasidium pullulans and Exophiala dermatitidis, whereas 15 strains, presumably belonging to new species, yet to be described, were also isolated. Results herein reported indicate that the Calderone Glacier, although currently considered a vanishing ice body due to the ongoing global-warming phenomenon, still harbors viable psychrophilic yeast populations. Differences of yeast and yeast-like diversity between the glacier under study and other worldwide cold habitats are also discussed. PMID:20402775

Branda, Eva; Turchetti, Benedetta; Diolaiuti, Guglielmina; Pecci, Massimo; Smiraglia, Claudio; Buzzini, Pietro

2010-06-01

306

Alarm toe switch. [Patent application  

DOEpatents

An alarm toe switch inserted within a shoe for energizing an alarm circuit in a covert manner includes an insole mounting pad into which a miniature reed switch is fixedly molded. An elongated slot perpendicular to the reed switch is formed in the bottom surface of the mounting pad. A permanent cylindrical magnet positioned in the forward portion of the slot with a diameter greater than the pad thickness causes a bump above the pad. A foam rubber block is also positioned in the slot rearwardly of the magnet and holds the magnet in normal inoperative relation. A non-magnetic support plate covers the slot and holds the magnet and foam rubber in the slot. The plate minimizes bending and frictional forces to improve movement of the magnet for reliable switch activation. The bump occupies the knuckle space beneath the big toe. When the big toe is scrunched rearwardly the magnet is moved within the slot relative to the reed switch, thus magnetically activating the switch. When toe pressure is released the foam rubber block forces the magnet back into normal inoperative position to deactivate the reed switch.

Ganyard, F.P.

1980-11-18

307

[Regulation of gene expression in methylotrophic yeasts].  

PubMed

Methylotrophic yeasts are unique eukaryotic organisms, that can metabolize toxic one-carbon substrate, methyl alcohol or methanol. About 50 species of methylotrophic yeasts is known, among them 4 species are the best studied: Pichia methanolica, Hansenula polymorpha, Pichia pastoris i Candida boidinii. These organisms, especially P. pastoris i H. polymorpha appeared to be very perspective overproducers of heterologous proteins and nowadays are used for industrial production of some of them. In this review, we provide information on the organization of the genome, mechanisms of regulation of gene expression and the use of strong promoters of these yeast species to construct the producers of heterologous proteins. In more details, we analyze genetic control of carbon and nitrogen catabolic repression in H. polymorpha and also the identification of metabolites inducing catabolite repression or peroxisome selective autophagy in the medium with ethanol in the Pichia methanolica yeast. PMID:23821948

Grabek-Lejko, Dorota; Sibirny, Vladimir; Sibirny, Andriy

2013-01-01

308

Comparative Functional Genomics of the Fission Yeasts  

E-print Network

The fission yeast clade—comprising Schizosaccharomyces pombe, S. octosporus, S. cryophilus, and S. japonicus—occupies the basal branch of Ascomycete fungi and is an important model of eukaryote biology. A comparative ...

Regev, Aviv

309

Yeasts in ensiled high-moisture corn.  

PubMed

A total of 1,365 yeasts were selected from ensiled high-moisture corn at various stages in the ensiling process to determine the sequence and relative numbers of yeast species. The yeast species most frequently isolated from freshly harvested corn were Candida parapsilosis and C. intermedia; these two species were isolated infrequently after the third week of storage. Species of yeasts that predominate after the 12th day of storage were Hansenula anomala (66% of the isolates studied) and C. krusei (26% of the isolates studied). The preponderance of H. anomala and C. krusei in ensiled corn is believed to be associated with the ability of these two species to assimilate lactic acid. PMID:5914494

Burmeister, H R; Hartman, P A

1966-01-01

310

Functional analysis of the yeast genome  

Microsoft Academic Search

.   Just as Saccharomyces cerevisiae itself provides a model for so many processes essential to eukaryotic life, we anticipate that the methods and the mindset\\u000a that have moved yeast biological research \\

Petra Ross-Macdonald

2000-01-01

311

ENGINEERING THE BIOSYNTHESIS OF STYRENE IN YEAST  

EPA Science Inventory

The strategy pursued was to insert genes for phenylalanine ammonia lysase (pal) and phenolic acid decarboxylase (pad) into the yeast that would convert phenylalanine to styrene through a cinnamic acid intermediate. ...

312

Kinetochore Structure: Pulling Answers from Yeast  

E-print Network

Despite the identification of multiple kinetochore proteins, their structure and organization has remained unclear. New work uses electron microscopy to visualize isolated budding yeast kinetochore particles and reveal the ...

Cheeseman, Iain M.

313

Comparative functional genomics of the fission yeasts.  

PubMed

The fission yeast clade--comprising Schizosaccharomyces pombe, S. octosporus, S. cryophilus, and S. japonicus--occupies the basal branch of Ascomycete fungi and is an important model of eukaryote biology. A comparative annotation of these genomes identified a near extinction of transposons and the associated innovation of transposon-free centromeres. Expression analysis established that meiotic genes are subject to antisense transcription during vegetative growth, which suggests a mechanism for their tight regulation. In addition, trans-acting regulators control new genes within the context of expanded functional modules for meiosis and stress response. Differences in gene content and regulation also explain why, unlike the budding yeast of Saccharomycotina, fission yeasts cannot use ethanol as a primary carbon source. These analyses elucidate the genome structure and gene regulation of fission yeast and provide tools for investigation across the Schizosaccharomyces clade. PMID:21511999

Rhind, Nicholas; Chen, Zehua; Yassour, Moran; Thompson, Dawn A; Haas, Brian J; Habib, Naomi; Wapinski, Ilan; Roy, Sushmita; Lin, Michael F; Heiman, David I; Young, Sarah K; Furuya, Kanji; Guo, Yabin; Pidoux, Alison; Chen, Huei Mei; Robbertse, Barbara; Goldberg, Jonathan M; Aoki, Keita; Bayne, Elizabeth H; Berlin, Aaron M; Desjardins, Christopher A; Dobbs, Edward; Dukaj, Livio; Fan, Lin; FitzGerald, Michael G; French, Courtney; Gujja, Sharvari; Hansen, Klavs; Keifenheim, Dan; Levin, Joshua Z; Mosher, Rebecca A; Müller, Carolin A; Pfiffner, Jenna; Priest, Margaret; Russ, Carsten; Smialowska, Agata; Swoboda, Peter; Sykes, Sean M; Vaughn, Matthew; Vengrova, Sonya; Yoder, Ryan; Zeng, Qiandong; Allshire, Robin; Baulcombe, David; Birren, Bruce W; Brown, William; Ekwall, Karl; Kellis, Manolis; Leatherwood, Janet; Levin, Henry; Margalit, Hanah; Martienssen, Rob; Nieduszynski, Conrad A; Spatafora, Joseph W; Friedman, Nir; Dalgaard, Jacob Z; Baumann, Peter; Niki, Hironori; Regev, Aviv; Nusbaum, Chad

2011-05-20

314

Prion formation by a yeast GLFG nucleoporin  

E-print Network

The self-assembly of proteins into higher order structures is both central to normal biology and a dominant force in disease. Certain glutamine/asparagine (Q/N)-rich proteins in the budding yeast Saccharomyces cerevisiae ...

Halfmann, Randal

315

Macromolecular synthesis by yeasts under frozen conditions  

E-print Network

by the protein synthesis inhibitor cycloheximide. Experi- ments at -5°C under frozen and liquid conditionsMacromolecular synthesis by yeasts under frozen conditions Pierre Amato,* Shawn Doyle and Brent C

Christner, Brent C.

316

Monitoring Air Quality with Leaf Yeasts.  

ERIC Educational Resources Information Center

Proposes that leaf yeast serve as quick, inexpensive, and effective techniques for monitoring air quality. Outlines procedures and provides suggestions for data analysis. Includes results from sample school groups who employed this technique. (ML)

Richardson, D. H. S.; And Others

1985-01-01

317

49 CFR 236.342 - Switch circuit controller.  

Code of Federal Regulations, 2010 CFR

...342 Switch circuit controller. Switch circuit controller connected at the point to switch, derail, or movable-point frog, shall be maintained so that its contacts will not be in position corresponding to switch point closure when switch point...

2010-10-01

318

49 CFR 236.342 - Switch circuit controller.  

Code of Federal Regulations, 2011 CFR

...342 Switch circuit controller. Switch circuit controller connected at the point to switch, derail, or movable-point frog, shall be maintained so that its contacts will not be in position corresponding to switch point closure when switch point...

2011-10-01

319

49 CFR 236.342 - Switch circuit controller.  

Code of Federal Regulations, 2013 CFR

...342 Switch circuit controller. Switch circuit controller connected at the point to switch, derail, or movable-point frog, shall be maintained so that its contacts will not be in position corresponding to switch point closure when switch point...

2013-10-01

320

49 CFR 236.342 - Switch circuit controller.  

Code of Federal Regulations, 2012 CFR

...342 Switch circuit controller. Switch circuit controller connected at the point to switch, derail, or movable-point frog, shall be maintained so that its contacts will not be in position corresponding to switch point closure when switch point...

2012-10-01

321

Switch dynamics for stochastic model of genetic toggle switch  

NASA Astrophysics Data System (ADS)

Recently, more and more biological experiments have indicated that noise plays an important role in bistable systems, such as the case of the bimodal population distribution in the genetic toggle switch. In this paper, we further verify that noises in degradation rates can indeed induce switching in the genetic toggle switch. Meanwhile, we apply the theory of mean first passage time (MFPT) in high dimensional system to the above stochastic model. According to our assumption, the high order finite difference method is used to compute the MFPT (that the average time switching from one steady state to the other) and we find that the relationship between the MFPT and noise intensity is negative correlation. The result is also verified through another numerical simulation method.

Xu, Yong; Zhu, Ya-nan; Shen, Jianwei; Su, Jianbin

2014-12-01

322

Terahertz Optical Asymmetric Demultiplexer Switch with a Symmetrical Switching Window  

E-print Network

asymmetrical demultiplexer (TOAD) switch. This is achieved by saturating the semiconductor optical amplifier (SOA), located within the TOAD loop, from both directions. So that, both clockwise (CW) and counter], terahertz optical asymmetric demultiplexer (TOAD) [2], ultrafast nonlinear interferometer (UNI) [3

Haddadi, Hamed

323

Multidrug resistant yeasts in synanthropic wild birds  

PubMed Central

Background The aim of this study was to investigate the presence of multidrug resistant yeasts in the faeces of synanthropic wild birds from the Bangsar suburb of Kuala Lumpur. Methods Species characterisations of yeast isolates and determinations of antimycotic susceptibility profiles were undertaken using the commercial characterization kit, Integral System Yeasts Plus (Liofilchem, Italy). Results Fourteen species of yeasts were detected in the bird faecal samples.Candida albicans was present in 28.89% of bird faecal samples, Candida krusei (13.33%), Candida tropicalis (4.44%), Candida glabrata (4.44%), Candida parapsilosis (2.22%), Candida lambica (2.22%), Candida stellatoidea (2.22%), Candida rugosa (2.22%) and Candida lusitaniae (2.22%). Amongst the non-candidal yeast isolates, Cryptococcus laurentii was present in 6.67% of bird faecal samples, Cryptococcus uniguttulatus (4.44%), Saccharomyces cerevisiae (4.44%), Trichosporon pullulans (2.22%), Trichosporon pullulans/Cryptococcus albidus (8.89%) and Rhodotorula rubra/Rhodotorula glutinis (4.44%). Of the isolated yeasts, 18.1% (or 26/144) were found to be resistant to all 11 antimycotic agents they were tested against i.e. Nystatin, Amphotericin B, Flucytosine, Econazole, Ketoconazole, Clotrimazole, Miconazole, Itraconazole, Voriconazole, Fluconazole 16 and Fluconazole 64. 45.8% (or 66/144) of the bird faecal yeast isolates were resistant to four or more of the 11 antimycotic agents they were tested against. Conclusions This finding is of public health significance as these synanthropic wild birds may be reservoirs for transmission of drug resistant yeast infections to humans. PMID:20307325

2010-01-01

324

How to Make Yeast Cells Thrive  

NSDL National Science Digital Library

Students set up and run the experiments they designed in the Population Growth in Yeasts associated lesson, using simple yeast-molasses cultures in test tubes. Population growth is indicated by the amount of respiration occurring in the cultures, which in turn is indicated by the growth of carbon dioxide bubbles trapped within the culture tubes. Using this method, students test for a variety of environmental influences, such as temperature, food supply and pH.

Engineering K-Phd Program

325

The secretory pathway: exploring yeast diversity.  

PubMed

Protein secretion is an essential process for living organisms. In eukaryotes, this encompasses numerous steps mediated by several hundred cellular proteins. The core functions of translocation through the endoplasmic reticulum membrane, primary glycosylation, folding and quality control, and vesicle-mediated secretion are similar from yeasts to higher eukaryotes. However, recent research has revealed significant functional differences between yeasts and mammalian cells, and even among diverse yeast species. This review provides a current overview of the canonical protein secretion pathway in the model yeast Saccharomyces cerevisiae, highlighting differences to mammalian cells as well as currently unresolved questions, and provides a genomic comparison of the S. cerevisiae pathway to seven other yeast species where secretion has been investigated due to their attraction as protein production platforms, or for their relevance as pathogens. The analysis of Candida albicans, Candida glabrata, Kluyveromyces lactis, Pichia pastoris, Hansenula polymorpha, Yarrowia lipolytica, and Schizosaccharomyces pombe reveals that many - but not all - secretion steps are more redundant in S. cerevisiae due to duplicated genes, while some processes are even absent in this model yeast. Recent research obviates that even where homologous genes are present, small differences in protein sequence and/or differences in the regulation of gene expression may lead to quite different protein secretion phenotypes. PMID:23480475

Delic, Marizela; Valli, Minoska; Graf, Alexandra B; Pfeffer, Martin; Mattanovich, Diethard; Gasser, Brigitte

2013-11-01

326

Attempts to detect lycopersene formation in yeast  

PubMed Central

1. ?-Ionone vapour has been shown to cause an increase in the more saturated carotenes and a decrease in the less saturated carotenes of Rhodotorula glutinis. Lycopersene (dihydrophytoene) has been proposed as a precursor to phytoene. Attempts were made to isolate lycopersene from ?-ionone-treated cultures of R. glutinis. 2. Large samples of ?-ionone-treated cultures were examined for the presence of lycopersene. Spots were detected on silicic acid plates that could not be differentiated from synthetic lycopersene on the basis of column and thin-layer chromatographic separations and staining techniques. The lycopersene-like substance could be obtained from non-treated pigmented yeast as well as baker's yeast. 3. An extraction of bacterial-grade yeast extract also yielded a lycopersene-like substance. The extracts of R. glutinis cells cultured on media not containing yeast extract did not contain the lycopersene-like compound. 4. No significant carbon was incorporated into the lycopersene zone from 14C-labelled mevalonate, acetate and glucose by R. glutinis and baker's yeast. 5. These results indicate that compounds may exist with chromatographic properties similar to lycopersene, but that lycopersene could not be detected in either a pigmented or a non-pigmented yeast. PMID:5753091

Scharf, S. S.; Simpson, K. L.

1968-01-01

327

The growth of solar radiated yeast  

NASA Technical Reports Server (NTRS)

This researcher plans to determine if solar radiation affects the growth of yeast. The irradiated yeast was obtained from a sample exposed in space during a Space Shuttle flight of September 9-20, 1994. Further, the control groups were held at: (1) Goddard Space Flight Center (GSFC) in Greenbelt, Maryland; and (2) South Dakota School of Mines and Technology. The procedure used was based on the fact that yeast is most often used in consumable baked goods. Therefore, the yeast was incorporated into a basic Betty Crocker bread recipe. Data was collected by placing measured amounts of dough into sample containers with fifteen minute growth in height measurements collected and recorded. This researcher assumed the viability of yeast to be relative to its ability to produce carbon dioxide gas and cause the dough to rise. As all ingredients and surroundings were equal, this researcher assumed the yeast will produce the only significant difference in data collected. This researcher noted the approximate use date on all sample packages to be prior to arrival and experiment date. All dates equal, it was then assumed each would act in a similar manner of response. This assumption will allow for equally correct data collection.

Kraft, Tyrone

1995-01-01

328

The growth of solar radiated yeast  

SciTech Connect

This researcher plans to determine if solar radiation affects the growth of yeast. The irradiated yeast was obtained from a sample exposed in space during a Space Shuttle flight of September 9-20, 1994. Further, the control groups were held at: (1) Goddard Space Flight Center (GSFC) in Greenbelt, Maryland; and (2) South Dakota School of Mines and Technology. The procedure used was based on the fact that yeast is most often used in consumable baked goods. Therefore, the yeast was incorporated into a basic Betty Crocker bread recipe. Data was collected by placing measured amounts of dough into sample containers with fifteen minute growth in height measurements collected and recorded. This researcher assumed the viability of yeast to be relative to its ability to produce carbon dioxide gas and cause the dough to rise. As all ingredients and surroundings were equal, this researcher assumed the yeast will produce the only significant difference in data collected. This researcher noted the approximate use date on all sample packages to be prior to arrival and experiment date. All dates equal, it was then assumed each would act in a similar manner of response. This assumption will allow for equally correct data collection.

Kraft, T.

1995-09-01

329

Molecular-based chiroptical dipole switches  

NASA Astrophysics Data System (ADS)

A series of structurally varied organic molecular switches have been prepared and their switching behavior examined. For thermally active compounds, the switching rates have been extracted from variable temperature NMR experiments and simulation studies. Additionally, chromophores have been incorporated for optical activation of thermally stable switches. Supramolecular architectures for constructing optoelectronic devices are also described.

Parakka, James P.; Schumaker, Robert R.; Kesler, Brenda S.; Thoburn, John D.

2001-05-01

330

Hobetron current regulating switch tube  

SciTech Connect

This paper describes a novel high power electron tube that can hold off voltages up to hundreds of kilovolts, and switch hundreds of amps of current. They call the divide the Hobertron since it utilizes a hollow electron beam. Unlike magnetron injection gun (MIG) switch tubes, it does not require a magnet. Further, it uses nonintercepting control laments, and a dispenser cathode for long life and reliability. Finally, it features a double walled Faraday cage collector for high power dissipation capability. Current is very tightly controlled against changes in voltage across the switch (it is an almost perfect pentode), thus this tube is ideally suited for direct series switching applications. In the paper, various Hobertron designs, and the computer codes and methods used to create them, will be described.

True, R.B.; Hansen, R.J.; Deb, D.N.; Good, G.R.; Reass, W.A.

1999-07-01

331

Cholinergic Switching Within Neocortical Inhibitory  

E-print Network

. Cholinergic activation of subsets of cortical interneurons containing the inhibitory neurotransmitter -aminobuCholinergic Switching Within Neocortical Inhibitory Networks Zixiu Xiang, John R. Huguenard, David within cortical circuits. The functional relations between inhibitory and excitatory networks

Huguenard, John R.

332

Tagging Morphogenetic Genes by Insertional Mutagenesis in the Yeast Yarrowia lipolytica  

PubMed Central

The yeast Yarrowia lipolytica is distantly related to Saccharomyces cerevisiae, can be genetically modified, and can grow in both haploid and diploid states in either yeast, pseudomycelial, or mycelial forms, depending on environmental conditions. Previous results have indicated that the STE and RIM pathways, which mediate cellular switching in other dimorphic yeasts, are not required for Y. lipolytica morphogenesis. To identify the pathways involved in morphogenesis, we mutagenized a wild-type strain of Y. lipolytica with a Tn3 derivative. We isolated eight tagged mutants, entirely defective in hyphal formation, from a total of 40,000 mutants and identified seven genes homologous to S. cerevisiae CDC25, RAS2, BUD6, KEX2, GPI7, SNF5, and PPH21. We analyzed their abilities to invade agar and to form pseudomycelium or hyphae under inducing conditions and their sensitivity to temperature and to Calcofluor white. Chitin staining was used to detect defects in their cell walls. Our results indicate that a functional Ras-cyclic AMP pathway is required for the formation of hyphae in Y. lipolytica and that perturbations in the processing of extracellular, possibly parietal, proteins result in morphogenetic defects. PMID:11325938

Richard, Mathias; Quijano, Raymundo Rosas; Bezzate, Samira; Bordon-Pallier, Florence; Gaillardin, Claude

2001-01-01

333

Selection of Ethanol-Tolerant Yeast Hybrids in pH-Regulated Continuous Culture  

PubMed Central

Hybrids between naturally occurring wine yeast strains and laboratory strains were formed as a method of increasing genetic variability to improve the ethanol tolerance of yeast strains. The hybrids were subjected to competition experiments under continuous culture controlled by pH with increasing ethanol concentrations over a wide range to select the fastest-growing strain at any concentration of ethanol. The continuous culture system was obtained by controlling the dilution rate of a chemostat connected to a pH-meter. The nutrient pump of the chemostat was switched on and off in response to the pH of the culture, which was thereby kept near a critical value (pHc). Under these conditions, when the medium was supplemented with ethanol, the ethanol concentration of the culture increased with each pulse of dilution. A hybrid strain was selected by this procedure that was more tolerant than any of the highly ethanol-tolerant wine yeast strains at any concentration of ethanol and was able to grow at up to 16% (vol/vol) ethanol. This improvement in ethanol tolerance led to an increase in both the ethanol production rate and the total amount of ethanol produced. PMID:16347613

Jiménez, Juan; Benítez, Tahía

1988-01-01

334

The magnetoelectrochemical switch.  

PubMed

In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes' magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes' magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 10(3). The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits. PMID:25009179

Popa, Petru Lunca; Kemp, Neil T; Majjad, Hicham; Dalmas, Guillaume; Faramarzi, Vina; Andreas, Christian; Hertel, Riccardo; Doudin, Bernard

2014-07-22

335

The magnetoelectrochemical switch  

PubMed Central

In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes’ magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes’ magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 103. The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits. PMID:25009179

Lunca Popa, Petru; Kemp, Neil T.; Majjad, Hicham; Dalmas, Guillaume; Faramarzi, Vina; Andreas, Christian; Hertel, Riccardo; Doudin, Bernard

2014-01-01

336

MOS switched-capacitor filters  

Microsoft Academic Search

In the past several years, much progress has been made in bringing the economies of integrated-circuit technology to bear on the realization of voiceband frequency selective filters. This paper will review one approach to this problem, the use of switched-capacitor techniques. The paper emphasizes the practical aspects of switched-capacitor filter design under the constraints imposed by MOS integrated-circuit technology. The

R. W. Brodersen; P. R. Gray; D. A. Hodges

1979-01-01

337

Electromagnetic Activation of Capillary Switches  

Microsoft Academic Search

By designing coupled droplet pairs with the appropriate length scale to promote surface tension as the dominant force, one can create bi-stable capillary switches. This bi-stability can be triggered by pressure pulses, surface chemistry, electroosmosis, or body forces. To exploit the latter, we designed a capillary switch with electromagnetic activation. The resulting setup consists of a sub-millimeter tube, overfilled with

Bernie Malouin; Rohan Dayal; Leila Parsa; Amir Hirsa

2008-01-01

338

A Piezoelectric Cryogenic Heat Switch  

NASA Technical Reports Server (NTRS)

We have measured the thermal conductance of a mechanical heat switch actuated by a piezoelectric positioner, the PZHS (PieZo electric Heat Switch), at cryogenic temperatures. The thermal conductance of the PZHS was measured between 4 K and 10 K, and on/off conductance ratios greater than 100 were achieved when the positioner applied its maximum force of 8 N. We discuss the advantages of using this system in cryogenic applications, and estimate the ultimate performance of an optimized PZHS.

Jahromi, Amir E.; Sullivan, Dan F.

2014-01-01

339

High PRF high current switch  

DOEpatents

A triggerable, high voltage, high current, spark gap switch for use in pu power systems. The device comprises a pair of electrodes in a high pressure hydrogen environment that is triggered by introducing an arc between one electrode and a trigger pin. Unusually high repetition rates may be obtained by undervolting the switch, i.e., operating the trigger at voltages much below the self-breakdown voltage of the device.

Moran, Stuart L. (Fredericksburg, VA); Hutcherson, R. Kenneth (College Park, MD)

1990-03-27

340

A Systematic and Unified Approach to Modeling Switches in Switch-Mode Power Supplies  

Microsoft Academic Search

This paper describes a new, systematic, and unified approach to model the low-frequency behavior of power switches in Switch-Mode Power Supplies (SMPS). This approach starts with a simplification of the switching converter circuit to a Minimum Separable Switching Configuration (MISSCO) containing all power switches but a minimum number of other components, before analysis on the MISSCO is carried out. Then

Y. S. Lee

1985-01-01

341

Electronic logic for enhanced switch reliability  

DOEpatents

A logic circuit is used to enhance redundant switch reliability. Two or more switches are monitored for logical high or low output. The output for the logic circuit produces a redundant and fail-safe representation of the switch outputs. When both switch outputs are high, the output is high. Similarly, when both switch outputs are low, the logic circuit's output is low. When the output states of the two switches do not agree, the circuit resolves the conflict by memorizing the last output state which both switches were simultaneously in and produces the logical complement of this output state. Thus, the logic circuit of the present invention allows the redundant switches to be treated as if they were in parallel when the switches are open and as if they were in series when the switches are closed. A failsafe system having maximum reliability is thereby produced.

Cooper, J.A.

1984-01-20

342

Yeast through the ages: A statistical analysis of genetic changes in aging yeast  

E-print Network

Yeast through the ages: A statistical analysis of genetic changes in aging yeast A. Wise J. Hardin into the roles of specific genes and the associated changes across experimental conditions (e.g., aging, mutation sense of the experiment and thereby advance genetic, biological, and medical research. Likewise

Hardin, Jo

343

K-Band Latching Switches  

NASA Technical Reports Server (NTRS)

Design, development, and tests are described for two single-pole-double-throw latching waveguide ferrite switches: a K-band switch in WR-42 waveguide and a Ka-band switch in WR-28 waveguide. Both switches have structurally simple junctions, mechanically interlocked without the use of bonding materials; they are impervious to the effects of thermal, shock, and vibration stresses. Ferrite material for the Ka-band switch with a proper combination of magnetic and dielectric properties was available and resulted in excellent low loss, wideband performance. The high power handling requirement of the K-band switch limited the choice of ferrite to nickel-zinc compositions with adequate magnetic properties, but with too low relative dielectric constant. The relative dielectric constant determines the junction dimensions for given frequency responses. In this case the too low value unavoidably leads to a larger than optimum junction volume, increasing the insertion loss and restricting the operating bandwidth. Efforts to overcome the materials-related difficulties through the design of a composite junction with increased effective dielectric properties efforts to modify the relative dielectric constant of nickel-zinc ferrite are examined.

Piotrowski, W. S.; Raue, J. E.

1984-01-01

344

Yeast cell-wall synthesis  

PubMed Central

1. A study of wall synthesis has been made by following the incorporation of radioactive glucose and threonine into the cytoplasm and wall of yeast. 2. Both glucose and threonine are incorporated into a mannan glycopeptide. The glucose is also synthesized into a structural glucan of the wall. 3. The mannan glycopeptide contains high-molecular-weight mannan and low-molecular-weight mannose and oligosaccharide units composed of mannose. Both types of carbohydrate are attached to the peptide. The extent of radioactive incorporation into these different carbohydrate constituents of the glycopeptide remained constant during a pulse-chase experiment. No evidence of a sequential synthesis of oligosaccharides and high-molecular-weight mannan was obtained. 4. Cycloheximide inhibits the incorporation of threonine into the wall but only partially inhibits the incorporation of glucose. Thus not all the polysaccharide deposited into the wall is dependent on a simultaneous peptide synthesis and incorporation. 5. Protoplasts grown in an iso-osmotic medium secreted a mannan polymer that was probably a glycopeptide. PMID:5378380

Sentandreu, R.; Northcote, D. H.

1969-01-01

345

Non-latching relay switch assembly  

DOEpatents

A non-latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes a permanent magnet and an electromagnet. The respective sections are arranged in separate locations or cavities in the assembly. The switch has a "normal" position and is selectively switched by an overriding electromagnetic assembly. The switch returns to the "normal" position when the overriding electromagnetic assembly is inactive.

Duimstra, Frederick A. (Anaheim Hills, CA)

1991-01-01

346

Solid State Spark Gap Replacement Switches  

Microsoft Academic Search

Improvements in solid state high voltage switching technology now make it feasible to replace triggered spark gap switches, used in many medical and commercial applications to switch tens of kilovolts and thousands of amperes, with compact solid-state switches. We have developed a multi-stage high voltage solid-state switch that is triggered by a single 10 V isolated trigger pulse to only

S. C. Glidden; H. D. Sanders

2006-01-01

347

Optimized switching algorithm for synchronized switch damping for multimodal excitation  

NASA Astrophysics Data System (ADS)

Shunted piezoceramics can be used to dissipate vibration energy of a host structure and therefore reduce vibration amplitudes. The piezoceramic converts a portion of the mechanical energy into electric energy which is then dissipated in an electric network. One semi-active control technique is the synchronized switch damping on inductance (SSDI), which has a good damping performance and can adapt to a wide range of excitation frequencies. In the standard SSDI a switch is closed during maximum deformation for one half of the electrical period time. This results in an inversion of the electrical charge. For the rest of the half-period the switch is opened and the charge remains constant. This results in a nearly rectangular voltage signal, which is in antiphase with the deformation velocity. In case of multimodal excitation, more sophisticated switching laws are developed with the aim to extract vibration energy from higher modes (i.e. Richard). This paper describes a novel multimodal switching law for vibration damping. An observer is designed to obtain an estimation of the first two vibration modes, which are used to determine the switching times. In simulations the increase in energy dissipation is evaluated and compared to the standard SSDI technique. With the new switching algorithm an improvement in energy dissipation is observed. The theoretical results are validated by measurements carried out on a clamped-free beam. The location of the piezoceramics is chosen to optimize the electro-mechanical coupling with the first vibration mode of the beam. The modal observer is realized in a realtime environment. Measurements show a good agreement with the theoretical results.

Schwarzendahl, Sebastian M.; Han, Xu; Neubauer, Marcus; Wallaschek, Jörg

2010-04-01

348

Evidence for yeast autophagy during simulation of sparkling wine aging: a reappraisal of the mechanism of yeast autolysis in wine.  

PubMed

Yeast autolysis is the source of several molecules responsible for the quality of wines aged in contact with yeast cells. However, the mechanisms of yeast autolysis during wine aging are not completely understood. All descriptions of yeast autolysis in enological conditions emphasize the disturbance of cell organization as the starting event in the internal digestion of the cell, while no reference to autophagy is found in wine-related literature. By using yeast mutants defective in the autophagic or the Cvt pathways we have demonstrated that autophagy does take place in wine production conditions. This finding has implications for the genetic improvement of yeasts for accelerated autolysis. PMID:15801807

Cebollero, Eduardo; Carrascosa, Alfonso V; Gonzalez, Ramon

2005-01-01

349

OPA1 Processing Reconstituted in Yeast Depends on the Subunit Composition of the m-AAA Protease in Mitochondria  

PubMed Central

The morphology of mitochondria in mammalian cells is regulated by proteolytic cleavage of OPA1, a dynamin-like GTPase of the mitochondrial inner membrane. The mitochondrial rhomboid protease PARL, and paraplegin, a subunit of the ATP-dependent m-AAA protease, were proposed to be involved in this process. Here, we characterized individual OPA1 isoforms by mass spectrometry, and we reconstituted their processing in yeast to identify proteases involved in OPA1 cleavage. The yeast homologue of OPA1, Mgm1, was processed both by PARL and its yeast homologue Pcp1. Neither of these rhomboid proteases cleaved OPA1. The formation of small OPA1 isoforms was impaired in yeast cells lacking the m-AAA protease subunits Yta10 and Yta12 and was restored upon expression of murine or human m-AAA proteases. OPA1 processing depended on the subunit composition of mammalian m-AAA proteases. Homo-oligomeric m-AAA protease complexes composed of murine Afg3l1, Afg3l2, or human AFG3L2 subunits cleaved OPA1 with higher efficiency than paraplegin-containing m-AAA proteases. OPA1 processing proceeded normally in murine cell lines lacking paraplegin or PARL. Our results provide evidence for different substrate specificities of m-AAA proteases composed of different subunits and reveal a striking evolutionary switch of proteases involved in the proteolytic processing of dynamin-like GTPases in mitochondria. PMID:17615298

Duvezin-Caubet, Stéphane; Koppen, Mirko; Wagener, Johannes; Zick, Michael; Israel, Lars; Bernacchia, Andrea; Jagasia, Ravi; Rugarli, Elena I.; Imhof, Axel; Neupert, Walter

2007-01-01

350

Chapter 6: The genomes of lager yeasts.  

PubMed

Yeasts used in the production of lagers belong to the genus Saccharomyces pastorianus. Species within this genus arose from a natural hybridization event between two yeast species that appear to be closely related to Saccharomyces cerevisiae and Saccharomyces bayanus. The resultant hybrids contain complex allopolyploid genomes and retain genetic characteristics of both parental species. Recent genome analysis using both whole genome sequencing and competitive genomic hybridization techniques has revealed the underlying composition of lager yeasts genomes. There appear to be at least 36 unique chromosomes, many of which are lager specific, resulting from recombination events between the homeologous parental chromosomes. The recombination events are limited to a defined set of genetic loci, which are highly conserved within strains of lager yeasts. In addition to the hybrid chromosomes, several non-reciprocal chromosomal translocations and inversions are also observed. Remarkably, in response to exposure to environmental stresses such as high temperatures and high osmotic pressure, the genomes appear to be highly dynamic and undergo recombination events at defined loci and alterations in the telomeric regions. The ability of environmental stress to alter the structure and composition of the genomes of lager yeasts may point to mechanisms of adaptive evolution in these species. PMID:19729094

Bond, Ursula

2009-01-01

351

Yeasts associated with Sardinian ewe's dairy products.  

PubMed

In the present work, the occurrence of yeasts in different types of typical Sardinian ewe's cheeses (32 samples of pecorino, 32 of caciotta, 40 of feta, 56 of ricotta) was determined. For the strains isolated the following properties were studied: proteolytic and lipolytic activities, the ability to grow at different temperatures, different concentrations of salt, and to assimilate and/or ferment compounds like lactate, citrate, lactose, glucose, galactose, lactic acid. Of 160 samples analysed, 76.2% yielded growth of yeasts. Yeast counts showed a certain variability among the samples. The highest levels were observed in caciotta and feta cheeses. A total of 281 strains belonging to 16 genera and 25 species were identified. In general, Debaryomyces hansenii was the dominant species, representing 28.8% of the total isolates. Other frequently appearing species were Geotrichum candidum, Kluyveromyces lactis and K. marxianus. Other genera encountered were Pichia, Candida, Dekkera, Yarrowia and Rhodotorula. With regard to the biochemical and technological properties of the yeasts, only K. lactis, K. marxianus and Dek. anomala assimilated and fermented lactose, whereas the majority of the species assimilated lactic acid. The assimilation of citrate was a characteristic of D. hansenii, R. rubra and Y. lipolytica. On the whole, the yeasts were weakly proteolytic while lipolytic activity was present in several species. A high percentage of strains showed a certain tolerance to low temperatures while only some strains of D. hansenii and K. lactis were able to grow at a 10% NaCl concentration. PMID:11589560

Cosentino, S; Fadda, M E; Deplano, M; Mulargia, A F; Palmas, F

2001-09-19

352

Ecology of pathogenic yeasts in Amazonian soil.  

PubMed Central

In an investigation of Amazonian soil as a natural reservoir for pathogenic fungi, 1,949 soil samples collected from diverse geographical and ecological settings of the Brazilian Amazon Basin were analyzed for the presence of non-keratinophilic fungi by the indirect mouse inoculation procedure and for the presence of keratinophilic fungi by the hair bait technique. All soil samples were acidic with low pH values. From 12% of the soil samples, 241 yeast and yeastlike isolates pertaining to six genera and 82 species were recovered, of which 63% were Torulopsis and 26% were Candida species. Nine fungi with known pathogenic potentials were encountered among 43% (104) of the isolates: T. glabrata, C. guilliermondii, C. albicans, C. pseudotropicalis, C. stellatoidea, C. tropicalis, Rhodotorula rubra, and Wangiella dermatitidis. The yeast flora was marked by species diversity, low frequency of each species, random geographical distribution, and an apparent lack of species clustering. The composition and distribution of the yeast flora in soil differed from those of the yeast flora harbored by bats, suggesting that the Amazonian external environment and internal bat organs act as independent natural habitats for yeasts. PMID:6538774

Mok, W Y; Luizão, R C; do Socorro Barreto da Silva, M; Teixeira, M F; Muniz, E G

1984-01-01

353

Cryosectioning Yeast Communities for Examining Fluorescence Patterns  

PubMed Central

Microbes typically live in communities. The spatial organization of cells within a community is believed to impact the survival and function of the community1. Optical sectioning techniques, including confocal and two-photon microscopy, have proven useful for observing spatial organization of bacterial and archaeal communities2,3. A combination of confocal imaging and physical sectioning of yeast colonies has revealed internal organization of cells4. However, direct optical sectioning using confocal or two-photon microscopy has been only able to reach a few cell layers deep into yeast colonies. This limitation is likely because of strong scattering of light from yeast cells4. Here, we present a method based on fixing and cryosectioning to obtain spatial distribution of fluorescent cells within Saccharomyces cerevisiae communities. We use methanol as the fixative agent to preserve the spatial distribution of cells. Fixed communities are infiltrated with OCT compound, frozen, and cryosectioned in a cryostat. Fluorescence imaging of the sections reveals the internal organization of fluorescent cells within the community. Examples of yeast communities consisting of strains expressing red and green fluorescent proteins demonstrate the potentials of the cryosectioning method to reveal the spatial distribution of fluorescent cells as well as that of gene expression within yeast colonies2,3. Even though our focus has been on Saccharomyces cerevisiae communities, the same method can potentially be applied to examine other microbial communities. PMID:23287845

Momeni, Babak; Shou, Wenying

2012-01-01

354

Mitochondrial membrane lipidome defines yeast longevity  

PubMed Central

Our studies revealed that lithocholic acid (LCA), a bile acid, is a potent anti-aging natural compound that in yeast cultured under longevity-extending caloric restriction (CR) conditions acts in synergy with CR to enable a significant further increase in chronological lifespan. Here, we investigate a mechanism underlying this robust longevity-extending effect of LCA under CR. We found that exogenously added LCA enters yeast cells, is sorted to mitochondria, resides mainly in the inner mitochondrial membrane, and also associates with the outer mitochondrial membrane. LCA elicits an age-related remodeling of glycerophospholipid synthesis and movement within both mitochondrial membranes, thereby causing substantial changes in mitochondrial membrane lipidome and triggering major changes in mitochondrial size, number and morphology. In synergy, these changes in the membrane lipidome and morphology of mitochondria alter the age-related chronology of mitochondrial respiration, membrane potential, ATP synthesis and reactive oxygen species homeostasis. The LCA-driven alterations in the age-related dynamics of these vital mitochondrial processes extend yeast longevity. In sum, our findings suggest a mechanism underlying the ability of LCA to delay chronological aging in yeast by accumulating in both mitochondrial membranes and altering their glycerophospholipid compositions. We concluded that mitochondrial membrane lipidome plays an essential role in defining yeast longevity. PMID:23924582

Burstein, Michelle T.; Bourque, Simon D.; Koupaki, Olivia; Juneau, Mylène; Feldman, Rachel; Iouk, Tatiana; Titorenko, Vladimir I.

2013-01-01

355

Production of alpha-amylase by yeast  

SciTech Connect

The enzyme alpha-amylase confers to an organism the enzymatic activity for the degradation of polyglucosides with alpha-1,4 glycosidic bonds such as starch and glycogen which are among the major storage compounds in plants and animals. Most alpha-amylases are single polypeptides of molecular weights around 50,000 dalton. They are generally found in the digestive tract of animals and in germinating seeds. Among the products released upon enzymatic degradation of polyglucosides maltose, a sugar that can be utilized as carbon source by yeast, is a major constituent. A cDNA segment complementary to mouse salivary amylase messenger RNA has been inserted into the yeast expression vector pMA56 behind the promoter of the gene encoding alcohol dehydrogenase I of yeast. Yeast transformants harboring plasmids with the normal orientation of the promoter and the mouse amylase cDNA gene produce amylase and release the enzyme in free form into the culture medium. Approximately 90% of the amylase activity is found in the medium. Yeast strains carrying MAL allele and transformed with a plasmid which directed the synthesis of mouse alpha-amylase were tested on plates containing starch and in batch fermentations using different high molecular weight sugars and oligosaccharides as carbon source. The results of these experiments will be discussed. (Refs. 21).

Thomse, K.K.

1987-01-01

356

Binary switching in a ‘symmetric' potential landscape  

PubMed Central

A binary switch is the basic building block for information processing. The potential energy profile of a bistable binary switch is a ‘symmetric' double well. The traditional method of switching it from one state (one well) to the other is to tilt the profile towards the desired state. Here, we present a case, where no such tilting is necessary to switch successfully, even in the presence of thermal noise. This happens because of the built-in dynamics inside the switch itself. It differs from the general perception on binary switching that in a ‘symmetric' potential landscape, the switching probability is 50% in the presence of thermal noise. Our results, considering the complete three-dimensional potential landscape, demonstrate intriguing phenomena on binary switching mechanism. With experimentally feasible parameters, we theoretically demonstrate such intriguing possibility in electric field induced magnetization switching of a shape-anisotropic single-domain magnetostrictive nanomagnet with two stable states at room-temperature. PMID:24154561

Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

2013-01-01

357

HOLLOTRON switch for megawatt lightweight space inverters  

NASA Technical Reports Server (NTRS)

The feasibility of satisfying the switching requirements for a megawatt ultralight inverter system using HOLLOTRON switch technology was determined. The existing experimental switch hardware was modified to investigate a coaxial HOLLOTRON switch configuration and the results were compared with those obtained for a modified linear HOLLOTRON configuration. It was concluded that scaling the HOLLOTRON switch to the current and voltage specifications required for a megawatt converter system is indeed feasible using a modified linear configuration. The experimental HOLLOTRON switch operated at parameters comparable to the scaled coaxial HOLLOTRON. However, the linear HOLLOTRON data verified the capability for meeting all the design objectives simultaneously including current density (greater than 2 A/sq cm), voltage (5 kV), switching frequency (20 kHz), switching time (300 ns), and forward voltage drop (less than or equal to 20 V). Scaling relations were determined and a preliminary design was completed for an engineering model linear HOLLOTRON switch to meet the megawatt converter system specifications.

Poeschel, R. L.; Goebel, D. M.; Schumacher, R. W.

1991-01-01

358

Dissecting the fission yeast regulatory network reveals phase-specific control elements of its cell cycle  

Microsoft Academic Search

BACKGROUND: Fission yeast Schizosaccharomyces pombe and budding yeast Saccharomyces cerevisiae are among the original model organisms in the study of the cell-division cycle. Unlike budding yeast, no large-scale regulatory network has been constructed for fission yeast. It has only been partially characterized. As a result, important regulatory cascades in budding yeast have no known or complete counterpart in fission yeast.

Pierre R Bushel; Nicholas A Heard; Roee Gutman; Liwen Liu; Shyamal D Peddada; Saumyadipta Pyne

2009-01-01

359

Original article Chromium yeast affects growth performance but not  

E-print Network

Original article Chromium yeast affects growth performance but not whole carcass composition the effects of supplemented trivalent chromium (Cr) from chromium yeast on growth performance, carcass vs. ad libitum in other reported experiments). (© Elsevier / Inra) chromium / pig / carcass

Paris-Sud XI, Université de

360

YEASTS FROM THE NORTH SEA AND AMOCO CADIZ OIL  

EPA Science Inventory

The species and densities of yeasts isolated from North Sea waters before and after the production of oil were compared. Debaryomyces hansenii was the predominant species, but after oil production, Candida guillieromondii, a hydrocarbonoclastic yeast, was more commonly isolated a...

361

High speed packet switching  

NASA Technical Reports Server (NTRS)

This document constitutes the final report prepared by Proteon, Inc. of Westborough, Massachusetts under contract NAS 5-30629 entitled High-Speed Packet Switching (SBIR 87-1, Phase 2) prepared for NASA-Greenbelt, Maryland. The primary goal of this research project is to use the results of the SBIR Phase 1 effort to develop a sound, expandable hardware and software router architecture capable of forwarding 25,000 packets per second through the router and passing 300 megabits per second on the router's internal busses. The work being delivered under this contract received its funding from three different sources: the SNIPE/RIG contract (Contract Number F30602-89-C-0014, CDRL Sequence Number A002), the SBIR contract, and Proteon. The SNIPE/RIG and SBIR contracts had many overlapping requirements, which allowed the research done under SNIPE/RIG to be applied to SBIR. Proteon funded all of the work to develop new router interfaces other than FDDI, in addition to funding the productization of the router itself. The router being delivered under SBIR will be a fully product-quality machine. The work done during this contract produced many significant findings and results, summarized here and explained in detail in later sections of this report. The SNIPE/RIG contract was completed. That contract had many overlapping requirements with the SBIR contract, and resulted in the successful demonstration and delivery of a high speed router. The development that took place during the SNIPE/RIG contract produced findings that included the choice of processor and an understanding of the issues surrounding inter processor communications in a multiprocessor environment. Many significant speed enhancements to the router software were made during that time. Under the SBIR contract (and with help from Proteon-funded work), it was found that a single processor router achieved a throughput significantly higher than originally anticipated. For this reason, a single processor router was developed and the final delivery under this contract will include a single processor CNX-500 router. The router and its interface boards (2 FDDIs and 2 dual-ethernets) are all product-quality components.

1991-01-01

362

Photoresistance switching of plasmonic nanopores.  

PubMed

Fast and reversible modulation of ion flow through nanosized apertures is important for many nanofluidic applications, including sensing and separation systems. Here, we present the first demonstration of a reversible plasmon-controlled nanofluidic valve. We show that plasmonic nanopores (solid-state nanopores integrated with metal nanocavities) can be used as a fluidic switch upon optical excitation. We systematically investigate the effects of laser illumination of single plasmonic nanopores and experimentally demonstrate photoresistance switching where fluidic transport and ion flow are switched on or off. This is manifested as a large (?1-2 orders of magnitude) increase in the ionic nanopore resistance and an accompanying current rectification upon illumination at high laser powers (tens of milliwatts). At lower laser powers, the resistance decreases monotonically with increasing power, followed by an abrupt transition to high resistances at a certain threshold power. A similar rapid transition, although at a lower threshold power, is observed when the power is instead swept from high to low power. This hysteretic behavior is found to be dependent on the rate of the power sweep. The photoresistance switching effect is attributed to plasmon-induced formation and growth of nanobubbles that reversibly block the ionic current through the nanopore from one side of the membrane. This explanation is corroborated by finite-element simulations of a nanobubble in the nanopore that show the switching and the rectification. PMID:25514824

Li, Yi; Nicoli, Francesca; Chen, Chang; Lagae, Liesbet; Groeseneken, Guido; Stakenborg, Tim; Zandbergen, Henny W; Dekker, Cees; Van Dorpe, Pol; Jonsson, Magnus P

2015-01-14

363

Signal Transduction by MAP Kinases: Regulation by Phosphorylation-Dependent Switches  

NSDL National Science Digital Library

The kinases of mitogen-activated protein (MAP) kinase cascades transmit signals through sequential phosphorylation and activation of the enzymes. However, recent evidence indicates that protein-protein interactions between the kinases themselves or with substrates or other components are also a critical means of regulation. Whitmarsh and Davis summarize these findings with emphasis on new evidence from yeast that, when phosphorylated, a MAP kinase kinase actually switches from a negative regulator that binds to and inhibits its target MAP kinase to a positive regulator of that same enzyme.

Alan J. Whitmarsh (University of Massachusetts Medical School;Department of Biochemistry and Molecular Biology;Howard Hughes Medical Institute and Program in Molecular Medicine; REV); Roger J. Davis (University of Massachusetts Medical School;Department of Biochemistry and Molecular Biology;Howard Hughes Medical Institute and Program in Molecular Medicine; REV)

1999-09-28

364

Contribution of Yeast Models to Neurodegeneration Research  

PubMed Central

As a model organism Saccharomyces cerevisiae has greatly contributed to our understanding of many fundamental aspects of cellular biology in higher eukaryotes. More recently, engineered yeast models developed to study endogenous or heterologous proteins that lay at the root of a given disease have become powerful tools for unraveling the molecular basis of complex human diseases like neurodegeneration. Additionally, with the possibility of performing target-directed large-scale screenings, yeast models have emerged as promising first-line approaches in the discovery process of novel therapeutic opportunities against these pathologies. In this paper, several yeast models that have contributed to the uncovering of the etiology and pathogenesis of several neurodegenerative diseases are described, including the most common forms of neurodegeneration worldwide, Alzheimer's, Parkinson's, and Huntington's diseases. Moreover, the potential input of these cell systems in the development of more effective therapies in neurodegeneration, through the identification of genetic and chemical suppressors, is also addressed. PMID:22910375

Pereira, Clara; Bessa, Cláudia; Soares, Joana; Leão, Mariana; Saraiva, Lucília

2012-01-01

365

Rapid methods for identification of yeasts.  

PubMed Central

Opportunistic infections by yeasts have been implicated as one of the major causes of complications in the compromised patient. Rapid recognition and identification of these yeasts is essential for patient management, but conventional liquid medium methods for completing identification tests are cumbersome and time consuming. Rapid tests have been devised based on modifications of methods commonly used in bacteriology. These rapid methods included tests for carbohydrate and nitrate assimilation, fermentation, and urease production. These were compared with several current methods for accuracy of results, for time to final identification, and for economy of time and reagents. In addition, the usual tests for pseudogerm tube formation, for production of hyphae or pseudohyphae, and for growth temperatures were included. The rapid tests achieved 96% or better accuracy compared with expected results, and 46 species of yeasts were identified in 1 to 2 days compared with the 10 to 14 days required by conventional liquid culture methods. Images PMID:1241586

Huppert, M; Harper, G; Sun, S H; Delanerolle, V

1975-01-01

366

Alcoholic fermentation by 'non-fermentative' yeasts.  

PubMed

All type strains of 'non-fermentative' yeasts, available in the culture collection of the Centraalbureau voor Schimmelcultures, were reinvestigated for their capacity to ferment glucose in the classical Durham tube test. Although visible gas production was absent, nearly all strains produced significant amounts of ethanol under the test conditions. Under conditions of oxygen-limited growth, even strong alcoholic fermentation may occur in a number of yeasts hitherto considered as non-fermentative. Thus, shake-flask cultures of Hansenula nonfermentans and Candida silvae fermented more than half of the available sugar to ethanol. It is concluded that the taxonomic test for fermentation capacity, which relies on detection of gas formation in Durham tubes, is not reliable for a physiological classification of yeasts as fermentative and non-fermentative species. PMID:3333301

van Dijken, J P; van den Bosch, E; Hermans, J J; de Miranda, L R; Scheffers, W A

1986-06-01

367

Yeast Oligo-mediated Genome Engineering (YOGE)  

PubMed Central

High-frequency oligonucleotide-directed recombination engineering (recombineering) has enabled rapid modification of several prokaryotic genomes to date. Here, we present a method for oligonucleotide-mediated recombineering in the model eukaryote and industrial production host S. cerevisiae, which we call Yeast Oligo-mediated Genome Engineering (YOGE). Through a combination of overexpression and knockouts of relevant genes and optimization of transformation and oligonucleotide designs, we achieve high gene modification frequencies at levels that only require screening of dozens of cells. We demonstrate the robustness of our approach in three divergent yeast strains, including those involved in industrial production of bio-based chemicals. Furthermore, YOGE can be iteratively executed via cycling to generate genomic libraries up to 105 individuals at each round for diversity generation. YOGE cycling alone, or in combination with phenotypic selections or endonuclease-based negative genotypic selections, can be used to easily generate modified alleles in yeast populations with high frequencies. PMID:24160921

DiCarlo, JE; Conley, AJ; Penttilä, M; Jäntti, J; Wang, HH; Church, GM

2014-01-01

368

Comparative Functional Genomics of the Fission Yeasts  

PubMed Central

The fission yeast clade, comprising Schizosaccharomyces pombe, S. octosporus, S. cryophilus and S. japonicus, occupies the basal branch of Ascomycete fungi and is an important model of eukaryote biology. A comparative annotation of these genomes identified a near extinction of transposons and the associated innovation of transposon-free centromeres. Expression analysis established that meiotic genes are subject to antisense transcription during vegetative growth, suggesting a mechanism for their tight regulation. In addition, trans-acting regulators control new genes within the context of expanded functional modules for meiosis and stress response. Differences in gene content and regulation also explain why, unlike the Saccharomycotina, fission yeasts cannot use ethanol as a primary carbon source. These analyses elucidate the genome structure and gene regulation of fission yeast and provide tools for investigation across the Schizosaccharomyces clade. PMID:21511999

Rhind, Nicholas; Chen, Zehua; Yassour, Moran; Thompson, Dawn A; Haas, Brian J; Habib, Naomi; Wapinski, Ilan; Roy, Sushmita; Lin, Michael F.; Heiman, David I; Young, Sarah K; Furuya, Kanji; Guo, Yabin; Pidoux, Alison; Chen, Huei Mei; Robbertse, Barbara; Goldberg, Jonathan M.; Aoki, Keita; Bayne, Elizabeth H.; Berlin, Aaron M; Desjardins, Christopher A.; Dobbs, Edward; Dukaj, Livio; Fan, Lin; FitzGerald, Michael G; French, Courtney; Gujja, Sharvari; Hansen, Klavs; Keifenheim, Dan; Levin, Joshua Z.; Mosher, Rebecca A.; Müller, Carolin A.; Pfiffner, Jenna; Priest, Margaret; Russ, Carsten; Smialowska, Agata; Swoboda, Peter; Sykes, Sean M; Vaughn, Matthew; Vengrova, Sonya; Yoder, Ryan; Zeng, Qiandong; Allshire, Robin; Baulcombe, David; Birren, Bruce W.; Brown, William; Ekwall, Karl; Kellis, Manolis; Leatherwood, Janet; Levin, Henry; Margalit, Hanah; Martienssen, Rob; Nieduszynski, Conrad A.; Spatafora, Joseph W.; Friedman, Nir; Dalgaard, Jacob Z.; Baumann, Peter; Niki, Hironori; Regev, Aviv; Nusbaum, Chad

2011-01-01

369

Altered transcription in yeast expressing expanded polyglutamine  

PubMed Central

Expanded polyglutamine tracts are responsible for at least eight fatal neurodegenerative diseases. In mouse models, proteins with expanded polyglutamine cause transcriptional dysregulation before onset of symptoms, suggesting that this dysregulation may be an early event in polyglutamine pathogenesis. Transcriptional dysregulation and cellular toxicity may be due to interaction between expanded polyglutamine and the histone acetyltransferase CREB-binding protein. To determine whether polyglutamine-mediated transcriptional dysregulation occurs in yeast, we expressed polyglutamine tracts in Saccharomyces cerevisiae. Gene expression profiles were determined for strains expressing either a cytoplasmic or nuclear protein with 23 or 75 glutamines, and these profiles were compared to existing profiles of mutant yeast strains. Transcriptional induction of genes encoding chaperones and heat-shock factors was caused by expression of expanded polyglutamine in either the nucleus or cytoplasm. Transcriptional repression was most prominent in yeast expressing nuclear expanded polyglutamine and was similar to profiles of yeast strains deleted for components of the histone acetyltransferase complex Spt/Ada/Gcn5 acetyltransferase (SAGA). The promoter from one affected gene (PHO84) was repressed by expanded polyglutamine in a reporter gene assay, and this effect was mitigated by the histone deacetylase inhibitor, Trichostatin A. Consistent with an effect on SAGA, nuclear expanded polyglutamine enhanced the toxicity of a deletion in the SAGA component SPT3. Thus, an early component of polyglutamine toxicity, transcriptional dysregulation, is conserved in yeast and is pharmacologically antagonized by a histone deacetylase inhibitor. These results suggest a therapeutic approach for treatment of polyglutamine diseases and provide the potential for yeast-based screens for agents that reverse polyglutamine toxicity. PMID:11687606

Hughes, Robert E.; Lo, Russell S.; Davis, Colleen; Strand, Andrew D.; Neal, Cassandra L.; Olson, James M.; Fields, Stanley

2001-01-01

370

[The yeast biofilm in human medicine].  

PubMed

In recent years, the role of Candida yeasts as causative agents of nosocomial infections has increased. One of the important virulence factors contributing to the development of such infections is biofilm production. This virulence factor enables yeast to colonize both native surfaces and artificial implants. The most common sources of infection are patients themselves, in particular the gastrointestinal tract and skin. The vectors of exogenous yeast infections are predominantly the hands of the health personnel and contaminated medical instruments. The adhesion of yeasts to the implant surfaces is determined both by implant surface and yeast characteristics. This is followed by proliferation and production of microcolonies and extracellular matrix. The final biofilm structure is also influenced by the production of hyphae and pseudohyphae. The entire process of biofilm production is controlled by numerous regulatory systems, with the key role being played by the quorum sensing system. Like the adhered bacterial cultures, candidas growing in the form of a biofilm are highly resistant to antimicrobial therapy. Resistance of yeast biofilms to antifungals is a complex process with multiple contributing factors. These are especially increased gene expression (e.g. genes encoding the so called multidrug efflux pumps), limited penetration of substances through the extracellular matrix, inhibited cell growth and altered microenvironment in deeper biofilm layers. The concentrations of antifungals able to effectively affect the biofilm cells exceed, by several orders of magnitude, the values of conventionally determined MICs. High biofilm resistance results in ineffective antifungal therapy of biofilm infections. Therefore, if possible, the colonized implant should be removed. Conservative therapy should involve antifungals with a proven effect on the biofilm (e.g. caspofungin). The most effective measure in fighting biofilm infections is prevention, especially adhering to aseptic techniques when manipulating with implants and their correct maintenance. PMID:17929219

R?zicka, Filip; Holá, Veronika; Votava, Miroslav

2007-08-01

371

Properties of an Intergenic Terminator and Start Site Switch That Regulate IMD2 Transcription in Yeast  

Microsoft Academic Search

The IMD2 gene in Saccharomyces cerevisiae is regulated by intracellular guanine nucleotides. Regulation is exerted through the choice of alternative transcription start sites that results in synthesis of either an unstable short transcript terminating upstream of the start codon or a full-length productive IMD2 mRNA. Start site selection is dictated by the intracellular guanine nucleotide levels. Here we have mapped

M. Harley Jenks; Thomas W. O'Rourke; Daniel Reines

2008-01-01

372

Temporal system-level organization of the switch from glycolytic to gluconeogenic operation in yeast  

PubMed Central

The diauxic shift in Saccharomyces cerevisiae is an ideal model to study how eukaryotic cells readjust their metabolism from glycolytic to gluconeogenic operation. In this work, we generated time-resolved physiological data, quantitative metabolome (69 intracellular metabolites) and proteome (72 enzymes) profiles. We found that the diauxic shift is accomplished by three key events that are temporally organized: (i) a reduction in the glycolytic flux and the production of storage compounds before glucose depletion, mediated by downregulation of phosphofructokinase and pyruvate kinase reactions; (ii) upon glucose exhaustion, the reversion of carbon flow through glycolysis and onset of the glyoxylate cycle operation triggered by an increased expression of the enzymes that catalyze the malate synthase and cytosolic citrate synthase reactions; and (iii) in the later stages of the adaptation, the shutting down of the pentose phosphate pathway with a change in NADPH regeneration. Moreover, we identified the transcription factors associated with the observed changes in protein abundances. Taken together, our results represent an important contribution toward a systems-level understanding of how this adaptation is realized. PMID:23549479

Zampar, Guillermo G; Kümmel, Anne; Ewald, Jennifer; Jol, Stefan; Niebel, Bastian; Picotti, Paola; Aebersold, Ruedi; Sauer, Uwe; Zamboni, Nicola; Heinemann, Matthias

2013-01-01

373

A heritable switch in carbon source utilization driven by an unusual yeast prion  

E-print Network

Several well-characterized fungal proteins act as prions, proteins capable of multiple conformations, each with different activities, at least one of which is self-propagating. Through such self-propagating changes in ...

Lindquist, Susan

374

An explosive opening superconducting switch  

NASA Astrophysics Data System (ADS)

A superconducting YBCO tube was tested as an opening switch to demonstrate novel switching concepts for inductive energy storage. The tube was connected in series with a 1.2-mH inductor and a 4800 micro-F capacitor bank which was charged to a predetermined level and discharged through the circuit. No measurable dissipation was observed for test discharges of 8-ms duration, with maximum pulse amplitude increasing for each test while the YBCO was superconducting at 77 K. At the highest current pulse maximum of 95 A, the switch was opened by exploding a short length of detonating cord inserted into the center of the tube. The current decreased to zero, and the voltage increased to maximum in approximately 160 microsec, resulting in a voltage gain of over 25 for current commutation purposes. The data indicate that high-Tc ceramic materials have potential in this application.

Francavilla, T. L.; Ford, R. D.; Lupton, W. H.; Alford, N. Mcn.; Saunders, C. S.

1991-03-01

375

The p150-Glued Ssm4p regulates microtubular dynamics and nuclear movement in fission yeast.  

PubMed

During vegetative growth of the fission yeast Schizosaccharomyces pombe, microtubules nucleate from multiple microtubule organising centres (MTOCs) close to the nucleus, polymerising until they reach the end of the cell and then shrinking back to the cell centre. In response to mating pheromone, S. pombe undergoes a morphological switch from a vegetative to a shmooing growth pattern. The switch in growth mode is paralleled by a switch in microtubular dynamics. Microtubules nucleate mostly from a single MTOC and pull on the ends of the cell to move the nucleus back and forth. This movement continues after cellular and nuclear fusion in the zygote and is important to ensure correct chromosome pairing, recombination and segregation during meiosis. Here we show that Ssm4p, a p150-Glued protein, is induced specifically in response to pheromone and is required for this nuclear movement. Ssm4p is associated with the cytoplasmic dynein complex and together with the CLIP-170 homologue Tip1p regulates dynein heavy chain localisation. We also show that Ssm4p collaborates with Tip1p in establishing the shmooing microtubular array. PMID:15509865

Niccoli, Teresa; Yamashita, Akira; Nurse, Paul; Yamamoto, Masayuki

2004-11-01

376

21 CFR 172.590 - Yeast-malt sprout extract.  

...2014-04-01 2014-04-01 false Yeast-malt sprout extract. 172.590 Section 172.590 Food...Related Substances § 172.590 Yeast-malt sprout extract. Yeast-malt sprout extract, as described in this section,...

2014-04-01

377

21 CFR 172.590 - Yeast-malt sprout extract.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Yeast-malt sprout extract. 172.590 Section 172.590 Food...Related Substances § 172.590 Yeast-malt sprout extract. Yeast-malt sprout extract, as described in this section,...

2011-04-01

378

21 CFR 172.590 - Yeast-malt sprout extract.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Yeast-malt sprout extract. 172.590 Section 172.590 Food...Related Substances § 172.590 Yeast-malt sprout extract. Yeast-malt sprout extract, as described in this section,...

2012-04-01

379

21 CFR 172.590 - Yeast-malt sprout extract.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Yeast-malt sprout extract. 172.590 Section 172.590 Food...Related Substances § 172.590 Yeast-malt sprout extract. Yeast-malt sprout extract, as described in this section,...

2013-04-01

380

Production of lipid compounds in the yeast Saccharomyces cerevisiae  

Microsoft Academic Search

This review describes progress using the yeast Saccharomyces cerevisiae as a model organism for the fast and efficient analysis of genes and enzyme activities involved in the lipid biosynthetic pathways of several donor organisms. Furthermore, we assess the impact of baker's yeast on the production of novel, high-value lipid compounds. Yeast can be genetically modified to produce selected substances in

M. Veen; C. Lang

2004-01-01

381

Yeast Metabolism Lab Purpose: To determine the effects of different  

E-print Network

O + energy sugar + oxygen carbon dioxide + water + energy Hypothesis: Make a prediction about which treatment (yeast+water, yeast+glucose, or yeast+sweetener) will produce the most carbon dioxide (CO2) from cellular respiration. Materials: Empty water bottles (3), glucose, artificial sweetener, warm water (~40°C

Rose, Michael R.

382

Media for preservative resistant yeasts: a collaborative study  

Microsoft Academic Search

An international collaborative study was carried out to determine the most effective medium for selective isolation and enumeration of preservative resistant yeasts. Such a medium should prevent the growth of other yeasts such as Saccharomyces cerevisiae that are tolerant to lower levels of commonly used food preservatives, and sensitive yeasts such as Rhodotomla species. The study compared two non-selective media

Ailsa D. Hocking

1996-01-01

383

DETECTION, IDENTIFICATION AND ENUMERATION METHODS FOR SPOILAGE YEASTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Microbiological spoilage of foods and beverages is caused by a wide variety of bacteria, molds and yeasts. Yeast growth is favored by low pH, generally 5.5 or lower, and by the presence of sugars, organic acids and other easily metabolized carbon sources. Yeast spoilage is often manifested by grow...

384

The plasma erosion opening switch  

NASA Astrophysics Data System (ADS)

The Plasma Erosion Opening Switch (PEOS) can conduct high current (approx. MA), open quickly (<10ns), and withstand high voltage (approx. MV). This switching technique has been used in inductive energy storage experiments and can be used with existing generators for pulse compression, voltage multiplication and power multiplication. The PEOS is used routinely for other types of power conditioning including prepulse suppression, pulse sharpening and multimodule jitter reduction. This paper is a review of the PEOS work to date. It reviews basic physics principles of the PEOS and outlines the operational limits of a system that employs a PEOS. Examples of present applications of the PEOS are also discussed.

Commisso, R. J.; Cooperstein, G.; Meger, R. A.; Neri, J. M.; Ottinger, P. F.

1985-05-01

385

A piezoelectric cryogenic heat switch.  

PubMed

We have measured the thermal conductance of a mechanical heat switch actuated by a piezoelectric positioner, the PZHS (PieZo electric Heat Switch), at cryogenic temperatures. The thermal conductance of the PZHS was measured between 4 K and 10 K, and on/off conductance ratios of about 100-200 at lowest and highest measures temperature were achieved when the positioner applied its maximum force of 8 N, respectively. We discuss the advantages of using this system in cryogenic applications, and estimate the ultimate performance of an ideal PZHS. PMID:24985863

Jahromi, Amir E; Sullivan, Dan F

2014-06-01

386

Optical Switch Using Risley Prisms  

SciTech Connect

An optical switch using Risley prisms and rotary microactuators to independently rotate the wedge prisms of each Risley prism pair is disclosed. The optical switch comprises an array of input Risley prism pairs that selectively redirect light beams from a plurality of input ports to an array of output Risley prism pairs that similarly direct the light beams to a plurality of output ports. Each wedge prism of each Risley prism pair can be independently rotated by a variable-reluctance stepping rotary microactuator that is fabricated by a multi-layer LIGA process. Each wedge prism can be formed integral to the annular rotor of the rotary microactuator by a DXRL process.

Sweatt, William C. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2005-02-22

387

Optical switch using Risley prisms  

SciTech Connect

An optical switch using Risley prisms and rotary microactuators to independently rotate the wedge prisms of each Risley prism pair is disclosed. The optical switch comprises an array of input Risley prism pairs that selectively redirect light beams from a plurality of input ports to an array of output Risley prism pairs that similarly direct the light beams to a plurality of output ports. Each wedge prism of each Risley prism pair can be independently rotated by a variable-reluctance stepping rotary microactuator that is fabricated by a multi-layer LIGA process. Each wedge prism can be formed integral to the annular rotor of the rotary microactuator by a DXRL process.

Sweatt, William C. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2003-04-15

388

Engineering of Ribozyme-Based Aminoglycoside Switches of Gene Expression by In Vivo Genetic Selection in Saccharomyces cerevisiae.  

PubMed

Synthetic RNA-based switches are a growing class of genetic controllers applied in synthetic biology to engineer cellular functions. In this chapter, we detail a protocol for the selection of posttranscriptional controllers of gene expression in yeast using the Schistosoma mansoni hammerhead ribozyme as a central catalytic unit. Incorporation of a small molecule-sensing aptamer domain into the ribozyme renders its activity ligand-dependent. Aptazymes display numerous advantages over conventional protein-based transcriptional controllers, namely, the use of little genomic space for encryption, their modular architecture allowing for easy reprogramming to new inputs, the physical linkage to the message to be controlled, and the ability to function without protein cofactors. Herein, we describe the method to select ribozyme-based switches of gene expression in Saccharomyces cerevisiae that we successfully implemented to engineer neomycin- and theophylline-responsive switches. We also highlight how to adapt the protocol to screen for switches responsive to other ligands. Reprogramming of the sensor unit and incorporation into any RNA of interest enables the fulfillment of a variety of regulatory functions. However, proper functioning of the aptazyme is largely dependent on optimal connection between the aptamer and the catalytic core. We obtained functional switches from a pool of variants carrying randomized connection sequences by an in vivo selection in MaV203 yeast cells that allows screening of a large sequence space of up to 1×10(9) variants. The protocol given explains how to construct aptazyme libraries, carry out the in vivo selection and characterize novel ON- and OFF-switches. PMID:25605392

Klauser, Benedikt; Rehm, Charlotte; Summerer, Daniel; Hartig, Jörg S

2015-01-01

389

Optimized switching algorithm for synchronized switch damping for multimodal excitation  

Microsoft Academic Search

Shunted piezoceramics can be used to dissipate vibration energy of a host structure and therefore reduce vibration amplitudes. The piezoceramic converts a portion of the mechanical energy into electric energy which is then dissipated in an electric network. One semi-active control technique is the synchronized switch damping on inductance (SSDI), which has a good damping performance and can adapt to

Sebastian M. Schwarzendahl; Xu Han; Marcus Neubauer; Jörg Wallaschek

2010-01-01

390

Schizosaccharomyces japonicus: the fission yeast is a fusion of yeast and hyphae.  

PubMed

The clade of Schizosaccharomyces includes 4 species: S. pombe, S. octosporus, S. cryophilus, and S. japonicus. Although all 4 species exhibit unicellular growth with a binary fission mode of cell division, S. japonicus alone is dimorphic yeast, which can transit from unicellular yeast to long filamentous hyphae. Recently it was found that the hyphal cells response to light and then synchronously activate cytokinesis of hyphae. In addition to hyphal growth, S. japonicas has many properties that aren't shared with other fission yeast. Mitosis of S. japonicas is referred to as semi-open mitosis because dynamics of nuclear membrane is an intermediate mode between open mitosis and closed mitosis. Novel genetic tools and the whole genomic sequencing of S. japonicas now provide us with an opportunity for revealing unique characters of the dimorphic yeast. PMID:24375690

Niki, Hironori

2014-03-01

391

Dynamic changes in brewing yeast cells in culture revealed by statistical analyses of yeast morphological data.  

PubMed

The vitality of brewing yeasts has been used to monitor their physiological state during fermentation. To investigate the fermentation process, we used the image processing software, CalMorph, which generates morphological data on yeast mother cells and bud shape, nuclear shape and location, and actin distribution. We found that 248 parameters changed significantly during fermentation. Successive use of principal component analysis (PCA) revealed several important features of yeast, providing insight into the dynamic changes in the yeast population. First, PCA indicated that much of the observed variability in the experiment was summarized in just two components: a change with a peak and a change over time. Second, PCA indicated the independent and important morphological features responsible for dynamic changes: budding ratio, nucleus position, neck position, and actin organization. Thus, the large amount of data provided by imaging analysis can be used to monitor the fermentation processes involved in beer and bioethanol production. PMID:24012106

Ohnuki, Shinsuke; Enomoto, Kenichi; Yoshimoto, Hiroyuki; Ohya, Yoshikazu

2014-03-01

392

Bilateral, Zero-Impedance Static Semiconductor Switch  

NASA Technical Reports Server (NTRS)

Static semiconductor switching circuit eliminates the undesirable features of electromechanical relays and conventional semiconductor switching circuits. There is a net zero voltage drop at the terminals and thus a zero impedance for bilateral currents there.

Doughman, C. L.

1968-01-01

393

Interactions Between Yeasts and Grapevines: Filamentous Growth, Endopolygalacturonase and Phytopathogenicity of Colonizing Yeasts  

Microsoft Academic Search

It has been clearly established that phytopathogenic fungi, bacteria, and viruses exert biotic stresses on plants. Much less\\u000a is known, however, about the interactions between enological species of yeast and their host plants. In a previous study,\\u000a we described how Saccharomyces cerevisiae, the most common enological yeast, can act as a grapevine (Vitis vinifera L.) pathogen, causing growth retardation or

Sabine Gognies; Essaïd Ait Barka; Angélique Gainvors-Claisse; Abdel Belarbi

2006-01-01

394

Reaction characteristics of an immobilized yeast producing ethanol.  

PubMed

The reaction behavior of Saccharomyces formaosensis imobilized by polyacrylamide gel is presented. Two types of the immobilized yeast are studied, i. e. the immobilized resting yeast and the immobilized growing yeast. For both of the yeast, reaction retes are expressed by the Michaelis-Menten type equation with a linear ethanol inhibition factor. The Michaelis constants aere close each other, but considerably larger that of native S. cerevisiae. Distribution of the growing yeast cell inside the carrier gel is presented. It is found that the cell density is somewhat higher near the surface of the carrier. PMID:18548627

Furusaki, S; Seki, M; Fukumura, K

1983-12-01

395

A new architecture of photonic ATM switches  

Microsoft Academic Search

A photonic asynchronous transfer mode (ATM) switch architecture for ATM operation at throughputs greater than 1 Tbit\\/s is proposed. The switch uses vertical-to-surface transmission electrophotonic devices (VSTEPs) for the optical buffer memory, and an optical-header-driven self-routing circuit in contrast with conventional photonic ATM switches using electrically controlled optical matrix switches. The optical buffer memory using massively parallel optical interconnections is

Makoto Nishio; Shuji Suzuki; Kazuo Takagi; I. Ogura; T. Numai; K. Kasahara; K. Kaede

1993-01-01

396

Energy loss in spark gap switches  

SciTech Connect

The paper reports on numerical study of the energy loss in spark gap switches. The operation of the switches is analyzed using the Braginsky model which allows calculation of the time dependence of the spark channel resistance. The Braginsky equation is solved simultaneously with generator circuit equations for different load types. Based on the numerical solutions, expressions which determine both the energy released in a spark gap switch and the switching time are derived.

Oreshkin, V. I., E-mail: oreshkin@ovpe.hcei.tsc.ru; Lavrinovich, I. V. [Institute of High Current Electronics SB RAS, Akademichesky Ave. 2/3, 634055 Tomsk (Russian Federation) [Institute of High Current Electronics SB RAS, Akademichesky Ave. 2/3, 634055 Tomsk (Russian Federation); National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk (Russian Federation)

2014-04-15

397

Voluntary Task Switching: Chasing the Elusive Homunculus  

Microsoft Academic Search

In the voluntary task switching procedure, subjects choose the task to perform on a series of bivalent stimuli, requiring top-down control of task switching. Experiments 1–3 contrasted voluntary task switching and explicit task cuing. Choice behavior showed small, inconsistent effects of external stimulus characteristics, supporting the assumption of top-down control of task choice. Switch costs were smaller when subjects chose

Catherine M. Arrington; Gordon D. Logan

2005-01-01

398

Carbon source dependent promoters in yeasts  

PubMed Central

Budding yeasts are important expression hosts for the production of recombinant proteins. The choice of the right promoter is a crucial point for efficient gene expression, as most regulations take place at the transcriptional level. A wide and constantly increasing range of inducible, derepressed and constitutive promoters have been applied for gene expression in yeasts in the past; their different behaviours were a reflection of the different needs of individual processes. Within this review we summarize the majority of the large available set of carbon source dependent promoters for protein expression in yeasts, either induced or derepressed by the particular carbon source provided. We examined the most common derepressed promoters for Saccharomyces cerevisiae and other yeasts, and described carbon source inducible promoters and promoters induced by non-sugar carbon sources. A special focus is given to promoters that are activated as soon as glucose is depleted, since such promoters can be very effective and offer an uncomplicated and scalable cultivation procedure. PMID:24401081

2014-01-01

399

Morphology of the Yeast Endocytic Pathway  

PubMed Central

Positively charged Nanogold (Nanoprobes, Stony Brook, NY) has been developed as a new marker to follow the endocytic pathway in yeast. Positively charged Nanogold binds extensively to the surface of yeast spheroplasts and is internalized in an energy-dependent manner. Internalization of gold is blocked in the end3 mutant. During a time course of incubation of yeast spheroplasts with positively charged Nanogold at 15°C, the gold was detected sequentially in small vesicles, a peripheral, vesicular/tubular compartment that we designate as an early endosome, a multivesicular body corresponding to the late endosome near the vacuole, and in the vacuole. Experiments examining endocytosis in the sec18 mutant showed an accumulation of positively charged Nanogold in approximately 30–50 nm diameter vesicles. These vesicles most likely represent the primary endocytic vesicles as no other intermediates were detected in the mutant cells, and they correspond in size to the first vesicles detected in wild-type spheroplasts at 15°C. These data lend strong support to the idea that the internalization step of endocytosis in yeast involves formation of small vesicles of uniform size from the plasma membrane. PMID:9436999

Prescianotto-Baschong, Cristina; Riezman, Howard

1998-01-01

400

Histone acetylation and deacetylation in yeast  

Microsoft Academic Search

Histone acetylation and deacetylation in the yeast Saccharomyces cerevisiae occur by targeting acetyltransferase and deacetylase enzymes to gene promoters and, in an untargeted and global manner, by affecting most nucleosomes. Recently, new roles for histone acetylation have been uncovered, not only in transcription but also in DNA replication, repair and heterochromatin formation. Interestingly, specific acetylatable lysines can function as binding

Siavash K. Kurdistani; Michael Grunstein

2003-01-01

401

The glucose signaling network in yeast  

PubMed Central

Background Most cells possess a sophisticated mechanism for sensing glucose and responsing to it appropriately. Glucose sensing and signaling in the budding yeast Saccharomyces cerevisiae represents an important paradigm for understanding how extracellular signals lead to changes in the gene expression program in eukaryotes. Scope of review This review focuses on the yeast glucose sensing and signaling pathways that operate in a highly regulated and cooperative manner to bring about glucose-induction of HXT gene expression. Major conclusions The yeast cells possess a family of glucose transporters (HXTs), with different kinetic properties. They employ three major glucose signaling pathways— Rgt2/Snf3, AMPK, and cAMP-PKA—to express only those transporters best suited for the amounts of glucose available. We discuss the current understanding of how these pathways are integrated into a regulatory network to ensure efficient uptake and utilization of glucose. General significance Elucidating the role of multiple glucose signals and pathways involved in glucose uptake and metabolism in yeast may reveal the molecular basis of glucose homeostasis in humans, especially under pathological conditions, such as hyperglycemia in diabetics and the elevated rate of glycolysis observed in many solid tumors. PMID:23911748

Kim, Jeong-Ho; Roy, Adhiraj; Jouandot, David; Cho, Kyu Hong

2013-01-01

402

Glucose-Induced Acidification in Yeast Cultures  

ERIC Educational Resources Information Center

We present an investigation (for A-level biology students and equivalent) into the mechanism of glucose-induced extracellular acidification in unbuffered yeast suspensions. The investigation is designed to enhance understanding of aspects of the A-level curriculum that relate to the phenomenon (notably glucose catabolism) and to develop key skills…

Myers, Alan; Bourn, Julia; Pool, Brynne

2005-01-01

403

Actin and Endocytosis in Budding Yeast  

PubMed Central

Endocytosis, the process whereby the plasma membrane invaginates to form vesicles, is essential for bringing many substances into the cell and for membrane turnover. The mechanism driving clathrin-mediated endocytosis (CME) involves > 50 different protein components assembling at a single location on the plasma membrane in a temporally ordered and hierarchal pathway. These proteins perform precisely choreographed steps that promote receptor recognition and clustering, membrane remodeling, and force-generating actin-filament assembly and turnover to drive membrane invagination and vesicle scission. Many critical aspects of the CME mechanism are conserved from yeast to mammals and were first elucidated in yeast, demonstrating that it is a powerful system for studying endocytosis. In this review, we describe our current mechanistic understanding of each step in the process of yeast CME, and the essential roles played by actin polymerization at these sites, while providing a historical perspective of how the landscape has changed since the preceding version of the YeastBook was published 17 years ago (1997). Finally, we discuss the key unresolved issues and where future studies might be headed. PMID:25657349

Goode, Bruce L.; Eskin, Julian A.; Wendland, Beverly

2015-01-01

404

Deoxyribonucleic Acid Base Composition in Yeasts  

PubMed Central

The deoxyribonucleic acid base composition of 15 species of yeasts was determined to obtain further clues to or supporting evidence for their taxonomic position. Species examined belonged to the genera Saccharomyces, Debaryomyces, Lodderomyces, Metschnikowia, and Candida. The range of moles per cent guanine plus cytosine (GC content) for all yeasts examined extended from 34.9 to 48.3%. The sporogenous species and the asporogenous yeasts spanned the range with 36.6 to 48.3% GC and 34.9 to 48% GC, respectively. Three Saccharomyces species (S. rosei and related species) exhibited significantly higher GC contents than S. cerevisiae, whereas the fermentative species D. globosus revealed a%GC more aligned to the S. rosei group than to the nonfermentative D. hansenii. Similar GC contents were demonstrated by L. elongasporus and its proposed imperfect form C. parapsilosis. The range of GC contents of various strains of three Metschnikowia species studied was 6.1%, with the type strain of M. pulcherrima having the highest GC content (48.3%) of all of the yeasts examined. PMID:5764346

Meyer, Sally A.; Phaff, H. J.

1969-01-01

405

Coenzyme Q systems in ascomycetous black yeasts  

Microsoft Academic Search

72 Strains belonging to 44 species of ascomycetous black yeasts were analyzed for their coenzyme Q systems. Prevalent were Q-10 and dihydrogenated Q-10 systems. Members of the Dothidealean suborder Dothideineae have Q-10 (H2), while those belonging to the suborder Pseudosphaeriineae mostly have Q-10. The anamorph genus Exophiala Carmichael and the teleomorph genus Capronia Sacc. seem to be heterogenous.

Y. Yamada; Kazue Sugihara; G. W. Eijk; H. J. Roeijmans; G. S. Hoog

1989-01-01

406

Replication Dynamics of the Yeast Genome  

Microsoft Academic Search

Oligonucleotide microarrays were used to map the detailed topography of chromosome replication in the budding yeast Saccharomyces cerevisiae. The times of replication of thousands of sites across the genome were determined by hybridizing replicated and unreplicated DNAs, isolated at different times in S phase, to the microarrays. Origin activations take place continuously throughout S phase but with most firings near

M. K. Raghuraman; Elizabeth A. Winzeler; David Collingwood; Sonia Hunt; Lisa Wodicka; Andrew Conway; David J. Lockhart; Ronald W. Davis; Bonita J. Brewer; Walton L. Fangman

2001-01-01

407

A yeast model of Down syndrome  

Microsoft Academic Search

The recent discovery that cellular proliferation was reduced in aneuploid haploid yeast supports a long-standing argument that the developmental neurophenotype of Down syndrome is not uniquely a result of the effects of increased gene dosage. Instead, some phenotypic outcomes appear to resemble those caused by disrupted cellular homeostasis induced by aneuploidy. Decreased cellular proliferation has been identified in the cerebellum

Randal X. Moldrich

2007-01-01

408

Commitment to meiosis in fission yeast  

Microsoft Academic Search

Mutants of Schizosaccharomyces pombe blocked during meiosis were analysed with respect to the induction of diploid mitotic division. Wild type zygotes of this yeast can form diploid colonies with a low probability (ca. 1%) when they are transferred to fresh growth medium. Mutants of three genes affecting meiosis responded to the shift by forming diploid colonies with high yield (ca.

Richard Egel

1973-01-01

409

Antarctic Yeasts: Biodiversity and Potential Applications  

NASA Astrophysics Data System (ADS)

This review is an attempt in cataloguing the diversity of yeasts in Antarctica, highlight their biotechnological potential and understand the basis of adaptation to low temperature. As of now several psychrophilic and psychrotolerant yeasts from Antarctic soils and marine waters have been characterized with respect to their growth characteristics, ecological distribution and taxonomic significance. Interestingly most of these species belonged to basidiomycetous yeasts which as a group are known for their ability to circumvent and survive under stress conditions. Simultaneously their possible role as work horses in the biotechnological industry was recognized due to their ability to produce novel enzymes and biomolecules such as agents for the breakdown of xenobiotics, and novel pharmaceutical chemi cals. The high activity of psychrophilic enzymes at low and moderate temperatures offers potential economic benefits. As of now lipases from Pseudozyma antarctica have been extensively studied to understand their unique thermal stability at 90°C and also because of its use in the pharmaceutical, agriculture, food, cosmetics and chemical industry. A few of the other enzymes which have been studied include extracellular alpha-amylase and glucoamylase from the yeast Pseudozyma antarctica (Candida antarctica), an extra-cellular protease from Cryptococcus humicola, an aspartyl proteinase from Cryptococcus humicola, a novel extracellular subtilase from Leucosporidium antarcticum, and a xylanase from Cryptococcus adeliensis

Shivaji, S.; Prasad, G. S.

410

Microfermentation Test For Identification Of Yeast  

NASA Technical Reports Server (NTRS)

Microfermentation test developed as supplementary method for use in identifying yeasts, especially in clinical and environmental studies. In comparison with traditional fermentation tests, simpler and easier, and requiries less equipment, material, and laboratory space. Results obtained in days instead of weeks.

Pierson, D. L.; Mishra, S. K.; Molina, Thomas C.

1995-01-01

411

A comparison of switching energy of resonant and nonresonant electro-optic switches  

NASA Astrophysics Data System (ADS)

Optical space switching is an important functionality in dense wavelength division multiplexing (DWDM) optical communication systems, particularly within reconfigurable optical add-drop multiplexers (ROADMs) [1]. Current commercially available ROADMs are based on micro-electromechanical systems (MEMS) or liquid crystal switches but these do not have sufficient switching speed for future network requirements. Power consumption (i.e. energy per switching operation multiplied by switching rate) is a very important parameter in the selection of a switching technology. Space switches based on current injection in silicon have been reported with nanosecond switching speeds and average power consumption on the order of mW [2], which becomes significant if many switches are required in a fabric. Electro-optic (EO) switches, which utilize the Pockels effect in which the refractive index changes when an external voltage is applied [3], only dissipate power when the switch state is changed. Electro-optic switches can be implemented either as non-resonant designs (for example the Mach-Zehnder interferometer (MZI)) or as resonant designs (for example the Fabry Perot interferometer (FPI)). In this study we compare the switching energies of electro optic MZI and FPI switches by considering the capacitance of the switch, which is determined by the length of the active region of the switch. We show that for a non-resonant switch, switching energy increases linearly with device length, regardless of applied voltage, and so is simply determined by the strength of the electro-optic coefficient. We assume that the resonant switch is implemented as a switchable comb filter [4], with a free-spectral range equal to twice the wavelength spacing. This then fixes the interferometer length. As a result the resonant switch has requires significantly less switching energy for the same material parameters and is thus of interest for future ROADM implementations.

Soltani, Fatemeh; Kirk, Andrew G.

2012-10-01

412

Degree of Conversational Code-Switching Enhances Verbal Task Switching in Cantonese-English Bilinguals  

ERIC Educational Resources Information Center

The study examined individual differences in code-switching to determine the relationship between code-switching frequency and performance in verbal and non-verbal task switching. Seventy-eight Cantonese-English bilinguals completed a semi-structured conversation to quantify natural code-switching, a verbal fluency task requiring language…

Yim, Odilia; Bialystok, Ellen

2012-01-01

413

Switching processes in financial markets  

PubMed Central

For an intriguing variety of switching processes in nature, the underlying complex system abruptly changes from one state to another in a highly discontinuous fashion. Financial market fluctuations are characterized by many abrupt switchings creating upward trends and downward trends, on time scales ranging from macroscopic trends persisting for hundreds of days to microscopic trends persisting for a few minutes. The question arises whether these ubiquitous switching processes have quantifiable features independent of the time horizon studied. We find striking scale-free behavior of the transaction volume after each switching. Our findings can be interpreted as being consistent with time-dependent collective behavior of financial market participants. We test the possible universality of our result by performing a parallel analysis of fluctuations in time intervals between transactions. We suggest that the well known catastrophic bubbles that occur on large time scales—such as the most recent financial crisis—may not be outliers but single dramatic representatives caused by the formation of increasing and decreasing trends on time scales varying over nine orders of magnitude from very large down to very small. PMID:21521789

Preis, Tobias; Schneider, Johannes J.; Stanley, H. Eugene

2011-01-01

414

Fast superconducting magnetic field switch  

SciTech Connect

The superconducting magnetic switch or fast kicker magnet is employed with an electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater than the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. Magnetic switches and particularly fast kicker magnets are used in the accelerator industry to quickly deflect particle beams into and out of various transport lines, storage rings, dumps, and specifically to differentially route individual bunches of particles from a train of bunches which are injected or ejected from a given ring.

Goren, Y.; Mahale, N.K.

1995-12-31

415

MOS switched capacitor ladder filters  

Microsoft Academic Search

A new technique for designing precision, fully integrated, high-order filters using standard MOS technology is described. Switched capacitor integrators have been used to realize long time constants in small areas, and by interconnecting these integrators in a `leapfrog' configuration, monolithic high-order filters have been implemented with transfer functions that are very insensitive to component variations. Experimental results are presented for

D. J. Allstot; ROBERT W. BRODERSEN; PAUL R. GRAY

1978-01-01

416

Fast all-optical switch  

NASA Technical Reports Server (NTRS)

An apparatus and method wherein polarization rotation in alkali vapors or other mediums is used for all-optical switching and digital logic and where the rate of operation is proportional to the amplitude of the pump field. High rates of speed are accomplished by Rabi flopping of the atomic states using a continuously operating monochromatic atomic beam as the pump.

Shay, Thomas M. (Inventor); Poliakov, Evgeni Y. (Inventor); Hazzard, David A. (Inventor)

2001-01-01

417

ERGODIC CONTROL OF SWITCHING DIFFUSIONS  

Microsoft Academic Search

A b st r ac t . We study the ergodic control problem of switching diffusions representing a typical hybrid system that arises in numerous applications such as fault-tolerant control systems, flexible manufacturing systems, etc. Under fairly general conditions, we establish the existence of a stable, nonrandomized Markov policy which almost surely minimizes the pathwise long-run average cost. We then

Mrinal K. Ghosh; Aristotle Arapostathis; Steven I. Marcus

418

Solar array switching power management  

NASA Technical Reports Server (NTRS)

Solar array power switching concepts are explored for a 250 kWe manned LEO platform, a 50-250 kWe load for an orbit transfer vehicle (OTV), and an unmanned platform with a 50 kWe load in GEO. A solar array switching power management (SASPM) system is under study to satisfy the switching demands. Direct connections to arrays would be implemented for voltage regulations, power distribution, and the capability of reconfiguring the arrays to meet requirements. Mission characteristics that would require the power sources were explored. The LEO platform was projected to use a concentrator, have no reconfigurability, use 250 NiH2 batteries, supply 80-0 Vdc to an ion drive, and have a 20-30 yr life. Both GEO and OTV arrays were planar, would feature reconfigurability, and supply 800 Vdc to an ion drive. NiH2 batteries would be on the OTV, while the GEO spacecraft would use AgH2 cells. A block diagram of the basic switching configuration is presented.

Cassinelli, J. E.; Smith, L. D.; Valgora, M.

1982-01-01

419

Low engine oil sensing switch  

Microsoft Academic Search

A pneumatic switch is described responsive to the vacuum in a closed crankcase of a reciprocating piston engine, the crankcase containing a volume of lubricating oil, the engine having a check valve connected for venting positive gas pressure from the crankcase to maintain an average vacuum in the crankcase, such vacuum varying as a function of the quantity of oil

M. Lenk; R. S. Podiak

1986-01-01

420

A new very high voltage semiconductor switch  

NASA Technical Reports Server (NTRS)

A new family of semiconductor switches using double injection techniques and compensated deep impurities is described. They have the potential to raise switching voltages a factor of 10 higher (up to 100 kV) than p-n junction devices while exhibiting extremely low (or zero) forward voltage. Several potential power switching applications are indicated.

Sundberg, G. R.

1985-01-01

421

Algorithmic aspects of high speed switching  

E-print Network

A major drawback of the traditional output queuing technique is that it requires a switch speedup of N, where N is the size of the switch. This dependence on N makes the switch non-scalable at high speeds. Input queuing ...

Mneimneh, Saadeddine S

2002-01-01

422

Asynchronous vs Synchronous Input-Queued Switches  

E-print Network

to their limited techno- logical requirements. Basically, IQ switches trade a lower internal data transfer capacity (i.e., very limited speed-ups of the switching fabric) for a larger complexity in switch control in fixed- size data units, which are transferred to outputs, where they are re-assembled in variable

423

Photoconductive switching for high power microwave generation  

SciTech Connect

Photoconductive switching is a technology that is being increasingly applied to generation of high power microwaves. Two primary semiconductors used for these devices are silicon and gallium arsenide. Diamond is a promising future candidate material. This paper discusses the important material parameters and switching modes, critical issues for microwave generation, and future directions for this high power, photoconductive switching technology.

Pocha, M.D.; Hofer, W.W.

1990-10-01

424

Switch for serial or parallel communication networks  

DOEpatents

A communication switch apparatus and a method for use in a geographically extensive serial, parallel or hybrid communication network linking a multi-processor or parallel processing system has a very low software processing overhead in order to accommodate random burst of high density data. Associated with each processor is a communication switch. A data source and a data destination, a sensor suite or robot for example, may also be associated with a switch. The configuration of the switches in the network are coordinated through a master processor node and depends on the operational phase of the multi-processor network: data acquisition, data processing, and data exchange. The master processor node passes information on the state to be assumed by each switch to the processor node associated with the switch. The processor node then operates a series of multi-state switches internal to each communication switch. The communication switch does not parse and interpret communication protocol and message routing information. During a data acquisition phase, the communication switch couples sensors producing data to the processor node associated with the switch, to a downlink destination on the communications network, or to both. It also may couple an uplink data source to its processor node. During the data exchange phase, the switch couples its processor node or an uplink data source to a downlink destination (which may include a processor node or a robot), or couples an uplink source to its processor node and its processor node to a downlink destination.

Crosette, Dario B. (DeSoto, TX)

1994-01-01

425

Switch for serial or parallel communication networks  

DOEpatents

A communication switch apparatus and a method for use in a geographically extensive serial, parallel or hybrid communication network linking a multi-processor or parallel processing system has a very low software processing overhead in order to accommodate random burst of high density data. Associated with each processor is a communication switch. A data source and a data destination, a sensor suite or robot for example, may also be associated with a switch. The configuration of the switches in the network are coordinated through a master processor node and depends on the operational phase of the multi-processor network: data acquisition, data processing, and data exchange. The master processor node passes information on the state to be assumed by each switch to the processor node associated with the switch. The processor node then operates a series of multi-state switches internal to each communication switch. The communication switch does not parse and interpret communication protocol and message routing information. During a data acquisition phase, the communication switch couples sensors producing data to the processor node associated with the switch, to a downlink destination on the communications network, or to both. It also may couple an uplink data source to its processor node. During the data exchange phase, the switch couples its processor node or an uplink data source to a downlink destination (which may include a processor node or a robot), or couples an uplink source to its processor node and its processor node to a downlink destination. 9 figs.

Crosette, D.B.

1994-07-19

426

Environmental Qualification of an Actuator Torque Switch  

Microsoft Academic Search

Environmental qualification testing was performed on a modified Limitorque torque switch for the torque switch safety functions in the Limitorque type SMB actuators located inside and outside containment in a nuclear power plant. The torque switch specimen was installed in a Limitorque SMB-1 electric actuator mounted on an 8'' Velan gate valve and operated with a customized programmable logic controller

A. M. Chan; S. L. Barreca; T. Kostela

2006-01-01

427

Voluntary Task Switching: Chasing the Elusive Homunculus  

ERIC Educational Resources Information Center

In the voluntary task switching procedure, subjects choose the task to perform on a series of bivalent stimuli, requiring top-down control of task switching. Experiments 1-3 contrasted voluntary task switching and explicit task cuing. Choice behavior showed small, inconsistent effects of external stimulus characteristics, supporting the assumption…

Arrington, Catherine M.; Logan, Gordon D.

2005-01-01

428

A computer-based substation switching scheme  

Microsoft Academic Search

This paper describes a digital computer based substation switching scheme which employs generalized rules for interlocking and sequence switching. The scheme can handle different configurations of substations which are recognized from the input data that describes the interconnections of switches. The scheme is, therefore, applicable to substations of all practical configurations. It also considers factors such as, generation and load

P. Dhakal; M. S. Sachdev

1995-01-01

429

The Octopus switch This chapter1  

E-print Network

The Octopus switch This chapter1 discusses the interconnection architecture of the Mobile Digital on the data path, where it is needed. A reconfigurable internal communication network switch called Octopus is based on a switch, called Octopus, which interconnects a general-purpose processor, (multimedia) devices

Havinga, Paul J.M.

430

Implementation of firmware on SPC switching systems  

Microsoft Academic Search

The recent trend toward distributed processing in stored-program-controlled (SPC) switching systems has resulted in increased use of firmware. The impact of firmware on SPC switching system reliability and maintainability, after sale of the product to user companies, can be substantial. The author examines both life cycle practices for firmware and the impact of firmware on switching systems, and he suggests

S. R. Ali

1988-01-01

431

A Reliability Analysis of Local Telecommunication Switches  

Microsoft Academic Search

Abstract This paper presents a reliability analysis of Local Exchange Carrier telecommunication switches in the United States, based upon empirical data. Telecommunication switch outage statistics are analyzed for a multiyear period, allowing examination into switch failure frequency, causes, and trends. Failure categories are created by reported outage cause codes, including human error, design error, hardware failure, and external factor causality

Andrew P. Snow

432

A CW Gunn Diode Switching Element.  

ERIC Educational Resources Information Center

As part of a study of the application of communication satellites to educational development, certain technical aspects of such a system were examined. A current controlled bistable switching element using a CW Gunn diode is reported on here. With modest circuits switching rates of the order of 10 MHz have been obtained. Switching is initiated by…

Hurtado, Marco; Rosenbaum, Fred J.

433

Architectural Choices in Large Scale ATM Switches  

E-print Network

, reliability and cost-effectiveness. The pressure of the competing requirements on switching systems, together networks of arbitrary size using switching systems of limited capacity, it turns out to be far more cost-effective as telephone switches require capacities of 1-10 Gb/s to provide cost/effective service to large user

Turner, Jonathan S.

434

Plug-In RF Selector Switch  

NASA Technical Reports Server (NTRS)

Short, direct link between switch and filters reduces signal loss. New switch attaches directly to filter housing, eliminating cables and connectors. As result, losses in transmitter and receiver paths reduced by about 0.4 dB. Because connectors and cables are not used, RF path loss for selected signal through switch and filter is smaller than usual.

Hwon, A. H.; Steidel, C. F.

1986-01-01

435

14 CFR 27.1145 - Ignition switches.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Ignition switches. 27.1145 Section 27...Controls and Accessories § 27.1145 Ignition switches. (a) There must be means to quickly shut off all ignition by the grouping of switches or by...

2010-01-01

436

Inventions on baker's yeast strains and specialty ingredients.  

PubMed

Baker's yeast is one of the oldest food microbial starters. Between 1927 and 2008, 165 inventions on more than 337 baker's yeast strains were patented. The first generation of patented yeast strains claimed improved biomass yield at the yeast plant, higher gassing power in dough or better survival to drying to prepare active dry baker's yeast. Especially between 1980 and 1995, a major interest was given to strains for multiple bakery applications such as dough with variable sugar content and stored at refrigeration (cold) or freezing temperatures. During the same period, genetically engineered yeast strains became very popular but did not find applications in the baking industry. Since year 2000, patented baker's yeast strains claimed aroma, anti-moulding or nutritive properties to better meet the needs of the baking industry. In addition to patents on yeast strains, 47 patents were issued on baker's yeast specialty ingredients for niche markets. This review shows that patents on baker's yeast with improved characteristics such as aromatic or nutritive properties have regularly been issued since the 1920's. Overall, it also confirms recent interest for a very wide range of tailored-made yeast-based ingredients for bakery applications. PMID:20653532

Gélinas, Pierre

2009-06-01

437

Carbon isotope controlled molecular switches  

NASA Astrophysics Data System (ADS)

Single molecules represent one fundamental limit to the downscaling of electronics. As a prototype element for carbon-based nanoscale science and technology, the detailed behavior of carbon monoxide (CO) on the copper surface Cu(111) has been investigated. These investigations span from individual carbon isotope resolution, to single molecules, to compact clusters assembled by molecular manipulation via a homemade scanning tunneling microscope (STM). Sub-nanoscale devices, composed of only a few molecules, which exploit both lone CO properties and molecule-molecule interaction, have been designed and assembled. The devices function as bi-stable switches and can serve as classical bits with densities > 50 Tbits/cm2. Operated in the nuclear mass sensitive regime, each switch can also function as a molecular "centrifuge" capable of identifying the isotope of a single carbon atom in real-time. A model, based on electron-vibron couping and inelastic tunneling, has been developed and explains the dynamic behavior of the switch. The interaction between pairs of switches was also explored and it was found that their behavior ranges from completely independent to strongly coupled. Larger nanostructures, which were composed of many sub-switches organized to leverage the fully coupled interaction, link two spatially separated "bits" on the surface. Such a linked system can set or read a state non-locally, which is equivalent to bidirectional information transfer. The linked system has also exhibited logic functionality. These experiments demonstrate scalable molecular cells for information storage, and for information processing through cellular automata logic schemes.

Foster, Brian K.

438

Electronic logic to enhance switch reliability in detecting openings and closures of redundant switches  

DOEpatents

A logic circuit is used to enhance redundant switch reliability. Two or more switches are monitored for logical high or low output. The output for the logic circuit produces a redundant and failsafe representation of the switch outputs. When both switch outputs are high, the output is high. Similarly, when both switch outputs are low, the logic circuit's output is low. When the output states of the two switches do not agree, the circuit resolves the conflict by memorizing the last output state which both switches were simultaneously in and produces the logical complement of this output state. Thus, the logic circuit of the present invention allows the redundant switches to be treated as if they were in parallel when the switches are open and as if they were in series when the switches are closed. A failsafe system having maximum reliability is thereby produced.

Cooper, James A. (Albuquerque, NM)

1986-01-01

439

Wide Bandgap Extrinsic Photoconductive Switches  

NASA Astrophysics Data System (ADS)

Wide Bandgap Extrinsic Photoconductive Switches Semi-insulating Gallium Nitride, 4H and 6H Silicon Carbide are attractive materials for compact, high voltage, extrinsic, photoconductive switches due to their wide bandgap, high dark resistance, high critical electric field strength and high electron saturation velocity. These wide bandgap semiconductors are made semi-insulating by the addition of vanadium (4H and 6H-SiC) and iron (2H-GaN) impurities that form deep acceptors. These deep acceptors trap electrons donated from shallow donor impurities. The electrons can be optically excited from these deep acceptor levels into the conduction band to transition the wide bandgap semiconductor materials from a semi-insulating to a conducting state. Extrinsic photoconductive switches with opposing electrodes have been constructed using vanadium compensated 6H-SiC and iron compensated 2H-GaN. These extrinsic photoconductive switches were tested at high voltage and high power to determine if they could be successfully used as the closing switch in compact medical accelerators. The successful development of a vanadium compensated, 6H-SiC extrinsic photoconductive switch for use as a closing switch for compact accelerator applications was realized by improvements made to the vanadium, nitrogen and boron impurity densities. The changes made to the impurity densities were based on the physical intuition outlined and simple rate equation models. The final 6H-SiC impurity 'recipe' calls for vanadium, nitrogen and boron densities of 2.5 e17 cm-3, 1.25e17 cm-3 and ? 1e16 cm-3, respectively. This recipe was originally developed to maximize the quantum efficiency of the vanadium compensated 6H-SiC, while maintaining a thermally stable semi-insulating material. The rate equation models indicate that, besides increasing the quantum efficiency, the impurity recipe should be expected to also increase the carrier recombination time. Three generations of 6H-SiC materials were tested. The third generation vanadium compensated 6H-SiC has average impurity densities close to the recipe values. Extrinsic photoconductive switches constructed from the third generation vanadium compensated, 6H-SiC, 1 mm thick, 1 cm2, substrates have achieved high power operation at 16 kV with pulsed currents exceeding 1400 Amperes and a minimum on resistance of 1 ohm. The extrinsic photoconductive switch performance of the third generation 6H-SiC material was improved by a factor of up to 50 for excitation at the 532 nm wavelength compared to the initial 6H-SiC material. Switches based on this material have been incorporated into a prototype compact proton medical accelerator being developed by the Compact Particle Acceleration Corporation (CPAC). The vanadium compensated, 6H-SiC, extrinsic photoconductive switch operates differently when excited by 1064, or 532 nm, wavelength light. The 6H-SiC extrinsic photoconductive switch is a unipolar device when excited with 1064 nm light. The carriers are electrons excited from filled vanadium acceptor levels and other electron traps located within 1.17 eV of the conduction band. The switch is bipolar at 532 nm since the carriers consist of holes, as well as electrons. The holes are primarily generated by the excitation of valence band electrons into empty trap/acceptor levels and by two-photon absorption. Carrier generation by two-photon absorption becomes more important at high applied optical intensity at 532 nm and contributes to the supralinear behavior of switch conductance as a function of optical power. The 6H-SiC switch material is trap dominated at low nitrogen to vanadium ratios. The trap dominated vanadium compensated 6H-SiC exhibits low quantum efficiency when excited with 1064 and 532 nm light and has a carrier recombination time of ˜ 150 - 300 ps. The vanadium compensated 6H-SiC transitions to an impurity dominated material as the ratio of nitrogen to vanadium is increased to 0.5. The increased nitrogen doping produces a material with much higher quantum efficiency and carrier recombination time of 0.9 to 1.0 ns.

Sullivan, James Stephen

440

Adaptive neural control for a class of switched nonlinear systems  

Microsoft Academic Search

In this paper, adaptive neural control is presented for a class of switched nonlinear systems with switching jumps and uncertainties in both system models and switching signals. Condition on limiting variation of the Lyapunov function is given for input-to-state asymptotic stability of switched systems with switching jumps. The control objective is achieved uniformly with respect to a class of switching

Thanh-Trung Han; Shuzhi Sam Ge; Tong Heng Lee

2009-01-01

441

CS Network Testbed Switches: Cisco, Asant, Packeteer, ...  

E-print Network

/5/06 Tornado C2 C2C2 36-port Fast Ethernet Switch 3Com SuperStack II 3900 N1 Typhoon C1 C1 C1 36-port Fast Ethernet Switch 3Com SuperStack II 3900 C1a C1aC1a 36-port Fast Ethernet Switch 3Com SuperStack II 3900 12-port Gigabit Ethernet Switch 3Com SuperStack II 9300 S2 24-port Fast Ethernet Switch Comp. Sci

Lewis, Robert Michael

442

Switch-phase distributions and stochastic resonance  

NASA Astrophysics Data System (ADS)

The de-synchronization mechanism that occurs for noise intensities above stochastic resonance is analyzed in terms of switch-time and switch-phase distributions. In particular, we observed that (i) the switch-time distributions exhibit thicker peak structures with maxima at the multiples (both odd and even) of the half forcing period; (ii) the switch-phase distributions are doubly peaked, being dominated by the in-phase and ? out-of-phase events. The appearance of these properties of the switch statistics is discussed on the grounds of numerical simulations.

Marchesoni, F.; Apostolico, F.; Santucci, S.

1998-11-01

443

Secure videoconferencing equipment switching system and method  

DOEpatents

A switching system and method are provided to facilitate use of videoconference facilities over a plurality of security levels. The system includes a switch coupled to a plurality of codecs and communication networks. Audio/Visual peripheral components are connected to the switch. The switch couples control and data signals between the Audio/Visual peripheral components and one but nor both of the plurality of codecs. The switch additionally couples communication networks of the appropriate security level to each of the codecs. In this manner, a videoconferencing facility is provided for use on both secure and non-secure networks.

Hansen, Michael E. (Livermore, CA)

2009-01-13

444

Genetic regulation of differentiation towards meiosis in the yeast Saccharomyces cerevisiae.  

PubMed

Normally, meiosis and sporulation in Saccharomyces cerevisiae occur only in diploid strains and only when the cells are exposed to starvation conditions. Diploidy is determined by the mating-type system (the genes MAT, RME1, IME1), whereas the starvation signal is transmitted through the adenylate cyclase - protein kinase pathway (the genes CDC25, RAS2, CDC35 (CYR1), BCY1, TPK1, TPK2, TPK3). The two regulatory pathways converge at the gene IME1, which is a positive regulator of meiosis and whose early expression in sporulating cells correlates with the initiation of meiosis. Sites upstream (5') of IME1 appear to mediate in the repression of the gene by repressors originating from both the mating-type and the cyclase--kinase pathways. PMID:2687111

Simchen, G; Kassir, Y

1989-01-01

445

Misidentification of clinical yeast isolates by using the updated Vitek Yeast Biochemical Card.  

PubMed Central

The Vitek Yeast Biochemical Card (YBC) is widely used as a rapid identification (RI) (within 48 h) system for clinical yeast isolates. We compared the RI results obtained by the YBC technique with matched results obtained with the API 20C system. The RI of germ tube-negative yeasts isolated from 222 clinical specimens was performed with the YBC system, and the results were compared with those of standard identifications obtained by using the API 20C system and morphology, with additional biochemical reactions performed as required. Commonly isolated yeasts (Candida albicans [n = 29], Candida tropicalis [n = 40], Torulopsis [Candida] glabrata [n = 28], Candida parapsilosis [n = 12], and Cryptococcus neoformans [n = 14]) were generally well identified (115 of 123 [93%] identified correctly, with only C. albicans, C. tropicalis, and C. neoformans mis- or unidentified more than once). The RI of less commonly isolated yeasts included in the YBC database, however, was less successful (54 of 99 [55%] correct). The YBC card failed to identify 42% (10 of 24) of Candida krusei isolates, 80% (4 of 5) of Candida lambica isolates, 88% (7 of 8) of Trichosporon beigelii isolates, and 83% (10 of 12) of Cryptococcus isolates (non-C. neoformans species). For most identification failures (79%; 42 of 53) there was no identification by the end of 48 h; the other identification failures (21%; 11 of 53) gave definite but incorrect identifications. Of eight rare clinical yeast isolates not included in the Vitek database, six were correctly, not identified, while two (25%) were falsely assigned a definite RI (one Hansenula fabianii isolate was identified as Rhodotorula glutinis, and one Hansenula isolate [non-Hansenula anomala] was identified as Hansenula anomala). While the Vitek YBC rapidly and adequately identifies common yeast isolates, it fails in the RI of more unusual organisms. PMID:7883873

Dooley, D P; Beckius, M L; Jeffrey, B S

1994-01-01

446

Misidentification of clinical yeast isolates by using the updated Vitek Yeast Biochemical Card.  

PubMed

The Vitek Yeast Biochemical Card (YBC) is widely used as a rapid identification (RI) (within 48 h) system for clinical yeast isolates. We compared the RI results obtained by the YBC technique with matched results obtained with the API 20C system. The RI of germ tube-negative yeasts isolated from 222 clinical specimens was performed with the YBC system, and the results were compared with those of standard identifications obtained by using the API 20C system and morphology, with additional biochemical reactions performed as required. Commonly isolated yeasts (Candida albicans [n = 29], Candida tropicalis [n = 40], Torulopsis [Candida] glabrata [n = 28], Candida parapsilosis [n = 12], and Cryptococcus neoformans [n = 14]) were generally well identified (115 of 123 [93%] identified correctly, with only C. albicans, C. tropicalis, and C. neoformans mis- or unidentified more than once). The RI of less commonly isolated yeasts included in the YBC database, however, was less successful (54 of 99 [55%] correct). The YBC card failed to identify 42% (10 of 24) of Candida krusei isolates, 80% (4 of 5) of Candida lambica isolates, 88% (7 of 8) of Trichosporon beigelii isolates, and 83% (10 of 12) of Cryptococcus isolates (non-C. neoformans species). For most identification failures (79%; 42 of 53) there was no identification by the end of 48 h; the other identification failures (21%; 11 of 53) gave definite but incorrect identifications. Of eight rare clinical yeast isolates not included in the Vitek database, six were correctly, not identified, while two (25%) were falsely assigned a definite RI (one Hansenula fabianii isolate was identified as Rhodotorula glutinis, and one Hansenula isolate [non-Hansenula anomala] was identified as Hansenula anomala). While the Vitek YBC rapidly and adequately identifies common yeast isolates, it fails in the RI of more unusual organisms. PMID:7883873

Dooley, D P; Beckius, M L; Jeffrey, B S

1994-12-01

447

Electrical switching in cadmium boracite single crystals  

NASA Technical Reports Server (NTRS)

Cadmium boracite single crystals at high temperatures ( 300 C) were found to exhibit a reversible electric field-induced transition between a highly insulative and a conductive state. The switching threshold is smaller than a few volts for an electrode spacing of a few tenth of a millimeter corresponding to an electric field of 100 to 1000 V/cm. This is much smaller than the dielectric break-down field for an insulator such as boracite. The insulative state reappears after voltage removal. A pulse technique revealed two different types of switching. Unstable switching occurs when the pulse voltage slightly exceeds the switching threshold and is characterized by a pre-switching delay and also a residual current after voltage pulse removal. A stable type of switching occurs when the voltage becomes sufficiently high. Possible device applications of this switching phenomenon are discussed.

Takahashi, T.; Yamada, O.

1981-01-01

448

Bioreduction of ?,?-unsaturated ketones and aldehydes by non-conventional yeast (NCY) whole-cells.  

PubMed

The bioreduction of ?,?-unsaturated ketones (ketoisophorone, 2-methyl- and 3-methyl-cyclopentenone) and aldehydes [(S)-(-)-perillaldehyde and ?-methyl-cinnamaldehyde] by 23 "non-conventional" yeasts (NCYs) belonging to 21 species of the genera Candida, Cryptococcus, Debaryomyces, Hanseniaspora, Kazachstania, Kluyveromyces, Lindnera, Nakaseomyces, Vanderwaltozyma, and Wickerhamomyces was reported. The results highlight the potential of NCYs as whole-cell biocatalysts for selective biotransformation of electron-poor alkenes. A few NCYs exhibited extremely high (>90%) or even total ketoisophorone and 2-methyl-cyclopentenone bioconversion yields via asymmetric reduction of the conjugated CC bond catalyzed by enoate reductases. Catalytic efficiency declined after switching from ketones to aldehydes. High chemoselectivity due to low competing carbonyl reductases was also sometimes observed. PMID:21232941

Goretti, Marta; Ponzoni, Chiara; Caselli, Elisa; Marchegiani, Elisabetta; Cramarossa, Maria Rita; Turchetti, Benedetta; Forti, Luca; Buzzini, Pietro

2011-03-01

449

Origin of Irreversibility of Cell Cycle Start in Budding Yeast  

PubMed Central

Budding yeast cells irreversibly commit to a new division cycle at a regulatory transition called Start. This essential decision-making step involves the activation of the SBF/MBF transcription factors. SBF/MBF promote expression of the G1 cyclins encoded by CLN1 and CLN2. Cln1,2 can activate their own expression by inactivating the Whi5 repressor of SBF/MBF. The resulting transcriptional positive feedback provides an appealing, but as yet unproven, candidate for generating irreversibility of Start. Here, we investigate the logic of the Start regulatory module by quantitative single-cell time-lapse microscopy, using strains in which expression of key regulators is efficiently controlled by changes of inducers in a microfluidic chamber. We show that Start activation is ultrasensitive to G1 cyclin. In the absence of CLN1,2-dependent positive feedback, we observe that Start transit is reversible, due to reactivation of the Whi5 transcriptional repressor. Introduction of the positive feedback loop makes Whi5 inactivation and Start activation irreversible, which therefore guarantees unidirectional entry into S phase. A simple mathematical model to describe G1 cyclin turn on at Start, entirely constrained by empirically measured parameters, shows that the experimentally measured ultrasensitivity and transcriptional positive feedback are necessary and sufficient dynamical characteristics to make the Start transition a bistable and irreversible switch. Our study thus demonstrates that Start irreversibility is a property that arises from the architecture of the system (Whi5/SBF/Cln2 loop), rather than the consequence of the regulation of a single component (e.g., irreversible protein degradation). PMID:20087409

Charvin, Gilles; Oikonomou, Catherine; Siggia, Eric D.; Cross, Frederick R.

2010-01-01

450

High power ferrite microwave switch  

NASA Technical Reports Server (NTRS)

A high power ferrite microwave switch was developed along with associated electronic driver circuits for operation in a spaceborne high power microwave transmitter in geostationary orbit. Three units were built and tested in a space environment to demonstrate conformance to the required performance characteristics. Each unit consisted of an input magic-tee hybrid, two non-reciprocal latching ferrite phase shifters, an out short-slot 3 db quadrature coupler, a dual driver electronic circuit, and input logic interface circuitry. The basic mode of operation of the high power ferrite microwave switch is identical to that of a four-port, differential phase shift, switchable circulator. By appropriately designing the phase shifters and electronic driver circuits to operate in the flux-transfer magnetization mode, power and temperature insensitive operation was achieved. A list of the realized characteristics of the developed units is given.

Bardash, I.; Roschak, N. K.

1975-01-01

451

Synthetic ferrimagnets with thermomagnetic switching  

NASA Astrophysics Data System (ADS)

Interlayer exchange coupling in strong/weak/strong ferromagnetic multilayers is investigated as a function of external magnetic field and temperature, with the focus on the magnetization switching near the Curie transition in the spacer composed of a diluted ferromagnet of concentration paramagnetic in the bulk. The effect of an externally applied reversing magnetic field on the width of the thermomagnetic transition is studied experimentally and explained theoretically as a result of the interplay between the proximity-induced exchange and the Zeeman effects in the system. Of high potential for applications should be the ability to switch one of the ferromagnetic outer layers using magnetic field, temperature, or a combination of the two.

Kravets, A. F.; Dzhezherya, Yu. I.; Tovstolytkin, A. I.; Kozak, I. M.; Gryshchuk, A.; Savina, Yu. O.; Pashchenko, V. A.; Gnatchenko, S. L.; Koop, B.; Korenivski, V.

2014-09-01

452

MEMS-switched reconfigurable antennas  

Microsoft Academic Search

The integration and use of RF MEMS switches in microstrip patch antennas and feed structures were investigated for developing reconfigurable multi-band antennas. The current application focuses on the development of a dual L\\/X-band antenna that would support several satellite or UAV-based communications and radar applications such as SAR, terrain mapping, GMTI, AMTI, etc. A reconfigurable patch module (RPM) was designed

William H. Weedon; William J. Payne; Gabriel M. Rebeiz

2001-01-01

453

DNA Bending and Sugar Switching  

Microsoft Academic Search

Using high frequency antiphase NMR spectroscopy and computer simulations of the antiphase spectra, we studied the equlibria in the sugar conformations in the DNA duplex 11-mer containing the AAA tract surrounded by cytosines. We demonstrate that at the 3?-end of the A-tract, the sugar switches from the common S-conformer (B-like form) to the N-conformer (A-like form) with the probability of

Shantaram Kamath; Mukti H. Sarma; Victor B. Zhurkin; Christopher J. Turner; Ramaswamy H. Sarma

2000-01-01

454

QPSK switching modulator, phase 2  

Microsoft Academic Search

A breadboard QPSK modulator based on a series connected, dual gate FET switching approach was developed to meet a specification provided by ESA. Direct high level modulation immediatly prior to the downlink output on a satellite repeater avoids amplitude and phase distortions. The characteristics include 8.2 GHz center frequency, 650 MHz 3 dB bandwidth, 0 dB nominal gain, emitter coupled

W. Konu; R. Bouchard

1983-01-01

455

Fast superconducting magnetic field switch  

DOEpatents

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles.

Goren, Yehuda (Mountain View, CA); Mahale, Narayan K. (The Woodlands, TX)

1996-01-01

456

Fast superconducting magnetic field switch  

DOEpatents

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition.