Relevant bibliographies by topics / Fungal cell walls

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'Fungal cell walls'

Author: Grafiati
Published: 4 June 2021
Last updated: 24 January 2023

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Journal articles on the topic "Fungal cell walls"

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Levitz, Stuart M. "Innate Recognition of Fungal Cell Walls." PLoS Pathogens 6, no. 4 (2010): e1000758. http://dx.doi.org/10.1371/journal.ppat.1000758.

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SASAKI, Shoji, Kenjiro KODAMA, Kazuo UCHIDA, and Hiroshi YOSHINO. "Fungal cell walls. Part II. Antitumor activity of cell walls of microorganisms." Agricultural and Biological Chemistry 49, no. 9 (1985): 2807–8. http://dx.doi.org/10.1271/bbb1961.49.2807.

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Ouellette, G. B., H. Chamberland, A. Goulet, M. Lachapelle, and J. G. Lafontaine. "Fine structure of the extracellular sheath and cell walls inOphiostoma novo-ulmigrowing on various substrates." Canadian Journal of Microbiology 45, no. 7 (1999): 582–97. http://dx.doi.org/10.1139/w99-045.

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The presence of microfilamentous-like structures of tubular appearance (MFS) in cell walls and extracellular sheath material (ES) in a number of isolates of Ophiostoma novo-ulmi Brasier grown on various substrates and following various treatments is reported. Standard fixation or high-pressure freezing methods were used, and cytochemical tests were carried out to detect fungal and host wall components and, in some cases, fungal DNA. In some cases, serial 0.2-μm-thick sections were examined at 120 kV and tilted to obtain stereoscopic images. Whether the fungal cell walls were thick and composed of an outer opaque and inner more electron-lucent layers, or thin and barely perceptible, MFS were observed to extend from the cell cytoplasm as parallel structures across the walls into the surrounding medium, including host cell components in infected elm tissues. MFS were associated (in samples from inoculated trees) with cleavage and desquamation of fungal walls. ES and MFS did not label for cellulose or chitin, but generally labelled slightly for β-(1-3)-glucan and mannose, and strongly for galactose. Only the lucent, inner fungal wall layer labelled for chitin and cellulose. DNA labelling was confined to nuclei and mitochondria in fungal cells from cultures on agar medium; in cells from cultures on millipore membranes, it was pronounced over imprecisely delimited cell regions. The possible ontogeny of MFS components and their importance are discussed. Key words: chitin, Dutch elm disease, fungal fimbriae, fungal walls, gold-complexed probes, microfilamentous structures (MFS).
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Sripathineni, Usha, Bill J. Moss, Liming Zhao, Robert W. Roberson, David Schaefer, and Mark R. Marten. "Effect of Rapamycin on Filamentous Fungal Cell Walls." Biophysical Journal 100, no. 3 (2011): 484a. http://dx.doi.org/10.1016/j.bpj.2010.12.2840.

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Hale, Michael D., and Rodney A. Eaton. "Oscillatory growth of fungal hyphae in wood cell walls." Transactions of the British Mycological Society 84, no. 2 (1985): 277–88. http://dx.doi.org/10.1016/s0007-1536(85)80079-6.

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Farkaš, V. "Structure and biosynthesis of fungal cell walls: Methodological approaches." Folia Microbiologica 48, no. 4 (2003): 469–78. http://dx.doi.org/10.1007/bf02931327.

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Dufrêne, Yves F. "Atomic force microscopy of fungal cell walls: an update." Yeast 27, no. 8 (2010): 465–71. http://dx.doi.org/10.1002/yea.1773.

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Xie, Xianfa, and Peter N. Lipke. "On the evolution of fungal and yeast cell walls." Yeast 27, no. 8 (2010): 479–88. http://dx.doi.org/10.1002/yea.1787.

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Farka?, V. "Fungal cell walls: Their structure, biosynthesis and biotechnological aspects." Acta Biotechnologica 10, no. 3 (1990): 225–38. http://dx.doi.org/10.1002/abio.370100303.

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Moore, Carol W., Judith McKoy, Robert Del Valle, et al. "Fungal Cell Wall Septation and Cytokinesis Are Inhibited by Bleomycins." Antimicrobial Agents and Chemotherapy 47, no. 10 (2003): 3281–89. http://dx.doi.org/10.1128/aac.47.10.3281-3289.2003.

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ABSTRACT When the essential and distinctive cell walls of either pathogenic or nonpathogenic fungi break, cytoplasmic membranes rupture and fungi die. This fungicidal activity was discovered previously on nonproliferating Saccharomyces cerevisiae cells treated briefly with the oxidative tool and anticancer drug family of bleomycins. The present studies investigated effects of bleomycin on growing fungal organisms. These included the medically important Aspergillus fumigatus and Cryptococcus neoformans, as well as the emerging human pathogen and fungal model, S. cerevisiae. Bleomycin had its highest potency against A. fumigatus. Scanning electron microscopy and thin-section transmission electron microscopy were used to study morphological growth characteristics. Killing and growth inhibition were also measured. Long, thin, and segmented hyphae were observed when A. fumigatus was grown without bleomycin but were never observed when the mold was grown with the drug. Bleomycin arrested conidial germination, hyphal development, and the progression and completion of cell wall septation. Similarly, the drug inhibited the construction of yeast cell wall septa, preventing cytokinesis and progression in the cell division cycle of S. cerevisiae. Even when cytoplasms of mother and daughter cells separated, septation and cell division did not necessarily occur. Bizarre cell configurations, abnormally thickened cell walls at mother-daughter necks, abnormal polarized growth, large undivided cells, fragmented cells, and empty cell ghosts were also produced. This is the first report of a fungicidal agent that arrests fungal growth and development, septum formation, and cytokinesis and that also preferentially localizes to cell walls and alters isolated cell walls as well as intact cell walls on nongrowing cells.
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Dissertations / Theses on the topic "Fungal cell walls"

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Mackenzie, Ashleigh. "The role of Rhynchosporium commune cell wall components in cell wall integrity and pathogenicity." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225718.

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Rhynchosporium commune is one of the most destructive pathogens of barley worldwide. It can cause crop yield losses of up to 40% in the UK and decrease in grain quality. Populations of R. commune can change rapidly, defeating new barley resistance (R) genes and fungicides after just a few seasons of their use. Fungicide use is one of the major modes of management of Rhynchosporium and is heavily relied on the agricultural industry. Fungicides that were effective in the past are no longer effective in controlling the disease and many are only effective when used in mixtures. Beyond the currently effective fungicides there is limited new chemistry available so there is a very real need for development in this area. In pathogenic fungi, the cell wall components play a key role in the establishment of pathogenesis. The cell wall forms the outer structure protecting the fungus from the host defence mechanisms. It is involved in initiating the direct contact with the host cells by adhering to their surface. The fungal cell wall also contains important antigens and other compounds modulating host immune responses. R. commune germinated conidia and interaction transcriptome sequencing generated a list of over 30 different cell wall proteins (CWPs) potentially involved in pathogenicity. R. commune genome and interaction transcriptome sequencing provided further information about the extent of CWP families as well as a subset of genes expressed during barley colonisation by R. commune. The use of bioinformatic techniques allowed for the analysis of gene sequences. Putative cell wall associated genes were compared to the sequences from the fungal database via sequence similarity, sequence alignments 15 and conserved domain searches to better understand their function. Phylogenetic analysis also allowed us to understand the evolutionary relationship between R. commune genes and related genes in other organisms. Transcription profiling of R. commune CWPs during the development of infection helped to prioritise them for functional characterisation. Targeted gene disruption unfortunately did not yield mutants but has furthered our understanding of this technique in R. commune for future attempts. Functional complementation was successful however and allowed the uncovering of the function of RSA9. The results show that R. commune RSA9 functions as an allantoicase, an enzyme which breaks down purines as a source of nitrogen when conditions are nitrogen limited. The use of chemical cell wall inhibitors allowed us to better understand the role of carbohydrate cell wall components in R. commune fitness and virulence. Inhibition of cellulose production by DCB showed reduced growth, germination and pathogenicity of R. commune. Similar results were observed when beta-glucan synthesis was impaired; as inhibitor concentration increased, growth and germination of the fungus decreased. The composition of R. commune cell wall was also uncovered during this research. Techniques such as HPLC and FTIR eluded the composition of monosaccharides and polysaccharides respectively. In addition the structure of R. commune cell wall was observed by microscopy, namely TEM. This project revealed some much needed information on the R. commune cell wall and the relation of its components to fitness and virulence during infection of barley.
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Ball, Lucy Margaret. "Antifungals and the trichophyton rubrum cell wall." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670146.

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Lamon, Gaëlle. "Structural characterization of fungal cell walls architecture by solid-state NMR." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0314.

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Il existe une grande variété de champignons pathogènes humains qui sont à l’origine de maladies bénignes à mortelles. La plupart du temps, ces infections sont associées à d’autres pathologies ou traitements médicaux comme l’asthmes, les leucémies, les transplantations d’organes, le SIDA ou les traitement immunosuppresseurs à base de corticostéroides. Malgré le nombre important de décès et le nombre grandissant d’occurrence des mycoses sévères à travers le monde, les infections fongiques sont encore négligées par les autorités sanitaires.Parmi ces pathogènes fongiques, le champignon filamenteux Aspergillus fumigatus est un des pathogènes principaux du système respiratoire. L’aspergillose, dont les taux de d’infection et de mortalité demeurent élevés, devient un enjeu de santé publique. Les spores d’A. fumigatus sont entourés d’une paroi, essentielle pour leur croissance et leur permettant de résister face au système immunitaire de l’hôte. Cette paroi est composée d’un réseau de polysaccharides recouvert d’un pigment appelé DHN-mélanine et d’une couche de protéines appelées hydrophobines. Ce projet a pour but d’établir l’architecture structurale de la paroi des spores d’A. fumigatus à l’échelle atomique en utilisant la RMN du solide (ssNMR) en rotation à l’angle magique (MAS).D’un autre côté, Cryptococcus neoformans est l’agent pathogène responsable de la cryptococcose ; une mycose affectant le système nerveux central. Cette maladie fongique est, encore de nos jours, une cause significative de mortalité à travers le monde puisqu’elle entraîne de graves symptômes tels que la méningo-encéphalite ; particulièrement fréquente chez les patients déjà infectés par le VIH. C. neoformans se présente sous la forme d’une cellule encapsulée de 5 à 7 μm de diamètre entourée d’une paroi et d’une capsule. Cette paroi, rigide, est liée à la membrane plasmique et composée de polymères d’α-glucan, de β-glucan, de chitine et de chitosan. De plus, la capsule de C. neoformans est majoritairement composée de carbohydrates tels que le glucuronoxylomannan (GXM) (jusqu’à 90 %) ou le glucuronoxylomannogalactan (GXMGal) mais aussi de mannoprotéines et de lipides. Le but de ce projet de thèse est d’identifier les différents composants de la paroi mais aussi de la capsule de C. neoformans par ssNMR et d’établir l’architecture de ces deux entités. Un des aspects de ce projet est aussi d’explorer les possibilités et les limitations des méthodes de détection proton en RMN couplée à un MAS élevé (100 kHz) comme outil d’analyse des parois fongiques.En résumé, puisque la RMN des solides est une méthode de spectroscopie non invasive, nous avons appliqué ce type d’analyses dans le cadre de l’étude de l’architecture moléculaire de systèmes complexes (parois fongiques, capsules, …) dans des conditions aussi proches que possible de l’état natif des cellules. Pendant ces trois années de thèse, nous avons mis en place une méthodologie robuste et rapide permettant d’étudier la composition complexe des structures externes présentes dans les cellules fongiques ainsi que leur architecture au sein des cellules entières. De plus, puisque dans le cadre des infections microbiennes la pathogénicité du microbe repose souvent sur les structures externes des cellules infectieuses, les résultats obtenus au court de cette thèse, apportant une meilleure compréhension de l’organisation cellulaire d’A. fumigatus et C. neoformans, pourraient ainsi être utilisés dans le cadre du développement et de la mise en place de nouvelles stratégies thérapeutiques afin de combattre plus efficacement ces infections fongiques<br>There is a broad range of fungal pathogen infecting humans and causing diseases that can be from mild to lethal. Severe fungal infections are due to opportunistic pathogens that infect immunosuppressed individuals and are most of the time associated with other diseases or medical conditions such as asthma, leukemia, organ transplants, AIDS or immunosuppressive corticosteroid therapies. Despite the number of deaths and the increase in severe mycosis, fungal infections remain neglected by public health authorities.Among fungal pathogens, the filamentous fungus Aspergillus fumigatus is one of the major pathogen of the respiratory system. Aspergillosis displaying both high incidence and mortality rates, is becoming a massive public health issue. The spores of Aspergillus fumigatus are surrounded by a cell wall, essential for their growth and allowing them to resist against host defense mechanisms. The cell wall is composed of a set of polysaccharides covered by the DHN-melanin pigment and a layer of proteins called hydrophobins. In this project, we aimed at investigated the structural architecture of Aspergillus fumigatus cell wall at atomic resolution using MAS ssNMR spectroscopy.In another hand, Cryptococcus neoformans is the etiological agent of cryptococcosis; which consists in mycosis affecting the central nervous system. This fungal disease remains a significant cause of mortality worldwide by leading to severe symptoms such as meningoencephalitis - especially for immunocompromised individuals suffering from AIDS. C. neoformans results in encapsulated particles with a size of 5-7μm with a two-layers external structure composed of a cell wall and a capsule. The cell wall, rigid, is bounded to the plasma membrane and composed of polymers of α-glucan, β-glucan, chitin and chitosan45. Then, the capsule of C. neoformans is mainly composed of carbohydrates such as glucuronoxylomannan (GXM) (up to 90%), glucuronoxylomannogalactan (GXMGal), mannoproteins and lipids. During this thesis project, we aimed at identifying the different components of C.neoformans cell wall and capsule by ssNMR and to investigate the architecture of these two layers. Part of this project was also the exploration of possibilities and limits of 1H detection methods at fast MAS regime (100 kHz) as the tool to analyze intact cell walls.To sum up, as the solid-state NMR is a non-destructive spectroscopy, we applied this method to the study of the molecular architecture of complex systems (cell wall, capsule…) in cellular conditions – as close as possible to the native state. During these three years, we set up a methodology allowing studying the complex composition of fungal external structures as well as their architecture in the cell context. Finally, because in microbial infections, the pathogenesis often relies on the external structures of the pathogen, all these results could give a better comprehension of the A. fumigatus and C. neoformans cell organization that may help to find new therapeutic strategies to fight, more efficiently, against fungal infections
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Ibe, Chibuike. "Understanding the role of stress induced cell wall proteins in C. albicans cell wall compensatory response and pathogenicity." Thesis, University of Aberdeen, 2019. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=240548.

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Lee, Keunsook Kathy. "Echinocandin resistance of Candida albicans due to elevated cell wall chitin." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=210190.

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De, Almeida Nogueira Maria Filomena. "Candida albicans signalling pathways and the regulation of cell wall biosynthesis under stress." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=203748.

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The main aim of this project was to study Candida albicans cell wall biosynthesis in response to stress. The role of the MAPK, Ca2+/calcineurin and cAMP/PKA signal transduction pathways in regulating the C. albicans cell wall stress response was investigated. A library of mutants lacking receptors, signalling elements and transcription factors were screened for alterations in their ability to respond to a range of cell wall stressing agents, including CaCl2, Calcofluor White and caspofungin. Pretreatment of wild-type cells with CaCl2 and CFW, activates the Ca2+/calcineurin and PKC pathways, leading to an increase in chitin content, and reduced susceptibility to caspofungin. Although elevation of cell wall chitin content often resulted in decreased sensitivity to caspofungin, I show here that some strains with increased chitin levels remained sensitive to caspofungin. The results show that elevation of chitin is a common property of a range of mutants that are affected in coordinating cell wall stress pathways, but that multiple mechanisms are likely to operate in maintaining the robustness of the C. albicans cell wall. Some of the mutant strains of the MAPK, Ca2+/calcineurin and cAMP signalling pathways showed evidence of paradoxical growth, whereby less inhibition was achieved by higher concentrations of antifungal drug. The role of chitin-related genes and stress signalling pathways in regulating C. albicans paradoxical growth was also investigated. Based on these results, more detailed analyses were performed to investigate the correlations between sensitivity and resistance to caspofungin, in relation to paradoxical growth. The MAPK-Mkc1 and the calcineurin pathways played major roles in the paradoxical growth effect. There was a proportional relationship between echinocandin concentration and the chitin content of the cell wall although the chitin content did not continue to be upregulated by the highest echinocandin concentration. Different echinocandins, carbon source, cell morphology and medium composition influenced the extent of paradoxical growth effect. The existence of paradoxical growth in resistant strains such as Fks1 also highlights association of paradoxical growth with resistance mechanisms.
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Horstmann, Carl Ulrich. "Manipulating cell wall biosynthesis in yeast and higher plants." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5288.

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Thesis (MSc (Genetics))--University of Stellenbosch, 2010.<br>Includes bibliography.<br>Title page: Dept. of Genetics, Faculty of Science.<br>ENGLISH ABSTRACT: Undeniably, changes in the environment and dwindling traditional energy resources have resulted in the search for viable, renewable energy alternatives such as biofuels. Cellulose is one of the most abundant polymers on earth and can be converted to simple sugars and fermented to ethanol biofuel fairly easily. Cellulose rich biomass that can serve to supply ethanol biofuel production can be sourced from unexploited agricultural waste. The main drawback to using vegetative tissue as opposed to harvested food stocks from crops results from the structural properties of plant cell walls. Although cellulose is abundant, the contaminating hemicellulose and lignin fibres within the cell wall matrix have a negative impact on the digestibility of the cellulose present. Thus, an important step in creating an effective biofuel production system from agricultural excess is developing crops with improved cell wall polymer characteristics that can be converted to ethanol more efficiently. This project consisted of two parts. Firstly, the aim was to assess lignin production in transgenic sugarcane transformed with a construct aimed at down-regulating the 4- (hydroxyl) cinnamoyl CoA ligase (4CL) gene in the lignin biosynthesis pathway. The second part of the project revolved around discovering the mechanism of impared cell growth caused by expressing the gene encoding cellulose synthase from a marine invertebrate, Ciona savignyi, in the yeast Saccharomyces cerevisiae. Several sugarcane lines that had been previously transformed with a hairpin RNAi construct aimed at down-regulating the 4CL gene in the monolignol biosynthesis pathway were subjected to analysis to determine if lignification had been reduced. Although the presence of the hairpin construct in the genomic DNA had been confirmed for all of the transgenic lines, there was no significant decrease in the lignin levels in any of the transgenic lines. PCR analysis of the mRNA and enzyme assays also confirmed that the 4CL gene was still being expressed. Ongoing work will determine the cause of the unsuccessful down-regulation. Previously, it had been proven that the cellulose synthase gene from C. savignyi could be functionally expressed in S. cerevisiae. However, cellulose production resulted in extremely retarded growth of colonies and cultures, to the point of the apparent death of the cultures. The aim of this part of the project was to determine the mechanism (either metabolic or physical) that causes this effect. To generate enough cell mass to perform metabolic analysis, several strategies to impede cellulose production in transgenic yeast were explored. Attempts to stop cellulose production and induce better growth by introducing Isoxaben (a traditional weed killer that targets cellulose synthases) into the growth medium used for the transgenic yeast proved unsuccessful. To control the expression of the transgene, it was attempted to clone the cellulose synthase gene into an expression system containing an inducible promoter. The cloning exercise proved extremely difficult and multiple attempts with several strategies proved unsuccessful. This process is still ongoing as the growth retarding process induced by cellulose production in yeast remains to be identified.<br>AFRIKAAANSE OPSOMMING: Dit is onontkenbaar dat veranderinge in die omgewing en minderwordende tradisionele energiebronne veroorsaak dat lewensvatbare en hernubare energiebronne soos biobrandstof gevind moet word. Sellulose is een van die mees volop polimere op aarde en kan redelik maklik omgeskakel word na eenvoudige suikers en gefermenteer word tot etanol-biobrandstof. Sellulose-ryk biomassa wat etanol-biobrandstof kan verskaf, kan herwin word van tot op hede ongebruikte landbou-afval. Die komplekse struktuur van plantselwande is die hoofstruikelblok in die omskakeling van vegetatiewe weefsel tot biobrandstof. Hoewel sellulose volop is, het die kontaminerende hemisellulose- en lignienvesels binne die selwand-matriks ’n negatiewe impak op die verteerbaarheid van die sellulose teenwoordig in die selwand. Daarom is ’n belangrike stap in die ontwikkeling van effektiewe biobrandstof-produksiesisteme vanaf landbou-afval om gewasse te ontwikkel met verbeterde selwandpolimeer-eienskappe wat etanol-produksie kan vergemakilik. Hierdie projek het bestaan uit twee dele. Eerstens was die doel om vas te stel of die lignienproduksie geaffekteer is in transgeniese suikerriet getransformeer met ’n konstruk wat mik om die 4-(hidroksie)-cinnamoyl CoA ligase (4CL) geen te af-reguleer in die lignienbiosintese- padweg. Die tweede deel van die projek het daarop gefokus om die meganisme te ondek wat die belemmerde selgroei veroorsaak, as gevolg van die uitdrukking van die geen wat kodeer vir sellulose-sintase in ’n mariene ongewerwelde, Ciona savignyi, in Saccharomyces cerevisiae. Verskeie suikerriet-lyne, wat voorheen getransformeer is met ’n haarnaald-RNAi-konstruk om die 4CL-geen te af-reguleer in die monolignol-biosintese-padweg, is onderwerp aan analise om vas te stel of lignifikasie verminder is. Hoewel die teenwoordigheid van die haarnaald-konstruk in die genomiese DNA bevestig is vir al die transgeniese lyne, was daar geen beduidende vermindering in die lignienvlakke in die transgeniese lyne nie. PKRanalise van die mRNA en ensiem-aktiwiteitstoetse het ook bevestig dat die 4CL-geen steeds uitgedruk word. Verdere ondersoek sal kan vasstel wat die oorsaak van die onsuksesvolle af-regulering is. Voorheen is bewys dat die sellulose-sintase-geen van C. savignyi funksioneel uitgedruk kon word in Saccharomyces cerevisiae. Egter, selluloseproduksie het die gevolg gehad dat groei in die transgeniese kolonies en kulture erg gestrem is, tot die punt dat die kulture dood voorgekom het. Die doel van hierdie deel van die projek was om vas te stel wat die meganisme (òf metabolies òf fisies) is wat hierdie verskynsel veroorsaak het. Om genoeg selmassa te genereer om metaboliese analise uit te voer, is verskeie strategieë om selluloseproduksie in transgeniese gis te verhinder, ondersoek. Pogings om selluloseproduksie te stop en om groei te verbeter deur Isoxaben by te voeg in die groeimedium gebruik vir transgeniese gis, was onsuksesvol. Isoxaben is ’n tradisionele onkruiddoder wat sellulose-sintases teiken en inhibeer. Om die uitdrukking van die transgeen te beheer, is ’n poging aangewend om dié sellulose-sintase-geen in ’n uitdrukking-sisteem te kloon met ’n induseerbare promotor. Die kloneringsoefening was uiters moeilik en veelvoudige pogings met verskeie strategieë was onsuksesvol. Hierdie proses moet verder gevoer word aangesien die groeistremmingsmeganisme veroorsaak deur selluloseproduksie in gis nog geïdentifiseer moet word.
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Raziunaite, Ingrida. "Use of C-type lectin receptor probes and human monoclonal antibodies to map the dynamics of the fungal cell wall." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=238675.

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Nakai, Toru. "Antifungal Characterization of FK463, an Inhibitor of 1,3-β-D-Glucan Synthesis in Fungal Cell Walls". Kyoto University, 2004. http://hdl.handle.net/2433/148347.

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Levinson, Joshua N. "Functional and cell biological characterization of Saccharomyces cerevisiae Kre5p." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33798.

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Saccharomyces cerevisiae Kre5p is important for the biosynthesis of beta-1,6-glucan, which is required for proper cell wall assembly and architecture. A functional and cell biological analysis of Kre5p was conducted to further elucidate its role in beta-1,6-glucan synthesis. Kre5p was found to be a primarily soluble N-glycoprotein of &sim;200 kD that localizes to the endoplasmic reticulum. Observation of Kre5p-deficient cells reveals a severe cell wall morphological defect, and kre5Delta cells were shown to have only residual levels of beta-1,6-glucan. KRE6 was identified as a multicopy suppressor of a temperature-sensitive kre5 allele, suggesting these proteins participate in a common pathway. An analysis of truncated versions of Kre5p indicates that it may have two independent, essential activities, or that it functions in a homodimeric state. Finally, Candida albicans KRE5 was shown to partially restore growth to kre5Delta cells, suggesting it has a function similar to that of the S. cerevisiae protein.
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Books on the topic "Fungal cell walls"

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Fungal cell wall: Structure, synthesis, and assembly. CRC Press, 1992.

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NATO Advanced Research Workshop on Fungal Cell Wall and Immune Response (1990 Eloúnda, Greece). Fungal cell wall and immune response. Springer-Verlag, 1991.

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A, Gurevich G., and Fikhte B. A, eds. Mekhanicheskie svoĭstva mikrobnykh obolochek. Nauch. t͡sentr biologicheskikh issledovaniĭ AN SSSR, 1988.

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Larsen, Michael J. Mycofibrillar cell wall extensions in the hyphal sheath of Postia placenta. U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory, 1992.

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Ruiz-Herrera, José. Fungal cell wall: Structure, synthesis, and assembly. 2nd ed. CRC Press, 2012.

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Biosintez uglevodnykh komponentov kletochnoĭ stenki drozhzheĭ. Nauch. t͡s︡entr biologicheskikh issledovaniĭ AN SSSR, 1988.

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Kasumov, Kh M. Molekuli͡a︡rnyĭ mekhanizm vzaimodeĭstvii͡a︡ polienovykh antibiotikov s lipidnymi membranami. "Ėlm", 1986.

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Latgé, Jean-Paul, ed. The Fungal Cell Wall. Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-49928-0.

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Latgé, J. P., and D. Boucias, eds. Fungal Cell Wall and Immune Response. Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76074-7.

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The Fungal Cell Wall. Nova Science Pub Inc, 2013.

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Book chapters on the topic "Fungal cell walls"

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Peberdy, J. F. "Fungal Cell Walls — A Review." In Biochemistry of Cell Walls and Membranes in Fungi. Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-74215-6_2.

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Benhamou, N. "Electron Microscopic Localization of Polysaccharides in Fungal Cell Walls." In Fungal Cell Wall and Immune Response. Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76074-7_16.

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Wessels, J. G. H., P. C. Mol, J. H. Sietsma, and C. A. Vermeulen. "Wall Structure, Wall Growth, and Fungal Cell Morphogenesis." In Biochemistry of Cell Walls and Membranes in Fungi. Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-74215-6_6.

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Vanden Bossche, H. "Importance and Role of Sterols in Fungal Membranes." In Biochemistry of Cell Walls and Membranes in Fungi. Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-74215-6_10.

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Slayman, C. L., P. Kaminski, and D. Stetson. "Structure and Function of Fungal Plasma-Membrane ATPases." In Biochemistry of Cell Walls and Membranes in Fungi. Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-74215-6_19.

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Koch, Barbara, and Ana Traven. "Mitochondrial Control of Fungal Cell Walls: Models and Relevance in Fungal Pathogens." In Current Topics in Microbiology and Immunology. Springer International Publishing, 2019. http://dx.doi.org/10.1007/82_2019_183.

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Lösel, D. M. "Lipids in the Structure and Function of Fungal Membranes." In Biochemistry of Cell Walls and Membranes in Fungi. Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-74215-6_9.

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Santos, Cledir, Paula Galeano, Reginaldo Lima Neto, Manoel Marques Evangelista Oliveira, and Nelson Lima. "MALDI-TOF MS and its requirements for fungal identification." In Trends in the systematics of bacteria and fungi. CABI, 2021. http://dx.doi.org/10.1079/9781789244984.0119.

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Abstract Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) is now used as a routine technique for the fast and reliable identification of fungi at the species level and, currently, it represents an important phenotypic methodology based on proteomic profiles. The main limitations to MALDI-TOF MS for fungal identification are related to sample quality (e.g. quality of biological material such as rigidity or pigmentation of cell walls), sample preparation (e.g. the myriad of sample preparation methodologies that deliver different data sets to different MALDI-TOF MS databases) and the databases themselves (e.g. the 'black-box' commercial databases). This chapter presents an overview and discussion of the use of MALDI-TOF MS for fungal identification. The major known limitations of the technique for fungal taxonomy, and how to overcome these, are also discussed.
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Bartnicki-Garcia, S., F. Hergert, and G. Gierz. "A Novel Computer Model for Generating Cell Shape: Application to Fungal Morphogenesis." In Biochemistry of Cell Walls and Membranes in Fungi. Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-74215-6_4.

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Pengelly, Andrew. "Polysaccharides." In The constituents of medicinal plants, 3rd ed. CABI, 2021. http://dx.doi.org/10.1079/9781789243079.0009.

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Abstract Polysaccharides are universal in the plant and fungal kingdoms. Their functions include food storage, protection of membranes, and maintaining rigidity of cell walls in plants and fungi, whereas for seaweeds they help maintain the flexibility required for life in the ocean. Polysaccharides play significant roles in the activity of numerous herbs used in traditional Chinese medicine and Japanese (Kampo) medicine. Polysaccharides are insoluble in organic solvents; they precipitate in alcohol. Herbal tinctures, which are made using alcoholic solvents of 45% strength or higher, are therefore of little use for polysaccharide extraction. The degree of water solubility depends on the polysaccharide structure. Linear polymers (mucilages) are less water soluble and tend to precipitate at high temperatures and form viscous or slimy solutions. Branched polymers (gums) are more water soluble and form gels, often referred to as 'gummy' or 'sticky'. Examples of carbohydrate polymers and their sources and significance to plants and humans are shown in this chapter. Tabulated data are also given on selected medicinal mushrooms, their polysaccharides and therapeutic uses, as well as on inulin-containing species of herbs from the Asteraceae family.
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Conference papers on the topic "Fungal cell walls"

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Stopinsek, Sanja, Alojz Ihan, Branka Wraber, et al. "Reactivity To Fungal Cell Wall Agents (FCWA) In Peripheral Blood Mononuclear Cells From Patients With Sarcoidosis." In American Thoracic Society 2010 International Conference, May 14-19, 2010 • New Orleans. American Thoracic Society, 2010. http://dx.doi.org/10.1164/ajrccm-conference.2010.181.1_meetingabstracts.a5709.

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Kosheva, Nataliia, Sylwia Stączek, Agnieszka Zdybicka-Barabas, Małgorzata Cytryńska, Adrian Wiater та Monika Koziej. "Immunomodulatory activity of glucooligosaccharides obtained from fungal cell wall α-1,3-glucans". У 1st International PhD Student’s Conference at the University of Life Sciences in Lublin, Poland: ENVIRONMENT – PLANT – ANIMAL – PRODUCT. Publishing House of The University of Life Sciences in Lublin, 2022. http://dx.doi.org/10.24326/icdsupl1.p010.

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Shi, Lei, Tong Zhao, Yuantao Zhang, Liang Zou, and Li Zhang. "Reactive Molecular Dynamics Simulation on Plasma-induced Destruction of Fungal Cell Wall Components." In 2017 IEEE International Conference on Plasma Science (ICOPS). IEEE, 2017. http://dx.doi.org/10.1109/plasma.2017.8496155.

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Liedke, Susie, Allan Guimarães, and José Peralta. "Evaluation of antifungal properties of the chimeric protein WGA-Fc against the fungal cell wall." In III Seminário Anual Científico e Tecnológico de Bio-Manguinhos. Instituto de Tecnologia em Imunobiológicos, 2016. http://dx.doi.org/10.35259/isi.sact.2016_28284.

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Ricks, David M., Mingquan Zheng, and Jay K. Kolls. "Conserved Natural Igm Antibodies Targeting Fungal Cell Wall Polysaccharides Are Secreted By B-1 Cells And Mediate Host Defense Against Pneumocystis." In American Thoracic Society 2011 International Conference, May 13-18, 2011 • Denver Colorado. American Thoracic Society, 2011. http://dx.doi.org/10.1164/ajrccm-conference.2011.183.1_meetingabstracts.a4133.

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Campos-Takaki, G. M., and Sônia M. C. Dietrich. "Characterization of Cell Walls from Mucoralean Fungi by Biochemical Composition, Transmission Electron Microscopy and X-Ray Microanalysis." In Proceedings of the II International Conference on Environmental, Industrial and Applied Microbiology (BioMicroWorld2007). WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789812837554_0025.

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Wang, Ruoya, and Rudolph L. Gleason. "A New Form of Residual Deformation in the Coronary Artery: Implications for In Vivo Mechanical Behavior." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53705.

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Vascular residual stress has been the subject of numerous studies for more than two decades. The importance of residual stress on vascular mechanics was first recognized by Chuong and Fung [1]. They demonstrated that when circumferential residual stress was considered in the mechanical analysis, a nearly uniform stress distribution was predicted across the vessel wall. This suggested that vascular cells, despite being at different radial locations, experience the same stress environment. Residual stress is also known to exist longitudinally, and recent studies have shown that this highly effects the stress environment as well [2]. This study presents a new form of vascular residual stress, one that occurs in shear, within the porcine coronary artery. The effects of residual shear stress on the transmural stress profile are examined. We hope the results can lead to a better understanding of the residual stress field, and therefore help develop more robust and predictive models for vascular diseases.
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Jayaprakash, Nirmala, Kanchana Manivasakan, and Sai Tejeshwini Rajaram. "Investigation of mechanism and effectiveness of metal nanoparticles in self-sterilizing packaging." In 11th International Symposium on Graphic Engineering and Design. University of Novi Sad, Faculty of technical sciences, Department of graphic engineering and design, 2022. http://dx.doi.org/10.24867/grid-2022-p53.

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Microbial contaminants intimidate food safety and shelf-life. Metal nanoparticles (NPs) have become a leading area of interest and research in barrier packaging materials that ensure food safety. Traits such as small size, high surface-to-volume ratio and multi-functionality make them ideal materials for producing self-sterilizing packaging. Numerous metal NPs have proven to fight against a wide range of pathogenic microbes through various methods. Further, metal NPs exhibit more biocompatibility than metal ions. This study investigates the role and the mechanism of action of the various NPs in selfsterilizing packaging. AgNPs, TiO2NPs, MgONPs, ZnONPs, AuNPs, FeONPs, Cu-based NPs and SnO2NPs have been explored for their biocidal action in self-sterilizing surfaces and food packaging applications in this work. The size, shape, surface structure, surface reactivity and other environmental factors (like pH) influence the biocidal properties of these metal NPs. From the literature survey, it was inferred that it was necessary for the metal NPs to be smaller than 50 nm in size to exhibit effective biocidal action against pathogenic microbes. The mechanisms followed by the metal NPs against bacteria and fungi include disturbing the cell wall, the metabolic process by inducing reactive oxygen species (ROS) and/or the DNA synthesis mechanism. It was inferred that AgNPs, MgNPs and ZnONPs are some of the NPs that have a significant share in self-sterilizing surfaces. Being expensive, the works of literature on AuNPs and their application in this subject are very few. This paper aims to study the biocidal behaviour and rank the effectiveness of these metal NPs to act as ideal materials for self-sterilising packaging.
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Chow, Ming-Jay, Jarred Raymund Mondonedo, and Katherine Yanhang Zhang. "Quantifying the Structural and Mechanical Changes in Elastase Degraded Arteries as an In Vitro Model of Aortic Aneurysm." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53576.

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Common characteristics of aortic aneurysm include loss of elastin/smooth muscle cells, increase in fibrillary collagen, and increase in artery diameter [5]. Because of the high mortality rate of aneurysm rupture, it is desirable to be able to predict when a patient should have surgery to repair the dilated tissue. Current clinical practices involve predicting aneurysm rupture based on artery expansion rate and diameter. However, other parameters such as wall stiffness and peak wall stress may offer better predictions as to when an aneurysm will fail [8]. Previous studies have investigated the differences in elastin and collagen content of abdominal aortic tissue with and without abdominal aortic aneurysm (AAA) [1]. In another study, human aortic aneurysm tissue was tested in a biaxial tensile tester and the resulting stress strain curves were fitted using Fung type exponential strain energy function [7]. More extensive modeling of aneurysm tissue has been done by modifying the Holzapfel model to incorporate a parameter that characterizes the tissue weakening before the failure of the inner elastic laminae, ground matrix, or collagen fibers themselves [6]. Previous studies have found compositional and mechanical differences between aneurysm and healthy tissue. In addition, good structurally based models for arteries that are developing aneurysm exist but these are mostly theoretical [6]. In order to improve aneurysm rupture prediction techniques, a better understanding of how structural changes affect the mechanical properties of the artery is necessary.
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Reports on the topic "Fungal cell walls"

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Sharon, Amir, and Maor Bar-Peled. Identification of new glycan metabolic pathways in the fungal pathogen Botrytis cinerea and their role in fungus-plant interactions. United States Department of Agriculture, 2012. http://dx.doi.org/10.32747/2012.7597916.bard.

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The involvement of glycans in microbial adherence, recognition and signaling is often a critical determinant of pathogenesis. Although the major glycan components of fungal cell walls have been identified there is limited information available on its ‘minor sugar components’ and how these change during different stages of fungal development. Our aim was to define the role of Rhacontaining-glycans in the gray mold disease caused by the necrotrophic fungus B. cinerea. The research was built on the discovery of two genes, Bcdhand bcer, that are involved in formation of UDP-KDG and UDP-Rha, two UDP- sugars that may serve as donors for the synthesis of cell surface glycans. Objectives of the proposed research included: 1) To determine the function of B. cinereaBcDh and BcEr in glycan biosynthesis and in pathogenesis, 2) To determine the expression pattern of BcDH and BcERand cellular localization of their encoded proteins, 3) Characterize the structure and distribution of Rha- containing glycans, 4) Characterization of the UDP-sugar enzymes and potential of GTs involved in glycanrhamnosylation. To address these objectives we generated a series of B. cinereamutants with modifications in the bchdhand bcergenes and the phenotype and sugar metabolism in the resulting strains were characterized. Analysis of sugar metabolites showed that changes in the genes caused changes in primary and secondary sugars, including abolishment of rhamnose, however abolishment of rhamnose synthesis did not cause changes in the fungal phenotype. In contrast, we found that deletion of the second gene, bcer, leads to accumulation of the intermediate sugar – UDP- KDG, and that such mutants suffer from a range of defects including reduced virulence. Further analyses confirmed that UDP-KDG is toxic to the fungus. Studies on mode of action suggested that UDP-KDG might affect integrity of the fungal cell wall, possibly by inhibiting UDP-sugars metabolic enzymes. Our results confirm that bcdhand bcerrepresent a single pathway of rhamnose synthesis in B. cinerea, that rhamnose does not affect in vitro development or virulence of the fungus. We also concluded that UDP-KDG is toxic to B. cinereaand hence UDP-KDG or compounds that inhibit Er enzymes and lead to accumulation of UDP-KDG might have antifungal activity. This toxicity is likely the case with other fungi, this became apparent in a collaborative work with Prof. Bart Thomma of Wageningen University, NETHERLANDS . We have shown the deletion of ER mutant in Verticillium dahlia gave plants resistance to the fungal infection.
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Thomashow, Linda, Leonid Chernin, Ilan Chet, David M. Weller, and Dmitri Mavrodi. Genetically Engineered Microbial Agents for Biocontrol of Plant Fungal Diseases. United States Department of Agriculture, 2005. http://dx.doi.org/10.32747/2005.7696521.bard.

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The objectives of the project were: a) to construct the site-specific integrative expression cassettes carrying: (i) the chiA gene for a 58-kDa endochitinase, (ii) the pyrrolnitrin biosynthesis operon, and (iii) the acdS gene encoding ACC deaminase; b) to employ these constructs to engineer stable recombinant strains with an expanded repertoire of beneficial activities; c) to evaluate the rhizosphere competence and antifungal activity of the WT and modified strains against pathogenic fungi under laboratory and greenhouse conditions; and d) to monitor the persistence and impact of the introduced strains on culturable and nonculturable rhizosphere microbial populations in the greenhouse and the field. The research generally support our concepts that combining strategically selected genes conferring diverse modes of action against plant pathogens into one organism can improve the efficacy of biological control agents. We hypothesized that biocontrol agents (BCAs) engineered to expand their repertoire of beneficial activities will more effectively control soilborne plant pathogens. In this work, we demonstrated that biocontrol activity of Pseudomonas fluorescens Q8r1-96 and Q2-87, both producing the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) effective against the plant pathogenic fungus Rhizoctonia solani, can be improved significantly by introducing and expressing either the 1.6-kb gene chiA, encoding the 58-kDa endochitinase ChiA from the rhizosphere strain SerratiaplymuthicaIC1270, or the 5.8-kb prnABCDoperon encoding the broad-range antibiotic pyrrolnitrin (Prn) from another rhizosphere strain, P. fluorescens Pf-5. The PₜₐcchiAandPₜₐcprnABCDcassettes were cloned into the integrative pBK-miniTn7-ΩGm plasmid, and inserted into the genomic DNA of the recipient bacteria. Recombinant derivatives of strains Q8r1-96 and Q2-87 expressing the PₜₐcchiA or PₜₐcprnABCD cassettes produced endochitinase ChiA, or Prn, respectively, in addition to 2,4-DAPG, and the recombinants gave significantly better biocontrol of R. solani on beans under greenhouse conditions. The disease reduction index increased in comparison to the parental strains Q8r1-96 and Q2-87 to 17.5 and 39.0% from 3.2 and 12.4%, respectively, in the case of derivatives carrying the PₜₐcchiAcassette and to 63.1 and 70% vs. 2.8 and 12,4%, respectively, in the case of derivatives carrying the PₜₐcprnABCDcassette. The genetically modified strains exhibited persistence and non-target effects comparable to those of the parental strains in greenhouse soil. Three integrative cassettes carrying the acdS gene encoding ACC deaminase cloned under the control of different promoters were constructed and tested for enhancement of plant growth promotion by biocontrol strains of P. fluorescens and S. plymuthica. The integrative cassettes constructed in this work are already being used as a simple and efficient tool to improve biocontrol activity of various PGPR bacteria against fungi containing chitin in the cell walls or highly sensitive to Prn. Some parts of the work (e. g., construction of integrative cassettes) was collaborative while other parts e.g., (enzyme and antibiotic activity analyses) were fully synergistic. The US partners isolated and provided to the Israeli collaborators the original biocontrol strains P. fluorescens strains Q8r1-96 and Q2-87 and their mutants deficient in 2,4-DAPG production, which were used to evaluate the relative importance of introduction of Prn, chitinase or ACC deaminase genes for improvement of the biocontrol activity of the parental strains. The recombinant strains obtained at HUJI were supplied to the US collaborators for further analysis.
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Harman, Gary E., and Ilan Chet. Discovery and Use of Genes and Gene Combinations Coding for Proteins Useful in Biological Control. United States Department of Agriculture, 1994. http://dx.doi.org/10.32747/1994.7568787.bard.

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The objectives of the research in this proposal were to (A) identify synergy among proteins that provide enhanced activity over single proteins for control of plant pathogenic fungi, (B) clone and characterize genetic sequences coding for proteins with ability to control pathogenic fungi, (C) produce transgenic organisms with enhanced biocontrol ability using genes and gene combinations and determine their efficiency in protecting plants against plant pathogenic fungi. A related objective was to produce disease-resistant plants. Fungal cell wall degrading enzymes from any source are strongly synergistic with any membrane active compound and, further, different classes of cell wall degrading enzymes are also strongly synergistic. We have cloned and sequenced a number of genes from bacterial and fungal sources including five that are structurally unrelated. We have prepared transgenic fungi that are deficient in production of enzymes and useful in mechanistic studies. Others are hyperproducers of specific enzymes that permit us, for the first time, to produce enzymes from T. harzianum in sufficient quantity to conduct tests of their potential use in commercial agriculture. Finally, genes from these studies have been inserted into several species of crop plants were they produce a high level of resistance to several plant pathogenic fungi.
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Dickman, Martin B., and Oded Yarden. Characterization of the chorismate mutase effector (SsCm1) from Sclerotinia sclerotiorum. United States Department of Agriculture, 2015. http://dx.doi.org/10.32747/2015.7600027.bard.

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Sclerotinia sclerotiorum is a filamentous fungus (mold) that causes plant disease. It has an extremely wide range of hosts (&gt;400 species) and causes considerable damage (annual multimillion dollar losses) in economically important crops. It has proven difficult to control (culturally or chemically) and host resistance to this fungus has generally been inadequate. It is believed that this fungus occurs in almost every country. Virulence of this aggressive pathogen is bolstered by a wide array of plant cell wall degrading enzymes and various compounds (secondary metabolites) produced by the fungus. It is well established that plant pathogenic fungi secrete proteins and small molecules that interact with host cells and play a critical role in disease development. Such secreted proteins have been collectively designated as “effectors”. Plant resistance against some pathogens can be mediated by recognition of such effectors. Alternatively, effectors can interfere with plant defense. Some such effectors are recognized by the host plant and can culminate in a programmed cell death (PCD) resistant response. During the course of this study, we analyzed an effector in Sclerotiniasclerotiorum. This specific effector, SsCM1 is the protein chorismatemutase, which is an enzyme involved in a pathway which is important in the production of important amino acids, such a Tryptophan. We have characterized the Sclerotiniaeffector, SsCM1, and have shown that inactivation of Sscm1 does not affect fungal vegetative growth, development or production of oxalic acid (one of this fungus’ secondary metabolites associated with disease) production. However, yhis does result in reduced fungal virulence. We show that, unexpectedly, the SsCM1 protein translocates to the host chloroplast, and demonstrated that this process is required for full fungal virulence. We have also determined that the fungal SsCM1 protein can interact with similar proteins produced by the host. In addition, we have shown that the fungal SsCM1 is able to suppress at least some of the effects imposed by reactive oxygen species which are produced as a defense mechanism by the host. Last, but not least, the results of our studies have provided evidence contradicting the current dogma on at least some of the mechanist aspects of how this pathogen infects the host. Contrary to previousons, indicating that this pathogen kills its host by use of metabolites and enzymes that degrade the host tissue (a process called necrotrophy), we now know that at least in the early phases of infection, the fungus interacts with live host tissue (a phenomenon known as biotrophy). Taken together, the results of our studies provide novel insights concerning the mechanistic aspects of Sclerotinia-host interactions. We hope this information will be used to interfere with the disease cycle in a manner that will protect plants from this devastating fungus.
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Chalutz, Edo, Michael Wisniewski, Samir Droby, Yael Eilam, and Ilan Chet. Mode of Action of Yeast Biocontrol Agents of Postharvest Diseases of Fruits. United States Department of Agriculture, 1996. http://dx.doi.org/10.32747/1996.7613025.bard.

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In a previous BARD-supported study, three of the investigators of this research were involved in a study on biological control of postharvest diseases of citrus and deciduous fruits. Several naturally occurring, non-antibiotic producing yeast antagonists were identified. Application of some of these antagonists resulted in very high levels of biocontrol under laboratory conditions but lower efficacy in semi-commercial tests. It was felt that the lack of knowledge on the mode of action of the biocontrol agents was limiting their efficient use. The current study was aimed at narrowing this gap in our knowledge. Two specific objectives were outlined: to study the mechanism by which calcium salts enhance biocontrol activity and to determine the role, if any, of the yeast extracellular materials and/or enzymes which degrade fungal cell walls during the interaction between the antagonists, the pathogen and the host. CaCl2 but not MgCl2, inhibited spore germination, and germ-tube elongation of Botrytis cinerea, Penicillium expansum and P. digitatum in culture. It also inhibited the pectinolytic activity of the pathogens. Biocontrol of apple decay by isolate 182 of Candida oleophila, an effective biocontrol agent, was enhanced by the addition of CaCl2 whereas there was no effect on the biocontrol activity of isolate 247 of this yeast. Similarly, CaCl2 enhanced efficacy of the US-7 isolate of Pichia guilliermondii in reducing infection of P. digitatum in citrus fruit. CaCl2 by itself also reduced the infection of peel wounds and stimulated ethylene production by grapefruit peel. This antagonist exhibited a very high ability to maintain cytosolic Ca2+ homeostasis when exposed to high CaCl2 concentrations. It is postulated, therefore, that enhanced biocontrol activity by calcium is the result of direct inhibition of the pathogen by calcium ions on spore germination and metabolism and indirectly due to the ability of the biocontrol agent to maintain normal metabolism in the presence of high levels of calcium. The extracellular materials produced by P. guilliermondii in culture and on the fruit inhibited, at low concentrations, the pathogen in culture and reduced percent infection of the fruit. The direct inhibition of the pathogen by these materials may thus be involved in the mode of action of the antagonist. This study contributed to our knowledge on the action of calcium salts and the yeast antagonist extracellular materials on biocontrol activity and will contribute to a more efficient use of this technology in the control of postharvest diseases of fruits.
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Prusky, Dov, Noel T. Keen, and Stanley Freeman. Elicitation of Preformed Antifungal Compounds by Non-Pathogenic Fungus Mutants and their Use for the Prevention of Postharvest Decay in Avocado Fruits. United States Department of Agriculture, 1996. http://dx.doi.org/10.32747/1996.7570573.bard.

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C. gloeosporioides attacks unripe avocado fruits in the orchard. Germinated spores produce appressoria that germinate and breach the cuticle, but the resultant subcuticular hyphae become quiescent and do not develop further until fruit is harvested and ripens. Resistance of unripe avocado to attach by C. gloeosporioides is correlated with the presence of fungitoxic concentrations of the preformed antifungal compound, 1-acetoxy-2-hydroxy-4-oxoheneicosa-12, 15 diene in the pericarp of unripe fruits. The objective of this proposal was to study the signal transduction process by which elicitors induce resistance in avocado. It was found that abiotic elicitors, infection of avocado fruit with C. gloeosporioides or treatment of avocado cell suspension with cell-wall elicitor induced a significant production of reactive oxygen species (ROS). Ripe and unripe fruit tissue differ with regard to the ROS production. The unripe, resistant fruit are physiologically able to react and to produce high levels of ROS and increased activity of H+ATPase that can enhance the phenylpropanoid pathway ad regulate the levels of the antifungal compound-diene, inhibit fungal development, resulting in its quiescence. Interestingly, it was also found that growth regulators like cytokinin could do activation of the mechanism of resistance. Postharvest treatments of cytokinins strongly activated the phenylpropanoid pathway and induce resistance. We have developed non-pathogenic strains of C. gloeosporioides by Random Enzyme Mediated Integration and selected a hygromycin resistance, non-pathogenic strain Cg-142 out of 3500 transformants. This non-pathogenic isolate activates H+ATPase and induces resistance against Colletotrichum attack. As a basis for studying the importance of PL in pathogenicity, we have carried out heterologous expression of pel from C. gloeosporioides in the non-pathogenic C. magna and determine the significant increase in pathogenicity of the non-pathogenic strain. Based on these results we can state that pectate lyase is an important pathogenicity factor of C. gloeosporioides and found that fungal pathogenicity is affected not by pel but by PL secretion. Our results suggest that PH regulates the secretion of pectate lyase, and support its importance as a pathogenicity factor during the attack of avocado fruit by C. gloeosporioides . This implicates that if these findings are of universal importance in fungi, control of disease development could be done by regulation of secretion of pathogenicity factors.
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Droby, Samir, Michael Wisniewski, Martin Goldway, Wojciech Janisiewicz, and Charles Wilson. Enhancement of Postharvest Biocontrol Activity of the Yeast Candida oleophila by Overexpression of Lytic Enzymes. United States Department of Agriculture, 2003. http://dx.doi.org/10.32747/2003.7586481.bard.

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Enhancing the activity of biocontrol agents could be the most important factor in their success in controlling fruit disease and their ultimate acceptance in commercial disease management. Direct manipulation of a biocontrol agent resulting in enhancement of diseases control could be achieved by using recent advances in molecular biology techniques. The objectives of this project were to isolate genes from yeast species that were used as postharvest biocontrol agents against postharvest diseases and to determine their role in biocontrol efficacy. The emphasis was to be placed on the yeast, Candida oleophila, which was jointly discovered and developed in our laboratories, and commercialized as the product, Aspire. The general plan was to develop a transformation system for C . oleophila and either knockout or overexpress particular genes of interest. Additionally, biochemical characterization of the lytic peptides was conducted in the wild-type and transgenic isolates. In addition to developing a better understanding of the mode of action of the yeast biocontrol agents, it was also our intent to demonstrate the feasibility of enhancing biocontrol activity via genetic enhancement of yeast with genes known to code for proteins with antimicrobial activity. Major achievements are: 1) Characterization of extracellular lytic enzymes produced by the yeast biocontrol agent Candida oleophila; 2) Development of a transformation system for Candida oleophila; 3) Cloning and analysis of C.oleophila glucanase gene; 4) Overexpression of and knockout of C. oleophila glucanase gene and evaluating its role in the biocontrol activity of C. oleophila; 5) Characterization of defensin gene and its expression in the yeast Pichiapastoris; 6) Cloning and Analysis of Chitinase and Adhesin Genes; 7) Characterization of the rnase secreted by C . oleophila and its inhibitory activity against P. digitatum. This project has resulted in information that enhanced our understanding of the mode of action of the yeast C . oleophila. This was important step towards enhancing the biocontrol activity of the yeast. Fungal cell wall enzymes produced by the yeast antagonist were characterized. Different substrates were identified to enhance there production in vitro. Exo-b-1, 3 glucanase, chitinase and protease production was stimulated by the presence of cell-wall fragments of Penicillium digitatum in the growing medium, in addition to glucose. A transformation system developed was used to study the role of lytic enzymes in the biocontrol activity of the yeast antagonist and was essential for genetic manipulation of C . oleqphila. After cloning and characterization of the exo-glucanase gene from the yeast, the transformation system was efficiently used to study the role of the enzyme in the biocontrol activity by over-expressing or knocking out the activity of the enzyme. At the last phase of the research (still ongoing) the transformation system is being used to study the role of chitinase gene in the mode of action. Knockout and over expression experiments are underway.
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