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Cell Wall Structure (cell + wall_structure)
Selected AbstractsDynamics of cell wall structure in Saccharomyces cerevisiaeFEMS MICROBIOLOGY REVIEWS, Issue 3 2002Frans M Klis Abstract The cell wall of Saccharomyces cerevisiae is an elastic structure that provides osmotic and physical protection and determines the shape of the cell. The inner layer of the wall is largely responsible for the mechanical strength of the wall and also provides the attachment sites for the proteins that form the outer layer of the wall. Here we find among others the sexual agglutinins and the flocculins. The outer protein layer also limits the permeability of the cell wall, thus shielding the plasma membrane from attack by foreign enzymes and membrane-perturbing compounds. The main features of the molecular organization of the yeast cell wall are now known. Importantly, the molecular composition and organization of the cell wall may vary considerably. For example, the incorporation of many cell wall proteins is temporally and spatially controlled and depends strongly on environmental conditions. Similarly, the formation of specific cell wall protein,polysaccharide complexes is strongly affected by external conditions. This points to a tight regulation of cell wall construction. Indeed, all five mitogen-activated protein kinase pathways in bakers' yeast affect the cell wall, and additional cell wall-related signaling routes have been identified. Finally, some potential targets for new antifungal compounds related to cell wall construction are discussed. [source] Movement of yeast 1,3-,-glucan synthase is essential for uniform cell wall synthesisGENES TO CELLS, Issue 1 2002Takahiko Utsugi Background:, The cell wall has an important role in maintaining cell shape. In the budding yeast Saccharomyces cerevisiae, the major filamentous component of the cell wall responsible for its rigidity is 1,3-,-glucan and is synthesized by 1,3-,-glucan synthase (GS), localized on the plasma membrane. Results:, Observations of green fluorescent protein (GFP)-conjugated Fks1p, a catalytic subunit of GS, revealed that it is co-localized with cortical actin patches and moves on the cell surface at the sites of cell wall remodelling. Mutants with impaired actin patch movement show immobility of Fks1p-GFP spots, indicating that actin patch motility is required for the movement of Fks1p. Cells with immobilized Fks1p exhibit defective cell wall structure and function. The cell wall thickness of the mutants becomes irregular, eventually leading to cell lysis. Conclusion:, We propose that GS movement is necessary for proper cell wall remodelling. [source] Dormant ascospores of Talaromyces macrosporus are activated to germinate after treatment with ultra high pressureJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2004J. Dijksterhuis Abstract Aims:, Ascospores of Talaromyces macrosporus are constitutively dormant and germinate after a strong external shock, classically a heat treatment. This fungus is used as a model system to study heat resistance leading to food spoilage after pasteurization. This study evaluates the effect of high pressure on the germination behaviour of these spores. Methods and Results:, Ascospore containing bags were subjected to ultra high pressure and spores were plated out on agar surfaces. Untreated suspensions showed invariably very low germination. Increased germination of ascospores occurred after short treatments at very high pressure (between 400 and 800 MPa). Activation is partial compared with heat activation and did not exceed 6·9% (65 times that of untreated suspensions) of the spore population. Maximum activation was attained shortly (10 s,3 min) after the pressure was applied and accompanied by cell wall deformations as judged by scanning electron microscopy. The spores observed in this study were harvested from cultures that were 39,58 days old. The maturity of spores at similar developmental stages was measured by assessing the heat resistance of ascospores. Between 20 and 40 days heat resistance increased 2·4-fold, but only an additional increase of 1·3-fold was observed at later stages (40,67 days). Conclusions:, Our investigations show that high pressure constitutes a second type of shock that can activate heat-resistant ascospores to germinate. Activation is maximal after very short treatments and accompanied with changes in the cell wall structure. High-pressure activation is not the result of immaturity of the ascospores. Significance and Impact of the Study: These observations are relevant for the application of high pressure as a novel pasteurization method. [source] Kin1 is a plasma membrane-associated kinase that regulates the cell surface in fission yeastMOLECULAR MICROBIOLOGY, Issue 5 2010Angela Cadou Summary Cell morphogenesis is a complex process that depends on cytoskeleton and membrane organization, intracellular signalling and vesicular trafficking. The rod shape of the fission yeast Schizosaccharomyces pombe and the availability of powerful genetic tools make this species an excellent model to study cell morphology. Here we have investigated the function of the conserved Kin1 kinase. Kin1-GFP associates dynamically with the plasma membrane at sites of active cell surface remodelling and is present in the membrane fraction. Kin1, null cells show severe defects in cell wall structure and are unable to maintain a rod shape. To explore Kin1 primary function, we constructed an ATP analogue-sensitive allele kin1-as1. Kin1 inhibition primarily promotes delocalization of plasma membrane-associated markers of actively growing cell surface regions. Kin1 itself is depolarized and its mobility is strongly reduced. Subsequently, amorphous cell wall material accumulates at the cell surface, a phenotype that is dependent on vesicular trafficking, and the cell wall integrity mitogen-activated protein kinase pathway is activated. Deletion of cell wall integrity mitogen-activated protein kinase components reduces kin1, hypersensitivity to stresses such as those induced by Calcofluor white and SDS. We propose that Kin1 is required for a tight link between the plasma membrane and the cell wall. [source] CPMK2, an SLT2-homologous mitogen-activated protein (MAP) kinase, is essential for pathogenesis of Claviceps purpurea on rye: evidence for a second conserved pathogenesis-related MAP kinase cascade in phytopathogenic fungiMOLECULAR MICROBIOLOGY, Issue 2 2002Géraldine Mey Summary Cpmk2 , encoding a mitogen-activated protein (MAP) kinase from the ascomycete Claviceps purpurea , is an orthologue of SLT2 from Saccharomyces cerevisiae , the first isolated from a biotrophic, non-appressorium-forming pathogen. Deletion mutants obtained by a gene replacement approach show impaired vegetative properties (no conidiation) and a significantly reduced virulence, although they retain a limited ability to colonize the host tissue. Increased sensitivity to protoplasting enzymes indicates that the cell wall structure of the mutants may be altered. As the phenotypes of these mutants are similar to those observed in strains of the rice pathogen, Magnaporthe grisea , that have been deprived of their MAP kinase gene mps1 , the ability of cpmk2 to complement the defects of , mps1 was investigated. Interestingly, the C. purpurea gene, under the control of its own promoter, was able to complement the M. grisea mutant phenotype: transformants were able to sporulate and form infection hyphae on onion epidermis and were fully pathogenic on barley leaves. This indicates that, despite the differences in infection strategies, which include host and organ specificity, mode of penetration and colonization of host tissue, CPMK2 / MPS1 defines a second MAP kinase cascade (after the Fus3p/PMK1 cascade) essential for fungal pathogenicity. [source] Persistence of the gelatinous layer within altered tension-wood fibres of beech degraded by Ustulina deustaNEW PHYTOLOGIST, Issue 2 2000S. BAUM The gelatinous layer (G-layer) of tension-wood fibres in reaction wood of beech showed alterations as a result of the physiological processes involved in the conversion of sapwood into false heartwood or reaction-zone tissue. Using transmitted-light, fluorescence and UV microscopy, polyphenolic compounds were found to infiltrate and encrust the cellulose microfibrils within the G-layer. Experiments with naturally infected and artificially inoculated wood showed that these processes affect the rate and mode of degradation by wood-decaying fungi. Thus, although the ascomycete Ustulina deusta was able to degrade the G-layer from within the lumina of tension-wood fibres in unaltered sapwood, it failed to do so for a prolonged period within false heartwood and reaction zones. In both situations, however, there was some degradation of the underlying secondary wall in the form of erosion troughs which can be attributed to soft rot ,type II', and internal cavity formation typical for ,type I' attack. The present study indicates that not only cell type, but also alterations in the cell wall structure, affect the activity and degradation mode of decay fungi in beech. [source] Relationship between boron and calcium in the N2 -fixing legume,rhizobia symbiosisPLANT CELL & ENVIRONMENT, Issue 11 2003M. REDONDO-NIETO ABSTRACT Because boron (B) and calcium (Ca2+) seem to have a strong effect on legume nodulation and nitrogen fixation, rhizobial symbiosis with leguminous plants, grown under varying concentrations of both nutrients, was investigated. The study of early pre-infection events included the capacity of root exudates to induce nod genes, and the degree of adsorption of bacteria to the root surface. Both phenomena were inhibited by B deficiency, and increased by addition of Ca2+, resulting in an increase of the number of nodules. The infection and invasion steps were investigated by fluorescence microscopy in pea nodules harbouring a Rhizobium leguminosarum strain that constitutively expresses green fluorescent protein. High Ca2+ enhanced cell and tissue invasion by Rhizobium, which was highly inhibited after B deficiency. This was combined with an increased B concentration in nodules of plants grown on B-free medium and supplemented with high Ca2+ concentrations, and that can be attributed to an increased B import to the nodules. Histological examination of indeterminate (pea) and determinate (bean) nodules showed an altered nodule anatomy at low B content of the tissue. The moderate increase in nodular B due to additional Ca2+ was not sufficient to prevent the abnormal cell wall structure and the aberrant distribution of pectin polysaccharides in B-deficient treatments. Overall results indicate that the development of the symbiosis depends of the concentration of B and Ca2+, and that both nutrients are essential for nodule structure and function. [source] Physical and computational analysis of the yeast Kluyveromyces lactis secreted proteomePROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 13 2008Catherine L. Swaim Abstract Secretion of proteins is the most common approach to protein expression in Kluyveromyces lactis. A proteomic analysis was performed on spent fermentation medium following bioreactor propagation of a wild-type industrial strain to identify proteins naturally secreted by K. lactis cells. Multidimensional separations were conducted and RP online ESI-MS/MS analysis identified 81 secreted proteins. In addition, an in silico analysis predicted 178 K. lactis proteins to be secreted via the general secretory pathway (GSP). These two datasets were compared and approximately 70% of the K. lactis proteins detected in the culture medium possessed a GSP sequence. The detected proteins included those involved with cell wall structure and synthesis, carbohydrate metabolism, and proteolysis, a result that may have significant bearing on heterologous protein expression. Additionally, both the experimental and in silico datasets were compared to similar, previously published datasets for Candida albicans. With the methodology presented here, we provide the deepest penetration into a yeast secretome yet reported. [source] Characterization of a new xyloglucan endotransglucosylase/hydrolase (XTH) from ripening tomato fruit and implications for the diverse modes of enzymic actionTHE PLANT JOURNAL, Issue 2 2006Montserrat Saladié Summary Xyloglucan endotransglucosylase/hydrolases (XTHs) are cell wall-modifying enzymes that align within three or four distinct phylogenetic subgroups. One explanation for this grouping is association with different enzymic modes of action, as XTHs can have xyloglucan endotransglucosylase (XET) or endohydrolase (XEH) activities. While Group 1 and 2 XTHs predominantly exhibit XET activity, to date the activity of only one member of Group 3 has been reported: nasturtium TmXH1, which has a highly specialized function and hydrolyses seed-storage xyloglucan rather than modifying cell wall structure. Tomato fruit ripening was selected as a model to test the hypothesis that preferential XEH activity might be a defining characteristic of Group 3 XTHs, which would be expressed during processes where net xyloglucan depolymerization occurs. Database searches identified 25 tomato XTHs, and one gene (SlXTH5) was of particular interest as it aligned within Group 3 and was expressed abundantly during ripening. Recombinant SlXTH5 protein acted primarily as a transglucosylase in vitro and depolymerized xyloglucan more rapidly in the presence than in the absence of xyloglucan oligosaccharides (XGOs), indicative of XET activity. Thus, there is no correlation between the XTH phylogenetic grouping and the preferential enzymic activities (XET or XEH) of the proteins in those groups. Similar analyses of SlXTH2, a Group 2 tomato XTH, and nasturtium seed TmXTH1 revealed a spectrum of modes of action, suggesting that all XTHs have the capacity to function in both modes. The biomechanical properties of plant walls were unaffected by incubation with SlXTH5, with or without XGOs, suggesting that XTHs do not represent primary cell wall-loosening agents. The possible roles of SlXTH5 in vivo are discussed. [source] THE SYSTEMATICS OF A SMALL SPINELESS DESMODESMUS SPECIES, D. COSTATO-GRANULATUS (SPHAEROPLEALES, CHLOROPHYCEAE), BASED ON ITS2 rDNA SEQUENCE ANALYSES AND CELL WALL MORPHOLOGY,JOURNAL OF PHYCOLOGY, Issue 2 2007Pieter Vanormelingen Desmodesmus species taxonomy is one of the most long-standing issues in green microalgal systematics due to problems associated with phenotypic plasticity. Whereas more recent species descriptions and identifications are mainly based on cell wall structures and the use of cultures, comparisons with molecular phylogenies are largely lacking. In this study, the phylogenetic relationships between 22 clones identified as Desmodesmus costato-granulatus (Skuja) E. H. Hegew. were assessed using ITS2 rDNA sequence data in combination with cell wall morphology. The unrooted ITS2 phylogeny showed that the clones cluster into five groups, which also differ in their cell wall structures. Therefore, the taxon is split into five species: D. costato-granulatus, D. elegans, D. fennicus, D. regularis, and D. ultrasquamatus. Compared with other Desmodesmus species, intraspecific sequence variation is extensive and may contain additional (pseudo)cryptic diversity. Compensatory base changes were near-absent within the species and varied from one to 11 between species. Relationships among the species were unresolved. Despite this, they clustered together with the two other Desmodesmus species having a combination of small and large warts in a well-supported lineage. Remarkably, ITS2 sequence variation in this lineage is as high as between all other included Desmodesmus species, even though the morphology of its members is rather uniform. [source] Characterization of nonderivatized plant cell walls using high-resolution solution-state NMR spectroscopy,MAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2008Daniel J. Yelle Abstract A recently described plant cell wall dissolution system has been modified to use perdeuterated solvents to allow direct in-NMR-tube dissolution and high-resolution solution-state NMR of the whole cell wall without derivatization. Finely ground cell wall material dissolves in a solvent system containing dimethylsulfoxide- d6 and 1-methylimidazole- d6 in a ratio of 4:1 (v/v), keeping wood component structures mainly intact in their near-native state. Two-dimensional NMR experiments, using gradient-HSQC (heteronuclear single quantum coherence) 1-bond 13C1H correlation spectroscopy, on nonderivatized cell wall material from a representative gymnosperm pinus taeda (loblolly pine), an angiosperm Populus tremuloides (quaking aspen), and a herbaceous plant Hibiscus cannabinus (kenaf) demonstrate the efficacy of the system. We describe a method to synthesize 1-methylimidazole- d6 with a high degree of perdeuteration, thus allowing cell wall dissolution and NMR characterization of nonderivatized plant cell wall structures. Copyright © 2008 John Wiley & Sons, Ltd. [source] Electron microscopic examination of uncultured soil-dwelling bacteriaMICROBIOLOGY AND IMMUNOLOGY, Issue 5 2008Kazunobu Amako ABSTRACT Bacteria living in soil collected from a rice paddy in Fukuoka, Japan, were examined by electron microscopy using a freeze-substitution fixation method. Most of the observed bacteria could be categorized, based on the structure of the cell envelope and overall morphology, into one of five groups: (i) bacterial spore; (ii) Gram-positive type; (iii) Gram-negative type; (iv) Mycobacterium like; and (v) Archaea like. However, a few of the bacteria could not be readily categorized into one of these groups because they had unique cell wall structures, basically resembling those of Gram-negative bacteria, but with the layer corresponding to the peptidoglycan layer in Gram-negative bacteria being extremely thick, like that of the cortex of a bacterial spore. The characteristic morphological features found in many of these uncultured, soil-dwelling cells were the nucleoid being in a condensed state and the cytoplasm being shrunken. We were able to produce similar morphologies in vitro using a Salmonella sp. by culturing under low-temperature, low-nutrient conditions, similar to those found in some natural environments. These unusual morphologies are therefore hypothesized to be characteristic of bacteria in resting or dormant stages. [source] | |||||||||||||||||||||||||