JOURNAL OF PHYCOLOGY, Issue 1 2003
Maki Yamamoto
The cell division mechanisms of seven strains from six species of Nannochloris Naumann were analyzed and compared with those of three species of Chlorella Beijerinck and Trebouxia erici Ahmadjian using differential interference microscopy and fluorescence microscopy. Nannochloris bacillaris Naumann divides by binary fission and N. coccoides Naumann divides by budding. Distinct triangular spaces or mother cell walls were found in the dividing autosporangia of the other five strains from four species of Nannochloris, three species of Chlorella, and T. erici. In an attempt to infer an evolutionary relationship between nonautosporic and autosporic species of Nannochloris, we constructed a phylogenetic tree of the actin genes using seven strains from six species of Nannochloris, three species of Chlorella, and T. erici. Nannochloris species were polyphyletic in the Trebouxiophyceae group. Two nonautosporic species of N. bacillaris and N. coccoides were monophyletic and positioned distally. Moreover, to determine their phylogenetic position within the Trebouxiophyceae, we constructed phylogenetic tree of 18S rRNA genes adding other species of Trebouxiophyceae. Nannochloris species were polyphyletic in the Trebouxiophyceae and appeared in two different lineages, a Chlorella,Nannochloris group and a Trebouxia,Choricystis group. The nonautosporic species, N. bacillaris and N. coccoides, and three autosporic species of Nannochloris belonged to the Chlorella,Nannochloris group. Nannochloris bacillaris and N. coccoides were also monophyletic and positioned distally in the phylogenetic tree of 18S rRNA genes. These results suggest that autosporulation is the ancestral mode of cell division in Nannochloris and that nonautosporulative mechanisms, such as binary fission and budding, evolved secondarily. [source]

Synthesis of Oligoarabinofuranosides from the Mycobacterial Cell Wall.

CHEMINFORM, Issue 1 2004
Karine Marotte
No abstract is available for this article. [source]

Interrelation between Lignin Deposition and Polysaccharide Matrices during the Assembly of Plant Cell Walls

PLANT BIOLOGY, Issue 1 2002
K. Ruel
Abstract: The modifications caused by genetic down-regulation of the enzyme cinnamoyl CoA reductase (CCR) from monolignol biosynthetic pathways on tobacco and Arabidopsis thaliana were investigated at the ultrastructural level. A typical result was that the same transformation led to similar abnormality in secondary wall formation of fibres in both plants. The cell wall alterations mainly consisted in an important disorganization and loosening of cellulose microfibrils in the inner part of the S2 layer. This inability of the transformants to form a coherent cell wall coincided with a lack of synthesis of non-condensed forms of lignin in this disorganized region of the wall, as demonstrated by immunolabelling of lignin subunits. A similar disorganization was observed during fibre wall formation in the differentiating tissues of young Populus and A. thaliana plants. The transitory lack of organization of cellulose microfibrils, also coincided with a depletion in non-condensed forms of lignins. These results suggest that such lignin substructures may be involved in the cohesion of secondary walls during cell wall biogenesis. The mutual influence of the cellulose-hemicellulose environment and monolignol local polymerization is discussed. [source]

ISOLATION AND CHARACTERIZATION OF A CELL WALL-DEFECTIVE MUTANT OF CHLAMYDOMONAS MONOICA (CHLOROPHYTA),

JOURNAL OF PHYCOLOGY, Issue 6 2003
Cesar Fuentes
Cell wall,defective strains of Chlamydomonas have played an important role in the development of transformation protocols for introducing exogenous DNA (foreign genes or cloned Chlamydomonas genes) into C. reinhardtii. To promote the development of similar protocols for transformation of the distantly related homothallic species, C. monoica, we used UV mutagenesis to obtain a mutant strain with a defective cell wall. The mutant, cw-1, was first identified on the basis of irregular colony shape and was subsequently shown to have reduced plating efficiency and increased sensitivity to lysis by a non-ionic detergent as compared with wild-type cells. Tetrad analysis of crosses involving the cw-1 mutant confirmed 2:2 segregation of the cw:cw+ phenotypes, indicating that the wall defect resulted from mutation of a single nuclear gene. The phenotype showed incomplete penetrance and variable expressivity. Although some cells had apparently normal cell walls as viewed by TEM, many cells of the cw-1 strain had broken cell walls and others were protoplasts completely devoid of a cell wall. Several cw-1 isolates obtained from crosses involving the original mutant strain showed a marked enhancement of the mutant phenotype and may prove especially useful for future work involving somatic cell fusions or development of transformation protocols. [source]

Cell wall ,-1,3-glucan is required to anchor the Cryptococcus neoformans capsule

MOLECULAR MICROBIOLOGY, Issue 4 2003
Amy J. Reese
Summary Cryptococcus neoformans is an opportunistic pathogen responsible for serious disease in humans. Critical for virulence of this fungus is an elaborate polysaccharide capsule, which impedes the host immune response. We found that association of the capsule with the cell requires a specific component of the cell wall, ,-1,3-glucan. Post-transcriptional inhibition of ,-1,3-glucan synthase expression, using double-stranded RNA interference, yields cells that are unable to assemble a capsule although they generate its polysaccharide components. The resulting cryptococci are slow-growing and acapsular. This finding demonstrates a novel mode of polysaccharide attachment and an important application of RNA interference in fungi. The elimination of the capsule by reducing the expression of a single gene suggests a potential avenue for antifungal chemotherapy. [source]

Plant cell wall biosynthesis: genetic, biochemical and functional genomics approaches to the identification of key genes

PLANT BIOTECHNOLOGY JOURNAL, Issue 2 2006
Naser Farrokhi
Summary Cell walls are dynamic structures that represent key determinants of overall plant form, plant growth and development, and the responses of plants to environmental and pathogen-induced stresses. Walls play centrally important roles in the quality and processing of plant-based foods for both human and animal consumption, and in the production of fibres during pulp and paper manufacture. In the future, wall material that constitutes the major proportion of cereal straws and other crop residues will find increasing application as a source of renewable fuel and composite manufacture. Although the chemical structures of most wall constituents have been defined in detail, the enzymes involved in their synthesis and remodelling remain largely undefined, particularly those involved in polysaccharide biosynthesis. There have been real recent advances in our understanding of cellulose biosynthesis in plants, but, with few exceptions, the identities and modes of action of polysaccharide synthases and other glycosyltransferases that mediate the biosynthesis of the major non-cellulosic wall polysaccharides are not known. Nevertheless, emerging functional genomics and molecular genetics technologies are now allowing us to re-examine the central questions related to wall biosynthesis. The availability of the rice, Populus trichocarpa and Arabidopsis genome sequences, a variety of mutant populations, high-density genetic maps for cereals and other industrially important plants, high-throughput genome and transcript analysis systems, extensive publicly available genomics resources and an increasing armoury of analysis systems for the definition of candidate gene function will together allow us to take a systems approach to the description of wall biosynthesis in plants. [source]

Centrioles are freed from cilia by severing prior to mitosis,

CYTOSKELETON, Issue 7 2010
Jeremy D.K. Parker
Abstract Cilia are necessary for normal tissue development and homeostasis and are generally present during interphase, but not in mitosis. The precise mechanism of premitotic ciliary loss has been controversial, with data supporting either sequential disassembly through the transition zone or, alternatively, a severing event at the base of the cilia. Here we show by live cell imaging and immunofluoresence microscopy that resorbing flagella of Chlamydomonas leave remnants associated with the mother cell wall. We postulated that the remnants are the product of severing of doublet microtubules between the basal bodies and the flagellar transition zone, thereby freeing the centrioles to participate in spindle organization. We show via TEM that flagellar remnants are indeed flagellar transition zones encased in vesicles derived from the flagellar membrane. This transition zone vesicle can be lodged within the cell wall or it can be expelled into the environment. This process is observable in Chlamydomonas, first because the released flagellar remnants can remain associated with the cell by virtue of attachments to the cell wall, and second because the Chlamydomonas transition zone is particularly rich with electron-dense structure. However, release of basal bodies for spindle-associated function is likely to be conserved among the eukaryotes. © 2010 Wiley-Liss, Inc. [source]

Analyzing and monitoring of phage,bacteria interaction using CE

ELECTROPHORESIS, Issue 20 2009
Esra Acar Soykut
Abstract The utilization of CE for monitoring bacteria,phage interaction was investigated in this study. Streptococcus thermophilus and Lactobacillus bulgaricus strains and their phages were used as model bacteria and phages for the purpose of validation in this study. CE with heterogeneous polymer polyethylene oxide was utilized for the separation of intact bacteria and investigation of phage,bacteria interaction. An intact phage detection was carried out with CZE by adding SDS in the running buffer. Calibration graphs of bacteria and phages were obtained with R2 values of 0.963 and 0.937, respectively. S. thermophilus strain was infected with its virulent phage B3-X18 for investigation of phage,bacteria interaction. It was observed in capillary electropherogram that the culture was lysed depending on the multiplicity of infection value and it showed to be completely lysed when the multiplicity of infection value was 10. The interaction of S. thermophilus strain with L. bulgaricus phage was also investigated by using a CE and a microbiological method and it was observed that the L. bulgaricus phage attached itself to the cell wall of S. thermophilus strain without damaging the cell. [source]

Improved 2-DE of microorganisms after acidic extraction

ELECTROPHORESIS, Issue 8 2006
Ben R. Herbert Professor
Abstract 2-DE separations of protein extracts sometimes have problems with poor resolution and streaking. This problem is particularly apparent with microorganisms, most notably those with a large cell wall. Here we describe a novel, rapid protocol for the extraction of microorganisms in acidic conditions, leading to increased resolution and 2-D gel quality. The efficiency of the protocol is demonstrated with extracts of bacteria, Escherichia coli and Bacillus subtilis; fungus, Trichoderma harzianum and yeast, Saccharomyces cerevisiae. We also demonstrate using a membrane centrifugal filtration, that large acidic molecules in excess of 100,kDa, probably including cell wall material, are responsible for the separation difficulties. A range of acidic extraction conditions were investigated, and it was found that optimal extraction is achieved using an extraction solution acidified to pH,3 by 80,mM citric acid. These findings have significant implications for the proteomic study of many medically, agriculturally and environmentally significant microorganisms, as the cell walls of these organisms are often considerably more complex than many commonly studied laboratory strains. [source]

Critical aspects of analysis of Micrococcus luteus, Neisseria cinerea, and Pseudomonas fluorescens by means of capillary electrophoresis

ELECTROPHORESIS, Issue 18-19 2004
Verena Hoerr
Abstract Within the frame of our study we investigated Microccocus luteus, Neisseria cinerea, and Pseudomonas fluorescens by means of capillary zone electrophoresis (CZE). They form chains and clusters on a different scale, which can be reflected in the electropherograms. A low buffer concentration of Tris-borate and Na2 EDTA containing a polymeric matrix of 0.0125% poly(ethylene) oxide (PEO) was used. Key factors were the standardization and optimization of CE conditions, buffer solution, and pretreatment of bacterial samples, which are not transferable to different bacterial strains, in general. The different compositions of the cell wall of on the one hand Gram-positive (M. luteus) and Gram-negative (N. cinerea) cocci and on the other hand Gram-negative, rod-shaped bacteria (P.fluorescens), are probably responsible for the different pretreatment conditions. [source]

Indigestibility of plant cell wall by the Australian plague locust, Chortoicetes terminifera

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2004
F.J. Clissold
Abstract The plant cell wall may play an important role in defence against herbivores since it can be both a barrier to, and nutrient diluter of, the easily digested cell contents. The aim of this study was to investigate the digestibility of the cell wall of three grasses, Triticum aestivum L., Dactyloctenium radulans (R. Br.) Beauv., and Astrebla lappacea (Lindl.) Domin, by the Australian plague locust, Chortoicetes terminifera Walker (Orthoptera: Acrididae, Acridinae) as determined by the Van Soest method [Van Soest PJ, Robertson JB & Lewis BA (1991) Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74: 3583,3597]. Determination of plant cell wall digestion by locusts required a precise methodological procedure to determine both the exact intake and the concentration of cell wall in the diet and the faeces. Plant cell wall determination is affected by the particle size distribution of the dried plant material. All three grasses differed in the percentage of cell wall per gram dry matter and the proportions of hemicellulose, cellulose, and acid-detergent sulphuric lignin within the cell wall. The locust was unable to digest the cell wall of any of the grasses. Thus, plant cell walls are a mechanical barrier hindering locusts assimilating nutrients. That is, access, rather than nutrient concentration per se, may be limiting nutrient factor. [source]

Descriptions and biological notes of Ctenoplectra bees from Southeast Asia and Taiwan (Hymenoptera: Apidae: Ctenoplectrini) with a new species from North Borneo

ENTOMOLOGICAL SCIENCE, Issue 3 2009
I-Hsin SUNG
Abstract Six Ctenoplectra species are recorded from Southeast Asia and Taiwan. They are C. chalybea Smith, C. cornuta Gribodo, C. davidi Vachal, C. elsei Engel, C. sandakana sp. nov. and C. vagans Cockerell. Females of C. sandakana sp. nov. from North Borneo are similar to the mainland species C. chalybea, but differ mainly in the clypeal keel and the length of the antennal segments. The small blackish species, C. cornuta, is distributed in Myanmar, China and Taiwan and C. davidi is distributed in China, Russia and Taiwan; both species are seen at the flowers of Thladiantha. Ctenoplectra chalybea was collected from the Malay Peninsula, Myanmar, Taiwan and Vietnam. Ctenoplectra apicalis Smith and C. kelloggi Cockerell are allied to C. chalybea; however, C. kelloggi is excluded from this study due to insufficient material. A key to the six known Ctenoplectra species is given. The large metallic species, C. chalybea and C. elsei, visit flowers of Momordica cochinchinensis (Lour.) Spreng. For the first time observations on the nest structures of C. chalybea and C. cornuta are presented. They choose remarkable places, such as artificial structures and buildings, for nest sites. The nest architecture prevents rain and direct sunlight from entering the nest. Bees used pre-existing holes or crevices in wood for nesting shelters and collected soil and appeared to mix it with some other substance to build nests. The cell lining materials and rubbing behaviors against the cell wall suggest that Ctenoplectra bees use floral oil mainly for cell lining materials. [source]

Cold adaptation in the marine bacterium, Sphingopyxis alaskensis, assessed using quantitative proteomics

ENVIRONMENTAL MICROBIOLOGY, Issue 10 2010
Lily Ting
Summary The cold marine environment constitutes a large proportion of the Earth's biosphere. Sphingopyxis alaskensis was isolated as a numerically abundant bacterium from several cold marine locations, and has been extensively studied as a model marine bacterium. Recently, a metabolic labelling platform was developed to comprehensively identify and quantify proteins from S. alaskensis. The approach incorporated data normalization and statistical validation for the purpose of generating highly confident quantitative proteomics data. Using this approach, we determined quantitative differences between cells grown at 10°C (low temperature) and 30°C (high temperature). Cold adaptation was linked to specific aspects of gene expression: a dedicated protein-folding system using GroESL, DnaK, DnaJ, GrpE, SecB, ClpB and PPIase; polyhydroxyalkanoate-associated storage materials; a link between enzymes in fatty acid metabolism and energy generation; de novo synthesis of polyunsaturated fatty acids in the membrane and cell wall; inorganic phosphate ion transport by a phosphate import PstB homologue; TonB-dependent receptor and bacterioferritin in iron homeostasis; histidine, tryptophan and proline amino acid metabolism; and a large number of proteins without annotated functions. This study provides a new level of understanding on how important marine bacteria can adapt to compete effectively in cold marine environments. This study is also a benchmark for comparative proteomic analyses with other important marine bacteria and other cold-adapted organisms. [source]

Bioreductive deposition of palladium (0) nanoparticles on Shewanella oneidensis with catalytic activity towards reductive dechlorination of polychlorinated biphenyls

ENVIRONMENTAL MICROBIOLOGY, Issue 3 2005
Wim De Windt
Summary Microbial reduction of soluble Pd(II) by cells of Shewanella oneidensis MR-1 and of an autoaggregating mutant (COAG) resulted in precipitation of palladium Pd(0) nanoparticles on the cell wall and inside the periplasmic space (bioPd). As a result of biosorption and subsequent bioreduction of Pd(II) with H2, formate, lactate, pyruvate or ethanol as electron donors, recoveries higher than 90% of Pd associated with biomass could be obtained. The bioPd(0) nanoparticles thus obtained had the ability to reductively dehalogenate polychlorinated biphenyl (PCB) congeners in aqueous and sediment matrices. Bioreduction was observed in assays with concentrations up to 1000 mg Pd(II) l,1 with depletion of soluble Pd(II) of 77.4% and higher. More than 90% decrease of PCB 21 (2,3,4-chloro biphenyl) coupled to formation of its dechlorination products PCB 5 (2,3-chloro biphenyl) and PCB 1 (2-chloro biphenyl) was obtained at a concentration of 1 mg l,1 within 5 h at 28°C. Bioreductive precipitation of bioPd by S. oneidensis cells mixed with sediment samples contaminated with a mixture of PCB congeners, resulted in dechlorination of both highly and lightly chlorinated PCB congeners adsorbed to the contaminated sediment matrix within 48 h at 28°C. Fifty milligrams per litre of bioPd resulted in a catalytic activity that was comparable to 500 mg l,1 commercial Pd(0) powder. The high reactivity of 50 mg l,1 bioPd in the soil suspension was reflected in the reduction of the sum of seven most toxic PCBs to 27% of their initial concentration. [source]

Requirement of phospholipase C-,2 (PLC,2) for Dectin-1-induced antigen presentation and induction of TH1/TH17 polarization

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2009
Ilaria Tassi
Abstract DC recognize microbial components through an array of receptors known as PRR. PRR initiate intracellular signals, which engender DC with the capacity to stimulate T-cell responses. Dectin-1 is a PRR that recognizes ,-glucan, a major constituent of many fungi's outer cell wall. Here we show that Dectin-1 activates DC through phospholipase (PLC),2 signaling. PLC,2-deficient DC were unable to expand antigen-specific T cells and induce TH1 and TH17 differentiation in response to ,-glucan. Mechanistically, PLC,2-deficiency impaired the capacity of DC to secrete polarizing cytokines following exposure to ,-glucan. Dectin-1 required PLC,2 to activate MAPK, AP-1 and NF-,B, which induce cytokine gene expression. Moreover, PLC,2 controlled Dectin-1-mediated NFAT activation and induction of NFAT-dependent genes such as IL-2, cyclooxigenase-2 and Egr transcription factors. We conclude that PLC,2 is a crucial signaling mediator that modifies DC gene expression program to activate DC responses to ,-glucan-containing pathogens. [source]

Nod1 and Nod2 induce CCL5/RANTES through the NF-,B pathway

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2007
Catherine Werts
Abstract The Nod-like receptor proteins Nod1 and Nod2 participate in innate immune responses against bacteria through intracellular detection of peptidoglycan, a component of bacterial cell wall. Recent evidence has demonstrated that Nod1 stimulates the release of chemokines that attract neutrophils at the site of infection, such as CXCL8/IL-8 in humans, and CXCL1/keratinocyte-derived chemokine and CXCL2/MIP-2 in mice. We aimed to determine whether Nod proteins could trigger the release of CCL5/RANTES, a chemokine known to attract a number of immune cells, but not neutrophils. Our results demonstrate that activation of both Nod1 and Nod2 results in substantial secretion of CCL5 by murine macrophages. Moreover, in vivo, the intraperitoneal injection of murine Nod1 or Nod2 agonists resulted in a rapid secretion of CCL5 into the bloodstream. We also observed that Nod-dependent secretion of CCL5 did not correlate with the induction of the interferon-, pathway, a major signaling cascade for the activation of CCL5 by viruses. In contrast, we identified a key role of the NF-,B pathway in Nod-dependent stimulation of the CCL5 promoter. Together, these results identify a novel target downstream of Nod1 and Nod2, which is likely to play a key role in orchestrating the global Nod-dependent immune defense during bacterial infections. [source]

Synthesis of a New Type of Glycosidic Linkage: Acetal-Linked Disaccharides and Trisaccharides of Acyclic and Cyclic Sugars,

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2005
Soni Kamlesh Madhusudan
Abstract New types of di- and trisaccharides related to a unique trisaccharide present in the cell walls of Proteus have been synthesized by coupling of acyclic sugar dithioacetals and di- and monohydroxy cyclic sugars. In this class of compounds an acyclic sugar is linked to a cyclic sugar through an acetal linkage. The formation of these acetal-linked pseudodi- and-trisaccharides has been achieved by a generalized reaction procedure mediated by 1,3-dibromo-5,5-dimethylhydantoin under mild, metal-free and neutral conditions. Sixteen protected and twelve deprotected di- and trisaccharides related to the trisaccharide found in the Proteus cell wall have been synthesized. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Copper is required for prion protein-associated superoxide dismutase-l activity in Pichia pastoris

FEBS JOURNAL, Issue 5 2007
Carina Treiber
The prion protein (PrP) is the key protein implicated in transmissible spongiform encephalopathies. It is a metalloprotein that binds manganese and copper. The latter is involved in the physiological function of the protein. We have previously found that PrP expression in Pichia pastoris affects intracellular metal ion concentrations and that formation of protease-resistant PrP is induced by additional copper and/or manganese. In this study, we show that heterologously expressed PrP is post-translationally modified and transported to the cell wall. We found by combining three different test systems that PrP itself had gained superoxide dismutase-like activity in P. pastoris. However, this activity could not be inhibited by KCN and depended on additional copper in the medium. Thus, this study defines the conditions under which PrP exhibits superoxide dismutase-like activity by showing that copper must be present for the protein to participate in scavenging and detoxification of reactive oxygen species. [source]

Inhibition of the D -alanine:D -alanyl carrier protein ligase from Bacillus subtilis increases the bacterium's susceptibility to antibiotics that target the cell wall

FEBS JOURNAL, Issue 12 2005
Juergen J. May
The surface charge as well as the electrochemical properties and ligand binding abilities of the Gram-positive cell wall is controlled by the d -alanylation of the lipoteichoic acid. The incorporation of d -Ala into lipoteichoic acid requires the d -alanine:d -alanyl carrier protein ligase (DltA) and the carrier protein (DltC). We have heterologously expressed, purified, and assayed the substrate selectivity of the recombinant proteins DltA with its substrate DltC. We found that apo-DltC is recognized by both endogenous 4,-phosphopantetheinyl transferases AcpS and Sfp. After the biochemical characterization of DltA and DltC, we designed an inhibitor (d -alanylacyl-sulfamoyl-adenosine), which is able to block the d -Ala adenylation by DltA at a Ki value of 232 nmin vitro. We also performed in vivo studies and determined a significant inhibition of growth for different Bacillus subtilis strains when the inhibitor is used in combination with vancomycin. [source]

Expression of MsPG3-GFP fusions in Medicago truncatula,hairy roots' reveals preferential tip localization of the protein in root hairs

FEBS JOURNAL, Issue 2 2003
Ignacio D. Rodríguez-Llorente
Tip growth is a specialized type of polar growth where new cell wall is deposited in a localized region of the cell, the growing tip. These cells show a characteristic zonation, with a high accumulation of secretory vesicles containing cell wall components at the tip, followed by an organelle-enriched zone. MsPG3 is a Medicago sativa polygalacturonase gene isolated in our laboratory, specifically expressed during the interaction of this plant with its symbiotic partner Sinorhizobium meliloti and which might participate in tip growth processes during symbiosis. We have used MsPG3-GFP fusions to study in vivo protein transport processes and localization during root hair growth. Different MsPG3-GFP fusions were expressed in Medicago truncatula,hairy roots' following a protocol developed for this study and also tested by transient expression in onion epidermal cells. Preferential accumulation of an MsPG3-GFP fusion protein in the tip of the growing root hair at different developmental stages was found, confirming the delivery of MsPG3 to the newly synthesized cell wall. This indicates that this protein may participate in tip growth processes during symbiosis and, in addition, that this fusion could be a useful tool to study this process in plants. [source]

Structural determination of the O-chain polysaccharide from Agrobacterium tumefaciens, strain DSM 30205

FEBS JOURNAL, Issue 12 2002
Cristina De Castro
Agrobacterium tumefaciens is a Gram-negative, phytopathogenic bacterium and is characterized by an unique mode of action on dicotyledonous plants: it is able to genetically modify the host, and because of this feature, it is used as a tool for transgenic plants. Many experiments have demonstrated that lipopolysaccharides (LPSs) play an important role for the disease development, as they are involved in the adhesion process of the bacterium on the plant cell wall. Despite the wealth of information on the role of LPS on phytopathogenesis, the present paper appears as the first report on the molecular primary structure of the O-chain produced from Agrobacterium. Its repeating unit was determined by means of chemical and spectroscopical analysis, and has the following structure: (3)-,- d -Araf -(1,3)-,- l -Fucp -(1,. [source]

Asparagus khorasanensis (Asparagaceae), a new species from Iran

FEDDES REPERTORIUM, Issue 7-8 2009
S. M. M. Hamdi
Asparagus khorasanensis is described as a new species from Khorasan province. This species belongs to the section Asparagus. The new species is compared with its closest relative Asparagus breslerianus Schult. (1830). This species is similar to Asparagus breslerianus Schult. (1830) in having unequal cladodes, height stems, scale leaves. Asparagus khorasanensis differs from A. breslerianus in having a higher cladod number (2,4 vs. 1,3), a higher cladod diameter (1.5,2 vs. 1,1.5 mm), longer internodes (5,15 vs. 15,20 mm), longer scale like leaves (2,2.5 vs. 0.5,0.7 mm), one flowers at base of branches vs. two flowers, longer anther (3,4 vs. 1.7,2 mm), bigger berries (7,8 vs. 5,5.5 mm), longer surface of periclinal cell wall (32,48 (,50) × 12,2,(,23) vs. 12,36 (,40) × 12,18(,20) µm), surface of periclinal cell wall is convex vs. surface of periclinal cell wall is concave and shape of surface cells of seed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Seed morphology of some species of Convolvulaceae from Egypt (Identification of species and systematic significance)

FEDDES REPERTORIUM, Issue 1-2 2007
K. Abdel Khalik
Seed morphology of 31 taxa belong to six genera of Convolvulaceae from Egypt were examined by using light and scanning electron microscopy. Macro- and micromorphological characters, including seed shape, colour, size, surface, epidermal cell shape, anticlinal boundaries, outer periclinal cell wall and relief of outer cell walls, are presented. Three types of basic anticlinal cell wall boundaries and three types of relief outer cell walls are recognized and four different shapes of the outer periclinal cell wall are described. A key for the identification of the investigated taxa based on seed characters is provided. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Morphologie der Samen einiger Arten der Convolvulaceae aus Ägypten (Bestimmung von Arten und systematische Bedeutung) Unter Anwendung von Licht- und Elektronenmikroskopie wurde die Morphologie der Samen von 31 Arten aus sechs Gattungen der Convolvulaceae untersucht. Berücksichtigt wurden die makro- und mikromorphologischen Merkmale der Samen umfassend äußere Form, Farbe, Größe, Oberfläche, Form der Epidermiszellen, antiklinale und periklinale Zellwände und Relief der äußeren Zellwände. Drei Typen basaler antiklinaler Zellwände und drei Typen des Reliefs der äußeren Zellwände wurden nachgewiesen; ferner werden vier Formen der äußeren periklinalen Zellwände beschrieben. Ein Schlüssel zur Bestimmung der untersuchten Taxa auf der Basis der Merkmale der Samen wird vorgelegt. [source]

Seed morphology of Cuscuta L. (Convolvulaceae) in Egypt and its systematic significance

FEDDES REPERTORIUM, Issue 3-4 2006
K. N. Abdel Khalik
The seed morphology of eight taxa of Cuscuta from Egypt has been studied using light and scanning electron microscopy, to determine the significance of seed coat features as taxonomic characters. Macro- and micromorphological characters, including seed shape, colour, size, epidermal cell shape, anticlinal boundaries, outer periclinal cell wall and relief of outer cell walls are presented. Three types of anticlinal cell wall boundaries are recognized and two different shapes of outer periclinal cell wall are described. The secondary sculpture of the cell wall varies from striate to micro-reticulate, and smooth to fine folds. A key for the identification of the investigated taxa based on seed characters is provided. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Samenmorphologie von Cuscuta L. (Convolvulaceae) in Ägypten und ihre systematische Bedeutung Die Morphologie des Samens von acht ägyptischen Cuscuta -Taxa wurde mittels Licht- und Elektronenmikroskopie untersucht, um die Bedeutung der Merkmale der Samenschale für die Taxonomie zu ermitteln. Makro- und mikromorphologische Merkmale einschließlich Samengestalt, Farbe, Größe, Form der Epidermiszellen, antiklinale Zellwände, äußere Periklinal-Zellwände und Relief der äußeren Zellwände umfassend, wurden untersucht. Drei Typen antiklinaler Zellwand-Umrisse und zwei unterschiedliche Formen der äußeren Periklinal-Zellwände werden beschrieben. Die sekundäre Skulptur der Zellwände variiert von striat bis mikro-reticulat, und von glatt zu leicht gefaltet. Ein Bestimmungsschlüssel basierend auf den Samenmerkmalen der untersuchten Sippen wird vorgelegt. [source]

High relative content of lysophospholipids of Helicobacter pylori mediates increased risk for ulcer disease

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2005
Tone Tannaes
Abstract Helicobacter pylori phospholipase A (OMPLA) degrades bacterial membrane phospholipids to lysophospholipids. High levels of lysophospholipids are associated with higher hemolytic activity, increased release of urease and vacA and better adherence to epithelial cells in vitro. The phospholipase A gene (pldA) displays phase variation due to a slippage in a homopolymeric tract. The aim of this study was to determine if the relative amount of lysophospholipids in the cell wall is associated with ulcer disease, and to further investigate the significance of pldA phase variation. H. pylori isolates of 40 patients were examined. The relative lysophospholipid content of each isolate was determined and the pldA gene was sequenced. The study indicated that H. pylori can regulate its OMPLA activity by phase variation in the pldA gene or by protein level regulation among phase variants in the pldA,ON' status. We found a significant difference between the relative amount of lysophospholipids of the ulcer group and the non-ulcer group (p= 0.022). When the lysophospholipid/phospholipid ratios were compared with outcome, the OR for ulcer disease was 9.0 (95% CI 1.6,49.4; p= 0.014). Isolates with a high OMPLA activity are significantly associated with patients with ulcer disease. [source]

Role of anti-,-glucan antibody in host defense against fungi

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2005
Ken-ichi Ishibashi
Abstract We have recently detected an anti-,-glucan antibody in normal human and normal mouse sera. The anti-,-glucan antibody showed reactivity to pathogenic fungal Aspergillus and Candida cell wall glucan. Anti-,-glucan antibody could bind whole Candida cells. It also enhanced the candidacidal activity of macrophages in vitro. The anti-,-glucan antibody titer of DBA/2 mice intravenously administered either Candida or Aspergillus solubilized cell wall ,-glucan decreased remarkably dependent on dose. Moreover, in deep mycosis patients, the anti-,-glucan antibody titer decreased, and this change correlated with clinical symptoms and other parameters such as C-reactive protein. It was suggested that the anti-,-glucan antibody formed an antigen,antibody complex and participated in the immune response as a molecule recognizing pathogenic fungi. [source]

Antibody response to Candida albicans cell wall antigens

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 3 2004
José L López-Ribot
Abstract The cell wall of Candida albicans is not only the structure where many essential biological functions reside but is also a significant source of candidal antigens. The major cell wall components that elicit a response from the host immune system are proteins and glycoproteins, the latter being predominantly mannoproteins. Both carbohydrate and protein moieties are able to trigger immune responses. Proteins and glycoproteins exposed at the most external layers of the wall structure are involved in several types of interactions of fungal cells with the exocellular environment. Thus, coating of fungal cells with host antibodies has the potential to profoundly influence the host,parasite interaction by affecting antibody-mediated functions such as opsonin-enhanced phagocytosis and blocking the binding activity of fungal adhesins to host ligands. In this review we examine various members of the protein and glycoprotein fraction of the C. albicans cell wall that elicit an antibody response in vivo. Some of the studies demonstrate that certain cell wall antigens and anti-cell wall antibodies may be the basis for developing specific and sensitive serologic tests for the diagnosis of candidiasis, particularly the disseminated form. In addition, recent studies have focused on the potential of antibodies against the cell wall protein determinants in protecting the host against infection. Hence, a better understanding of the humoral response triggered by the cell wall antigens of C. albicans may provide the basis for the development of (i) effective procedures for the serodiagnosis of disseminated candidiasis, and (ii) novel prophylactic (vaccination) and therapeutic strategies to control this type of infections. [source]

Cell-surface phytase on Pichia pastoris cell wall offers great potential as a feed supplement

FEMS MICROBIOLOGY LETTERS, Issue 1 2010
Piyanun Harnpicharnchai
Abstract Cell-surface expression of phytase allows the enzyme to be expressed and anchored on the cell surface of Pichia pastoris. This avoids tedious downstream processes such as purification and separation involved with extracellular expression. In addition, yeast cells with anchored proteins can be used as a whole-cell biocatalyst with high value added. In this work, the phytase was expressed on the cell surface of P. pastoris with a glycosylphosphatidylinositol anchoring system. The recombinant phytase was shown to be located at the cell surface. The cell-surface phytase exhibited high activity with an optimal temperature at 50,55 °C and two optimal pH peaks of 3 and 5.5. The surface-displayed phytase also exhibited similar pH stability and pepsin resistance to the native and secreted phytase. In vitro digestibility test showed that P. pastoris containing cell-surface phytase released phosphorus from feedstuff at a level similar to secreted phytase. Yeast cells expressing phytase also provide additional nutrients, especially biotin and niacin. Thus, P. pastoris with phytase displayed on its surface has a great potential as a whole-cell supplement to animal feed. [source]

The localization change of Ybr078w/Ecm33, a yeast GPI-associated protein, from the plasma membrane to the cell wall, affecting the cellular function

FEMS MICROBIOLOGY LETTERS, Issue 1 2003
Hiromichi Terashima
Abstract The YBR078W/ECM33 gene of Saccharomyces cerevisiae encodes a glycosylphosphatidylinositol (GPI)-attached protein and its disruptant strain exhibited a temperature-sensitive (ts) growth defect. A HA-tagged Ybr078w protein, which complemented the ts growth phenotype of the ybr078w, strain, was predominantly located on the plasma membrane by GPI anchoring. To examine the requirement of the GPI anchoring on the plasma membrane for the function, the ,-minus region of Ybr078w was replaced with those of Ydr534c/Fit1 and Ynl327w/Egt2, which are known as GPI-dependent cell wall proteins. The replacement induced the change in localization of the mutant proteins from the plasma membrane to the cell wall and the mutant proteins lost the function to complement the ts cell growth defect of the ybr078w, strain. In addition, a similar result was obtained in a mutant protein, where the authentic SKKSK sequence at the ,-5 to ,-1 site of Ybr078w was replaced with a synthetic ISSYS sequence. It is concluded that the GPI anchoring on the plasma membrane is required for the Ybr078w function. [source]

Peptidoglycan structure and architecture

FEMS MICROBIOLOGY REVIEWS, Issue 2 2008
Waldemar Vollmer
Abstract The peptidoglycan (murein) sacculus is a unique and essential structural element in the cell wall of most bacteria. Made of glycan strands cross-linked by short peptides, the sacculus forms a closed, bag-shaped structure surrounding the cytoplasmic membrane. There is a high diversity in the composition and sequence of the peptides in the peptidoglycan from different species. Furthermore, in several species examined, the fine structure of the peptidoglycan significantly varies with the growth conditions. Limited number of biophysical data on the thickness, elasticity and porosity of peptidoglycan are available. The different models for the architecture of peptidoglycan are discussed with respect to structural and physical parameters. [source]