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At least 703 records · Page 39Linked to original sources
PubMed1997

Developmental regulation of cell interactions in the Arabidopsis fiddlehead-1 mutant: a role for the epidermal cell wall and cuticle.

Although the plant epidermis serves primarily a protective role, during plant development some epidermal cells specialize, becoming competent to interact not only with pollen but also with other epidermal cells. In the former case, these interactions mediate recognition, germination, and pollen growth responses and, in the latter case, result in interorgan fusions which, most commonly, alter floral architecture in ways that are thought to promote reproductive success. In either case, all of the initial signaling events must take place across the cell wall and cuticle. In Arabidopsis, mutation of the FIDDLEHEAD gene alters the shoot epidermis such that all epidermal cells become competent to participate in both types of interactions. In fdh-1 mutants, epidermal cells manifest not only a contact-mediated fusion response but also interact with pollen. Since carpel epidermal derivatives manifest both of these properties, we postulated that fdh-1 epidermal cells were ectopically expressing a carpel-like program. In this report we demonstrate that manifestation of the fdh-1 phenotype does not require the product of the AGAMOUS gene, indicating that the phenotype is either independent of the carpel development program or that fdh-1 mutations activate a carpel-specific developmental program downstream of the AG gene. Furthermore, we demonstrate that plants bearing mutations in the fdh-1 gene show significant changes in cell wall and cuticular permeability. Biochemical analyses of the lipid composition of the crude cell wall fraction reveal that fdh-1 cell walls differ from wild-type and manifest significant changes in high-molecular-weight lipid peaks. These results suggest that cell wall and cuticular permeability may be important determinants in developmental signaling between interacting cells and implicate lipids as important factors in modulating the selectivity of the permeability barrier presented by the epidermal cell wall and cuticle.

Arabidopsis↗
PubMed2000

The effects of chlorpromazine on the outer cell wall of Salmonella typhimurium in ensuring resistance to the drug.

Chlorpromazine (CPZ), a compound employed for the management of psychosis, has a wide ranging antibacterial activity. The growth of Salmonella typhimurium100 mg/l), was initially inhibited during the first 8-16 h of exposure to concentrations of CPZ below the MIC. During this period of transient susceptibility, the distribution of ribosomes was markedly altered in a concentration dependent manner; the rough cell wall was transformed into a smooth form. The protein composition of the outer cell wall of 55 kDa was markedly decreased, whilst there was an increased number of high molecular weight proteins. After 16 h of exposure to sub-MIC levels of CPZ, the inhibitory effect of the drug was no longer apparent whereas the effects noted on the cell wall were retained. These Salmonella were, as the control, agglutinated by O antigen specific antibody. Whereas agglutination of the control Salmonella was blocked by the presence of CPZ at concentrations that induced the cell-wall effects, agglutination of CPZ exposed-Salmonella for periods in excess of 16 h was not blocked by any concentration of CPZ. These results suggested that eventual resistance to CPZ was dependent upon changes induced by CPZ at the cell wall level. The results also suggested that the CPZ binds to the 55 kDa protein and that such binding interfered with the recognition of the O antigen by antibody.

Agglutination↗
PubMed1997

X-ray photoelectron spectroscopy analysis of whole cells and isolated cell walls of gram-positive bacteria: comparison with biochemical analysis.

The surface chemical composition of whole cells and isolated cell walls of four coryneform bacteria and of a Bacillus brevis strain has been determined by X-ray photoelectron spectroscopy (XPS). The XPS data were converted into concentrations of model compounds: peptides, polysaccharides, and hydrocarbonlike compounds. The composition of the surface of B. brevis differed markedly from that of coryneforms: the peptide concentration was about twice higher in the former case, which is attributed to the presence of an S-layer at the cell surface; in contrast, the surface of coryneforms was rich in hydrocarbonlike compounds (about 40%), which was concomitant with a high water contact angle. The peptide surface concentration of the isolated cell walls of the five strains deduced from XPS data fitted well with the total peptide content determined by biochemical analysis, which supports the validity of XPS to determine the overall macromolecular composition of the bacterial cell surface. Compared to biochemical analysis of isolated cell walls, XPS analysis of whole cells provides information which concerns directly the cell surface (2- to 5-nm-thick layer) and is less subject to alteration via losses of cell wall constituents or contamination by intracellular compounds.

Actinomycetales↗
PubMed1974

Hemagglutinin in cell walls of Chlamydia psittaci.

Intact purified elementary bodies (EB) of Chlamydia psittaci agglutinate chicken erythrocytes in low titer, whereas homogenates of EB and of EB cell walls agglutinate at much higher titers depending on the extent of disruption by shaking and sonication. The hemagglutinin is contained in the cell envelope and can be purified with cell wall fractions. Treatment of cell wall with sodium dodecyl sulfate completely inactivated the hemagglutinin. Purified hemagglutinin was found to have an identical polypeptide composition to EB cell walls. Preparations of purified reticulate forms, the reproductive intracellular form of the organism, were almost totally devoid of hemagglutinin.

Animals↗
PubMedDate not supplied

[Effect of environmental factors on the composition of lipopolysaccharides released from the Rhodobacter capsulatus cell wall].

The goal of this study was to compare the environmental factors that determine viability of the gram-negative photosynthesizing bacteria Rhodobacter capsulatus (specifically, light and growth medium composition) and to assess the effect of these factors on the synthesis and composition of lipopolysaccharides released from the cell wall. Depletion of medium resulted in the release of lipopolysaccharides with a truncated polysaccharide fragment. It is concluded that, due to high viability of these bacteria, the main factor that induced lipopolysaccharide release from the cell wall, irrespective of culturing conditions, is cell division rather than cell death.

Cell Wall↗
PubMed2000

Molecular organization of the alkali-insoluble fraction of Aspergillus fumigatus cell wall.

Physical and biological properties of the fungal cell wall are determined by the composition and arrangement of the structural polysaccharides. Cell wall polymers of fungi are classically divided into two groups depending on their solubility in hot alkali. We have analyzed the alkali-insoluble fraction of the Aspergillus fumigatus cell wall, which is the fraction believed to be responsible for fungal cell wall rigidity. Using enzymatic digestions with recombinant endo-beta-1,3-glucanase and chitinase, fractionation by gel filtration, affinity chromatography with immobilized lectins, and high performance liquid chromatography, several fractions that contained specific interpolysaccharide covalent linkages were isolated. Unique features of the A. fumigatus cell wall are (i) the absence of beta-1,6-glucan and (ii) the presence of a linear beta-1, 3/1,4-glucan, never previously described in fungi. Galactomannan, chitin, and beta-1,3-glucan were also found in the alkali-insoluble fraction. The beta-1,3-glucan is a branched polymer with 4% of beta-1,6 branch points. Chitin, galactomannan, and the linear beta-1, 3/1,4-glucan were covalently linked to the nonreducing end of beta-1, 3-glucan side chains. As in Saccharomyces cerevisiae, chitin was linked via a beta-1,4 linkage to beta-1,3-glucan. The data obtained suggested that the branching of beta-1,3-glucan is an early event in the construction of the cell wall, resulting in an increase of potential acceptor sites for chitin, galactomannan, and the linear beta-1,3/1,4-glucan.

Aspergillus fumigatus↗
PubMed2002

Dynamics of cell wall structure in Saccharomyces cerevisiae.

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.

Cell Wall↗
PubMed2002

Determination of subunit composition of Clostridium cellulovorans cellulosomes that degrade plant cell walls.

Clostridium cellulovorans produces a cellulase enzyme complex (cellulosome). In this study, we isolated two plant cell wall-degrading cellulosomal fractions from culture supernatant of C. cellulovorans and determined their subunit compositions and enzymatic activities. One of the cellulosomal fractions showed fourfold-higher plant cell wall-degrading activity than the other. Both cellulosomal fractions contained the same nine subunits (the scaffolding protein CbpA, endoglucanases EngE and EngK, cellobiohydrolase ExgS, xylanase XynA, mannanase ManA, and three unknown proteins), although the relative amounts of the subunits differed. Since only cellobiose was released from plant cell walls by the cellulosomal fractions, cellobiohydrolases were considered to be key enzymes for plant cell wall degradation.

Amino Acid Sequence↗
PubMed2006

Chemical imaging of poplar wood cell walls by confocal Raman microscopy.

Confocal Raman microscopy was used to illustrate changes of molecular composition in secondary plant cell wall tissues of poplar (Populus nigra x Populus deltoids) wood. Two-dimensional spectral maps were acquired and chemical images calculated by integrating the intensity of characteristic spectral bands. This enabled direct visualization of the spatial variation of the lignin content without any chemical treatment or staining of the cell wall. A small (0.5 microm) lignified border toward the lumen was observed in the gelatinous layer of poplar tension wood. The variable orientation of the cellulose was also characterized, leading to visualization of the S1 layer with dimensions smaller than 0.5 mum. Scanning Raman microscopy was thus shown to be a powerful, nondestructive tool for imaging changes in molecular cell wall organization with high spatial resolution.

Cell Wall↗
PubMed2004

Mechanisms of biosorption of different heavy metals by brown marine macroalgae.

The biosorption mechanisms of different heavy metallic cations (Cd, Ni, Pb) to active chemical groups on the cell wall matrix of the nonliving brown marine macroalga, Sargassum vulgaris in its natural form, were examined by the following instrumental and chemical techniques: Fourier-transform infrared (FTIR) analysis, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and extraction of alginic acid and sulfated polysaccharides, which act as metal-binding moieties present in cell wall. From the different techniques used and the known chemical composition of the algal cell wall, it was observed that biosorption of the metallic cations to the algal cell wall component was a surface process. The binding capacities of the different metal cations were between 1 and 1.2 mmol metal/g on a dry weight basis. The main chemical groups involved in the metallic cation biosorption were apparently carboxyl, amino, sulfhydryl, and sulfonate. These groups were part of the algal cell wall structural polymers, namely, polysaccharides (alginic acid, sulfated polysaccharides), proteins, and peptidoglycans. The main cadmium cation sequestration mechanism by the algal biomass was apparently chelation, while the nickel cation sequestration mechanism was mainly ion exchange. Lead cations exhibit higher affinity to the algal biomass, and their binding mechanism included a combination of ion exchange, chelation, and reduction reactions, accompanied by metallic lead precipitation on the cell wall matrix. During the ion exchange process, calcium, magnesium, hydrogen cations, and probably other cations (sodium and potassium) in the algal cell wall matrix were replaced by the tested heavy metals.

Absorption↗
PubMed1997

A temperature-sensitive mutation of Coprinus cinereus, hyt1-1, that causes swelling of hyphal tips.

The TU25 mutant strain of the basidiomycete Coprinus cinereus grows well at 28 degrees C but not at 37 degrees C. Microscopic examination revealed that TU25 exhibited swelling at hyphal apices after a shift-up from 28 degrees C to 37 degrees C. The temperature sensitivity and hyphal swelling co-segregated through meiosis as expected for a single Mendelian factor, designated hyt1 (hyphal tip). Both defects could be suppressed by the presence of osmotic stabilizers in the medium, suggesting that the hyt1 gene product is required for proper cell-wall function. Chemical analysis of the cell walls, however, failed to detect any clear difference in the composition of the cell-wall polysaccharides between the wild-type and TU25. A DNA fragment which complements the hyt1-1 mutation was cloned and sequenced. The predicted protein in the ORF essential for complementation of hyt1-1 is a novel protein.

Amino Acid Sequence↗
PubMed1970

Isolation of ribosomes from cell-wall preparations of barley (Hordeum vulgare).

Ribosomes can be released from highly purified preparations of the cell walls of barley shoots by passing the suspension of cell walls through a French press. The sedimentation coefficients and base composition of the cell-wall ribosomes are identical with those of cytoplasmic ribosomes. It is suggested that the ribosomes isolated from the walls were originally incorporated into the wall structure during formation of the primary wall.

Cell Wall↗
PubMed1968

The cell wall of Bacillus licheniformis N.C.T.C. 6346. Composition of the mucopeptide component.

1. The mucopeptide component of wall preparations from Bacillus licheniformis was obtained in soluble form by treatment of the acid-insoluble residue of walls with lysozyme. 2. The soluble mucopeptide contains glutamic acid, diaminopimelic acid, alanine, N-acetylglucosamine and N-acetylmuramic acid in the molecular proportions 1.0:1.0:1.6:0.8:0.7. In addition approx. 1 mole of amide/mole of glutamic acid is present. Essentially all of the dry weight and nitrogen content of soluble mucopeptide is accounted for by these constituents. 3. The optical configurations of the amino acids were determined. Approx. 0.6 mole of d-alanine and 1.0 mole of l-alanine are present/mole of glutamic acid. 4. The structures of several small peptides derived from soluble mucopeptide after mild acid hydrolysis were established. 5. The structure of soluble mucopeptide from B. licheniformis is discussed on the basis of these results together with data on the number of free amino groups present in soluble mucopeptide.

Alanine↗
PubMed1999

Chemical analysis and immunolocalisation of lignin and suberin in endodermal and hypodermal/rhizodermal cell walls of developing maize (Zea mays L.) primary roots.

The composition of suberin and lignin in endodermal cell walls (ECWs) and in rhizodermal/hypodermal cell walls (RHCWs) of developing primary maize (Zea mays L.) roots was analysed after depolymerisation of enzymatically isolated cell wall material. Absolute suberin amounts related to root length significantly increased from primary ECWs (Casparian strips) to secondary ECWs (suberin lamella). During further maturation of the endodermis, reaching the final tertiary developmental state characterised by the deposition of lignified secondary cell walls (u-shaped cell wall deposits), suberin amounts remained constant. Absolute amounts of lignin related to root length constantly increased throughout the change from primary to tertiary ECWs. The suberin of Casparian strips contained high amounts of carboxylic and 2-hydroxy acids, and differed substantially from the suberin of secondary and tertiary ECWs, which was dominated by high contents of omega-hydroxycarboxylic and 1,omega-dicarboxylic acids. Furthermore, the chain-length distribution of suberin monomers in primary ECWs ranged from C(16) to C(24), whereas in secondary and tertiary ECWs a shift towards higher chain lengths (C(16) to C(28)) was observed. The lignin composition of Casparian strips (primary ECWs) showed a high syringyl content and was similar to lignin in secondary cell walls of the tertiary ECWs, whereas lignin in secondary ECWs contained higher amounts of p-hydroxyphenyl units. The suberin and lignin compositions of RHCWs rarely changed with increasing root age. However, compared to the suberin in ECWs, where C(16) and C(18) were the most prominent chain lengths, the suberin of RHCWs was dominated by the higher chain lengths (C(24) and C(26)). The composition of RHCW lignin was similar to that of secondary-ECW lignin. Using lignin-specific antibodies, lignin epitopes were indeed found to be located in the Casparian strip. Surprisingly, the mature suberin layers of tertiary ECWs contained comparable amounts of lignin-like epitopes.

Cell Wall↗
PubMed1999

Antisense inhibition of the GDP-mannose pyrophosphorylase reduces the ascorbate content in transgenic plants leading to developmental changes during senescence.

GDP-mannose pyrophosphorylase (GMPase, EC 2.7.7.22) catalyses the synthesis of GDP-D-mannose and represents the first committed step in the formation of all guanosin-containing sugar nucleotides found in plants which are precursors for cell wall biosynthesis and, probably more important, the synthesis of ascorbate. A full-length cDNA encoding GMPase from S. tuberosum was isolated. Transgenic potato plants were generated in which the GMPase cDNA was introduced in antisense orientation to the 35S promoter. Transformants with reduced GMPase activity were selected. Transgenic plants were indistinguishable from the wild-type when held under tissue culture conditions, however, a major change was seen 10 weeks after transfer into soil. Transgenic plants showed dark spots on leaf veins and stems with this phenotype developing from the bottom to the top of the plant. In case of the line with the strongest reduction, all aerial parts finally dried out after 3 months in soil, in contrast to the wild-type plants which did not start to senesce at this time. This coincides with a reduction of ascorbate contents in the transgenic plants, which is in agreement with the recently proposed pathway of ascorbate biosynthesis. Furthermore, leaf cell walls of the transgenic potato plants had mannose contents that were reduced to 30-50% of the wild-type levels, whereas the composition of tuber cell walls was unchanged. The glycosylation pattern of proteins was unaffected by GMPase inhibition, as studied by affinoblot analysis.

Amino Acid Sequence↗
PubMed1978

Chemical composition of the peptidoglycan-free cell walls of methanogenic bacteria.

Cell walls were prepared from freeze-dried samples of 7 strains of Methanobacterium by mechanical disintegration of the cells followed by incubation with trypsin. Electron microscopy revealed the presence of sacculi exhibiting the shape of the original cells, on which no surface structure could be detected. Ultrathin sections of the isolated sacculi showed a homogenously electron dense layer of about 10--15 nm in width. The ash content varied between 8 and 18% of dry weight. The sacculi of all the strains contained Lys: Ala:Glu:GlcNAc or GalNAc in a molar ratio of about 1:1.2:2:1. In one strain (M. ruminantium M1) alanine is replaced by threonine, however, Neutral sugars and--in some strains--additional amounts of the amino sugars were present in variable amounts, and could be removed by formamide extraction or HF treatment without destroying the sacculi. No muramic acid or D-amino acids typical of peptidoglycan were found. Therefore, the sacculi of the methanobacteria consist of a different polymer containing a set of three L-amino acids and one N-acetylated amino sugar. From cells of Methanospirillum hungatii no sacculi, but tube-like sheaths could be isolated, which tend to fracture perpendicularly to the long axis of the sheath along the fibrills seen on the surface. The sheaths consist of protein containing 18 amino acids and small amounts of neutral sugars. They are resistent to the proteinases tested and are not disintegrated by boiling in 2% sodium dodecylsulfate for 30 min. The three Gram-negative strains Black Sea isolate JR-1, Cariaco isolate JR-1 and Methanobacterium mobile do not contain a rigid sacculus, but merely a SDS-sensitive surface layer composed of regularly arranged protein subunits. This evidence indicates that, within the methanogens, different cell wall polymers characteristic of particular groups of organisms may have evolved during evolution, and supports the hypothesis that the evolution of the methanogens was separated from that of the peptidoglycan-containing procaryotic organisms at a very early stage.

Acetates↗