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PubMed1996

Cell-Wall Polysaccharides of Developing Flax Plants.

Flax (Linum usitatissimum L.) fibers originate from procambial cells of the protophloem and develop in cortical bundles that encircle the vascular cylinder. We determined the polysaccharide composition of the cell walls from various organs of the developing flax plant, from fiber-rich strips peeled from the stem, and from the xylem. Ammonium oxalate-soluble polysaccharides from all tissues contained 5-linked arabinans with low degrees of branching, rhamnogalacturonans, and polygalacturonic acid. The fiber-rich peels contained, in addition, substantial amounts of a buffer-soluble, 4-linked galactan branched at the 0-2 and 0-3 positions with nonreducing terminal-galactosyl units. The cross-linking glycans from all tissues were (fucogalacto)xyloglucan, typical of type-I cell walls, xylans containing (1->)-[beta]-D-xylosyl units branched exclusively at the xylosyl O-2 with t-(4-O-methyl)-glucosyluronic acid units, and (galacto)glucomannans. Tissues containing predominantly primary cell wall contained a larger proportion of xyloglucan. The xylem cells were composed of about 60% 4-xylans, 32% cellulose, and small amounts of pectin and the other cross-linking polysaccharides. The noncellulosic polysaccharides of flax exhibit an uncommonly low degree of branching compared to similar polysaccharides from other flowering plants. Although the relative abundance of the various noncellulosic polysaccharides varies widely among the different cell types, the linkage structure and degree of branching of several of the noncellulosic polysaccharides are invariant.

Journal Article↗
PubMed1985

Transient Nature of a (1 --> 3), (1 --> 4)-beta-d-Glucan in Zea mays Coleoptile Cell Walls.

Excised Zea mays L. embryos were cultured on Linsmaier and Skoog medium. Coleoptiles were sampled at regular intervals and the length, fresh weight, cell wall weight, and cell wall neutral sugar composition were determined. A specific beta-d-glucanase from Bacillus subtilis was used to determine the content of a (1 --> 3),(1 --> 4)-beta-d-glucan.Coleoptiles elongated through the 5th day following imbibition with the most rapid elongation occurring between days 3 and 4. The greatest net rate of incorporation of cell wall per coleoptile occurred between the 2nd and 3rd days when deposition of approximately one-third of the maximum net glucan level was observed. By day 5, the amount of glucan present had increased 34-fold from the 6 micrograms per coleoptile on day 1 and accounted for about 14% of the cell wall (w/w). Thereafter, the glucan content declined until only 3.3% (w/w) remained by day 10. In this 10-day interval, xylose increased 32% and cellulose content doubled, while proportions of other neutral sugars changed less dramatically.These results are consistent with a possible role for the beta-d-glucan in elongation of the Zea coleoptile. Moreover, changes in the quantity of this wall component clearly reflect the dynamic nature of plant cell wall polysaccharides. An evaluation of glucan dynamics in vivo suggests that in vitro autolysis studies employing Zea coleoptile walls may overestimate the actual rate of glucan turnover in the intact tissue.

Journal Article↗
PubMed2002

Rhodococcus jostii sp. nov., isolated from a medieval grave.

The taxonomic position of a bacterial strain isolated from the femur of the remains of Jost Lucemburský, margrave in Moravia, Brno (Czech Republic), was investigated by phenotypic, chemotaxonomic and molecular taxonomic methods. The chemotaxonomic characteristics, including the cell-wall amino acid and sugar compositions, the quinone system and the fatty acid profile, were in good agreement with those of the genus Rhodococcus. The G+C content of the DNA was 67.4 mol%. Comparative 16S rRNA gene sequencing demonstrated that the unknown strain represents a distinct line of descent within the genus Rhodococcus. The nearest relatives of the bacterium were Rhodococcus opacus and Rhodococcus percolatus. The unknown bacterium was readily distinguished from these species by using phenotypic methods. On the basis of phylogenetic and phenotypic evidence, it is proposed that the unknown bacterium be classified as Rhodococcus jostii sp. nov. The type strain is strain IFO 16295T (= CCM 4760T).

Amino Acids↗
PubMed1985

Pathogenic JK group corynebacteria and their similarity to human cutaneous lipophilic diphtheroids.

Aerobic diphtheroids from human skin (commonly referred to as lipophilic diphtheroids), pathogenic bacteria of the JK group, and classic species of the genus Corynebacterium were studied for their cellular fatty acids and mycolates, composition of their cell wall peptidoglycans, nutritional requirements, biochemical reactions, and antibiotic sensitivities. Lipophilic diphtheroids and JK strains were catalase positive and contained corynemycolic acid and meso-diaminopimelic acid in their cell walls, a characteristic shared with all corynebacteria. The lipophilic diphtheroid and JK strains were found to have a strict nutritional requirement for lipid and a similar composition of cellular fatty acid, mycolic acid, and peptidoglycan; they differed only in the multiple antibiotic resistance of the JK strains. Results of the biochemical reactions were inconclusive and did not permit grouping of lipophilic diphtheroids or JK with any of the reference strains. The reference strains did not require lipid and contained cellular fatty acids that were clearly distinct from those of the JK strains or lipophilic diphtheroids. These results suggest that JK bacteria are Corynebacterium spp. and may represent resident lipophilic diphtheroids that have acquired antibiotic resistance.

Anti-Bacterial Agents↗
PubMed1995

Molecular basis of cell integrity and morphogenesis in Saccharomyces cerevisiae.

In fungi and many other organisms, a thick outer cell wall is responsible for determining the shape of the cell and for maintaining its integrity. The budding yeast Saccharomyces cerevisiae has been a useful model organism for the study of cell wall synthesis, and over the past few decades, many aspects of the composition, structure, and enzymology of the cell wall have been elucidated. The cell wall of budding yeasts is a complex and dynamic structure; its arrangement alters as the cell grows, and its composition changes in response to different environmental conditions and at different times during the yeast life cycle. In the past few years, we have witnessed a profilic genetic and molecular characterization of some key aspects of cell wall polymer synthesis and hydrolysis in the budding yeast. Furthermore, this organism has been the target of numerous recent studies on the topic of morphogenesis, which have had an enormous impact on our understanding of the intracellular events that participate in directed cell wall synthesis. A number of components that direct polarized secretion, including those involved in assembly and organization of the actin cytoskeleton, secretory pathways, and a series of novel signal transduction systems and regulatory components have been identified. Analysis of these different components has suggested pathways by which polarized secretion is directed and controlled. Our aim is to offer an overall view of the current understanding of cell wall dynamics and of the complex network that controls polarized growth at particular stages of the budding yeast cell cycle and life cycle.

Cell Wall↗
PubMed1988

Characterization of beta-fructosidase, an extracellular glycoprotein of carrot cells.

Seedlings and suspension-cultured cells of carrot (Daucus carota) contain a cell wall associated as well as a soluble form of beta-fructosidase (beta F). These two forms have different pH optima: 4.6 for cell wall beta F and 5.6 for soluble beta F. Soluble beta F is relatively more abundant in the seedlings and cell wall beta F is relatively much more abundant in the cultured cells. Protoplasts of cultured cells have only the soluble form (pH optimum 5.6) indicating that the cell wall associated form is indeed extracellular in situ. Cell wall beta F was purified to homogeneity and has an Mr = 63,000. Antibodies raised against the deglycosylated enzyme cross-reacted with two soluble enzyme forms: in cultured cells, the soluble enzyme has an Mr = 58,000 and, in seedlings, there are two forms of Mr = 58,000 and 52,000. Treatment of purified cell wall beta F with endoglycosidase H and trifluoromethanesulfonic acid (complete deglycosylation) indicated that the enzyme probably has one high mannose and two complex glycans. This was confirmed by HPLC analysis of [3H]GlcNAc- and [3H]fucose-labeled glycopeptides obtained after trypsin digestion of radioactively-labeled beta F. The amino acid composition shows that cell wall beta F has 18.6% glycine.

Cell Wall↗
PubMed1991

[The biochemical and immunological properties of group A type M 29 streptococci cultured in the presence of a bovine blood serum preparation].

The influence of the preparation of cattle blood serum on group A streptococcus, type M 29, has been studied. The study has revealed that the addition of 17% of dialysis water obtained from a fraction of cattle blood serum to the standard culture medium (3% Todd-Hewitt broth) produces changes in the amino acid composition of the cell walls of M+ variant without altering the antiphagocytic resistance of the mutant thus obtained. The dialysate of the pepsin digest of the cell walls of the mutant contains Fc-receptors and receptors to fibrinogen, while the initial strain contains only receptors to fibrinogen which are, in this case, the pepsin fragments of M protein. The study has revealed similarity in the amino acid compositions of these proteins (receptors to fibrinogens) of phenotypes M+ and M2+. Thus, our data confirm that the initial strain and the mutant belong to different phenotypes of group A streptococcus, type M 29.

Amino Acids↗
PubMed2005

Glucan-associated protein modulations and ultrastructural changes of the cell wall in Candida albicans treated with micafungin, a water-soluble, lipopeptide antimycotic.

The composition of glucan-associated proteins (GAP) in the cell wall of Candida albicans was strongly affected by treatment with a sub-MIC yet beta-glucan synthesis inhibitory concentration (0.01 microg/ml) of FK463 (micafungin). Namely, a decrease in enzymes of glucose metabolism (mostly enolase and a novel 40 kDaltons component, here identified as the enzyme fructose-1,6-biphosphate aldolase) was observed, and this was coupled with an increase in two beta1-3 exo-glucanase isoforms (34 and 44 kDa, respectively). No GAP changes were detected in the same strain of the fungus made resistant to the drug, attesting to the specificity of the observed cell wall protein modulation. In addition, GAP changes were accompanied by marked ultrastructural alterations upon treatment with the sub-MIC dose of the drug, the majority of which was an aberrant cell surface morphology and a derangement of the normal layering of the cell wall. Our data demonstrate that sub-MIC doses of micafungin do critically affect not only the beta-glucan synthetic machinery but also protein composition and the whole cell wall structure of Candida albicans.

Antifungal Agents↗
PubMed2002

Preliminary analysis of the genetic basis for vancomycin resistance in Staphylococcus aureus strain Mu50.

Glycopeptides, such as vancomycin, are frequently the antibiotics of choice for treatment of infections caused by the now common methicillin-resistant Staphylococcus aureus (MRSA). Incidences of vancomycin resistance in S. aureus (VRSA) have been increasing worldwide for the last 5 years. Complex mechanisms producing changes in cell wall content and composition generate the VRSA phenotype, but the genetic basis of these changes has not yet been determined. To facilitate the genetic investigation, entire genome sequences of the archetypal VRSA (Mu50), and vancomycin-susceptible MRSA strains N315, EMRSA 16 and COL were compared. The in silico analysis revealed several loss-of-function mutations in Mu50, affecting important cell wall biosynthesis and intermediary metabolism genes, not previously reported. The new findings provide further evidence for the hypothesis that vancomycin resistance in Mu50 is due to fundamental changes, important to metabolic pathways that impinge on peptidoglycan biosynthesis. These observations will inform targeted experiments aimed at a complete understanding of the mechanism(s) of vancomycin resistance in S. aureus Mu50 and other VRSA strains.

Humans↗
PubMed1984

Lipid and wall amino acid composition in the classification of Rothia dentocariosa.

Seven strains of Rothia dentocariosa were degraded by acid methanolysis and the nonhydroxylated fatty acid methyl esters released were examined by thin-layer and gas chromatography. The fatty acid profiles were composed of iso-, anteiso- and straight chain saturated fatty acids with 12-methyltetradecanoic (anteiso-C15), 14-methylpentadecanoic (iso-C16), 14-methylhexadecanoic (anteiso-C17) and hexadecanoic acid (C16) as major components. A small scale integrated procedure was used for the sequential extraction of isoprenoid quinones and polar lipids. The latter were examined by two-dimensional thin-layer chromatography and all of the test strains contained diphosphatidylglycerol, phosphatidylglycerol and two uncharacterised glycolipids. In all cases the major isoprenoid quinones were unsaturated menaquinones with seven isoprene units. Analyses of the cell wall amino acid composition using gas chromatography showed that the strains contained 2.5 to 5 moles of alanine and 1 mole each of glutamic acid and lysine. The chemical data support the integrity of Rothia dentocariosa and can be used to separate it from all other actinomycetes especially those which contain lysine in the wall peptidoglycan.

Actinomycetaceae↗
PubMed2006

Molecular organization of the cell wall of Candida albicans and its relation to pathogenicity.

Candida albicans is one of the most important opportunistic pathogenic fungi. Weakening of the defense mechanisms of the host, and the ability of the microorganism to adapt to the environment prevailing in the host tissues, turn the fungus from a rather harmless saprophyte into an aggressive pathogen. The disease, candidiasis, ranges from light superficial infections to deep processes that endanger the life of the patient. In the establishment of the pathogenic process, the cell wall of C. albicans (as in other pathogenic fungi) plays an important role. It is the outer structure that protects the fungus from the host defense mechanisms and initiates the direct contact with the host cells by adhering to their surface. The wall also contains important antigens and other compounds that affect the homeostatic equilibrium of the host in favor of the parasite. In this review, we discuss our present knowledge of the structure of the cell wall of C. albicans, the synthesis of its different components, and the mechanisms involved in their organization to give rise to a coherent composite. Furthermore, special emphasis has been placed on two further aspects: how the composition and structure of C. albicans cell wall compare with those from other fungi, and establishing the role of some specific wall components in pathogenesis. From the data presented here, it becomes clear that the composition, structure and synthesis of the cell wall of C. albicans display both subtle and important differences with the wall of different saprophytic fungi, and that some of these differences are of utmost importance for its pathogenic behavior.

Animals↗
PubMed1982

Teichoic acids from chemostat-grown cultures of Streptococcus mutans and Lactobacillus plantarum.

We examined the effect of growth conditions in chemostat culture on the quantity and composition of the cell wall teichoic acids of Streptococcus mutans BHT and Lactobacillus plantarum NCIB 7220 and the membrane lipoteichoic acid from S. mutans Ingbritt. With the cell wall teichoic acids, which are covalently linked to peptidoglycan, the amount of teichoic acid is independent of the growth conditions employed. However, the extent of glucosyl substitution of the polymer from L. plantarum was dependent on growth conditions. S. mutans Ingbritt lipoteichoic acid, on the other hand, was little affected by growth conditions in terms of composition or serological activity, but the amount produced was markedly affected by changes in growth conditions.

Cell Wall↗
PubMed2006

Spectroscopic and biochemical analysis of regions of the cell wall of the unicellular 'mannan weed', Acetabularia acetabulum.

Although the Dasycladalean alga Acetabularia acetabulum has long been known to contain mannan-rich walls, it is not known to what extent wall composition varies as a function of the elaborate cellular differentiation of this cell, nor has it been determined what other polysaccharides accompany the mannans. Cell walls were prepared from rhizoids, stalks, hairs, hair scars, apical septa, gametophores and gametangia, subjected to nuclear magnetic resonance and Fourier transform infrared spectroscopy, and analyzed for monosaccharide composition and linkage, although material limitations prevented some cell regions from being analyzed by some of the methods. In diplophase, walls contain a para-crystalline mannan, with other polysaccharides accounting for 10-20% of the wall mass; in haplophase, gametangia have a cellulosic wall, with mannans and other polymers representing about a quarter of the mass. In the walls of the diplophase, the mannan appears less crystalline than typical of cellulose. The walls of both diploid and haploid phases contain little if any xyloglucan or pectic polysaccharides, but appear to contain small amounts of a homorhamnan, galactomannans and glucogalactomannans, and branched xylans. These ancillary polysaccharides are approximately as abundant in the cellulose-rich gametangia as in the mannan-rich diplophase. In the diplophase, different regions of the cell differ modestly but reproducibly in the composition of the cell wall. These results suggest unique cell wall architecture for the mannan-rich cell walls of the Dasycladales.

Acetabularia↗
PubMed1984

Structure of the Primary Cell Walls of Suspension-Cultured Rosa glauca Cells: I. Polysaccharides Associated with Cellulose.

Cell walls of suspension-cultured cells of Rosa glauca were fractionated by two different extraction procedures. The first involved a stepwise fractionation scheme based on alkaline extraction. The second took advantage of the powerful cellulose solvent system N-methylmorpholine N-oxide/dimethyl sulfoxide which is capable of solubilizing whole cell walls. From the analytical composition of each solubilized fraction and of the corresponding residues, the fate of each type of cell wall polysaccharide constituent was followed at each step of the extraction scheme and the mode of action of the extractant was interpreted. Although the two fractionation procedures were very different, they yielded very similar cellulosic complex residues and extracts, thus delimiting two blocks of polysaccharides in the cell wall. The cellulose residues still comprised uronic acid-containing polysaccharides and hemicelluloses in association with cellulose. Graded acid hydrolysis provided evidence for the central role of a homogalacturonan core interconnecting xyloglucans and arabinogalactans. A tentative model showing the possible interaction existing between the constituent polysaccharides still associated to cellulose after alkaline extraction is presented. Hydrogen bonding between xyloglucan and cellulose is confirmed, and glycosidic linkages between xyloglucans and pectic polymers are suggested.

Journal Article↗
PubMed2002

Texture of cooked potatoes (Solanum tuberosum). 3. Preheating and the consequences for the texture and cell wall chemistry.

Two potato cultivars representing extremes with regard to the texture of the cooked product were divided into subcategories based on size and dry matter (DM) content. The effects of the preheating temperature and time on both the instrumentally determined firmness and the sensory-perceived firmness were measured and compared. Increasing the preheating time at 60 degrees C followed by cooking resulted in greater force required to fracture the tissue, an increase in perceived firmness, and a less mashable product. A principal component analysis showed that with higher DM contents of the potato samples, preheating resulted in a larger force required to fracture the tissue and a firmer product. The changes in fracture force were not linearly related with the changes in perceived firmness. The effects of preheating on the pectin methylesterase (PME) activity, the enzyme assumed to be responsible for the firming effect upon preheating, showed that the activity of this enzyme remained rather constant during preheating at 60 degrees C for 1 h. Preheating at 78 degrees C for 10 min abolished virtually all PME activity. To obtain insight into the consequences of preheating and preheating followed by steam cooking on the yield and composition of the cell wall material (CWM) of potatoes, a cell wall isolation followed by a pectin fractionation study was performed. Attention was also paid to the consequences of the processing conditions applied on the chemical composition of the CWM and the sequentially extracted pectic fractions. Preheating resulted in an increase in yield of the CWM of cooked potatoes and, as a consequence, all of the sequentially extracted fractions, including the residue. Preheating did not have a pronounced effect on the composition of the pectin of the sequentially extracted fractions. This altogether strongly indicates that preheating causes a PME-based firming effect, resulting in an decrease in pectin degradation and, as a consequence, a larger yield of CWM. It seems reasonable to assume that this increase in amount of CWM results in a firmer texture. The contribution of starch-based degradation products to the texture after preheating can, however, not be excluded.

Carboxylic Ester Hydrolases↗
PubMed2004

Effects of boron deficiency in cell suspension cultures of Populus alba L.

Cell suspension cultures of Populus alba L. (original cells) require at least 10 microM boron for appropriate growth. Using original cells we established a cell line, T-5B, which can grow in a medium containing low levels of boron (5 microM). The level of boron localized in the cell walls of T-5B cells was one-half that found in the cell walls of original cells maintained in medium containing 100 microM boron, and the level of the rhamnogalacturonan II dimer, cross-linked by a borate ester, also decreased in the former. The sugar composition of whole cell walls of the T-5B cell line was similar that of the original cells, however pectic polysaccharides composed of arabinose or galacturonic acid were easily extracted from T-5B cell walls with 50 mM trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid. Our results suggest that boron deficiency causes a weakening of the interaction among pectic polysaccharides due to a decrease in boron-rhamnogalacturonanII cross-linkage.

Boron↗
PubMed2006

Changes in cell wall polysaccharide of harvested peach fruit during storage.

Changes in cell wall structure, decrease in tissue firmness and ethylene production in honey peach [Prunus persica (L.) Batsch, cv. 'Yuhuasanhao'] were investigated after various storage at 5 degrees C and at 20 degrees C. The results showed that during storage, the peak of ethylene production lagged significantly behind the rapid softening of peach fruit, which means that it is not ethylene causes the softening of peach fruit. The structural and compositional changes of cell wall of fruits stored at 5 degrees C and at 20 degrees C suggested that low temperature storage inhibited the changes in pectins and cell wall materials (CWM)-residue fraction and delayed the softening of peach fruit. Ruptures of the pectic main chains rich in galacturonic acid occurred. Loss of arabinose and galactose was detected both in pectins and CWM-residue. These results suggested that softening of harvested peach fruit involved the solubilization and degradation of side chains of pectin and CWM-residue fraction, which were probably due to the increased activities of cell wall polysaccharide-related enzymes. However, the loss of neutral sugars in hemicellulosic polysaccharides was not correlated with fruit softening.

Cell Wall↗
PubMed1998

RECENT ADVANCES IN UNDERSTANDING LIGNIN BIOSYNTHESIS.

After a long period of little change, the basic concepts of lignin biosynthesis have been challenged by new results from genetic modification of lignin content and composition. New techniques for making directed genetic changes in plants, as well as improvements in the analytical techniques used to determine lignin content and composition in plant cell walls, have been used in experimental tests of the accepted lignin biosynthetic pathway. The lignins obtained from genetically modified plants have shown unexpected properties, and these findings have extended the known range of variation in lignin content and composition. These results argue that the accepted lignin biosynthetic pathway is either incomplete or incorrect, or both; and also suggest that plants may have a high level of metabolic plasticity in the formation of lignins. If this is so, the properties of novel lignins could be of significant scientific and practical interest.

Journal Article↗