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At least 973 records · Page 54Linked to original sources
PubMed2003

Apoplasmic barriers and oxygen transport properties of hypodermal cell walls in roots from four amazonian tree species.

The formation of suberized and lignified barriers in the exodermis is suggested to be part of a suite of adaptations to flooded or waterlogged conditions, adjusting transport of solutes and gases in and out of roots. In this study, the composition of apoplasmic barriers in hypodermal cell walls and oxygen profiles in roots and the surrounding medium of four Amazon tree species that are subjected to long-term flooding at their habitat was analyzed. In hypodermal cell walls of the deciduous tree Crateva benthami, suberization is very weak and dominated by monoacids, 2-hydroxy acids, and omega-hydroxycarboxylic acids. This species does not show any morphological adaptations to flooding and overcomes the aquatic period in a dormant state. Hypodermal cells of Tabernaemontana juruana, a tree which is able to maintain its leaf system during the aquatic phase, are characterized by extensively suberized walls, incrusted mainly by the unsaturated C(18) omega-hydroxycarboxylic acid and the alpha,omega-dicarboxylic acid analogon, known as typical suberin markers. Two other evergreen species, Laetia corymbulosa and Salix martiana, contained 3- to 4-fold less aliphatic suberin in the exodermis, but more than 85% of the aromatic moiety of suberin are composed of para-hydroxybenzoic acid, suggesting a function of suberin in pathogen defense. No major differences in the lignin content among the species were observed. Determination of oxygen distribution in the roots and rhizosphere of the four species revealed that radial loss of oxygen can be effectively restricted by the formation of suberized barriers but not by lignification of exodermal cell walls.

Biological Transport↗
PubMed2005

Therapeutic targets in Paracoccidioides brasiliensis: post-transcriptome perspectives.

The rise in antifungal resistance, observed as a result of the increasing numbers of immunocompromised patients, has made the discovery of new targets for drug therapy imperative. The description of the Paracoccidioides brasiliensis transcriptome has allowed us to find alternatives to refine current therapy against paracoccidioidomycosis. We used comparative analysis of expressed sequence tags to find promising drug targets that have been addressed in other pathogens. We divided the analysis into six different categories, based on the involvement of the targeted mechanisms in the cell: i) cell wall construction, ii) plasma membrane composition, iii) cellular machinery, iv) cellular metabolism, v) signaling pathways, and vi) other essential processes. Through this approach, it has been possible to infer strategies to develop alternative drugs against this pathogen.

Antifungal Agents↗
PubMed1978

Acid-soluble nucleotides of Acholeplasma (Mycoplasma) laidlawii A.

A study was made of the acid-soluble nucleotides present in Acholeplasma (Mycoplasma) laidlawii A during growth. The nucleotide pool of this organism is meagre, both qualitatively and quantitatively. The main nucleotides are uridine mono- and diphosphates, and none of the more complex nucleotide compounds, such as uridine diphosphate (UDP) sugars or sugar peptides, required for cell wall formation, were detected. The nucleotide composition of A. laidlawii A is compared with that of the Streptococcus L-form.

Acholeplasma laidlawii↗
PubMed2005

Rsp5 ubiquitin ligase affects isoprenoid pathway and cell wall organization in S. cerevisiae.

Dimethylallyl diphosphate, an isomer of isopentenyl diphosphate, is a common substrate of Mod5p, a tRNA modifying enzyme, and the farnesyl diphosphate synthase Erg20p, the key enzyme of the isoprenoid pathway. rsp5 mutants, defective in the Rsp5 ubiquitin-protein ligase, were isolated and characterized as altering the mitochondrial/cytosolic distribution of Mod5p. To understand better how competition for the substrate determines the regulation at the molecular level, we analyzed the effect of the rsp5-13 mutation on Erg20p expression. The level of Erg20p was three times lower in rsp5-13 compared to the wild type strain and this effect was dependent on active Mod5p. Northern blot analysis indicated a regulatory role of Rsp5p in ERG20 transcription. ERG20 expression was also impaired in pkc1Delta lacking a component of the cell wall integrity signaling pathway. Low expression of Erg20p in rsp5 cells was accompanied by low level of ergosterol, the main end product of the isoprenoid pathway. Additionally, rsp5 strains were resistant to nystatin, which binds to ergosterol present in the plasma membrane, and sensitive to calcofluor white, a drug destabilizing cell wall integrity by binding to chitin. Furthermore, the cell wall structure appeared abnormal in most rsp5-13 cells investigated by electron microscopy and chitin level in the cell wall was increased two-fold. These results indicate that Rsp5p affects the isoprenoid pathway which has important roles in ergosterol biosynthesis, protein glycosylation and transport and in this way may influence the composition of the plasma membrane and cell wall.

Cell Wall↗
PubMed2006

Multiple characterizations of Listeria monocytogenes sensitive and insensitive variants to divergicin M35, a new pediocin-like bacteriocin.

AIMS: Divergicin M35 is a new class IIa bacteriocin produced by Carnobacterium divergicin M35. The bactericidal activity of this antimicrobial peptide was tested against a set of 11 strains of Listeria monocytogenes isolated from food. METHODS AND RESULTS: The minimal inhibitory concentration (MIC) was determined by the microdilution method. The strains tested displayed a different level of sensitivity to divergicin M35. L. monocytogenes LSD530, referred to as DivS strain, was the most sensitive and appeared to be inhibited by concentration of divergicin M35 below 0.13 microg ml(-1). The mutant resistant to divergicin M35, called DivM, was obtained from L. monocytogenes LSD530 (DivS) by gradually increasing the amounts of divergicin M35 until 1.3 microg ml(-1). Notably, DivM was stable after 50 generations. DivS parental strain was inhibited by a concentration of 4 microg ml(-1). L. monocytogenes LSD530 was shown to be resistant to divergicin M35 at 1.3 microg ml(-1). Remarkably, in the presence of divalent cations such as Ca(2+), Mg(2+) and Mn(2+), the lethality caused by divergicin M35 was reduced by 0.48, 0.54 and 0.63 log CFU per ml (after 18 h at 30 degrees C), respectively. The total DNA profiles of DivS and DivM were similar. DivS and DivM showed variable sensitivity to antibiotics. The two-dimensional (2-D) electrophoresis of cell wall proteins did not show any significant difference between DivS and DivM strains but their fatty acid composition showed a significant difference in C(16:0) content. CONCLUSIONS: Resistance to divergicin M35 is likely ascribed to modification in cell wall fatty acid composition rather than protein modification. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides original results contributing to understanding of the resistance of L. monocytogenes to divergicin M35, a new class IIa bacteriocin.

Anti-Bacterial Agents↗
PubMedDate not supplied

Comparison of cell wall teichoic acid fractions isolated from three different encapsulated strains of Staphylococcus epidermidis.

Teichoic acid preparations extracted from the cell wall of three serologically different encapsulated strains of Staphylococcus epidermidis, ATCC-31432 (capsular type I), SE-360 (capsular type II) and SE-10 (capsular type III) were purified by DEAE-cellulose and Sephadex G-50 column chromatography. The preparations showed immunological heterogeneity by an agar diffusion test. The chemical properties of the cell wall teichoic acid preparations of capsular types I and III were regarded as N-acetyl-glucosaminyl glycerol-phosphate polymers containing N-acetylglucosamine and phosphate at molar ratios of 0.22-1.0 and 0.33-1.0, respectively. The preparation of capsular type II was assumed to be an alpha-glucosyl glycerol-phosphate polymer containing glucose and phosphate at a molar ratio of 0.49-1.0, and it reacted strongly with concanavalin A. Moreover, alanine, glycine, serine and lysine were shown, among these preparations, to be a common amino acid composition. These results indicate that cell wall teichoic acids obtained from these strains were biochemically and immunologically different from each other.

Cell Wall↗
PubMed1982

Effect of IAA on Growth and Soluble Cell Wall Polysaccharides Centrifuged from Pine Hypocotyl Sections.

Auxin-induced elongation and cell wall polysaccharide metabolism were studied in excised hypocotyl sections of ponderosa pine (Pinus ponderosa) seedlings. Sections excised from hypocotyls of ponderosa pine elongate in response to the addition of auxin. The neutral sugar composition of the extracellular solution removed from hypocotyl sections by centrifugation was examined. In cell wall solution from freshly excised sections, glucose, galactose, xylose, and arabinose make up more than 90% of the neutral sugars, while rhamnose, fucose, and mannose are relatively minor components. The neutral sugar composition of the polysaccharides of the pine cell wall solution is both qualitatively and quantitatively similar to that of pea. Following auxin treatment of pine hypocotyls, the neutral sugar composition of the cell wall changes; glucose, xylose, rhamnose, and fucose increase by nearly 2-fold relative to controls in buffer without auxin. These changes in neutral sugars in response to auxin treatment are similar to those found in pea, with the exception that in pea, rhamnose levels decline in response to auxin treatment.

Journal Article↗
PubMed1996

New contributions to the wall polysaccharide structure of vegetative mycelium and fruit body cell walls of Agaricus bisporus.

Significant differences in chemical composition and structure of wall polysaccharides were found in Agaricus bisporus vegetative mycelium in comparison with the fruit body mycelium. Chemical fractionation of the walls demonstrated distinct percentages of the successively solubilized polysaccharides in both walls, and different proportions of their respective sugar monomers. Permethylation of isolated fractions also showed striking differences relative to the sugar linkages between the two types of walls studied. Furthermore, infrared spectrophotometry exhibited a distinct polysaccharidic configuration in several fractions. All the described differences were correlated with the transition of vegetative mycelial walls to the fruiting stage of differentiation.

Agaricus↗
PubMed1999

Polyphasic taxonomy of a novel Halobacillus, Halobacillus thailandensis sp. nov. isolated from fish sauce.

In order to speed up fish sauce production, a more complete understanding of the microorganisms associated with the fermentation was needed. This study was undertaken to meet that need. A bacterium was isolated from a fish sauce production line containing 25% NaCl. It is a Gram-positive, rod-shaped bacillus with pointed ends, occurring as single cells, pairs, or short chains. Endospores are produced on a low nutrient medium and, in old cultures, the cells round up, even when undergoing division. The cell wall is relatively amorphous and similar to that of Gram-positive bacteria in structure and composition. Cells grown in a medium containing 10-20% salt possess thicker cell walls than those grown in a medium with 3% salt. Based on 16S rRNA sequence and DNA/DNA hybridization data, we conclude that the bacterium is a species of Halobacillus. This bacterium shares 99.2% and 97.2% 16S rRNA similarity with Halobacillus litoralis and Halobacillus halophilus respectively and DNA/DNA homology was lower than 70%, considered indicative of species similarity. Three highly expressed extra-cellular proteolytic enzymes with M(r) of approximately 100 kDa, 42 kDa and 17 kDa, respectively, were detected by gelatin-polyacrylamide gel electrophoresis. Activity of the 100 kDa and 17 kDa proteases was inhibited by phenylmethanesulphonyl fluoride (PMSF), without being affected by L-trans epoxysuccinyl-leucylamide 4-guanidino-butane (E-64), pepstatin, EDTA, or 1, 10-phenanthroline, leading to the conclusion that these enzymes are serine proteases. The 42-kDa protease was inhibited by EDTA and 1,10-phenanthroline, but not by PMSF, thus, being classified a metalloprotease. The strain has been successfully employed to improve fermentation in industrial production of fish sauce in Thailand.

Animals↗
PubMed1996

A method to increase silver biosorption by an industrial strain of Saccharomyces cerevisiae.

Ag+ biosorption by an industrial strain of Saccharomyces cerevisiae was investigated. Older (96 h old) biomass had half the biosorption capacity of younger (24 h old) biomass (0.187 and 0.387 mmol Ag+/g dry mass respectively). Comparisons of cell walls isolated from biomass of either age indicated that chemical composition and Ag+ biosorption capacity varied little over the time span examined and that cell walls from either age of culture had small Ag+ biosorption capacities compared to whole cells of a similar age. Silver-containing precipitates were observed both on the cell wall and within the cell, indicating that intracellular components sorbed Ag+. The concentration of these precipitates within the cell appeared visually to decrease with age in Ag(+)-exposed cells. Incorporation of L-cysteine into the growth medium resulted in biomass with increased silver biosorption capacities, protein and sulphydryl group content. Increasing the concentration of L-cysteine in the growth medium from 0 to 5.0 mM increased silver biosorption from 0.389 to 0.556 mmol Ag+/g dry mass. Isolated cell walls of biomass grown in supplemented media also showed a possible link between silver biosorption capacities, protein and sulphydryl group content. No precipitates were observed in silver-exposed biomass that had been grown in the presence of 5.0 mM L-cysteine.

Adsorption↗
PubMed1991

Adsorption of a hydrophobic mutagen to five contrasting dietary fiber preparations.

The ability of five plant cell wall (dietary fiber) preparations with contrasting compositions to adsorb in vitro the hydrophobic, environmental mutagen, 1,8-dinitropyrene (DNP), was investigated. Many of the fruits and vegetables in Western diets are from dicotyledonous (broad leaved) plants and the dietary fiber from these consists mainly of unlignified cell walls. A representative of this wall type, prepared from immature cabbage leaves, showed little ability to adsorb DNP. Two other cell-wall preparations, representing lignified walls of dicotyledons and unlignified walls of vegetative parts of grasses and cereals (monocotyledons belonging to the family Poaceae), adsorbed DNP much more effectively. However, two further preparations, representing suberized walls of cork cells and lignified walls of vegetative parts of grasses and cereals, were the most effective in adsorbing DNP. Extrapolation of these data to the in vivo situation would indicate that increased consumption of the vegetative parts of grasses or cereals and plant material containing cork cells, for example potato skins, could be effective in removing hydrophobic mutagens from potential contact with colonic mucosal cells.

Brassica↗
PubMed2003

Dodder hyphae invade the host: a structural and immunocytochemical characterization.

Dodder (Cuscuta pentagona) hyphae are unique amongst the parasitic weeds for their ability to apparently grow through the walls of the host plant. Closer examination reveals, however, that the hyphae do not grow through the host but rather induce the host to form a new cell wall (or extend the existing wall) to coat the growing hypha. This chimeric wall composed of walls from two species is even traversed by plasmodesmata that connect the two cytoplasms. Compositionally, the chimeric wall is quite different from the walls of either the host or in other cells of the dodder plant, on the basis of immunocytochemical labeling. The most striking differences were in the pectins, with much stronger labeling present in the chimeric wall than in either the host or other dodder walls. Interestingly, labeling with monoclonal antibodies specific to arabinan side chains of rhamnogalacturonan I pectin fraction was highly enriched in the chimeric wall, but antibodies to galactan side chains revealed no labeling. Arabinogalactan protein antibodies labeled the plasma membrane and vesicles at the tips of the hyphae and the complementary host wall, although the JIM8-reactive epitope, associated with very lipophilic arabinogalactan proteins, was found only in dodder cells and not the host. Callose was found in the plasmodesmata and along the forming hyphal wall but was found at low levels in the host wall. The low level of host wall labeling with anticallose indicates that a typical woundlike response was not induced by the dodder. When dodder infects leaf lamina, which have more abundant intercellular spaces than petioles or shoots, the hyphae grew both intra- and extracellularly. In the latter condition, a host wall did not ensheath the parasite and there was clear degradation of the host middle lamellae by the growing hyphae, allowing the dodder to pass between cells. These data indicate that the chimeric walls formed from the growth of the host cell wall in concert with the developing hyphae are unique in composition and structure and represent an induction of a wall type in the host that is not noted in surrounding walls.

Cell Wall↗
PubMed2006

Ion-exchange properties of cell walls of Spinacia oleracea L. roots under different environmental salt conditions.

Ion-exchange properties of the polymeric matrix of cell walls isolated from roots of 55-day-old Spinacia oleracea L. (Matador cv.) plants grown in nutrient solution in the presence of 0.5, 150, and 250 mM NaCl and from roots of Suaeda altissima L. Pall plants of the same age grown in the presence of 0.5 and 250 mM NaCl were studied. The ion-exchange capacity of the spinach cell walls was determined at pH values from 2 to 12 and different ionic strength of the solution (10 and 250 mM NaCl). In the structure of the root cell walls, four types of ionogenic groups were found: amine, two types of carboxyl (the first being galacturonic acid residue), and phenolic groups. The content of each type of group and their ionization constants were evaluated. The ion-exchange properties of spinach and the halophyte Suaeda altissima L. Pall were compared, and the qualitative composition of the ion-exchange groups in the cell walls of roots of these plants appeared to be the same and not depend on conditions of the root nutrition. The content of carboxyl groups of polygalacturonic acid changed in the cell walls of the glycophyte and halophyte depending on the salt concentration in the medium. These changes in the composition of functional groups of the cell wall polymers seemed to be a response of these plants to salt and were more pronounced in the halophyte. A sharp increase in the NaCl concentration in the medium caused a decrease in pH in the extracellular water space as a result of exchange reactions between sodium ions entering from the external solution and protons of carboxyl groups of the cell walls. The findings are discussed from the standpoint of involvement of root cell walls of different plant species in response to salinity.

Cell Wall↗
PubMed1974

Purification and characterization of Streptococcus mutans group d cell wall polysaccharide antigen.

The Streptococcus mutans group d antigen of strain B13 has been purified and characterized with respect to chemical composition and immunochemical properties. The antigen was extracted from lyophilized cells or cell walls by using 5% trichloroacetic acid at 5 C for 16 h. The antigen could also be extracted with water or 0.01 N HCl at 100 C for 20 min. The antigen was purified by ion-exchange and gel chromatography and was found to contain 96% carbohydrate, 1.6% protein, and 0.3% phosphorus. Characterization by gas chromatography indicated that the polysaccharide was composed of galactose and glucose in a 2:1 ratio. The antigen contained two serologically active sites: one site specific for group d and a second site common to both group d and group a strains. Agar diffusion and immunoelectrophoresis indicated that the two sites existed on a single molecule. The immunological specificity of the group d polysaccharide site depended on a terminal d-galactose. The purified B13 antigen did not react with antisera specific for the glycerol teichoic acid from streptococci. Anti-d serum rapidly agglutinated whole cells, indicating that the antibody receptor sites of the polysaccharide antigen were at the surface of the streptococcal cell.

Adsorption↗
PubMed2002

In muro fragmentation of the rhamnogalacturonan I backbone in potato (Solanum tuberosum L.) results in a reduction and altered location of the galactan and arabinan side-chains and abnormal periderm development.

Rhamnogalacturonan (RG) I is a branched pectic polysaccharide in plant cell walls. Rhamnogalacturonan lyase (eRGL) from Aspergillus aculeatus is able to cleave the RG I backbone at specific sites. Transgenic potato (Solanum tuberosum L.) plants were made by the introduction of the gene encoding eRGL, under the control of the granule-bound starch synthase promoter. The eRGL protein was successfully expressed and translated into an active form, demonstrated by eRGL activity in the tuber extracts. The transgenic plants produced tubers with clear morphological alterations, including radial swelling of the periderm cells and development of intercellular spaces in the cortex. Sugar compositional analysis of the isolated cell walls showed a large reduction in galactosyl and arabinosyl residues in transgenic tubers. Immunocytochemical studies using the LM5 (galactan) and LM6 (arabinan) antibodies also showed a large reduction in galactan and arabinan side-chains of RG I. Most of the remaining LM5 epitopes were located in the expanded middle lamella at cell corners of eRGL tubers, which is in contrast to their normal location in the primary wall of wild type tubers. These data suggest that RG I has an important role in anchoring galactans and arabinans at particular regions in the wall and in normal development of the periderm.

Aspergillus↗
PubMed1982

Mycolic acid composition and thermally adaptative changes in Nocardia asteroides.

The nocardomycolic acid compositions of extractable and the cell wall-bound lipids from five strains of Nocardia asteroides (A-23007, A-23094, B-23006, B-23095, and IFO 3384) were compared by using gas chromatography-mass spectrometry. The molecular species composition of mycolic acid differed significantly among the strains of N. asteroides. The A-23007 strain possessed the shortest species, centering at C(44(46)), and the A-23094 and IFO-3384 strains followed, each centering at C(52). The B-23006 and B-23095 strains possessed the longest species, centering at C(56) or C(54), thus indicating that N. asteroides strains accommodate a heterogeneous group in respect to carbon numbers of mycolic acids. The doublebond isomers of mycolic acids from the representative strain IFO 3384 were fully separated and analyzed by argentation thin-layer chromatography, followed by gas chromatography-mass spectrometry. The reference strain (IFO 3384) possessed up to four double bonds on the straight chain of mycolic acids ranging from C(46) to C(60). All of the species possessed a C(14) alkyl branch at C-2. The more highly unsaturated subclasses consisted of the longer-chain mycolic acids. Marked changes in mycolic acid composition were induced by altering the growth temperature of strain IFO 3384. The cells grown at the higher temperature (50 degrees C) contained more saturated mycolic acids, whereas those grown at the lower temperature (17 degrees C) had more polyunsaturated (up to tetraenoic) mycolic acids, although a significant difference in carbon chain length was not detected. These changes in the degree of unsaturation of mycolic acids occurred shortly after shifting the growth temperature from 17 to 50 degrees C at logarithmic stages of the bacterial growth, thus indicating that N. asteroides can adapt to changes in the environmental temperature by altering the structure of mycolic acids of the cell walls.

Chemical Phenomena↗
PubMed1994

Gram-positive cell wall structure of the A3 gamma type in heliobacteria.

The amino acid composition and structure of the peptidoglycan from Heliobacillus mobilis was determined by one- and two-dimensional thin-layer chromatography of completely and partially hydrolysed cell wall preparations. The structure was found to be of the A3 gamma type, with L,L-diaminopimelate in position 3, D-alanine in position 4 and a glycine interpeptide bridge, as found in certain groups of Gram-positive bacteria including Clostridium perfringens and Nocardioides simplex. The presence of a Gram-positive type of cell wall in heliobacteria is consistent with their phylogenetic relationship to the 'low G + C' Gram-positive bacteria, as previously demonstrated by 16S rRNA sequencing.

Amino Acid Sequence↗
PubMed1975

The effect of growth environment on the chloroform-methanol and alkali-extractable cell wall and cytoplasm lipid levels of Mucor rouxii.

The distribution of chloroform-methanol and alkali-extractable lipids in the cell walls of aerobically grown filamentous cells from Mucor rouxii has been determined. The results have been compared with the corresponding lipid composition of yeast-like cells from M. rouxii, which can be produced in two ways: by growth under anaerobic conditions and by aerobic growth in the presence of 0.22% phenethyl alcohol (PEA). It was observed that in most cases the crude cytoplasmic fraction contained higher levels of several lipids (i.e., squalene, sterols, triterpenes, and fatty acids) than did the corresponding cell walls. The cell walls did, however, contain both "free" (chloroform-methanol extractable) and "bound" (alkali extractable) lipids although the relative amounts were markedly dependent on the cell growth environment. The aerobically grown filamentous cell walls contained higher levels of squalene, sterols, triterpenes, and fatty acids than did aerobically grown yeast-like PEA-induced cell walls and there was also considerable variation in the "free"/"bound" ratios of the various lipid components. The lipid levels in both the cell walls and cytoplasm of the anaerobically grown cells were considerably lower than those of the cells grown under aerobic conditions. In addition, the differences in the growth environment were also reflected in the compositions of the individual lipid fractions from both the cell wall and the cytoplasm fraction.

Aerobiosis↗