Control of cell wall assembly by a histone-like protein in Mycobacteria

Bacteria coordinate assembly of the cell wall as well as synthesis of cellular components depending on the growth state. The mycobacterial cell wall is dominated by mycolic acids covalently linked to sugars, such as trehalose and arabinose, and is critical for pathogenesis of mycobacteria. Transfer of mycolic acids to sugars is necessary for cell wall biogenesis and is mediated by mycolyltransferases, which have been previously identified as three antigen 85 (Ag85) complex proteins. However, the regulation mechanism which links cell wall biogenesis and the growth state has not been elucidated. Here we found that a histone-like protein has a dual concentration-dependent regulatory effect on mycolyltransferase functions of the Ag85 complex through direct binding to both the Ag85 complex and the substrate, trehalose-6-monomycolate, in the cell wall. A histone-like protein-deficient Mycobacterium smegmatis strain has an unusual crenellated cell wall structure and exhibits impaired cessation of glycolipid biosynthesis in the growth-retarded phase. Furthermore, we found that artificial alteration of the amount of the extracellular histone-like protein and the Ag85 complex changes the growth rate of mycobacteria, perhaps due to impaired down-regulation of glycolipid biosynthesis. Our results demonstrate novel regulation of cell wall assembly which has an impact on bacterial growth.     

Interpreting cell wall 'virulence factors' of Mycobacterium tuberculosis

The complex structure of the cell wall of Mycobacterium tuberculosis clearly contributes to the outcome of the dialogue between this pathogen and its host. The effects of mutations in cell wall components are likely to be quite complex, as individual components of the wall could have indirect effects that extend well beyond the physical integrity of the wall itself. Affected processes include the surface exposure or secretion of the many lipid, glycolipid and proteinaceous molecules that can interact directly with components of the host cell.     

Structure of a cell wall polysaccharide isolated from Hypocrea gelatinosa.

The structure of a polysaccharide isolated from the cell wall of Hypocrea gelatinosa has been investigated by means of chemical analyses and 1D and 2D NMR spectroscopy. The polysacharide has an irregular structure, idealized as follows: [carbohydrate structure in text].     

Hemolytic effect of a glycolipid produced byPseudomonas aeruginosa

Summary The toxicity of the glycolipid ofPs. aeruginosa to mice has to be ascribed to the fact that it causes hemolysis by dissolving materials from the cell wall structure of the red blood cells.     

Multi-spectrometric analyses of lipoteichoic acids isolated from Lactobacillus plantarum

Lipoteichoic acid is a major cell wall virulence factor of gram-positive bacteria. LTAs from various bacteria have differential immunostimulatory potentials due to heterogeneity in their structures. Although recent studies have demonstrated that LTA isolated from Lactobacillus plantarum (pLTA) has anti-inflammatory properties and is less inflammatory than LTAs from pathogenic bacteria, little is known about the structure of pLTA. In this study, high-field NMR spectra of the pLTA were compared with those of LTA from pathogenic bacterium, Staphylococcus aureus (aLTA). The 2D NMR results demonstrated that pLTA possesses α-linked hexose sugar substituents on the poly-glycerophosphate backbone instead of N-acetylglucosamine substituents, and unsaturated fatty acids in its glycolipids. The sugar substituents were revealed as an approximately 29:1 molar ratio of the glucose to galactose by HPAEC-PAD analysis. MALDI-TOF/TOF MS analyses identified the presence of unsaturated fatty acids in the glycolipid moieties of pLTA. In addition, the glycolipid structure was found to be composed of trihexosyl-diacyl- and/or trihexosyl-triacyl-glycerol ceramide units by means of unique fragment ions of the glycolipids. These results enabled us to elucidate the pLTA structure, which is distinctively different from canonical LTA structure, and suggest that the unique immunological property of pLTA might be caused by the pLTA structure.     

Location, synthesis and function of glycolipids and polyglycerolphosphate lipoteichoic acid in Gram-positive bacteria of the phylum Firmicutes

Lipoteichoic acid (LTA) is a zwitterionic polymer found in the cell wall of many Gram-positive bacteria. A widespread and one of the best-studied forms of LTA consists of a polyglycerolphosphate (PGP) chain that is tethered to the membrane via a glycolipid anchor. In this review, we will summarize our current understanding of the enzymes involved in glycolipid and PGP backbone synthesis in a variety of different Gram-positive bacteria. The recent identification of key LTA synthesis proteins allowed the construction and analysis of mutant strains with defined defects in glycolipid or backbone synthesis. Using these strains, new information on the functions of LTA for bacterial growth, physiology and during developmental processes was gained and will be discussed. Furthermore, we will reintroduce the idea that LTA remains in close proximity to the bacterial membrane for its function during bacterial growth rather than as a surface-exposed structure.     

Mycoside G, a Specific Glycolipid in Mycobacterium marinum (Balnei).

Navalkar, R. G. (University of Wisconsin, Madison), E. Wiegeshaus, E. Kondo, H. K. Kim, and D. W. Smith. Mycoside G, a specific glycolipid in Mycobacterium marinum (Balnei). J. Bacteriol. 90:262-265. 1965.-A new specific glycolipid in extracts prepared from strains designated Mycobacterium marinum and M. balnei has been demonstrated by use of the techniques of column chromatography and infrared spectroscopy. Since there is now agreement among many workers that M. marinum and M. balnei are identical, the demonstration of the same specific glycolipid in both species is not surprising. This substance, which we have designated mycoside G, is chemically similar to mycosides A and B, and apparently differs only in the sugar moiety. In addition, the lipids extracted from these cultures contain phthiocerol dimycocerosate, a wax component found also in M. tuberculosis and M. bovis.     

Cell wall polysaccharides: before and after autolysis of brewer’s yeast

Brewer’s yeast is used in production of beer since millennia, and it is receiving increased attention because of its distinct fermentation ability and other biological properties. During fermentation, autolysis occurs naturally at the end of growth cycle of yeast. Yeast cell wall provides yeast with osmotic integrity and holds the cell shape upon the cell wall stresses. The cell wall of yeast consists of β-glucans, chitin, mannoproteins, and proteins that cross linked with glycans and a glycolipid anchor. The variation in composition and amount of cell wall polysaccharides during autolysis in response to cell wall stress, laying significant impacts on the autolysis ability of yeast, either benefiting or destroying the flavor of final products. On the other hand, polysaccharides from yeast cell wall show outstanding health effects and are recommended to be used in functional foods. This article reviews the influence of cell wall polysaccharides on yeast autolysis, covering cell wall structure changings during autolysis, and functions and possible applications of cell wall components derived from yeast autolysis.     

Cell Wall Galactofuranan of “Paenarthrobacter pyridinovorans” VKM Ac-1098D

Microbiology - The structure of the cell wall glycopolymer and the taxonomic position of the pyridine-degrading strain VKM Ac-1098D were established. By using chemical and NMR spectroscopic...     

Two-enzyme systems for glycolipid and polyglycerolphosphate lipoteichoic acid synthesis in Listeria monocytogenes

Lipoteichoic acid (LTA) is an important cell wall polymer in Gram-positive bacteria and often consists a polyglycerolphosphate backbone chain that is linked to the membrane by a glycolipid. In Listeria monocytogenes this glycolipid is Gal-Glc-DAG or Gal-Ptd-6Glc-DAG. Using a bioinformatics approach, we have identified L. monocytogenes genes predicted to be involved in glycolipid ( lmo2555 and lmo2554 ) and LTA backbone ( lmo0644 and lmo0927 ) synthesis. LTA and glycolipid analysis of wild-type and mutant strains confirmed the function of Lmo2555 and Lmo2554 as glycosyltransferases required for the formation of Glc-DAG and Gal-Glc-DAG. Deletion of a third gene, lmo2553 , located in the same operon resulted in the production of LTA with an altered structure. lmo0927 and lmo0644 encode proteins with high similarity to the staphylococcal LTA synthase LtaS, which is responsible for polyglycerolphosphate backbone synthesis. We show that both proteins are involved in LTA synthesis. Our data support a model whereby Lmo0644 acts as an LTA primase LtaP and transfers the initial glycerolphosphate onto the glycolipid anchor, and Lmo0927 functions as LTA synthase LtaS, which extends the glycerolphosphate backbone chain. Inactivation of LtaS leads to severe growth and cell division defects, underscoring the pivotal role of LTA in this Gram-positive pathogen.     

Isolation and immunochemical characteristics of the immunodepressive substance from Escherichia coli.

A substance, inhibiting the production of haemolysins against sheep erythrocytes in mice was isolated from two non-pathogenic strains of E. coli, 020:K4 and M-17, by the methods of differential centrifugation and gel filtration. Spectrophotometric studies and chemical analysis have shown the isolated substance to be glycolipid. The immunodepressive substance is localized in the cytoplasm of the microbial cell. The isolated and partly purified immunodepressive substance did not contain any admixture of O-antigen (endotoxin) of the cell wall or of antigens giving cross reactions with sheep erythrocytes. The isolated substance exhibited weak antigenic properties and was not toxic for mice when administered in a dose of 2 mg (dry weight).     

Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

The wall gives a Saccharomyces cerevisiae cell its osmotic integrity; defines cell shape during budding growth, mating, sporulation, and pseudohypha formation; and presents adhesive glycoproteins to other yeast cells. The wall consists of β1,3- and β1,6-glucans, a small amount of chitin, and many different proteins that may bear N- and O-linked glycans and a glycolipid anchor. These components become cross-linked in various ways to form higher-order complexes. Wall composition and degree of cross-linking vary during growth and development and change in response to cell wall stress. This article reviews wall biogenesis in vegetative cells, covering the structure of wall components and how they are cross-linked; the biosynthesis of N- and O-linked glycans, glycosylphosphatidylinositol membrane anchors, β1,3- and β1,6-linked glucans, and chitin; the reactions that cross-link wall components; and the possible functions of enzymatic and nonenzymatic cell wall proteins.     

Development of Epidermis on Banana Fruits

Fruit epidermis ofMusa (AAB) cv. Poovan (S) remains single-layered throughout its development. There is no change in stomatal number but its frequency and index decrease due to slight increase in epidermal cell number and size. The external wall of the epidermal cells shows stratification of wall layers that is characteristic of normal epidermal cell with cuticle and epicuticular wax deposits. Surface wax deposits show qualitative and quantitative variations during fruit development and ripening.     

Polar lipids from the radiation resistant bacterium Deinococcus radiodurans: structural investigations on glucosaminyl and N-acetyl glucosaminyl lipids

Deinococcus radiodurans, although a gram-positive bacterium, has a complex cell wall with multiple layers and associates to this structural particularity, a quite unusual lipid composition for gram-positive bacteria. The conventional phospholipids (phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl glycerol...) are absent. Among the nine polar lipids detected in the R1 Anderson strain, three are glycolipids only one is a phospholipid, the other ones are glycophospholipids. One of the latter compounds contains one free amino group. Analysis by aminoacid autoanalyser enables to identify glucosamine in one glycolipid and in two glycophospholipids. Sugar analysis by gas-liquid chromatography after acid methanolysis and trifluoroacetylation, reveals the occurrence of N-acetyl glucosaminyl residues in one glycolipid and in one phospholipid. The following identification for the two lipids of D. radiodurans is proposed: phosphatidyl glucosaminyl glycerol and phosphatidyl N-acetyl glucosaminyl glycerol.     

Characterization of a Lactobacillus gasseri JCM 1131T Lipoteichoic Acid with a Novel Glycolipid Anchor Structure

We determined the chemical structure of lipoteichoic acid (LTA) from Lactobacillus gasseri JCM 1131^T. The repeating unit was comprised of glycerolphosphate and 2-alanylglycerolphosphate. The glycolipid anchor was tetrahexosylglycerol with two or three acyl groups. To our knowledge, this is the first demonstration of a tetrahexose structure in an LTA glycolipid anchor.     

Studies on the Ultrastructure and Histochemistry of Plant Cuticles: The Cuticular Membrane of Agave americana L. in situ

The outer epidermal wall of Agave americana leaves was examinedin order to gain more information about the location and chemicalconstitution of the structural components. In middle aged leavesthe wall comprised six layers which were designated epicuticularwax, cuticle proper, exterior and interior cuticular layer,exterior and interior cellin wall. A lamellated structure, consistingof a series of electron translucent lamellae of uniform thicknessalternating with opaque ones of variable thickness, was observedin the thin cuticle proper on the outside of the cuticular membrane,even without heavy metal treatment. The cuticular layers underneathformed the bulk of the cuticular membrane and they also hadtwo components, an amorphous matrix permeated by a reticulumof fibrillae. Cutin, detected with osmium and with iodine/iodine-sulphuricacid–silver proteinate, was a major component of the opaquelamellae of the cuticle proper and the matrix of the cuticularlayer. Carbohydrates were absent from the cuticle proper butwere detected specifically in the fibrillae of the cuticularlayer and in the cellin wall. Pectic material seemed to be presenton both sides of the junction between cuticular membrane andcellin wall, but no discrete zone corresponding to light microscopicalobservations was detected in the electron microscope. Althoughthe lucent lamellae of the cuticle proper were tentatively ascribedto wax there was no structural or ultrahistochemical evidencefor the wax component of the cuticular layer. The various ultrahistochemicalreactions are discussed in relation to the known chemical compositionof the membrane. Agave americana L., epidermis wall, cuticular membrane, cuticle proper, cuticular layer, ultrahistochemistry, wax     

Molecular packing of cord factor and its interaction with phosphatidylinositol in mixed monolayers.

Cord factor (trehalose 6,6'-dimycolate, CF) is a glycolipid located in the outer mycobacterial cell wall that is implicated in the pathogenesis of mycobacteria. Furthermore, CF is a convenient model for studying mycolic acid residues, the major lipid constituents of the mycobacterial cell wall that are believed to form a barrier against drug penetration. The surface properties of CF and its interactions with phosphatidylinositol (PI) have been investigated using the monolayer technique. During compression/expansion/recompression cycles, CF monolayers switch from a loosely packed to a more tightly packed structure. The change in surface properties suggests a molecular rearrangement, perhaps involving interdigitation of long and short chains of the CF molecules. In CF-PI monolayers, maximal lateral packing density occurs between 0.5 and 0.7 mole fraction CF, which is close to the relative composition of mycolic acid residues and shorter-chain lipids in the mycobacterial cell wall. Low concentrations of CF increase the order in PI monolayers, consistent with CF toxicity involving rigidification of cell membranes.     

Mycolyltransferase-mediated glycolipid exchange in Mycobacteria

Trehalose dimycolate (TDM), also known as cord factor, is a major surface glycolipid of the cell wall of mycobacteria. Because of its potent biological functions in models of infection, adjuvancy, and immunotherapy, it is important to determine how its biosynthesis is regulated. Here we show that glucose, a host-derived product that is not readily available in the environment, causes Mycobacterium avium to down-regulate TDM expression while up-regulating production of another major glycolipid with immunological roles in T cell activation, glucose monomycolate (GMM). In vitro, the mechanism of reciprocal regulation of TDM and GMM involves competitive substrate selection by antigen 85A. The switch from TDM to GMM biosynthesis occurs near the physiological concentration of glucose present in mammalian hosts. We further demonstrate that GMM is produced in vivo by mycobacteria growing in mouse lung. These results establish an enzymatic pathway for GMM production. More generally, these observations provide a specific enzymatic mechanism for dynamic alterations of cell wall glycolipid remodeling in response to the transition from noncellular to cellular growth environments, including factors that are monitored by the host immune system.     

Absolute configuration of the unique 2,6-dideoxy-4-O-methyl-arabino-hexopyranose of the major phenolic glycolipid antigen from Mycobacterium kansasii

The antigenicity and the structure of the major phenolic glycolipid from Mycobacterium kansasii have been established. A monoacetylated tetrasaccharide structure was proposed for the oligosaccharide moiety in which the distal sugar, unique in nature, corresponds to 2,6-dideoxy-4-O-methyl-alpha-arabinohexopyranose. Its terminal position in the oligosaccharide part confers to this residue a key role in the antigen-antibody interaction. By improvement of the methanolysis procedure, this new kind of sugar was obtained in higher amounts than by hydrolysis of the glycolipid. Its 1H-NMR spectrum is presented and its optical rotatory power measurement agrees with a D absolute configuration while the deoxyhexoses involved in the glycolipid tetrasaccharide structure present the L absolute configuration.     

Differential chemical allocation and plant adaptation: A Py-MS Study of 24 species differing in relative growth rate

The chemical composition of leaves of 24 wild species differing in potential relative growth rate (RGR) was analysed by pyrolysis-mass spectrometry. The variation in RGR significantly correlated with differences in chemical composition: slow-growing species were richer in glucan-based polysaccharides and in C16:0 fatty acid, whereas fast growing ones contained more protein (other than those incorporated in cell walls) and chlorophyll, sterols and diglycerides. Other, apparently significant correlations, e.g. for pentose-based hemicellulose and for guaiacyl lignin appeared solely based on a group separation between mono- and dicotyledonous species.Considering the eleven monocotyledonous and thirteen dicotyledonous species separately, correlations were found in addition to the previously mentioned general ones. Within the group of the monocotyledons the low-RGR species were significantly enriched in pentose-based hemicellulose, ferulic acid and (hydroxy)proline-rich cell wall protein and nearly significant in guaiacyl and syringyl lignin, fast-growing species contained more potassium. Within the group of the dicotyledons slow-growing species were enriched in triterpenes and aliphatic wax esters.In general, the monocotyledons contained more cell wall material such as pentose-based hemicellulose, ferulic acid, glucans (including cellulose) and guaiacyl-lignin, and also more aliphatic wax esters, than the dicotyledons. The dicotyledons, on the other hand, contained somewhat more protein than the grasses.Per unit weight of cell wall, the amount of (hydroxy)proline- rich protein in low-RGR species was comparatively low. A higher investment of cell wall proteins to explain the low rate of photosynthesis per unit of leaf nitrogen of slow-growing species as suggested by Lambers and Poorter (1992), therefore, seems unlikely.Abbreviations HPRP (hydroxy)proline-rich protein(s) - LAR leaf area ratio - LWR leaf weight ratio - MVA multivariate analysis - NAR net assimilation rate - PC principal component - PNUE photosynthetic nitrogen use efficiency - PyGCMS pyrolysis-gas chromatography-mass spectrometry - PyMS pyrolysis mass spectrometry - RGR relative growth rate - SLA specific leaf area - SLM specific leaf mass