scholarly journals Induction of orientation of bacterial cellulose microfibrils by a novel terpenoid from Acetobacter xylinum

1973 ◽  
Vol 135 (1) ◽  
pp. 145-149 ◽  
Author(s):  
W. Geoffrey Haigh ◽  
Hans J. Förster ◽  
Klaus Biemann ◽  
Neil H. Tattrie ◽  
J. Ross Colvin
Keyword(s):  
Higher Plants ◽  
Specific Effect ◽  
Ring System ◽  
Acetobacter Xylinum ◽  
Cellulose Microfibrils ◽  
Common Mechanism ◽  
Bacterial Cells ◽  
Total Lipids ◽  
Crude Lipid ◽  
Saponifiable Fraction

1. The bacterium Acetobacter xylinum produces extracellular cellulose microfibrils that form a pellicle in the medium enmeshing the bacterial cells. These microfibrils may show some localized alignment, which can be seen as birefringence when the culture is viewed between crossed Polaroid sheets. 2. An increase in birefringence can be induced by the addition of small amounts of certain classes of lipids, particularly sterols, to the cultures. 3. A crude lipid extract from Acetobacter cells induced greatly increased birefringence when added to fresh cultures of this organism. 4. When the bacterial lipids were fractionated, most of the activity was recovered in a complex, polar lipid. The lipid is secreted into the medium during growth and is unstable. The non-saponifiable portion of this lipid is shown to be a 1:1 mixture of a saturated and a monounsaturated C35 tetrahydroxy terpene with a hopane ring system in the accompanying paper by Förster et al. (1973). The saturated molecule is referred to as tetrahydroxybacteriohopane. 5. Tetrahydroxybacteriohopane is itself capable of inducing birefringence in cultures as is 22-hydroxyhopane, which was also isolated from the non-saponifiable fraction of the total lipids. 6. The mechanism of induction of birefringence (orientation of microfibrils) is not known. This is unlikely to be a specific effect, since all the above compounds are active (intact lipid, tetrahydroxybacteriohopane, 22-hydroxyhopane), as are other classes of lipid. It is suggested, however, that a common mechanism may be involved and that similar compounds may be concerned with control of microfibril alignment in the cells of higher plants.

THE FORMATION OF SPHERULITES IN PELLICLES OF BACTERIAL CELLULOSE

1965 ◽  
Vol 11 (4) ◽  
pp. 641-643 ◽  
Author(s):  
J. Ross Colvin
Keyword(s):  
Bacterial Cellulose ◽  
Higher Plants ◽  
Synthetic Polymers ◽  
Acetobacter Xylinum ◽  
Cellulose Microfibrils ◽  
Two Dimensional ◽  
Radial Orientation ◽  
Great Complexity ◽  
Dendritic Structures

Two-dimensional analogues of spherulites are formed in the pellicle of bacterial cellulose produced by static cultures of Acetobacter xylinum. These spherulites are much larger (sometimes more than 1 cm diameter) than those usually observed in other natural or synthetic polymers. They are due to the radial orientation of bacterial cellulose microfibrils in limited regions of the plane of the pellicle. These spherulites interact to form characteristic, dendritic structures of great complexity which resemble leaves of higher plants.

The growth of cellulose microfibrils from Acetobacter xylinum

1957 ◽  
Vol 23 ◽  
pp. 652-653 ◽  
Author(s):  
J.R. Colvin ◽  
S.T. Bayley ◽  
M. Beer
Keyword(s):  
Acetobacter Xylinum ◽  
Cellulose Microfibrils

scholarly journals CD20+ B Cell Depletion in Systemic Autoimmune Diseases: Common Mechanism of Inhibition or Disease-Specific Effect on Humoral Immunity?

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Panagiotis Pateinakis ◽  
Athina Pyrpasopoulou
Keyword(s):  
Autoimmune Diseases ◽  
B Cell ◽  
Specific Effect ◽  
Cell Depletion ◽  
Common Mechanism ◽  
B Cell Depletion ◽  
Systemic Autoimmune Diseases ◽  
Mechanism Of Inhibition ◽  
End Effectors ◽  
Disease Specific

Autoimmunity remains a complex physiologic deviation, enabled and perpetuated by a variety of interplayers and pathways. Simplistic approaches, targeting either isolated end-effectors of more centrally placed interactors of these mechanisms, are continuously tried in an effort to comprehend and halt cascades with potential disabling and deleterious effects in the affected individuals. This review focuses on theoretical and clinically proved effects of rituximab-induced CD20+ B cell depletion on different systemic autoimmune diseases and extrapolates on pathogenetic mechanisms that may account for different interindividual or interdisease responses.

scholarly journals Studies of the Extracellular Glycocalyx of the Anaerobic Cellulolytic Bacterium Ruminococcus albus 7

2006 ◽  
Vol 72 (12) ◽  
pp. 7559-7566 ◽  
Author(s):  
Paul J. Weimer ◽  
Neil P. J. Price ◽  
Otini Kroukamp ◽  
Lydia-Marie Joubert ◽  
Gideon M. Wolfaardt ◽  
...  
Keyword(s):  
Energy Demand ◽  
Extracellular Polymeric Substances ◽  
Cellulose Microfibrils ◽  
Variable Pressure ◽  
Cellulolytic Bacterium ◽  
Detergent Solution ◽  
Bacterial Cells ◽  
Cellulolytic Bacteria ◽  
Ruminococcus Albus ◽  
Almost All

ABSTRACT Anaerobic cellulolytic bacteria are thought to adhere to cellulose via several mechanisms, including production of a glycocalyx containing extracellular polymeric substances (EPS). As the compositions and structures of these glycocalyces have not been elucidated, variable-pressure scanning electron microscopy (VP-SEM) and chemical analysis were used to characterize the glycocalyx of the ruminal bacterium Ruminococcus albus strain 7. VP-SEM revealed that growth of this strain was accompanied by the formation of thin cellular extensions that allowed the bacterium to adhere to cellulose, followed by formation of a ramifying network that interconnected individual cells to one another and to the unraveling cellulose microfibrils. Extraction of 48-h-old whole-culture pellets (bacterial cells plus glycocalyx [G] plus residual cellulose [C]) with 0.1 N NaOH released carbohydrate and protein in a ratio of 1:5. Boiling of the cellulose fermentation residue in a neutral detergent solution removed almost all of the adherent cells and protein while retaining a residual network of adhering noncellular material. Trifluoroacetic acid hydrolysis of this residue (G plus C) released primarily glucose, along with substantial amounts of xylose and mannose, but only traces of galactose, the most abundant sugar in most characterized bacterial exopolysaccharides. Linkage analysis and characterization by nuclear magnetic resonance suggested that most of the glucosyl units were not present as partially degraded cellulose. Calculations suggested that the energy demand for synthesis of the nonprotein fraction of EPS by this organism represents only a small fraction (<4%) of the anabolic ATP expenditure of the bacterium.

scholarly journals Antimicrobial and Antioxidant Activities of Extracts and Compounds From Trifolium Baccarinii With Their Mechanisms of Antibacterial Action

2020 ◽  
Author(s):  
Léonel Feugap ◽  
Irene Kengne ◽  
Jean-De-Dieu Tamokou ◽  
Claudia Ngnokam ◽  
Mahamat Djamalladine ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Bacterial Resistance ◽  
Antimicrobial Agents ◽  
Higher Plants ◽  
Antioxidant Activities ◽  
Antioxidant Defenses ◽  
Biochanin A ◽  
Antibacterial Action ◽  
Bacterial Cells ◽  
Whole Plant

Abstract The treatment of infectious diseases with antimicrobial agents continues to present problems in modern-day medicine with many studies showing significant increase in the incidence of bacterial resistance to several antibiotics. The screening of plant extracts and natural compounds for antimicrobial activity has demonstrated that higher plants represent a potential source of new anti-infective agents. The aim of this study was to evaluate the antimicrobial and antioxidant activities of extracts and compounds from the whole plant Trifolium baccarinii Chiov. with their mechanisms of antibacterial action. Biochanin A (1), formononetin (2), luteolin (3), luteolin-4'-O-β-D-glucopyranoside (4), 4,7,2'-trihydroxy-4'-methoxyisoflavanol (5), sissotrin (6), 1-méthyl-β-D-glucopyranoside (7), ononin (8), D-mannitol (9) and 3-O-β-D-glucuronopyranosylsoyasapogenol B (10) were isolated from T. baccarinii. The MeOH, EtOAc and n-BuOH extracts as well as compounds 1–6 from T. baccarinii displayed the most antimicrobial and antioxidant activities. The MeOH extract and compound 5 exhibited antibacterial activity through bacteriolytic effect and reduction of the antioxidant defenses in the bacterial cells. Interestingly, none of the tested samples showed cytotoxic activity against normal cells; highlighting their good selectivity toward pathogenic bacteria and yeasts. Hence, they are promising lead candidates with antibacterial potential against methicillin resistant S. aureus (MRSA).

scholarly journals Exploration of molecular mechanism underlying the self-flocculation of Zymomonas mobilis through comparative omics analyses and experimental validations for developing robust production systems

2021 ◽  
Author(s):  
Lian-Ying Cao ◽  
Yongfu Yang ◽  
Chen-Guang Liu ◽  
Yunhao Chen ◽  
Xue Zhang ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Zymomonas Mobilis ◽  
The Self ◽  
Cellulose Microfibrils ◽  
Comparative Genomic ◽  
Bacterial Cells ◽  
Single Nucleotide ◽  
Putative Gene ◽  
Nucleotide Mutation ◽  
Experimental Validations

Zymomonas mobilis metabolizes sugar through the Entner-Doudoroff pathway with less ATP generated for lower biomass accumulation and more substrate to product formation with improved yield, since ATP is dissipated predominately through growth for intracellular energy homeostasis, making it a platform to be engineered as microbial cell factories, particularly for producing bulk commodities with major cost from feedstock consumption. ZM401, a self-flocculating mutant, presents advantages for production including cost-effective biomass recovery through gravity sedimentation, self-immobilization within bioreactors for high cell density to improve productivity and enhanced tolerance to environmental stresses for high product titers, but molecular mechanism underlying this phenotype is largely unknown. In this work, we sequenced and assembled the genome of ZM401 to explore genetic basis for the self-flocculation of the bacterial cells through comparative genomic and transcriptomic analyses, molecular docking simulations for enzymes encoded by functional genes and their substrates/activators, and experimental validations. Our results demonstrated that the single nucleotide deletion in ZMO1082 disrupted its stop codon for the putative gene being fused with ZMO1083, which created an exciting gene encoding the subunit A of the bacterial cellulose synthase with unique function for synthesizing cellulose microfibrils to flocculate the bacterial cells, and the single nucleotide mutation in ZMO1055 compromised the function of bifunctional diguanylate cyclase/phosphodiesterase encoded by the gene on the degradation of c-di-GMP for its intracellular accumulation to activate the cellulose biosynthesis. These discoveries are significant not only for optimizing the self-flocculation of Z. mobilis, but also engineering other bacteria with the self-flocculating phenotype for robust production.

Interspecific comparison of elutable cell wall extensin precursors by transmission electron microscopy

1986 ◽  
Vol 44 ◽  
pp. 284-285
Author(s):  
J. W. Heckman ◽  
M. J. Kielszewski ◽  
D. T. A. Lamport ◽  
E. P. Muldoon ◽  
B. T. Terhune ◽  
...  
Keyword(s):  
Cell Wall ◽  
Higher Plants ◽  
Gel Filtration ◽  
Cellulose Microfibrils ◽  
Primary Cell Wall ◽  
Wall Model ◽  
Intact Cells ◽  
Transmission Electron ◽  
Macromolecular Network ◽  
Covalently Linked

In addition to cellulose microfibrils, the primary cell wall of many higher plants contains extensin, a class of hydroxyproline-rich glycoprotein (HRGP). Despite its predominately hydrophilic amino acid composition, most cell wall HRGP remains insoluble even after complete deglycosylation with anhydrous HF, suggesting a covalently linked macromolecular network. This led to the development of the "warp-weft" cell wall model, based on an extensin network ("weft") penetrated by cellulose microfibrils (the "warp")(FIG. 1). Extensin precursors elute rapidly from intact cells and cell wall preparations of tomato, carrot, and cucumber, with mild salt solutions. Tomato precursors, at least, are block copolymers of a few repeating sequences. Gel filtration data and immuno-crossreactivity suggest that tomato P2 and cucumber callus precursor are similar. TEM confirms the rod-like structure and the lengths of these molecules.

scholarly journals Kinetic evidence for a common mechanism of capping on lymphocytes

1982 ◽  
Vol 204 (1) ◽  
pp. 229-237 ◽  
Author(s):  
Anthony N. Corps ◽  
James C. Metcalfe ◽  
Tullio Pozzan
Keyword(s):  
Concanavalin A ◽  
Cytochalasin B ◽  
Specific Effect ◽  
Common Mechanism ◽  
Cross Linking ◽  
Detectable Effect ◽  
Membrane Flow ◽  
Surface Immunoglobulin ◽  
Fixed Times ◽  
Concanavalin A Receptors

1. Differences in the rates at which ligands cap various receptors on the same cells, and their sensitivity to various drugs, have been interpreted as evidence that there are distinct mechanisms for ‘fast’ and ‘slow’ cap formation. We have examined the factors which determine the rate of cap formation of three receptors on mouse splenic lymphocytes or thymocytes, and compared the effects of cytochalasin B or colchicine under conditions where the different receptors cap at similar rates. 2. When surface immunoglobulin, concanavalin A receptors, or θ antigen are induced to cap at their maximal rates by appropriate concentrations of one or more cross-linking ligands, the half-time for maximal capping of each receptor population is between 1.5 and 3.0min at 37°C. Slower rates of cap formation are obtained by using non-optimal concentrations of the cross-linking ligands. 3. When the three receptors were induced to cap at similar rates (either maximal or slower), 10μm-cytochalasin B caused a similar decrease in the rate of cap formation for each receptor, without affecting the eventual extent of capping. At comparable capping rates on control cells, colchicine (10μm) increased the rate of cap formation for surface immunoglobulin and concanavalin A receptors to a similar extent, without affecting the eventual extent of cap formation. In contrast, colchicine had no detectable effect on the capping of θ antigen. 4. From these results, we conclude that there are no intrinsic differences in the rates at which different receptors can be induced to cap that can be used to diagnose differences in their mechanisms of cap formation. The observation that ligand concentration and the drugs acting on the cytoskeleton generally affect the rate but not the extent of cap formation accounts for the wide variation in reported effects of the drugs on cap formation measured at fixed times. The receptor-specific effect of colchicine on surface immunoglobulin and concanavalin A receptors, but not θ antigen, is not readily compatible with models of cap formation which depend on lipid or membrane flow.

The structure of spherulites of bacterial cellulose from Acetobacter xylinum

1974 ◽  
Vol 20 (4) ◽  
pp. 509-512 ◽  
Author(s):  
L. C. Sowden ◽  
J. Ross Colvin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Bacterial Cellulose ◽  
Acetobacter Xylinum ◽  
Cellulose Microfibrils ◽  
Polarizing Microscopy ◽  
Scanning Electron

Evidence from phase and polarizing microscopy as well as scanning electron microscopy indicates that the cellulose microfibrils in the spherulites of bacterial cellulose are oriented tangentially, not radially. Also, the orientation may be limited to only a fraction of the thickness of the pellicle. It is suggested that the tangential deposition may be caused by a gradient of concentration of a weakly soluble inhibitor of cellulose formation about a center.

Somatostatin promotes accumulation of phospholipids in regenerating liver tissue of rats

1991 ◽  
Vol 11 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Cedomila Milin ◽  
Biserka Radosevic-Stasic ◽  
Madena Kirigin ◽  
Visnja Hinic ◽  
Daniel Rukavina ◽  
...  
Keyword(s):  
Growth Factors ◽  
Rapid Growth ◽  
Liver Tissue ◽  
Specific Effect ◽  
Protein Accumulation ◽  
Regenerating Liver ◽  
Total Lipids ◽  
Tissue Contents

Effects of somatostatin (SOM) on tissue contents of proteins, total lipids and phospholipids were investigated in regenerating and intact liver tissue of Y-59 rats. Whereas SOM inhibited protein accumulation in regenerating liver, the hormone evoked and increase in total lipids, and specially in phosphatidylcholine, phosphatidylethnolamine, phosphatidylserine (PS) and phosphatidylinositol (PI). Since the same effects were not seen when intact liver was analyzed, it is assumed that SOM acts primarily on tissue stimulated to rapid growth. The increase of PS+PI fractions indicates a specific effect of SOM on the metabolism of phosphatidylinositides. Such an effect might result from the interference of the hormone with the action of growth factors that accelerate phosphatidylinositol breakdown.

Sign in / Sign up

Export Citation Format

Share Document