scholarly journals SYNTHESIS OF CELLULOSE BY ACETOBACTER XYLINUM

1965 ◽  
Vol 25 (2) ◽  
pp. 191-207 ◽  
Author(s):  
G. Ben-Hayyim ◽  
I. Ohad
Keyword(s):  
Plant Cell Wall ◽  
Extracellular Enzymes ◽  
Relative Concentration ◽  
Acetobacter Xylinum ◽  
Cell Suspensions ◽  
Uridine Diphosphate ◽  
Whole Cells ◽  
Cellulose Fibrils ◽  
Carboxylic Groups ◽  
Diphosphate Glucose

The transfer of the glucosyl moiety from uridine diphosphate glucose in the presence of Acetobacter xylinum cell-free extracts led to the formation of a mixture of alkali-soluble and -insoluble cellodextrins. Typical cellulose fibrils could not be detected by electron microscopy in this product. Immediately after release into the medium, cellulose formed by whole cells is in a "prefibrous" form which passes through Millipore filters of 0.45 and 0.8 µ pore diameter. Non-filtrable fibrils arise from this material probably by a process of crystallization involving no extracellular enzymes. Fibrils formed in shaken cell suspensions intertwine and form aggregates visible to the naked eye. In quiet suspensions pellicles are formed which float on the surface. Soluble Na-carboxymethylcellulose (CMC) is incorporated into cellulose fibrils formed in its presence, probably by a process of co-crystallization. Aggregation of fibrils containing CMC is delayed because of electrostatic repulsion between carboxylic groups. The aggregation time depends on the amount of CMC incorporated, its degree of substitution, the pH of the medium, and the ionic strength. The amount of CMC incorporated depends on the relative concentration CMC/cellulose and on the similarity of the CMC and the cellulose molecules i.e. in molecular weight and the number of carboxyl substitutions. Cellulose pellicles formed in the presence of CMC by unshaken cell suspensions consist of crossed, superimposed layers of parallel oriented cellulose fibrils. The same phenomenon is observed when phosphomannan, but not levan, is substituted for CMC. The biogenesis of oriented cellulose fibrils is envisaged as a process comprising the following steps: polymerization of the monomeric precursor, diffusion of the molecule to crystallization sites, crystallization, and orientation. It is proposed that charged polysaccharides play a role similar to that of CMC in affecting the orientation of cellulose fibrils in the plant cell wall.

scholarly journals ULTRASTRUCTURAL STUDY OF MEMBRANE-BOUND ENZYMES IN THYMOCYTES

1974 ◽  
Vol 22 (12) ◽  
pp. 1128-1134 ◽  
Author(s):  
ARIANE MONNERON ◽  
JEAN-CLAUDE BENICHOU ◽  
INSTITUT PASTEUR ◽  
YVETTE FLORENTIN ◽  
ELIANE GUERRY
Keyword(s):  
Plasma Membrane ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Uridine Diphosphate ◽  
Lead Phosphate ◽  
Isolated Nuclei ◽  
Whole Cells ◽  
Diphosphate Glucose ◽  
Membrane Bound ◽  
Membrane Bound Enzymes ◽  
Phosphate Deposits

Calf thymocytes in suspension, as well as isolated calf thymocyte nuclei, were incubated in the presence of several phosphorylated substrates. 5'-Nucleotidase was easily detected on the plasma membrane of thymocytes (external side), but could be demonstrated on isolated nuclei only to a small extent. No other substrates were detectably hydrolyzed by isolated nuclei except adenosine triphosphate and 3'-thymidine monophosphate. The surface of whole cells was found to be much more reactive. A 3'-nucleotidase activity was shown to occur on the plasma membrane of a number of thymocytes and produced large lead phosphate deposits, some of them protruding into the cytoplasm. Enzymic activities splitting β-nicotinamide adenine dinucleotide phosphate and uridine diphosphate glucose were also readily detectable on the surface of cells. Since the pattern of the lead phosphate deposits and the number of reactive cells varied with the added substrate, and since cells were compared with their isolated nuclei, the positive reactions were considered to indicate the presence (on the exposed membranes) of the corresponding enzymes on the exposed membranes.

EXTRACELLULAR GLUCOSE-1-PHOSPHATE IN ACETOBACTER XYLINUM AND ITS ROLE IN CELLULOSE SYNTHESIS

1961 ◽  
Vol 39 (3) ◽  
pp. 493-497 ◽  
Author(s):  
J. Ross Colvin ◽  
S. M. Martin ◽  
G. G. Dearing
Keyword(s):  
Glucose Metabolism ◽  
Cell Membrane ◽  
Degradation Product ◽  
Complex Molecule ◽  
Acetobacter Xylinum ◽  
Cellulose Synthesis ◽  
Uridine Diphosphate ◽  
Extracellular Glucose ◽  
Diphosphate Glucose ◽  
Bacterial Cell Membrane

Extracellular glucose-1-phosphate (G-1-P) was identified and isolated from suspensions of intact, washed, glucose-metabolizing cells of Acetobacter xylinum. The presence of this extracellular hexose phosphate was closely correlated with active glucose metabolism of the cells but the compound was not the immediate precursor of bacterial cellulose. The extracellular G-1-P was not a degradation product of uridine diphosphate glucose but could have been a fragment of a still larger, more complex molecule. Possible modes of transport of the ester across the bacterial cell membrane are discussed.

The structure of cellulose-producing bacteria, Acetobacter xylinum and Acetobacter acetigenus

1977 ◽  
Vol 23 (6) ◽  
pp. 790-797 ◽  
Author(s):  
J. Ross Colvin ◽  
L. C. Sowden ◽  
Gary G. Leppard
Keyword(s):  
Cell Envelope ◽  
Acetobacter Xylinum ◽  
Cell Suspensions ◽  
Thin Sections ◽  
Quiescent Cells ◽  
Transmission Electron ◽  
Cellulose Fibrils ◽  
Surface Irregularities ◽  
Whole Mounts ◽  
Thin Cell Wall

The structure of the pellicles and cells of the cellulose-producing bacteria, Acetobacter xylinum and Acetobacter acetigenus, was studied by transmission electron microscopy of thin sections and freeze-etch replicas of glucose-stimulated cell suspensions, quiescent cell suspensions, and discrete pellicles. These bacteria have a relatively thin cell wall in section, with several irregular features superimposed on an otherwise simple, Gram-negative morphology. There are no flagella or pili. Unfixed, unextracted cells, viewed as whole mounts, show spherical or ellipsoidal bodies of undetermined composition which disappear after extraction with water or ethanol and propylene oxide. For both species, there are several kinds of cell surface irregularities, some of which are localized protrusions of the cell envelope. A variety of irregularities is seen frequently on cells in the first minutes of glucose incubation, on cells in a discrete pellicle, on quiescent cells, and on starved cells. Immediately after the addition of glucose to cellulose-free cells in suspension culture, fine fibrils appear on and (or) near the cell envelope. The fine fibrils are frequently as small as 3 nm in diameter in both freeze-etch and thin-section preparations and are frequently associated with freshly synthesized cellulose fibrils. Starved cells in suspensions free of (classical) microfibrils sometimes reveal stubs of an extracellular structure whose morphology resembles that of a nascent cellulose fibril.

scholarly journals Uridine Diphosphate Glucose in Cellulose Forming Cultures of Acetobacter xylinum.

1964 ◽  
Vol 18 ◽  
pp. 834-835 ◽  
Author(s):  
Bent Stig Enevoldsen ◽  
Raimo Raunio ◽  
Annikki Kari ◽  
Hans Halvarson ◽  
Lennart Nilsson
Keyword(s):  
Acetobacter Xylinum ◽  
Uridine Diphosphate ◽  
Uridine Diphosphate Glucose ◽  
Diphosphate Glucose

scholarly journals Half-sites oxidation of bovine liver uridine diphosphate glucose dehydrogenase

1978 ◽  
Vol 173 (2) ◽  
pp. 701-704 ◽  
Author(s):  
J S Franzen ◽  
P Marchetti ◽  
R Ishman ◽  
J Ashcom
Keyword(s):  
Catalytic Activity ◽  
Glucose Dehydrogenase ◽  
Bovine Liver ◽  
Thiol Group ◽  
Catalytic Site ◽  
Uridine Diphosphate ◽  
Thiol Groups ◽  
Irreversible Denaturation ◽  
Diphosphate Glucose ◽  
Uridine Diphosphate Glucose Dehydrogenase

6,6-Dithiodinicotinate shows half-of-the-sites reactivity towards the six catalytic-site thiol groups of bovine liver UDP-glucose dehydrogenase. The reagent introduces three intrasubunit disulphide linkages between catalytic-site thiol groups and non-catalytic-site thiol groups and abrogates 60% of the catalytic activity of the hexameric enzyme; excess 2-mercaptoethanol rapidly restores full catalytic activity. These results show the half-of-the-sites behaviour of the enzyme with the reagent and the presence of a non-catalytic-site thiol group capable of forming a disulphide linkage with a catalytic-site thiol group on the same subunit without irreversible denaturation.

THE EFFECT OF BACTERIAL CELL LYSIS AND OF PLANT EXTRACTS ON CELLULOSE PRODUCTION BY ACETOBACTER XYLINUM

1963 ◽  
Vol 41 (1) ◽  
pp. 1691-1702 ◽  
Author(s):  
T. E. Webb ◽  
J. Ross Colvin
Keyword(s):  
Bacterial Cell ◽  
Cell Envelope ◽  
Acetobacter Xylinum ◽  
Cellulose Synthesis ◽  
Additive Effects ◽  
Cellulose Production ◽  
Whole Cells ◽  
Negative Results ◽  
Heat Stable ◽  
Plant Sources

The production of cellulose by lysozyme lysates of Acetobacter xylinum is similar to that of a suspension of whole cells, in contrast to the negative results obtained with previous "cell-free" preparations. The results of differential centrifugation of these lysates suggests that most of the enzymes required for cellulose synthesis from glucose normally are held by the cell envelope and are not located in the cytoplasm. However, a heat-stable cofactor(s) is present in the supernatant derived from the cell contents which may stimulate cellulose synthesis by the cell envelopes.The addition of extracts from a number of plant sources increased cellulose synthesis by whole cells of A. xylinum. In particular, the supernatant prepared by centrifugation of an homogenate of tomatoes increased bacterial cellulose production at pH 6 by a factor of 3. Both dialyzable and non-dialyzable substances in the extract are responsible. Fractionation of the non-dialyzable portion of the extract by column chromatography suggests that the overall increase is due to additive effects of several compounds. Here also the compounds appear to act upon the bacterial cell envelope.

scholarly journals Studies on glycogen synthesis in pigeon liver homogenates. Glycogen synthesis from glucose monophosphates and uridine diphosphate glucose

1967 ◽  
Vol 105 (2) ◽  
pp. 515-519 ◽  
Author(s):  
V. N. Nigam
Keyword(s):  
Time Course ◽  
Initial Rate ◽  
Glycogen Synthesis ◽  
Uridine Diphosphate ◽  
Cytoplasmic Fraction ◽  
Uridine Diphosphate Glucose ◽  
Diphosphate Glucose ◽  
Liver Homogenates ◽  
Pigeon Liver ◽  
Glycogen Formation

Comparative time-course studies of glycogen synthesis from glucose 6-phosphate, glucose 1-phosphate and UDP-glucose show that glucose 1-phosphate forms glycogen at an initial rate faster than that obtained with glucose 6-phosphate and UDP-glucose. After 5min. the rates from glucose monophosphates are considerably slower. 2,4-Dinitrophenol decreases glycogen synthesis from both glucose monophosphates, whereas arsenate and EDTA increase glycogen synthesis from glucose 1-phosphate and inhibit the reaction from glucose 6-phosphate, galactose and galactose 1-phosphate. Mitochondria-free pigeon liver cytoplasmic fraction forms less glycogen from glucose monophosphates than does the whole homogenate. 2-Deoxyglucose 6-phosphate inhibits glycogen synthesis from glucose monophosphates. Glycogen formation from UDP-glucose is relatively unaffected by dinitrophenol, by arsenate, by EDTA, by 2-deoxyglucose 6-phosphate and by the removal of mitochondria from the whole homogenate.

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