Visualization of pores (export sites) correlated with cellulose production in the envelope of the gram-negative bacterium Acetobacter xylinum.

Zaar, K

doi:10.1083/jcb.80.3.773

Cited by 126 publications

(74 citation statements)

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“…The AcsC polypeptide was found to be homologous to bacterial proteins that are components of membrane channels or pores. Even though pore-like structures have been proposed for the extrusion of the cellulose microfibrils (56) (15), and ExoO (17) polypeptides were aligned using the GCG program PILEUP, and a region of conserved residues is shown. The amino acids displayed correspond to residues 151 to 241 of AcsAB, 151 to 241 of BcsA, 51 to 145 of NodC, 66 to 163 of HasA, and proteins involved in the secretion of macromolecules from bacteria suggests that the cellulose-synthesizing and extrusion complex has functions other than the polymerization of glucans.…”

Section: Resultsmentioning

confidence: 99%

“…To a large extent, these differences in the properties of cellulose may be a reflection of the organization of these complexes within the specified organism. We are interested in understanding the composition and organization of the cellulose-synthesizing complexes and how the organization of these complexes influences the assembly of the final cellulose product.The gram-negative bacterium Acetobacter xylinum synthesizes an extracellular ribbon of cellulose microfibrils from membrane-localized cellulose-synthesizing complexes (10) that are organized in a linear row along the long axis of the bacterial cell (8,56). Among the organisms known to produce cellulose, the mechanism of cellulose synthesis at present is best understood in this bacterium.…”

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“…The gram-negative bacterium Acetobacter xylinum synthesizes an extracellular ribbon of cellulose microfibrils from membrane-localized cellulose-synthesizing complexes (10) that are organized in a linear row along the long axis of the bacterial cell (8,56). Among the organisms known to produce cellulose, the mechanism of cellulose synthesis at present is best understood in this bacterium.…”

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confidence: 99%

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Characterization of genes in the cellulose-synthesizing operon (acs operon) of Acetobacter xylinum: implications for cellulose crystallization

et al. 1994

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The synthesis of an extracellular ribbon of cellulose in the bacterium Acetobacter xylinum takes place from linearly arranged, membrane-localized, cellulose-synthesizing and extrusion complexes that direct the coupled steps of polymerization and crystallization. To identify the different components involved in this process, we isolated an Acetobacter cellulose-synthesizing (acs) operon from this bacterium. Analysis of DNA sequence shows the presence of three genes in the acs operon, in which the first gene (acsAB) codes for a polypeptide with a molecular mass of 168 kDa, which was identified as the cellulose synthase. A single base change in the previously reported DNA sequence of this gene, resulting in a frameshift and synthesis of a larger protein, is described in the present paper, along with the sequences of the other two genes (acsC and acsD). The requirement of the acs operon genes for cellulose production was determined using site-determined TnphoA/ Kanr GenBlock insertion mutants. Mutant analysis showed that while the acsAB and acsC genes were essential for cellulose production in vivo, the acsD mutant produced reduced amounts of two cellulose allomorphs (cellulose I and cellulose II), suggesting that the acsD gene is involved in cellulose crystallization. The role of the acs operon genes in determining the linear array of intramembranous particles, which are believed to be sites of cellulose synthesis, was investigated for the different mutants; however, this arrangement was observed only in cells that actively produced cellulose microfibrils, suggesting that it may be influenced by the crystallization of the nascent glucan chains.Cellulose is an extracellular polysaccharide, synthesized as long f-1,4 glucan chains that associate to form the microfibrils commonly observed in cellulose-synthesizing organisms. The synthesis of this biopolymer takes place via a single polymerization step, utilizing UDP-glucose as the substrate and-catalyzed by the enzyme cellulose synthase (UDP-glucose: 1,4-p-D-glucosyltransferase), without the apparent involvement of any intermediates (40). However, the crystalline structure of cellulose microfibrils and their association with organized intramembranous particles observed in most cellulose-synthesizing organisms suggest a more intricate mechanism of cellulose biogenesis than that deduced from the polymerization reaction alone. Because of their association with cellulose microfibrils, the intramembranous particles are believed to be sites of cellulose synthesis and extrusion. The nature of these particles is incompletely understood at present, and it is not known at the molecular level how they become organized into structures that are referred to as terminal synthesizing complexes (TCs) that are characteristic for most organisms (5). In higher plants, the TC is arranged as a rosette; in a large number of algal species, the TC is arranged as a linear row(s) of particles (7). Even though the cellulose produced by all organisms chemically is the same in its primary compositi...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Characterization of genes in the cellulose-synthesizing operon (acs operon) of Acetobacter xylinum: implications for cellulose crystallization

et al. 1994

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“…CW, cross wall; CJ, circumferential junction; EL, external layer; JP, junctional pore with its counterpart in the outer membrane; OM, outer membrane; P, peptidoglycan; PS, periplasmic space; S, serrated surface of the external layer; SL, tetragonal S-layer. pearance of these outer membrane structures shows a high similarity with that of pores in Acetobacter xylinum (49), in which the pores are the export sites of cellulose fibers (1).…”

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confidence: 88%

Envelope structure of four gliding filamentous cyanobacteria

1995

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The cell walls of four gliding filamentous Oscillatoriaceae species comprising three different genera were studied by freeze substitution, freeze fracturing, and negative staining. In all species, the multilayered gramnegative cell wall is covered with a complex external double layer. The first layer is a tetragonal crystalline S-layer anchored on the outer membrane. The second array is formed by parallel, helically arranged surface fibrils with diameters of 8 to 12 nm. These fibrils have a serrated appearance in cross sections. In all cases, the orientation of the surface fibrils correlates with the sense of revolution of the filaments during gliding, i.e., clockwise in both Phormidium strains and counterclockwise in Oscillatoria princeps and Lyngbya aeruginosa. The lack of longitudinal corrugations or contractions of the surface fibrils and the identical appearances of motile and nonmotile filaments suggest that this structure plays a passive screw thread role in gliding. It is hypothesized that the necessary propulsive force is generated by shear forces between the surface fibrils and the continuing flow of secreted extracellular slime. Furthermore, the so-called junctional pores seem to be the extrusion sites of the slime. In motile cells, these pores exhibit a different staining behavior than that seen in nonmotile ones. In the former, the channels of the pores are filled with electron-dense material, whereas in the latter, the channels appear comparatively empty, highly contrasting the peptidoglycan. Finally, the presence of regular surface structures in other gliding prokaryotes is considered an indication that comparable structures are general features of the cell walls of gliding microbes.Many multicellular, filamentous cyanobacteria move on solid surfaces by a type of motility described as gliding. Gliding is not exclusive to cyanobacteria but rather is widespread among prokaryotes (for a review, see references 3 and 20). It is unknown whether gliding motility is in all cases based on a common mechanism.Gliding of the nonpolar, filamentous cyanobacteria appears as a slow uniform motion, occasionally interrupted by reversals (13). Neither wriggling nor contraction nor peristaltic alterations of the filamentous trichomes are detectable by light microscopy (38). Members of the Oscillatoriaceae translocate in a highly coordinated manner. Translational movements are accompanied in most species by revolution around the long axis of the filament (4). While moving, the trichomes secrete slime which is left behind as a twisted and collapsed thin tube (20). The sense of revolution is unique and species specific (46), as evinced by the handedness of the rotation.The lack of flagella or of other plausible locomotive organelles is puzzling. Electron microscopic studies have so far failed to identify motor structures common among gliders. A number of unusual structures have been described which may or may not be related to this peculiar type of motility. This list comprises spinning discs (37), fibrils within the ce...

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“…The most studied producer of bacterial cellulose is Acetobacter xylinum (13), a Gram-negative, obligately aerobic bacterium (10,14,15). The optimum pH for cellulose production is 5.0 (13,16), and 3 production is associated with and proportional to growth (17).…”

Section: Introductionmentioning

confidence: 99%

Production of Bacterial Cellulose from Alternate Feedstocks

Thompson

Hamilton

2001

ABAB

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SUMMARYProduction of bacterial cellulose by Acetobacter xylinum ATCC 10821 and 23770 in static cultures was tested from unamended food process effluents. Effluents included low-and high-solids potato effluents (LS & HS), cheese whey permeate (CW), and sugar beet raffinate (CSB). Strain 23770 produced 10% less cellulose from glucose than did 10821, and diverted more glucose to gluconate. Unamended HS, CW, and CSB were unsuitable for cellulose production by either strain, while LS was unsuitable for production by 10821. However, 23770 produced 17% more cellulose from LS than from glucose, indicating unamended LS could serve as a feedstock for bacterial cellulose.

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Visualization of pores (export sites) correlated with cellulose production in the envelope of the gram-negative bacterium Acetobacter xylinum.

Cited by 126 publications

References 3 publications

Characterization of genes in the cellulose-synthesizing operon (acs operon) of Acetobacter xylinum: implications for cellulose crystallization

Characterization of genes in the cellulose-synthesizing operon (acs operon) of Acetobacter xylinum: implications for cellulose crystallization

Envelope structure of four gliding filamentous cyanobacteria

Production of Bacterial Cellulose from Alternate Feedstocks

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