Cellulose ribbons

PF had been proposed as the terminal complex (23) and associated pores were reported on the outer membrane EF (24). Due to their proximity to the site of cellulose ribbon extrusion from the cell surface, these structures were assumed to be responsible for cellulose synthesis. A model was advanced in which cellulose synthase was localized on the outer membrane, which invoked adhesion sites between the outer and plasma membranes as a mechanism to explain the transfer of uridine-diphosphoryl-glucose (UDPG) from the cytoplasm to the cellulose synthases (25,26). However, when the outer and plasma membranes of Acetobacter were isolated separately by density-gradient centrifugation, the cellulose synthase activity was localized only in the plasma membrane fraction (27). Therefore, the linear structures observed on the Acetobacter outer membrane, while they may be associated in some manner with cellulose biosynthesis, are probably not the cellulose synthase terminal complexes. Since no ultrastructural evidence for adhesion sites between the outer and plasma membranes has been presented, a thorough investigation of the mechanism of / (1-4) glucan chain translocation from the cytoplasmic membrane to the outer membrane in Acetobacter xylinvm is now in order. 

Figure 1. Freeze-dried gel of A. xylinum cellulose ribbons deposited during normal growth. The arrows point to triple-stranded left-hand helical microfibrils averaging 36.8 3A in diameter (1). The sample was replicated with 17.3A Pt-C and backed with 90.2A of carbon. 

The model in Figure 9 predicts that each microfibril would rotate in the process of cellulose ribbon formation. If the A. xylinum cell were held stationary, then the ribbon would be left-hand twisted (2-5) however, if the ribbon were held stationary, then the cell would rotate (32). The latter case explains why ribbons appear untwisted in the pellicle of ribbons shown in Figure 1. Moreover, it has been demonstrated that an A. xylinum cell ceased rotation when Calcofluor (> 0.1 mM) was added to the solution... 

NMR) with cellulose and are probably partially trapped within cellulose ribbons (as judged by the requirement for strong alkali to release them). High molecular weight xyloglucans are able to extensively cross-link cellulose ribbons.6... 

C. Boisset, C. Fraschini, M. Schulein, B. Henrissat, and H. Chanzy, Imaging the enzymatic digestion of bacterial cellulose ribbons reveals the endo character of the cellobiohydrolase Cel6A from Humicola insolens and its mode of synergy with cellobiohydrolase Cel7A, Appl. Environ. Microbiol., 66 (2000) 1444-1452. 

Carboxymethyl Cellulose (CMC) -In vivo cellulose ribbon formation prevented normal fasciation of fibril bundles into a typical ribbon -Thinner ribbon width and smaller crystallite fibril size -Aggregates and pellicle show birefringence, and contain crossed, superimposed layers of cellulose fibrils oriented in parallel -Less resistant to stress... 

Cellulose derivatives -In vivo cellulose ribbon formation was altered... 

Haigler, C.H., White, A.R., Brown, R.M. Alteration of in vivo cellulose ribbon assembly by carboxymethylcellulose and other cellulose derivatives. J. Cell Biol. 94(1), 64-69 (1982)... 

The authors developed a unique form of i-glucan association, nematic ordered cellulose (NOC) that is molecularly ordered, yet noncrystalline. NOC has unique characteristics in particular, its surface properties provide with a function of tracks or scaffolds for regulated movements and fiber production of Acetobacter xylinum (=Gluconacetobacter xylinus), which produces cellulose ribbon-like nanofibers with 40-60 nm in width and moves due to the inverse force of the secretion of the fibers (Kondo et al. 2002). This review attempts to reveal the exclusive superstructure-property relationship in order to extend the usage of this nematic-ordered cellulose film as a functional template. In addition, this describes the other carbohydrate polymers with a variety of hierarchical nematic-ordered states at various scales, the so-called nano/micro hierarchical structures, which would allow development of new functional-ordered scaffolds. 

Figure 16-14. Successive images showing the motion of a bacterium as it secretes a cellulose ribbon using real-time video analysis. In (1), the bacterium is attached to and synthesizing its cellulose on the monomolecular rail track. In (2), the bacterium has jumped the track and is beginning to change its orientation. (3) to (5), the bacterium is generating the first complete spiral. In (6), the bacterium is on the second rotation of a spiral...

Figure 16-15. FE-SEM images of the cellulose ribbon deposition process, (a-c) examples of bacteria synthesizing cellulose ribbons on the oriented molecular track of NOC. In 15A, a bacterium shows a flat ribbon immediately behind its site of synthesis, (b) and (c) demonstrate the tight association between the molecular track and the cellulose ribbon, (d) is an example where the bacterium has just jumped off the track and following a spiral path, (e) demonstrates random cellulose deposition on the surface of a nonstretched NOC precursor. (1) shows random cellulose deposition on the surface of agar...

Acetobacter Extracellular pellicle Cellulose ribbons To keep in aerobic environment (1, 2, 8)... 

Fig. 14.1 Bacterial cellulose produced by acetic acid bacteria, (a) A pellicle produced on the surface of the culture, (b) A cellulose ribbon produced by a bacterial cell. (Modified from Tonouchi 2012)...

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