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The biogenesis of native cellulose is a complex process requiring the biosynthesis of high-molecular-weight β 1,4-glucans; the formation of highly crystalline, metastable cellulose I microfibrils; and, in many cases, the organization and orientation of these microfibrils into cell walls (Colvin, 1964). Proposed mechanisms of cellulose biogenesis have historically been intimately related to the contemporary understanding of the physical structure of cellulose (Ranby, 1952; Preston, 1964). It is evident that any proposed mechanism of cellulose biogenesis must be consistent with the ultimate physical properties of the macromolecule. Since almost all native cellulose is fibrillar cellulose I, it is probable that there is a common biosynthetic mechanism among all organisms that produce crystalline cellulose I microfibrils (Sarko and Muggli, 1974).

A novel C35 terpene and its monounsaturated analogue were isolated from cultures of Acetobacter xylinum, together with traces of their C36 homologues. These substances were found to be hopane derivatives substituted by a five-carbon chain bearing four vicinal hydroxyl groups. For the parent hydrocarbon the term bacteriohopane is proposed. The elucidation of the structures utilized high-resolution mass spectrometry of the terpenes, degradation to C32 hydrocarbons and detailed mass-spectrometric comparison of these with C32 hydrocarbons synthesized from known pentacyclic triterpenes. High-resolution mass-spectral data of the terpenes are presented. N.m.r. data are in agreement with the proposed structures, which are further supported by the isolation from the same organism of 22-hydroxyhopane and derivative hopene(s).

Some lipids, particularly diglycerides, cholesterol, or cholesterol derivatives, are able to induce visible birefringence in pellicles of extracellular bacterial cellulose produced by Acetobacter xylinum when they are added in small amounts to the surface of cultures. This birefringence is due to orientation of a fraction of the cellulose microfibrils, not the cells, in the pellicle. Orientation may begin with small microscopic domains which are present in pellicles of untreated cultures and some of which may overgrow others under the influence of a lipid. How the lipids induce alignment of the microfibrils in the bacterial culture is unknown but the process appears to involve an interaction between newly formed extracellular microfibrils and the microcrystalline surface of the lipid.

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 oxidation of malate to oxaloacetate in A. xylinum has been shown to be irreversible. It is catalyzed by a FAD flavoprotein which is not affected by high concentrations of oxaloacetate and is linked to the cytochrome chain by a vitamin K-like compound ( Benziman and Abeliovitz, 1964 ; Benziman and Galenter, 1964 ; Benziman and Perez, 1965 ). In the present communication it is shown that cell-free extracts of A. xylinum couple ATP formation with malate oxidation. The properties of this phosphorylation system are compared to the phosphorylation associated with the oxidation of other substrates by such extracts.

In general, biodegradability of a material decreases with an increase in its mechanical strength. Bacterial cellulose (BC) produced by Acetobacter xylinum (A. xylinum) is a very unique and interesting material, since it has naturally both high mechanical strength and biodegradability. We have succeeded in preparing an incorporated BC (BC composite) with water-soluble polymer, such as carboxymethyl cellulose (CMC) or methyl cellulose (MC) by adding water-soluble polymer into the standard medium of A. xylinum. Young's modulus of BC composites was about 1 - 3 times that of normal BC (30 - 40 GPa) and BC composites were almost degraded in soil after 28 days as well as normal BC. This preparation method has been applied to synthesize a new type of BC having both high biodegradability and other functions.

The change in the fine structure of the cellulose gel biosynthesized by Acetobacter zylinum with time was studied by means of electron microscopy. It was found that in the process of time, the inhomogeneous distribution cellulose chain arised in the vertical direction against the long axis of the amorphous fibril initially and finally many microscopic fibrils with the width of about 40∼50 A appeared simultaneously in the amorphous fibril. This microscopic fibril corresponds to the elementary fibril reported in the previous paper. It was also found that the bacterial cellulose microfibril is composed of the microscopic fibril.

The architecture of cellulose pellicles produced by the bacterium Acetobacter xylinum was observed using a scanning electron microscope. The existence of tunnels with regular orientation argues for some kind of coordination during the pellicle formation and against a random formation of cellulose microfibrils.

(1986). Occurrence of Free Ceramide in Acetobacter xylinum. Agricultural and Biological Chemistry: Vol. 50, No. 11, pp. 2949-2950.

FORMATION of bacterial cellulose in cell-free fractions of homogenates of Acetobacter xylinum, supplemented by either adenosine triphosphate1,2 or uridine diphosphoglucose3, has recently been reported. Such homogenate fractions are necessarily complex, and unequivocal identification of the immediate precursor of cellulose might be easier if a cell-free extract of cultures of this bacterium, which retains the capacity to form cellulose, could be prepared. This communication describes the preparation of such an extract.

CELLS of Acetobacter xylinum are known to produce cellulose. This synthesis has been demonstrated in resting fresh and lyophilized cells1,2. Enzymic synthesis of cellulose by preparations from A. xylinum has been shown with the aid of tracer techniques3,4 and electronmicrography5.

IT has been demonstrated both by electron ray and by ordinary and polarized light microscopy that the cellulose cell-wall of green plants has a fibrillar structure1,2. Since bacterial cellulose (Acetobacter xylinum zooglea) and animal cellulose (tunicin) may be assumed to be formed in conditions which differ radically from those which govern cell-wall deposition in green plants, it appeared to be of interest to investigate the microscopic structure of these natural cellulose membranes.

The goal of this study was to investigate the feasibility of bacterial cellulose (BC) scaffold to support osteoblast growth and bone formation. BC was produced by culturing Acetobacter xylinum supplemented with hydroxyapatite (HA) to form BC membranes (without HA) and BC/HA membranes. Membranes were subjected to X-ray photoelectron spectroscopy (XPS) analysis to determine surface element composition. The membranes were further used to evaluate osteoblast growth, alkaline phosphatase activity and bone nodule formation. BC was free of calcium and phosphate. However, XPS analysis revealed the presence of both calcium (10%) and phosphate (10%) at the surface of the BC/HA membrane. Osteoblast culture showed that BC alone was non-toxic and could sustain osteoblast adhesion. Furthermore, osteoblast adhesion and growth were significantly (p ≤0.05) increased on BC/HA membranes as compared to BC alone. Both BC and BC/HA membranes improved osteoconductivity, as confirmed by the level of alkaline phosphatase (ALP) activity that increased from 2.5 mM with BC alone to 5.3 mM with BC/HA. BC/HA membranes also showed greater nodule formation and mineralization than the BC membrane alone. This was confirmed by Alizarin red staining (ARS) and energy dispersive X-ray spectroscopy (EDX). This work demonstrates that both BC and BC/HA may be useful in bone tissue engineering.