132. Roberts, E. M., Saxena, I. M., and R. M. Brown, Jr. 1989. Biosynthesis of Cellulose II. In: Cellulose and Wood -Chemistry and Technology, Ed. C. Schuerch. John Wiley and Sons, Inc. N. Y., 689-704.

132. Synopsis

Mutants of Acetobacter xylinum that form smooth colonies on agar plates often fail to produce pellicles in stationary liquid culture. Several such mutants have been isolated and shown to produce small amounts of cellulose. X-ray diffraction of this material, isolated by cleaning with lysozyme and SDS, yields reflections consistent with cellulose II. Staining with the fluorochrome Tinopal LPW suggests that the cellulose is associated with large cell clusters (flocs). These flocs can be dispersed by treatment with cellulase. When cellulose from pellicle deficient mutants is examined by negative staining electron microscopy, it appears to be composed of mats of short rodlets about 1.5-4.5 nm wide. The morphology of these rodlets is similar to cellulose II synthesized in vitro by cell-free preparations of A. xylinum and cellulose II regenerated from solution. Preliminary data suggest that the weight-average degree of polymerization is approximately 600. Normal ribbon assembly in A. xylinum is thought to occur by a cell-directed self-assembly process. This process is disrupted in these mutants, possibly due to disorganization of some component of the cellulose synthesizing or export machinery. Organized particle rows, thought to be involved with ribbon assembly in wild-type A. xylinum cells, have not yet been observed in freeze-etch replicas of two pellicle deficient mutants that were examined.

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