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.
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