94. Abstract
In vivo
cellulose ribbon assembly by the Gram-negative bacterium Acetobacter
xylinum can be altered by incubation in carboxymethylcellulose
(CMC), a negatively charged water-soluble cellulose derivative,
and also by incubation in a variety of neutral, water-soluble
cellulose derivatives. In the presence of all of these substituted
celluloses, normal fasciation of microfibril bundles to form the
typical twisting ribbon is prevented. Alteration of ribbon assembly
is most extensive in the presence of CMC, which often induces
synthesis of separate, intertwining bundles of microfibrils.
Freeze-etch preparations of the bacterial outer membrane suggest
that particles that are thought to be associated with cellulose
synthesis or extrusion may be specifically organized to mediate
synthesis of microfibril bundles. These data support the previous
hypothesis that the cellulose ribbon of A. xylinum is formed
by a hierarchical, cell-directed, self-assembly process. The
relationship of these results to the regulation of cellulose microfibril
size and wall extensibility in plant cell walls is discussed.