84. Abstract
Calcofluor White ST, a stilbene derivative
used commercially as an optical brightener for cellulose, increased
the rate of glucose polymerization into cellulose by resting cells
of the gram-negative bacterium Acetobacter xylinum. This
bacterium normally produces a ribbon of cellulose that is a composite
of crystalline microfibrils. In concentrations above 0.1 mM,
Calcofluor disrupts the assembly of crystalline cellulose I microfibrils
and their integration into a composite ribbon by stoichiometric
binding to glucose residues of newly polymerized glucan chains.
Under these conditions, the rate of glucose polymerization increases
up to 4 times the control rate, whereas oxygen uptake increases
only 10-15%. These observed effects are readily reversible.
If free Calcofluor is washed away or depleted below the threshold
value by binding to cellulose as polymerization continues, ribbon
production and the normal rate of polymerization resume. It is
concluded that polymerization and crystallization are cell-directed,
coupled processes and that the rate of crystallization determines
the rate of polymerization. It is suggested that coupling must
be maintained for biogenesis of crystalline cellulose I.