Cellulose biogenesis: Polymerization and crystallization are coupled processes in Acetobacter xylinum

Area of Science:

• Microbiology
• Biochemistry
• Materials Science

Background:

• Acetobacter xylinum synthesizes crystalline cellulose ribbons.
• Cellulose biosynthesis involves polymerization and assembly of microfibrils.
• Optical brighteners like Calcofluor White ST interact with polysaccharides.

Purpose of the Study:

• Investigate the effect of Calcofluor White ST on Acetobacter xylinum cellulose production.
• Determine the mechanism by which Calcofluor White ST influences glucose polymerization and cellulose assembly.
• Explore the relationship between polymerization and crystallization in cellulose biogenesis.

Main Methods:

• Culturing Acetobacter xylinum cells in the presence of varying Calcofluor White ST concentrations.
• Measuring glucose polymerization rates and oxygen uptake.
• Observing changes in cellulose microfibril assembly and ribbon formation using microscopy.
• Assessing the reversibility of Calcofluor White ST effects.

Main Results:

• Calcofluor White ST significantly increased glucose polymerization rates (up to 4x) without a proportional increase in oxygen uptake.
• High concentrations of Calcofluor White ST disrupted the assembly of crystalline cellulose I microfibrils and ribbon integration.
• The observed effects were reversible upon removal or depletion of free Calcofluor White ST.
• Calcofluor White ST binds stoichiometrically to newly polymerized glucan chains, inhibiting crystallization.

Conclusions:

• Polymerization and crystallization of cellulose are coupled, cell-directed processes.
• The rate of cellulose crystallization dictates the rate of glucose polymerization.
• Maintaining the coupling between these processes is essential for the biogenesis of crystalline cellulose I.