THE EXTRACELLULAR PROTEINS OF ACETOBACTER XYLINUM AND THEIR RELATIONSHIP TO CELLULOSE SYNTHESIS

Abstract

Proteins and dialyzable substances which also react with Folin's reagent are released from washed cells of Acetobacter xylinum immediately upon resuspension of the cells in buffer at pH 6.0. Incubation of the cells without an energy source leads to an additional gradual loss of dialyzable material and proteins from the cells to the medium. Much of the soluble protein disappears from the medium if the pH is allowed to drop below 6.0. This decrease in concentration of soluble protein is probably due to pH-dependent adsorption to the cell walls or to precipitation of the protein. The extracellular protein is grossly heterogeneous.All attempts to inhibit the final step of cellulose synthesis by depleting the extracellular proteins of the enzyme which catalyzes the formation of cellulose extracellularly, failed. This failure is attributed to the strong adsorption of soluble proteins, including the enzyme, to the cells. Use of a microassay method for cellulose confirmed the existence of the enzyme which catalyzes the synthesis of cellulose from an ethanol-soluble precursor. The properties and significance of this enzyme in relation to the celluloseless mutants of A. xylinum are described.