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Infect Immun. 1974 December; 10(6): 1280-1291
Copyright © 1974 American Society for Microbiology. All Rights Reserved.

Degradation of Sucrose by Whole Cells and Plaque of Actinomyces naeslundii

Laboratory of Oral Microbiology, Indiana University, School of Dentistry, Indianapolis, Indiana 46202

ABSTRACT

Whole cells of Actinomyces naeslundii ATCC 12104, either in a dispersed form or in the form of plaque, enzymatically degraded sucrose to glucose and fructose. Washed whole cells expressed ß-fructofuranosidase specificity and hydrolyzed sucrose to essentially equimolar quantities of glucose and fructose. The cells readily hydrolyzed sucrose, raffinose, and Actinomyces viscosus or Aerobacter levanicum levan, but did not degrade melezitose, maltose, -methyl-D-glucoside, melibiose, glucose-1-phosphate, or dextran T-500. Sucrose degradation occurred at a temperature optimum of 37 to 45 C and at a pH optimum of 5.7 to 6.0. The K_m for sucrose was 0.05 M. Sucrose or raffinose in the growth medium resulted in cells with a specific activity that was fivefold greater than that of cells grown in medium supplemented with either glucose, fructose, maltose, lactose, or glucose and fructose, or grown in unsupplemented medium. Addition of sucrose to log-phase cells growing in glucose also increased the specific activity. Degradation of sucrose by whole cells in the form of plaque also occurred, but 6% less free fructose than free glucose was recovered. Sucrose-dependent synthesis of extracellular levan or glucan by whole cells or plaque could not be demonstrated. The ability of A. naeslundii to degrade sucrose and levan may be related to the pathogenic potential of this bacterium in plaque-associated oral diseases.