The growth of bacteria and the production of exoglycosidic enzymes in the dental plaque of macaque monkeys.

The rate of growth of the predominant bacterial strains of plaque from the developmental grooves of first deciduous molar teeth was determined. Median doubling times were 3.32, 3.45, 2.88 and 4.54 h for streptococci, lactobacilli, actinomyces and Neisseria mucosa respectively. Withdrawal of dietary food did not greatly influence the number of bacteria found in the grooves 18 h after they had been cleaned when compared to the number in fed monkeys; exceptions were significant increases in Streptococcus mitior and N. mucosa. Addition of 0.5 per cent (w/v) glucose to the drinking water of fasted monkeys also did not influence the size of this bacterial population 18 h after cleaning, so bacteria growing in cleaned grooves must gain a major part of their nutritional needs from their immediate environment, most likely salivary constituents. The ability of oral bacteria to use the oligosaccharide side-chains of salivary glycoproteins was then explored. Exoglycosidases for the preferred anomeric linkages of the principal monosaccharide units of salivary glycoproteins were produced both by oral bacteria in vitro and by dental plaque in vivo. Thus plaque flora has the potential to degrade glycoproteins and this may explain how bacteria in the grooves grow in the absence of dietary food.