Growth of mixed cultures of Actinomyces viscosus and Streptococcus mutans under dual limitation of glucose and oxygen

Abstract Streptococcus mutans and Actinomyces viscosus are among the dominant species in human dental plaque. In their natural environment, carbohydrate- and oxygen-limited conditions are likely to occur frequently. Therfore, mixed cultures of the 2 species were studied under dual limitation of glucose and oxygen. Over a wide range of oxygen-supply rates, coexistence of A. viscosus and S. mutans was observed, within this range A. viscosus increased almost linearly with oxygen supply. A mathematical model based on Monod-type type kinetics and accounting for uncompetitive inhibition of growth by oxygen was developed to simulate these mixed cultures. The model predicted coexistence over a fairly large range of aeration rates. This finding, in combination with the results of the chemostat experiments, led to the conclusion that coexistence of the two species