METABOLIC STUDIES OF A TYPE OF LACTOBACILLUS ASSOCIATED WITH CARIES

¹ Department of Microbiology, University of Colorado School of Medicine, Denver, Colo.

1. A study of the glycolytic activity of the resting cells of 10 strains of Type I and 10 strains of Type II lactobacilli showed the Type I strains to have greater glycolytic activity. The Type I strains have previously been shown to be more closely associated with caries than were Type II.

2. A study of the rate of growth and the acid production from dextrose by growing cells of 18 strains of Type I and 14 strains of Type II showed that a greater percentage of Type I strains produce larger amounts of acid and grow faster than Type II strains.

3. Very little acid was produced by resting cells of either type from sucrose or maltose.

4. Type II cells produce small but appreciable amounts of reducing sugar from sucrose in 24 hours. This is an additional property which is definitely different in the 2 types and further establishes them as 2 distinct types of lactobacillus.

5. O₂ uptake was very low for both types and no appreciable difference was seen.

6. Strains of Type I grown in media containing NaF produced less acid than the parent strains when grown in dextrose broth containing no fluoride. They also grew more slowly and the glycolytic activity of the resting cells was impaired.