GROWTH AND ACID PRODUCTION BY ORAL LACTOBACILLI IN THE PRESENCE OF VARYING AMOUNTS OF REQUIRED VITAMINS

¹ The Walter G. Zoller Memorial Dental Clinic and the Department of Bacteriology and Parasitology, University of Chicago, Chicago, Ill.

Vitamins needed for the growth of oral lactobacilli were each added in graded amounts to a basal medium of casein digest, glucose, and salts. When the amount of one needed vitamin was reduced, ample supplies of other needed vitamins and nutritive substances were present. The response of the lactobacilli was followed by measuring turbidity, pH, and titratable acid.

With allowance for some differences between individual strains, the following amounts of vitamins sufficed for maximal or practically maximal growth and acid production (about pH 4.0) under the conditions of these tests: in terms of micrograms per milliliter of medium, biotin 0.0003, nicotinic acid 0.05, calcium pantothenate 0.03-0.1, riboflavin 0.03, pteroylglutamic acid (folic acid) about 0.01, pyridoxamine hydrochloride 0.3 to 1.0, pyridoxal hydrochloride 0.03-0.3, and thiamine hydrochloride 0.01 to 0.03.

Smaller amounts of vitamins supported less growth and acid production, the response being usually in relation to the amount of vitamin supplied. In a general way, amounts of each vitamin approximately one-tenth of those specified above sufficed for attainment of about pH 5.0, except in the case of thiamine and the heterofermentative lactobacilli. Still smaller amounts supported detectable acid production.