Folic acid nutrition of the minute streptococci.

The minute streptococci comprise a unique group with respect to their physiological and serological characteristics, as well as their nutritional requirements. Serologically they constitute Lancefield's serological group F and type 1, group G. The type specific antigen that defines type 1 in both serological groups appears to be identical, thus resulting in cross reactions among these streptococci between the two serological groups. Preliminary nutritional studies on the minute streptococci (Niven, Washburn, and Sheran, 1946) revealed that all the minute streptococci could be cultured in a casein hydrolyzate medium supplemented with a vitamin mixture. All strains required nicotinic acid, riboflavin, biotin, pantothenic acid, and folic acid. Thiamin and pyridoxine stimulated growth. Contrary to results with other folic acid-requiring microorganisms, the pyrimidine (thymine) failed to replace the folic acid requirement of these streptococci. This study concerns additional studies on the minute streptococci with respect to their folic acid requirements.