RELATION OF FOLIC ACID CONCENTRATION OF MEDIUM TO RIBOFLAVIN METABOLISM OF STREPTOCOCCUS FAECALIS

Abstract

The influence of folic acid on the synthesis of riboflavin and oxidation of pyruvate by S. faecalis was determined. Growing cells showed an increase in riboflavin content as the folic acid was increased. The cells with a decreased riboflavin content were inoculated into riboflavin-calcium pantothenate free medium with none or 10 [mu]g per ml of folic acid. Both calcium pantothenate and folic acid were required for growth. After 24 hours on a shaker, aliquots of the nonproliferating cells and medium were assayed microbiologically for riboflavin. Ten experiments showed a greater concentration of riboflavin in flasks containing folic acid. No increase in riboflavin in flasks on the shaker with no folic acid was shown over controls held at 4t. The O2 uptake with pyruvate of cells shaken with 10 ug per ml of folic acid averaged 35% greater than those with no folic acid. Manometric measurements were made in the presence of lipoic acid and a supplement of magnesium sulfate, thiamin, glutamic acid and adenosine as described by Gunsalus with S. faecalis 10C1. Addition of varying amounts of riboflavin to the flasks containing cells shaken with no folic acid showed an increase in O2 uptake proportional to the concentration. The data supplies further evidence for a direct relationship between folic acid and the synthesis of riboflavin. Inhibition of folic acid utilization in this organism would be accompanied by altered riboflavin metabolism.