Observations on the synthesis and destruction of tyrosine by Streptococcus faecalis R

Streptococcus faecalis R when grown in a double-strength medium rendered the medium deficient in folic acid and tyrosine. The organism was found to be capable of removing approximately ten times as much folic acid from the medium during the 24-hr. incubation period as it requires for maximum growth.Although Streptococcus faecalis R achieved maximum growth in the absence of added tyrosine if pyridoxal was present in the medium, the growth response obtained in the presence of tyrosine was proportional to the amount of tyrosine added at concentrations of tyrosine greater than 10 μ./10 ml. medium.Growth of S. faecalis R in the presence but not in the absence of pyridoxal caused a tyrosine deficiency to develop in the double-strength medium.