Abstract
Summary
Bioautographs of several 4-amino analogues of folic acid indicated the presence of contaminants which corresponded to the demethylated, deaminated, or pteroic acid analogues. All the antagonists studied contained sufficient pteroylglutamic acid or pteroic acid to account for their apparent utilization for growth by an antagonist-resistant strain of Streptococcus faecalis. This strain had a lower requirement for PGA and pteroic acid and a much greater capacity to convert PGA to CF than did the parent antagonist-sensitive strain. Significant inhibition of the formation of CF from PGA by the resistant cells was obtained only with very high concentrations of Aminopterin or A-methopterin.
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