Inhibition of Methionine Synthesis in Escherichia coli by 2-Chloro-4-Aminobenzoic Acid and Sulfanilamide

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Abstract
Inhibition by 2-chloro-4-amino-benzoic acid (I) and by sul-fanilamide (II) of methionine synthesis by E. coli in a glu-cose-asparagine-iuorganic salt medium (pH 7), studied without duplicate tests, apparently showed that, since the ratio of bacteriostatic concs. of I/II for a II-resistant strain was the same as that for the parent strain (though with 10-fold greater absolute values) and because a I-resistant strain was actually more sensitive to II than was the parent strain, I-resistance is not a true sulfonamide resistance. Bacterio-stasis by I is completely reversed by methionine whereas that of II is partially reversed. Because, in the presence of methionine, a greater conc. of II was required to cause a. half-maximum growth of a I-resistant strain of E. coli than when no methionine was present, it is concluded that this strain cannot synthesize methionine in the presence of II and that II must inhibit a methionine synthesis mechanism not affected by I. -J. O. Thomas.