p-Hydroxybenzoic Acid: a New Bacterial Vitamin

Abstract

MUTANT 83-1 of Escherichia coli, isolated by the penicillin method¹, is blocked at an early stage in aromatic synthesis; it responds to a quadruple supplement of tyrosine, phenylalanine, tryptophane and p-aminobenzoic acid. Whereas the quantitative requirements for the three amino-acids are similar to those of mutants with single requirements for these compounds, growth is very slow with 0.005 µgm./ml. of p-aminobenzoic acid, a concentration sufficient for optimal growth of a mutant blocked specifically in p-aminobenzoic acid synthesis. Higher concentrations of the acid, up to 1 µgm./ml., provide more rapid, yet less than normal, growth of mutant 83-1. Normal growth-rate, however, appears with the addition of shikimic acid (a 2,3,4,5-tetrahydrogallic acid).