Abstract
It has been demonstrated that Acetobacter suboxydans requires p-aminobenzoic acid as a growth essential. 1 The p-aminobenzoic acid requirement of this organism forms the basis of a microbiological method for its determination. 2
We have observed that when the casein hydrolysate employed in the basal medium for the above assay method is treated with Darco G-60 charcoal (10% of weight of casein) at pH 2.5 for one half hour, growth response to lower concentrations of p-aminobenzoic acid is variable and generally subnormal. Of a variety of compounds examined for ability to increase growth at lower concentrations of p-aminobenzoic acid the purine bases∗ adenine, guanine, and xanthine were found to be effective. Not only was the quantity of growth increased, but the sensitivity of the Acetobacter response to p-aminobenzoic acid was increased considerably. While in the absence of purines the test organism responds to 0.01 μ of p-aminobenzoic acid, the presence of purines brings about readily measurable growth with 0.001 μ per culture. The purines are without effect in the absence of p-aminobenzoic acid or when p-aminobenzoic acid is supplied in amounts above 0.03 μ per culture, indicating that they are not essential for growth but act instead as growth accessories.†
The results of a typical experiment are given in Table I.
Adenine possesses the greatest activity and 150 /xg per culture can generally replace the combination of the 3 purines. Results with the 3 bases have, however, been more uniform and in the absence of detailed information on the purine requirements of this organism it seems desirable to employ all 3 purines. Hypo-xanthine was not available for test. The pyrimidine base uracil exerted no effect on growth under these test conditions.
Parallel assays on bacterial extracts with and without purines in the basal medium yielded values in agreement within ±15%.
Get full access to this article
View all access options for this article.