Abstract
In low concentration iso-propylthiolsulfinic acid ester (P. S. A.), which had been ascertain-ed as a strong germistatic, prolonged the lag phase of growth-curve of E. coli.
The growth-curve test proved that P. S. A. was antagonized by neither iso-prorpyldisulfide nor P. A. B. A. When the ratio of P. S. A. and cysteine was 1:1, cysteine did not stop the bacteriostatic activity of P. S. A., but when 1:2, cysteine stopped the activity completely.
From this fact, it is considered that, P. S. A. most likely combines reversibly with active SH-radical in living body, so P. S. A. displays the growth-inhibitory effect.
Glutamic acid and aspartic acid shortened the lag time which had been prolonged by P. S. A.
