Regulation of the Proteinase Production in Two Strains of Aeromonas

Cultures of Aeromonas liquefuciens' and Aeromonas salmonicida, grown in a basic salt medium, were examined for proteinase production after the addition to the medium of simple compounds, such as amino acids and sugars, and after the addition of compounds of higher molecular weight, such as casein, trypsinised casein, peptone, neopeptone and gelatin. Ae. liquejaciens grew in the basic medium, without any proteinase production, but it was possible to induce the production of proteinases by raising the pH from the original 6.2 to above 7.0 prior to the addition of arginine, asparagine, histidine, monosodium glutamate and, particularly by the addition of the higher molecular weight compounds. Growth of Ae. salmonicida could not be induced by the addition of amino acids, and proteinase production was dependent on the presence of higher molecular weight compounds. In addition a distinct difference wis demonstrated between casein on one hand, and trypsinised casein, neopeptone and gelatin on the other, in that casein inhibited the proteinase production while the others were potent inducers. Gelatin was particular in that it only induced the production of proteinase B of the two known proteinases (A and B) of Ae. liquefaciens. In using these inducable proteinases for taxonomical purposes it‐ is recommended that the examinations be performed in defined media under standard conditions as far as pH, incubation temperature and incubation time are concerned.