Growth inhibitory action of some quaternary ammonium-type detergents against baker's yeast was examined. Both lauryldimethylbenzyl ammonium chloride (L-Bz) and laurydimethyl-(3-chloro-2-hydroxypropyl) ammonium chloride (L-Ep) inhibited growth of the cells in the logarithmic phase of multiplication, and pH-growth inhibition curve similar to those well established in other cationic detergents was obtained. Supplementation of nitrogenous compounds, such as urea, L-aspartic acid, L-glutamic acid, casamino acid, pyrimidines, and purines, showed no significant effect on the inhibitory activity of the detergents. Exposure of the resting cells to the detergents at concentrations of 10
-5M to 10
-4M for 3 hr resulted in a progressive increase in the elution of 260 mμ-absorbing materials from the cells, as the detergent concentration increased, but its extent was reduced at a concentration of 10
-3M of the detergents. The yeast grown in the medium containing Bz-type detergents (L-Bz and cetyldimethylbenzylammonium chloride) at a concentration sufficient to inhibit the growth was found to contain more acid-soluble 260mμ-absorbing materials (per protein) as compared with the control cells, whereas in the case of Ep-type detergents (L-Ep and cetyldimethyl-3-chloro-2-hydroxypropyl ammonium chloride) little effect was observed. The syntheses of nucleic acids and protein in the growing cells were inhibited to approximately the same extent by the detergents tested.
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