Abstract
1. Thiamine-8-(methyl-6-acethyl-dihydrothioctate)-disulfide hydrochloride (TATD) showed almost the same activity as thiamine or thiamine disulfide on L. fermenti in the culture medium containing cysteine, but inhibited the growth of the organism at 10-2×1/4M. In the medium without cysteine the activity of TATD was reduced to one-tenth that of thiamine, i.e., about the same activity of thiamine disulfide but at concentrations above 10-3×1/4M TATD inhibited the growth of the bacterium.
2. TATD showed the same activity as thiamine or thiamine disulfide to Kl. apiculata. It showed no inhibitory effect at high concentrations.
3. The biological activity of TATD seems to be due to its reduction into thiamine, and the inhibitory effect to be due to the compound per se. Since this inhibition is partially recoveredby addition of thiamine, TATD seems to be competitive against thiamine.
