THIAMINE BIOSYNTHESIS FROM HYDROXYMETHYLPYRIMIDINE AND THIAZOLE BY WASHED CELLS AND CELL EXTRACTS OF ESCHERICHIA COLI AND ITS MUTANTS

1. The presence of a thiamine-sythesizing pathway from the pyrimidine and thiazole moieties in bakers' yeast was demonstrated by the washed cells and cell extracts by sonication of E. coli ATCC 9637, and the strains 70-17 and 26-43, the latter two of which were capable of growing in the presence of the pyrimidine (OMPm) or the thiazole moiety (Th) alone. 2. The thiamine-synthesizing activity was higher in the mutants than the parent strain. 3. Only the strain 70-23 strictly requires thiamine for growth, failed to synthesize thiamine from OMPm and Th, and no detectable OMPm-kinase activity was found in the cell extract. It is therefore assumed that the thiamine requirement of this mutant is due to the decrease or lack of OMPm-kinase activity.