INVOLVEMENT OF THE OXIDATIVE PENTOSE-PHOSPHATE PATHWAY IN THIAMINE BIOSYNTHESIS IN SALMONELLA-TYPHIMURIUM

purF mutants of Salmonella typhimurium are known to require a source o f both purine and thiamine; however, exogenous pantothenate may be sub stituted for the thiamine requirement. We show here that the effect of pantothenate is prevented by blocks in the oxidative pentose phosphat e pathway, gnd (encoding gluconate 6-phosphate [6-P] dehydrogenase) or zwf (encoding glucose 6-P dehydrogenase), We further show that the de fects caused by these mutations can be overcome by increasing ribose 5 -P, suggesting that ribose 5-P may play a role in the ability of panto thenate to substitute for thiamine.