Figure 3.

Trimethoprim treatment in minimal media leads to hierarchical depletion of folate-dependent metabolites. When drug-induced glycine starvation is prevented by addition of exogenous glycine, the first intracellular pool to be depleted is that of purines (ATP). Supplementation with both glycine and inosine (a purine source) leads to rapid methionine depletion. When glycine, inosine, and methionine are all supplemented, dTTP depletes much more rapidly, in which case cells die instead of simply not growing. In cases of exogenous glycine and/or methionine addition, glycine and methionine levels are not reported because intracellular pools could not be differentiated from extracellular pools. Error bars show ±1 SE of the mean (n ≥ 2 independent experiments).