FIG 1.

Loss of viability of E. coli optA1 gpt double mutants during dGTP starvation. Control (wt), optA1, gpt, and optA1 gpt strains were grown exponentially in minimal medium containing hypoxanthine (see Materials and Methods) to an OD₆₃₀ of 0.1 and then diluted 10-fold, to an OD₆₃₀ of 0.01, in medium with Hx (open symbols) and without Hx (closed symbols). Viability was assessed every 30 min for the next 6 h. Periodic dilutions were performed to keep the OD₆₃₀ at 0.1 or less (50-fold dilution of all cultures at 120 min and 25-fold dilution at 270 min, except for the optA1 gpt strain grown without Hx). Symbols: circles, wt; squares, optA1 strain; triangles, gpt strain; diamonds, optA1 gpt strain.