FIG. 5.

Bac8c inhibition of ATP synthesis and electron transport chain activity. (A) ATP concentration in logarithmically grown E. coli cells under normal conditions (diamonds), at the inhibitory concentration (crosses; 3 μg/ml), and the MBC (triangles; 6 μg/ml). (B) E. coli NAD⁺/NADH ratios after exposure to Bac8c (6 μg/ml) decreased as a function of time, reflecting decreased redox or electron transport. (C) The decrease in redox was a function of an increase in NADH and was concentration dependent. (D) Conditions that stimulated NAD⁺ biosynthesis also showed an increase in sublethal resistance to Bac8c. We tested the effects of supplementation with the NAD⁺ precursors nicotinamide (NAD⁺ salvage pathway), aspartate (NAD⁺ biosynthesis I), and glutamine (NAD⁺ biosynthesis I, glutamine dependent).