Exposure to tellurite in aerobically grown E. coli causes a loss of the transmembrane proton gradient leading to depletion of intracellular ATP . Therefore, we predicted that ATP levels in our experiments might be decreased. As expected, this was observed for E1, E4(1), RB3, and RB 16-17 (35.9%, 31.9%, 55.9%, and 48.8% decrease per unit protein, respectively) (Figure 1D). However, unexpectedly, E5 and KR99 cells produced higher levels of ATP in the presence of tellurite (38.9% and 15.2% increase, respectively) (Figure 1C). For these two strains, an increase was measured in both protein and ATP, and for E1, E4(1), RB3, and RB 16-17 a decrease in each case.