FIG. 5.

Effect of various sublethal H₂O₂ concentrations on the ATP content of S. pneumoniae. Strain D39 (wild type), P878 (spxB mutant), and P1221 (spxB complemented) were incubated at 37°C in TH+Y or TH+Y containing the indicated concentrations of H₂O₂. After 15 min, the ATP content of D39 (░⃞), P878 (□), or P1221 (▨) were assayed (see Materials and Methods). Values represent the change in ATP level corrected for colony counts and are expressed as a percentage of the control culture containing no H₂O₂. Values are the average of four independent determinations in duplicate ± the SD. ✽, P < 0.05; ✽✽, P < 0.005.