Production of hydrogen peroxide by wild-type and ρ0 cells.

Cells were grown in 24-well plates. After 2 hours of incubation in normoxia (20% O_2, N) or hypoxia (1% O₂, H), an aliquot of extracellular medium was removed in which the hydrogen peroxide (H₂O₂) concentration was measured (as described in “Materials and methods”). Cells were counted after the experiments: 143B cultures contained 218 000 ± 3000 cells/well (mean ± 1 SD), 206ρ0 171 000 ± 13 000 cells/well, A549 576 000 ± 85 000 cells/well, and B2ρ0 235 000 ± 24 000 cells/well.