FIG 6.

Intracellular ROS content of Δdps and Δric mutant strains and the effect of combining the Δhpx and Δric mutations on aconitase activity. (A) The E. coli wild-type and isogenic Δric, Δdps, and Δdps Δric mutant strains were grown to OD₆₀₀ of 0.6, and the intracellular ROS levels were measured by incubation of cell suspensions with 10 μM dichloro-dihydro-fluorescein diacetate (DCFH-DA) for 2 h. Fluorescence intensity was normalized according to the final OD (FI/OD). (B) Aconitase activity of the E. coli wild-type, Δric, Δhpx (ΔahpCF ΔkatE ΔkatG), and Δhpx Δric strains grown aerobically to the log phase (OD₆₀₀ = 0.6). Values are represented as normalized to the aconitase activity of wild-type cells. Values are means (±standard errors) from at least two independent cultures analyzed in duplicate. ***, P < 0.0005; ns, not significant (unpaired Student's t test).