Figure 7.

Calculated inhibition of Luc⁺⁺ luminescence as a function of [SOD] expressed in terms of biological units. One biological unit is defined as that concentration of SOD within E. coli which will cause 50% inhibition of Luc⁺⁺ luminescence. The curve was generated using the expression % inhibition = (n/n + 1)100, where n is the number of biological units of SOD. The sodA sodB strain was taken to contain no SOD since the CuZnSOD is present in ≈2% (29) the amount of SOD A plus SOD B and moreover is periplasmic (30). The positions of the other strains of E. coli are indicated on the assumptions that the single mutants contain ≈1/2 concentration of SOD contained in the parental strain and that the SOD B overproducer contains ≈5 times the [SOD] of the parental strain.