FIG. 4.

Effect of arginine on catalase and SOD activities in P. aeruginosa. (A) Catalase activity in planktonic cultures grown aerobically with or without 40 mM arginine and in planktonic cultures fermenting arginine. Catalase activity is shown as units of activity per milligram of protein, where 1 U is defined as the amount which decomposes 1 μmol of H₂O₂ min⁻¹. (B) SOD activity stain of a native gel used to resolve Mn-SOD and Fe-SOD activities (50 μg of total cell protein per lane). Oxygen and iron treatments are noted above each lane. (C) Catalase activity in aerobic (●) and anaerobic (○) planktonic cultures grown in the presence of 40 mM arginine and various concentrations of added iron. For all assays, the cell extract protein concentration was determined using a Bio-Rad protein assay kit with bovine serum albumin fraction V as a standard. In panels A and C, error bars, where visible, represent ±1 standard error of the mean for three replicate cultures. Results are from one representative experiment for each treatment. Each outcome was verified to be reproducible.