FIG. 2.

Catalase activity is increased in nitrate-respiring planktonic cultures of P. aeruginosa. Potassium nitrate (100 mM) was included in cultures incubated aerobically (open bars) and anaerobically (filled bars). Culture age is shown on the x axis; anaerobic cultures grew more slowly. Error bars, where visible, represent ±1 standard error of the mean for three separate cultures. Results are from one representative experiment of three independent experiments for each type of culture. 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.