The oxygen consumption rate is higher in the H. seropedicae fnr mutant strains. (A) Gas phase oxygen consumption in H. seropedicae SmR1 and fnr mutant strains. (B) Consumption of dissolved oxygen in liquid media of H. seropedicae strains SmR1 (black squares) and MB231 (grey circles) using a clark-type electrode. The arrow indicates addition of 100 μL of cells into the electrode chamber containing 1.6 ml of NfbHP-Malate supplemented with 5.0 mM of ammonium chloride. The inset shows the specific oxygen uptake rate (given as μmolar O2.mg protein.min−1) in liquid cultures, which was calculated considering the oxygen solubility in water as 233 μM . The asterisks indicate statistical significance according to the Student’s T-test (P < 0.05), derived from two independent experiments.