Figure 5.

The absorbance of the reduced cytochrome in intact L. ferrooxidans correlates with the absorbance of ferric ions produced during aerobic respiration on soluble iron. (A) Time courses of the absorbance changes at 355 and 443 nm obtained when 2.1 × 10⁹ cells of L. ferrooxidans were mixed with 100 μM ferrous sulfate in sulfuric acid, pH 1.7. (B) Schematic representation of the kinetic mechanism for aerobic respiration on soluble iron as catalyzed by intact L. ferrooxidans. The cross-hatched and solid rods represent bacteria that contain oxidized and iron-reduced cytochromes, respectively. (C) Dependence of the velocity of the absorbance change at 355 nm on the concentration of ferrous ions that remain in solution. (D) Dependence of the velocity of the absorbance changes at 355 nm on the difference in absorbance values at 443 nm, representing the value at 1.0 s minus the value at time t.