Inhibition of oxygen utilization and destruction of ubiquinone by ultraviolet irradiation of Thiobacillus thiooxidans.

Ultraviolet (UV) irradiation inhibited sulfur oxidation by cells of Thiobacillus thiooxidans. Sulfur-oxidizing activity decreased as the exposure time to UV light increased. A loss of the ability of cells of fix CO(2) paralleled the loss of sulfur-oxidizing activity. UV light photoinactivated ubiquinone purified from T. thiooxidans. The same percentage of sulfur-oxidizing activity and ubiquinone was destroyed after 15 min of UV exposure. Both the photoinactivation of sulfur oxidation and ubiquinone followed first-order reaction kinetics. The specific rate constants for both photoinactivations were nearly equal. Cells completely inactivated by UV light contained no ubiquinone. Ubiquinone was found to be a component of the cell wall-membrane complex.