Effect of Near-Ultraviolet Light on the Respiratory Chain of Escherichia coli

Abstract

Irradiation of a particulate fraction from E. coli with near-ultraviolet light destroyed NADH oxidase activity. This treatment did not affect markedly the levels of cytochromes b1 and o, and ubiquinone in this preparation. Cytochrome a2 was destroyed by irradiation. A progressive increase in the aerobic steady state level of cytochrome b1 reduction during irradiation confirmed that irradiation affected the cytochrome oxidase region of the respiratory chain. There was a second site of inactivation between substrate and cytochrome b1. This was indicated by lowered NADH:cytochrome b1 reductase activity. Partial reactivation of this activity was obtained by addition of ubiqumone-2 but not ubiquinone-8.