THE EFFECTS OF DECYL AURACHIN-C AND AURACHIN-D ON THE RESPIRATORY ELECTRON FLOW OF FACULTATIVE PHOTOTROPHIC BACTERIA

Decyl aurachins C and D are two synthetic compounds related to the nat ural products aurachins C and D extracted from Stigmatella aurantiaca. Titrations of a range of partial respiratory activities in membranes from facultative phototrophs indicate that decyl aurachin C is more ef fective than aurachin D in inhibiting the quinol oxidase. Decyl aurach in C also affects the NADH-ubiquinone oxidoreductase of Rhodobacter ca psulatus and the cytochrome be, complexes of Rb. capsulatus and Rhodos pirillum centenum. Titration of the light-induced respiration in Rsp.c entenum allowed us to estimate an upper limit for the ubiquinol oxidas e concentration of 1.5+/-0.2 nmol/mg protein, or a ubiquinol oxidase/c ytochrome c oxidase ratio of 3:1.