Photosynthetic and respiratory electron transport pathways of R. sphaeroides. DH, Qpool, bc1, RC, Qox, cyt c2, cyt cy, aa3-Cox, and cbb3-Cox correspond to the respiratory NADH and succinate dehydrogenases, membrane quinone pool, cyt bc1 complex, photochemical reaction center, hydroquinone oxidase, soluble electron carrier cyt c2, membrane-attached electron carrier cyt cy, aa3-type cyt c oxidase, and cbb3-type cyt c oxidase, respectively. Dotted arrows highlight the electron transfer pathways catalyzed by cyt cy. Antimycin A (Ant A) and myxothiazol (Myx) are inhibitors of the cyt bc1 complex.