Influence of iron deficiency on the cytochromes of Rhodopseudomonas spheroides.

Abstract

Rhodopseudomonas spheroides Y cells were grown photosynthetically in a denned medium supplemented with either a limiting amount of iron or with an excess of iron. Soluble and bound cytochromes were determined in both cases.The composition of the soluble cytochromes was not altered qualitatively by iron deficiency. In both culture conditions, a number of cytochromes were isolated by chromatography and purified to various extents: cytochromes c‐550 (c2 type), c′, c‐551, c‐552, and b‐559. In normal cells cytochrome c2, and to a lesser extent cytochrome c′ predominated whereas the amounts of both were greatly lowered in iron deficiency.Bound cytochromes were detected by difference spectroscopy of particles after chemically or light‐induced oxidoreductions. When iron was not limiting, cells were also grown in presence of diphenylamine, which inhibited carotenoid synthesis and facilitated detection of cytochromes. Particles from those cells, as well as particles from uninhibited cells contained cytochrome c‐551 (bound form of cytochrome c2), cytochrome b‐560, and a minor component, possibly b‐type. All reacted to illumination. In iron‐deficient cells, the bound heme b was almost completely suppressed; difference spectra suggested the presence only of cytochrome c2 and c′.