Some effects of iron deficiency on Rhodopseudomonas spheroides strain Y

Abstract

Rhodopseudomonas spheroides strain Y was grown photosynthetically in a synthetic medium containing defined amounts of iron. Two chromatophore fractions (“light” and “heavy”) were prepared by sucrose density gradient centrifugation of CsCl-treated chromatophores. They were found to differ in homogeneity, stability, specific bacteriochlorophyll content and infrared absorption spectra. Iron deficiency was found to cause excretion of porphyrins by whole cells and accumulation of poly-β-hydroxybutyrate. Inhibition of bacteriochlorophyll synthesis and decrease in the total iron and heme iron contents were also observed in whole cells and light particles; the total heme of low-iron cells and the heme bound to light particles were decreased, respectively, by factors of 20 and 16 whereas the total iron was much less affected. Variations in the infrared absorption of whole cells, light and heavy particles were caused by iron deficiency.