A Comparative Survey of the Iron-Sulphur Centres in the Cytoplasmic Membranes of Pseudomonas cichorii and Pseudomonas aptata

The respiratory chains of the related phytopathogenic bacteria Pseudomonas cichorii and Pseudomonas aptata were investigated using the technique of electron paramagnetic resonance which readily detects iron-sulphur centres. In the cytoplasmic membranes of both bacteria three ferredoxin-like centres and a centre detected in the oxidized state (gy = 2.015) were resolved. In addition, a Rieske-type iron-sulphur centre (gy = 1.90) was observed in P. cichorii but not in P. aptata. The absence of the Rieske centre in P. aptata parallels the absence of cytochromes c in this bacterium.