ELECTRON TRANSPORT SYSTEMS OF RHIZOBIUM JAPONICUM .2. RHIZOBIUM HAEMOGLOBIN CYTOCHROMES AND OXIDASES IN FREE-LIVING (CULTURED) CELLS

1. 1. This work characterizes the cytochromes, other haemoproteins and oxidases of Rhizobium japonicum grown in non N2-fixing pure culture, for comparison with the haemoproteins and oxidases found in Rhizobium bacteroids isolated from N2-fixing legume root nodules. 2. 2. In common with bacteroids, cultured cells possess cytochrome c and a cytochrome b (α-peak 559 nm at 20°, 556 nm at -196°) but they uniquely contain cytochromes a-a3, an autoxidizable cytochrome b (possibly equivalent to cytochrome o) and a soluble 'Rhizobium haemoglobin'. They also contain traces of other CO-reactive haemoproteins. 3. 3. Rhizobium haemoglobin is unrelated to leghaemoglobin, and is not a soluble, reactive form of cytochrome o. 4. 4. Photochemical action spectra prove the oxidase functions of the CO and CN--sensitive cytochromes a3 and o; there may also be present a third oxidase pathway, with a component sensitive to CN- and EDTA, but not to CO. The cytochrome a3 co-exists with a CO and CN--insensitive cytochrome a. © 1969.