ELECTRON TRANSPORT SYSTEMS OF RHIZOBIUM GROWN IN NODULES AND IN LABORATORY MEDIUM

Abstract

The electon transport systems of Rhizobium japonicum were studied, comparing cells harvested from effective nodules with those from artificial culture. Participation of the cytochrome system was confirmed in both forms of cells. Absorption peaks of the cytochromes of cultured cells were a, b, c type, resembling those of Bacillus subtilis, yeast and mammalian tissue. Cytochrome a could not be detected in the absorption spectrum of symbiotic cells, although the CO binding difference spectrum showed a peak at about 438 mμ, which can be attributed to a component a₃ or a₁. CO difference spectrum also showed a shoulder at about 416 mμ. Cells cultivated under the insufficient supply of oxygen showed the cytochrome absorption spectrum closely resembled that of symbiotic cells. Diaphorase activity was lower in symbiotic cells. These results are considered to be due to the insufficient supply of oxygen within nodule tissue. Succinate oxidation by the symbiotic cell paniculate was shown to be carbon monooxide resistant. NADH₂ oxidation by the supernatant fraction of symbiotic cells was accelerated by flavin mononucleotide, 2, 6-dichiorophenol indophenol, methylene blue and vitamin K₃.