Nitrogen fixation by the bacteroid fraction of breis of soybean root nodules

Enzymes of the Poly-β-Hydroxybutyrate and Citric Acid Cycles of Rhizobium japonicum Bacteroids

“…Duing the period of developing nitrogenase activity, the specfic activity of fumuase, hydroxybutyrate dehydrogenase, ,-ketothiohlse, and pyruvate dehydrogenase complex incesed whereas acetoacetate-succinyl-CoA transferase and isocitrate dehydrogenase decreased (2,8,9,15,17,21,25,28,29).…”

“…Duing the period of developing nitrogenase activity, the specfic activity of fumuase, hydroxybutyrate dehydrogenase, ,-ketothiohlse, and pyruvate dehydrogenase complex incesed whereas acetoacetate-succinyl-CoA transferase and isocitrate dehydrogenase decreased (2,8,9,15,17,21,25,28,29).The carbon metabolism of developing and senescing nodules and the metabolism of bacteroids have been reviewed recently (5,19,27 PHB has been measured in many rhizobia species (7,12,14 The purpose of this investigation was, first, to establish that PDC, selected enzymes from the citric acid cycle, (IDH, MDH, and FMR) and of the PHB cycle (KT, HBD, and AST) were present during the period of nitrogen fixation and PHB accumulation in R. japonicum; second, to follow their activity as a function ofage; and third, to relate temporal changes in activities to those of nitrogenase and PHB accumulation through the use of dispersion diagrams. …”

Uniformity of the Microsymbiont Population from Soybean Nodules with Respect to Buoyant Density

“…Ching et al (3) had reported that the latter activity was 2.5 times greater in the mature bacteroid fraction than in the bacterial fraction. Malate dehydrogenase, on the other hand, might be elevated in the mature bacteroid because organic acids, particularly malate, succinate, and fumarate, caused the greatest increase in acetylene reduction rates when added to isolated suspensions of soybean microsymbionts (2).…”

Effects of Oxygen Concentration and Leghemoglobin on Organic Acid Degradation by Isolated Soybean Nodule Bacteriods

“…Though the dependence of bacteroid nitrogenase activity on a continued supply of current photosynthate-to the nodule has been demonstrated, sucrose, the major translocatable photosynthate, does not stimulate nitrogen fixation of isolated soybean bacteroids. 2 ) The most effective substrates for stimulation of respiration and dinitrogen fixation (acetylene reduction) of isolated bacteroid suspensions were organic acids, especially succinate and malate. 3 ) Though pathways for conversion of sucrose to organic acids in nodule tissues have yet to be fully, understood, Kouchi and Yoneyama 4 ) extensively investigated 13C incorporation into various plant tissue constituents after the plants had assimilated 13C02 for 8 hr in a steady state, and showed rapid turnover and labeling of Abbreviations: ARA, acetylene reduction activity; DTT, dithiothreitol; ex-KG, ex-ketoglutarate.…”