Denitrification of nitrate to nitrogen gas by washed cells of Rhizobium japonicum and by bacteroids from Glycine max

Nitrate, nitrite and nitrous oxide were denitrified to N2 gas by washed cells of Rhizobium japonicum CC706 as well as by bacteroids prepared from root nodules of Glycine max (L.) Merr. (CV. Clark 63). Radiolabelled N2 was produced from either K15NO3 or Na15NO2 by washed cells of Rh. japonicum CC705 grown with either nitrate only (5 mM) or nitrate (5 mM) plus glutamate (10 mM). Nitrogen gas was also produced from N2O. Similar results were obtained with bacteroids of G. max. The stoichiometry for the utilization of ^{15}\mathrm{N}{\mathrm{O}}_{3}^{-}$ or ^{15}\mathrm{N}{\mathrm{O}}_{2}^{-}$ and the production of 15N2 was 2:1 and for N2O utilization and N2 production it was 1:1. Some of the 15N2 gas produced by denitrification of ^{15}\mathrm{N}{\mathrm{O}}_{3}^{-}$ in bacteroids was recycled via nitrogenase into cell nitrogen.