Denitrification of nitrate to nitrogen gas by washed cells ofRhizobium japonicum and by bacteroids fromGlycine max.

Nitrate, nitrite and nitrous oxide were denitrified to N2 gas by washed cells ofRhizobium japonicum CC706 as well as by bacteroids prepared from root nodules ofGlycine max (L.) Merr. (CV. Clark 63). Radiolabelled N2 was produced from either K(15)NO3 or Na(15)NO2 by washed cells ofRh. 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 ofG. max. The stoichiometry for the utilization of(15)NO 3 (-) or(15)NO 2 (-) and the produciton of(15)N2 was 2:1 and for N2O utilization and N2 production it was 1:1. Some of the(15)N2 gas produced by denitrification of(15)NO 3 (-) in bacteroids was recycled via nitrogenase into cell nitrogen.