Reduction of acetylene and nitrogen gas by breis and cell-free extracts of soybean root nodules.

Cell-free extracts of Clostridiiumii p(lste'rtr'i lm il (8) aind( of A2otoboctcr viiell(tlfdii (2) in the presence of an ATP generating system alndI anl appropriate electron donior, catalvze the redcuction of N. gas to ammonia. In recent investigations (3,4, 9) of the properties of nitrogenase from these organiisms, it has been established that the enzyme system is non-specific for electron acceptor and will catalyze the redulctioll of nitrotus oxide, cyanide. azide and acetylene in additioni to -'.. No repro(duicible proce(lutres have been reported for the preparation from legulme nodulles of cell-free extracts capable of catalyzing the redutction of N. gas. Bergerson (1) has (lescribed a method for the clemonstration of nitrogen-fixation with a brei from soybean root ilodtiles. In his proceduire, strictly anaerobic conditions were necessary for the preparation of the brei alnd the sensitive 5N' techniqtle was uised for the detectioni of N., fixation. In most of the experiments no more than 6 m,u atoms of N were fixed per mg of brei protein. Wre have approached the problem of nitrogen fixation by nodtiles of symbionts by meastiring the rate of redulction of acetylene to ethylene. Intact soybean nodules were shown to catalyze the reduictionl of acetylene to ethylene at a rapid rate and the conditions optimiium for the reduction determined (5). The purpose of this commuinication is to report conditions necessary for catalysis of acetylene reduiction by breis and cell-free extracts of nodtiles anid the catalysis of redtlction to ammonia by a cell-free extract of a nodulle bacteroid preparation. Soybean plants were cuiltulred in the greenhouise