Extracts of Closfridium pasfeurianum have been separated into five protein fractions, which are necessary for nitrogen fixation when pyruvate is used as the source of energy and electrons. Pyruvate oxidase is shown to be heat-stable and to have gel filtration properties corresponding to a molecular weight of 100,000 or greater. The function of ferredoxin as an electron carrier for nitrogen fixa...

Physiological and biochemical markers of metabolic competence were assayed in bacteroids isolated from root nodules of control, dark-stressed, and recovered plants of Glycine max Merr. cv ;Woodworth.' Nitrogenase-dependent acetylene reduction by the whole plant decreased to 8% of control rates after 4 days of dark stress and could not be detected in plants dark stressed for 8 days. However, in ...

Nitrogenase activity, determined by the acetylene reduction assay, in soybean cell suspensions infected with Rhizobium, was stimulated significantly by the addition of succinic acid or glutamine. Acetylene-dependent ethylene values as high as 4.6 mumoles of ethylene/gram dry weight.hour were observed.

The reduction of nitrogen, acetylene, azide, and cyanide at various oxygen concentrations by nitrogenase from Azotobacter vinelandii was measured with a well-defined system. Oxygen inhibited the reduction of each substrate uncompetitively. The inhibition constants (K(i)) were 0.014, 0.023, 0.008, and 0.003 atm of oxygen for reduction of nitrogen, acetylene, azide, and cyanide, respectively. The...

The involvement of epiphytic microorganisms in nitrogen fixation was investigated in a shallow freshwater pond near Ithaca, N.Y. The acetylene reduction technique was used to follow diel and seasonal cycles of nitrogen fixation by epiphytes of Myriophyllum spicatum. Acetylene-reducing activity was maximal between noon and 6 p.m., but substantial levels of activity relative to daytime rates cont...

Non-linear rates of acetylene reduction and concomitant H2 evolution were observed for the nitrogenase of Klebsiella pneumoniae at 10 degrees C. A lag phase of 1-4 min, dependent on the ratio of Mo-Fe protein to Fe protein present, occurred before linear rates of acetylene reduction were achieved. A complementary burst phase for concomitant H2 evolution in the presence of acetylene was also obs...

A new and extremely sensitive method for measuring nitrogenase activity through acetylene reduction is presented. Ethylene produced by nitrogenase-mediated reduction of acetylene is detected by using laser photoacoustics (LPA). This method possesses a detection limit making it 3 orders of magnitude more sensitive than traditional gas chromatographic analysis. Photoacoustic detection is based on...