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...

An earlier report (1) dealing with the distribution of isotopic nitrogen in cells of Axotobacter vinelandii fixing molecular nitrogen provided evidence that ammonia might be the initial stable form of nitrogen in the fixation process. This conclusion was based on the observation that the N’s supplied this organism accumulated in the glutamic acid fraction, as had been already observed in higher...

During the investigation of the Krebs cycle in Azotobacter agile, strain 4.4 (Repaske and Wilson, 1953), it was found that whole cells normally required 20 minutes before adaptation to succinate, but succinoxidase activity could be demonstrated in cell-free extracts made from unadapted cells. If extracts prepared in a 10 kc Raytheon sonic oscillator were centrifuged at 145,000 G for 30 minutes,...

NADH dehydrogenases have been isolated in a low-molecular weight form (56,500) from both low-iron and normal-iron grown cells of Azotobacter vinelandii. Unlike low-molecular weight forms of NADH dehydrogenases reported from mammalian mitchondria, the enzymes in this study have not undergone any unusual alterations in various reactivities with substrates and electron acceptors. The NADH dehydrog...

Ammonia is generally conceded to be the "key intermediate" in biological nitrogen fixation-that is, the compound which reacts to form the first stable organic compound, glutamic acid (Wilson and Burris, 1953). However, there is virtually no information concerning the reactions functioning in the conversion of N2 to ammonia. Reproducible nitrogen fixation by a cell-free preparation from bacteria...

Genes that seem to be involved in the initial steps of infection of a legume by Rhizobium have been transferred, by transformation, to mutant strains of Azotobacter vinelandii that are unable to fix nitrogen. These genes code for a surface antigen that binds specifically to a protein from the host plant.

Bacterial Nitrogenase, Nitrite Inhibition, Dinitrogenase Reductase Dinitrogen fixation by crude extracts from Rhodopseudomonas palustris and Rhodomicrobium vannielii and by purified nitrogenase preparations from Azotobacter vinelandii and Clostridium pasteurianum is inhibited by nitrite, whereas in the same preparations nitrate is without effect. In Clostridium nitrite seems to interact with di...

Few studies on purified bacterial reduced diphosphopyridine nucleotide (DPNH) or cytochrome oxidases have been reported, although cytochrome reduction by DPNH’ in crude bacterial extracts has repeatedly been described (l-6). Dolin (7, 8) purified a flavoprotein DPNH oxidase and peroxidase from Streptococcus jaecalis, and Lenhoff and Kaplan (9) and Lenhoff et al. (10) described the characteristi...