The catalysis of nitrogen reduction by extracts of nitrogen-fixing organisms requires an ATPgenerating system and a source of electrons (1, 2, 5, 11, 13). The phosplhoroclastic reaction provides botlh ATP anid electrons for the reduction of nitrogen by cell-free extracts of Clostridium1t pasteurianumn (2, 5, 13) and ferredoxin functions as the natural electron carrier from the phlosphoroclastic...

Stable strains of mutants of Azotobacter that do not fix nitrogen are difficult to obtain by traditional procedures (Karlsson and Barker, 1948; Lindstrom, 1948). Stumbo and Gainey (1938) demonstrated that culturing Azotobacter on a high nitrate medium resulted in strains that failed to fix nitrogen even after continued transfer in the absence of fixed nitrogen. However, since these strains were...

The alginate biofilm-producing bacterium Azotobacter vinelandii aerobically fixes nitrogen by oxygen-sensitive nitrogenases. Here we investigated the bacterial response to nitrogen/oxygen gas mixtures. A. vinelandii cells were cultured in nitrogen-free minimal media containing gas mixtures differing in their ratios of nitrogen and oxygen. The bacteria did not grow at oxygen concentrations >75% ...

The first direct evidence is provided for the presence of an interstitial carbide in the Fe-V cofactor of Azotobacter vinelandii vanadium nitrogenase. As for our identification of the central carbide in the Fe-Mo cofactor, we employed Fe Kβ valence-to-core X-ray emission spectroscopy and density functional theory calculations, and herein report the highly similar spectra of both variants of the...

The properties of CO-inhibited Azotobacter vinelandii (Av) Mo-nitrogenase (N2ase) have been examined by the combined application of nuclear resonance vibrational spectroscopy (NRVS), extended X-ray absorption fine structure (EXAFS), and density functional theory (DFT). Dramatic changes in the NRVS are seen under high-CO conditions, especially in a 188 cm(-1) mode associated with symmetric breat...

A unique method is described for inhibiting nitrogenase. When Clostridium pasteurianum nitrogenase is assayed in the presence of the Mo-Fe protein of Azotobacter vinelandii, all the characteristic activities of nitrogenase are inhibited. C. pasteurianum nitrogenase is unaffected by the Fe protein of A. vinelandii. The Fe protein, but not the Mo-Fe protein of C. pasteurianum, inhibits A. vinelan...

Azotobacter vinelandii cysts undergo conversion to vegetative cells in Burk's nitrogen-free medium utilizing glucose, sucrose, or acetate. In 1% glucose, this overall process was complete in 8 hr and consisted of a germination and an outgrowth phase. Respiration, ribonucleic acid, and protein synthesis began soon after the addition of the germinant, and these processes proceeded at rates charac...

Both molybdate and iron are metals that are required by the obligately aerobic organism Azotobacter vinelandii to survive in the nutrient-limited conditions of its natural soil environment. Previous studies have shown that a high concentration of molybdate (1 mM) affects the formation of A. vinelandii siderophores such that the tricatecholate protochelin is formed to the exclusion of the other ...

Alginate is essential for encystment in Azotobacter vinelandii. Transcription of the algD gene, which codes for GDP-mannose dehydrogenase, a key enzyme in the alginate biosynthetic pathway, is initiated at two promoters, one of which, p2, has sigmaE consensus sequences. AlgU is the A. vinelandii alternative sigmaE factor. In this study, we constructed an algU mutant (SMU88) which, as expected, ...

Phosphoenolpyruvate carboxylase (EC 4.1.1.31) from Azotobacter vinelandii, like the corresponding enzyme from other organisms, is activated by acetyl coenzyme A and inhibited by l-aspartate. Both modifiers affect primarily the affinity of the enzyme for phosphoenolpyruvate. This is the first enzyme with a strictly anaplerotic (intermediate-replacing) function to be tested for response to the ad...