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...

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...

A gene from Azotobacter vinelandii whose product exhibits primary sequence similarity to the NifY, NafY, NifX, and VnfX family of proteins, and which is required for effective V-dependent diazotrophic growth, was identified. Because this gene is located downstream from vnfK in an arrangement similar to the relative organization of the nifK and nifY genes, it was designated vnfY. A mutant strain...

Extremely small quantities of carbon monoxide in air inhibit nitrogen fixation by red clover plants inoculated with Rhizobium trifolii (Lind and Wilson, 1941). In preliminary trials with Azotobacter vinelandii Wyss (1941) found a similar inhibition at carbon monoxide concentrations about 10 times those required for the symbiotic system. We have made a detailed study of the inhibition of this az...