Nitrogenase activity and regeneration of the cellular ATP pool in Azotobacter vinelandii adapted to different oxygen concentrations

Linkerhägner, K; Oelze, J.

doi:10.1128/jb.179.4.1362-1367.1997

Cited by 26 publications

(19 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The FeSII protein, known as the Shethna protein and encoded by Avin01520, forms a protective complex with nitrogenase when the enzyme is exposed to oxygen (58). In addition, it has been determined that cellular levels of ATP also contribute to protection of nitrogenase against oxygen damage (53). High concentrations of ATP directly correlate with high electron flux to nitrogenase, which influences the dissociation rate constant of the nitrogenase components (84) and, consequently, the susceptibility of the Fe protein to oxygen damage (83).…”

Section: Strain Descriptionmentioning

confidence: 99%

Genome Sequence ofAzotobacter vinelandii, an Obligate Aerobe Specialized To Support Diverse Anaerobic Metabolic Processes

et al. 2009

View full text Add to dashboard Cite

Azotobacter vinelandii is a soil bacterium related to the Pseudomonas genus that fixes nitrogen under aerobic conditions while simultaneously protecting nitrogenase from oxygen damage. In response to carbon availability, this organism undergoes a simple differentiation process to form cysts that are resistant to drought and other physical and chemical agents. Here we report the complete genome sequence of A. vinelandii DJ, which has a single circular genome of 5,365,318 bp. In order to reconcile an obligate aerobic lifestyle with exquisitely oxygen-sensitive processes, A. vinelandii is specialized in terms of its complement of respiratory proteins. It is able to produce alginate, a polymer that further protects the organism from excess exogenous oxygen, and it has multiple duplications of alginate modification genes, which may alter alginate composition in response to oxygen availability. The genome analysis identified the chromosomal locations of the genes coding for the three known oxygen-sensitive nitrogenases, as well as genes coding for other oxygen-sensitive enzymes, such as carbon monoxide dehydrogenase and formate dehydrogenase. These findings offer new prospects for the wider application of A. vinelandii as a host for the production and characterization of oxygen-sensitive proteins.

show abstract

Section: Strain Descriptionmentioning

confidence: 99%

Genome Sequence ofAzotobacter vinelandii, an Obligate Aerobe Specialized To Support Diverse Anaerobic Metabolic Processes

et al. 2009

View full text Add to dashboard Cite

show abstract

“…The biological fixation of dinitrogen depends on the activity of the highly oxygen-sensitive nitrogenase enzyme complex (25). Despite this sensitivity, species of the diazotrophic azotobacters are able to grow under fully aerobic conditions (9,26,33).…”

mentioning

confidence: 99%

“…A possible link between alginate formation and protection of nitrogenase in this organism has not been examined so far in the literature. Studies of the nitrogenase protection mechanisms of Azotobacter have mostly been based on either the respiration rates or acetylene reduction measurements as indications of nitrogenase activity (25,26,29). In fact, the biological function of alginate formation in bacteria is not fully understood.…”

mentioning

confidence: 99%

“…The first mechanism is believed to explain the function of nitrogenase when cells grow diazotrophically in the presence of O 2 . The second mechanism is considered to be used to protect the reversibly inactivated enzyme from O 2 damage when the respiratory protection becomes overburdened, such as with a sudden increase in the ambient O 2 concentration (21,25) or under conditions of phosphate limitation (43). In the latter case, the respiration rate of cells is limited due to shortage of phosphate for the oxidative phosphorylation.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Effect of Oxygen on Formation and Structure of Azotobacter vinelandii Alginate and Its Role in Protecting Nitrogenase

Sabra

Zeng

Lünsdorf

et al. 2000

Appl Environ Microbiol

183

139

View full text Add to dashboard Cite

The activity of nitrogenase in the nitrogen-fixing bacterium Azotobacter vinelandii grown diazotrophically under aerobic conditions is generally considered to be protected against O 2 by a high respiration rate. In this work, we have shown that a high rate of respiration is not the prevailing mechanism for nitrogenase protection in A. vinelandii grown in phosphate-limited nitrogen-free chemostat culture. Instead, the formation of alginate appeared to play a decisive role in protecting the nitrogenase that is required for cell growth in this culture. Depending on the O 2 tension and cell growth rate, the formation rate and composition of alginate released into the culture broth varied significantly. Furthermore, transmission electron microscopic analysis of cell morphology and the cell surface revealed the existence of an alginate capsule on the surface of A. vinelandii. The composition, thickness, and compactness of this alginate capsule also varied significantly. In general, increasing O 2 tension led to the formation of alginate with a higher molecular weight and a greater L-guluronic acid content. The alginate capsule was accordingly thicker and more compact. In addition, the formation of the alginate capsule was found to be strongly affected by the shear rate in a bioreactor. Based on these experimental results, it is suggested that the production of alginate, especially the formation of an alginate capsule on the cell surface, forms an effective barrier for O 2 transfer into the cell. It is obviously the quality, not the quantity, of alginate that is decisive for the protection of nitrogenase.

show abstract

“…caulinodans potentially terminates in four oxidases : two quinol oxidases (cytochromes o and 6 d ) and two cytochome c oxidases (cytochromes aa, and 6663) (Kitts & Ludwig, 1994;Mandon et al, 1994;Kaminski et al, 1996). Oxidative phosphorylation is most efficient when electrons are transported via the 6c, complex and cytochrome aa, and less efficient when electrons are transferred via either of the quinol oxidases.…”

Section: Introductionmentioning

confidence: 99%

Oxygen protection of nitrogen fixation in free-living Azorhizobium caulinodans: the role of cytochrome aa3

Boogerd¹,

Pronk²,

Mashingaidze³

et al. 1998

Microbiology

View full text Add to dashboard Cite

~~ _____The growth properties of Azorhizobium caulinodans wild-type and a cytochrome aa, mutant strain, both growing with N, as N source at fixed dissolved partial oxygen pressures in the range 0.5400 kPa, were studied by making use of continuous cultures (chemostats and pH-auxostats) and transient cultures. In succinate-limited chemostats, the wild-type exhibited a higher growth yield than the aa, mutant at every dissolved oxygen tension tested, indicating activity of cytochrome aa, in this entire oxygen regime. The growth yield of both the wild-type and the aa, mutant declined when the dissolved oxygen tension was raised. In contrast, for growth on ammonia a t the same dilution rate, the wild-type showed an increase in growth yield with increasing dissolved oxygen tension, whereas the growth yield of the aa, mutant remained constant. The transient changes in growth properties observed in chemostat cultures after pulsing with succinate pointed to a negative effect of oxygen on the maximum specific growth rate. This was studied further in steady-state pHauxostat cultures. The specific growth rate of both strains decreased with increasing dissolved oxygen tension. The less steep decline in growth rate of the wild-type compared to the aa, mutant confirmed that cytochrome aa, is active in the wild-type. Again, the growth yield of both strains decreased with the dissolved oxygen tension, but in contrast to the results obtained with chemostats, no difference in growth yield was observed between wild-type and mutant at any oxygen tension. In either type of continuous culture a decrease in the overall P/O ratio with increasing dissolved oxygen tension is improbable for the wild-type, and even more so for the aa, mutant. Therefore, the adverse effects of oxygen on the growth of A. caulinodans are not readily explained by respiratory protection; alternatively, it is proposed that the catalytic oxidation of nitrogen-fixationspecific redox enzymes by oxygen (auto-protection) enables the bacterium to deal with intracellular oxygen at the expense of reducing equivalents and free energy. To compensate for the loss of free energy, respiration increases and an active cytochrome aa, contributes to this by keeping the P/O ratio high.

show abstract

Nitrogenase activity and regeneration of the cellular ATP pool in Azotobacter vinelandii adapted to different oxygen concentrations

Cited by 26 publications

References 31 publications

Genome Sequence ofAzotobacter vinelandii, an Obligate Aerobe Specialized To Support Diverse Anaerobic Metabolic Processes

Genome Sequence ofAzotobacter vinelandii, an Obligate Aerobe Specialized To Support Diverse Anaerobic Metabolic Processes

Effect of Oxygen on Formation and Structure of Azotobacter vinelandii Alginate and Its Role in Protecting Nitrogenase

Oxygen protection of nitrogen fixation in free-living Azorhizobium caulinodans: the role of cytochrome aa3

Contact Info

Product

Resources

About