Respiratory protection of nitrogenase in <i>Azotobacter vinelandii</i>

Jones, Colin W.; Brice, Joan M.; Wright, Veronica; Ackrell, Brian A.C.

doi:10.1016/0014-5793(73)80530-7

Cited by 64 publications

(35 citation statements)

References 16 publications

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“…Also, higher levels of d-type and b-type cytochromes and NADH and succinate oxidase activities were observed in the mutants. The rate-limiting step in NADH oxidation is the activity of the NADH dehydrogenase [9,20,33]. Thus, the increase in the NADH oxidase activity in the mutants is not the result of higher levels of d-type or b-typc cytochromcs.…”

Section: Discussionmentioning

confidence: 99%

“…Haaker and Veeger [34] showed that under oxygen-limited growth the levels of o-type and c-type cytochromes and ascorbate (Ph(NMe,), oxidase activity increased. NADH and NADPH dehydrogenase activities and thc level of catochrome dincrease as A. cinelandiiis shifted from oxygen-limited to oxygen-excess growth [9,20,33,34]. Data of Jones et al [20] show that this is the result of de nouo protein synthesis.…”

Section: Discussionmentioning

confidence: 99%

“…NADH and NADPH dehydrogenase activities and thc level of catochrome dincrease as A. cinelandiiis shifted from oxygen-limited to oxygen-excess growth [9,20,33,34]. Data of Jones et al [20] show that this is the result of de nouo protein synthesis. However, it is not possible to determine if one or more regulatory functions were affected.…”

Section: Discussionmentioning

confidence: 99%

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Respiratory mutants of Azotobacter vinelandii with elevated levels of cytochrome d

et al. 1984

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A method is described for the isolation of respiratory mutants of Azotobacter cinelundii with incrcascd amounts of cl-type cytochrome by selecting for the inability to reduce tctrazolium red. Five stable mutants were obtained that had six-fold higher levels of cytochrome d, increased amounts of b-type and lower amounts of o-type and c-type cytochromes than the wild-type strain. Spectral alterations in cytochrome al were also observed in the mutants. N A D H and succinate oxidase activities of membrane particles were about two fold higher in the mutants compared to the wild-type strain. Ascorbate-N,N,N',N'-tetramethyl-p-phenylene diaminc oxidase activity was barely detectable in membranc particles of the mutants. These results are consistent with an increasc in the amount of the cytochrome d oxidase branch and a decrease in the amount and activity of the cytochrome 0, a1 oxidase branch in the mutants. Growth rates under oxygen-excess conditions and respiratory-linked proton translocation ratios of the mutant and wild-type strains were similar as were the photochemical spectral and kinetic properties of cytochrome d.The respiratory chain of Azotobacter vinelundii has been extensively studied [l, 21. The components of the respiratory chain include highly active flavin-dependent NADH and malate dehydrogenases, hydrogenase, ubiquinone-8, and at least seven spectroscopically detectable cytochromes, b-560. [3,9: 141. Sites of cncrgy conservation occur at the level of NADH dchydrogenase, hydrogenase, the ubiquinone region [4,9,7,16,17,33]. Recent studies diminish the possibility that the cytochrome c-al, o branch is involved in the energy conservation cfficicncy under non-oxygen-limiting growth conditions [11,12.13:15].In addition to its role in energy conservation, it has been proposed that the high activity of the respiratory chain protects the oxygen-sensitive nitrogenase complex in Azotohacter from inactivation [18 -201. Respiratory protection of nitrogenase at higher dissolved oxygen tensions is provided by an increase in whole cell respiration rate which is accompanied by increases in N A D H oxidase activity and levels of cytochrome d [18 -201. The study of respiratory mutants of A . uinelandii has proven to be useful in determining the contribution of each branch of the respiratory chain in the oxidation of physiological substrates and in the efficiency of encrgy conservation. Biochemical studies of mutants unable to reoxidize Ph(NMe,), could not demonstrate a significant role for the MATbRIALS A N D METHODS Bacterial strainsThe wild-type strain AVOP of Azobacter rinelandii was used. Strains AV90 and AVZ 07 are Ph(NMe,),-oxidasenegative mutants of AVOP [I1 -131 (Hoffman and Dcr Vartanian, unpublished results). Mt.dia and conditions of cultiuatiorzEach strain was routinely grown in 1.5 1 of modified Burk's medium [21] with 2 '4 sucrose (wiv) without an added nitrogen source. Other ctrbon sourccs were added at a final concentration of 0.2 ,d (wlv) and nitrogen sources were added to givc a final combined niiro...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Respiratory mutants of Azotobacter vinelandii with elevated levels of cytochrome d

et al. 1984

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“…activities of growing cultures, and of washed cells + added substrates, were assayed by standard procedures [9,11,17]. Potassium cyanide was freshly prepared for each batch of experiments.…”

Section: Miscellaneousmentioning

confidence: 99%

“…Energy conservation at site I is absent from membranes prepared from cells grown at very high oxygen concentrations [8,11 ]. The Azotobacter respiratory system would thus be capable of considerable flexibility with respect to its energy conservation efficiency according to the exact electron transfer pathways employed.…”

mentioning

confidence: 99%

Respiration‐linked proton translocation in Azotobacter vinelandii

Downs¹,

Jones²

1975

FEBS Letters

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Effect of dissolved oxygen on nitrogen fixation by A. vinelandii. I. Free cell cultures

DiLuccio¹,

Kirwan²

1984

Biotech & Bioengineering

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As part of an investigation into the use of biological nitrogen fixation for fertilizer ammonia production, continuous culture studies of respiration and nitrogen fixation in the aerobic bacteria Azotobacter vinelandii under oxygen-limited conditions were conducted. Respiration and growth rates followed Monod forms with respect to dissolved oxygen concentration. However, specific nitrogen fixation rate and nitrogenase activity exhibited maximum values at dissolved oxygen concentrations of ca. 0.02 mM (10% of air saturation). These results suggest careful control of oxygen in the environment is necessary to optimize fixed nitrogen production by this organism.

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Respiratory protection of nitrogenase in Azotobacter vinelandii

Cited by 64 publications

References 16 publications

Respiratory mutants of Azotobacter vinelandii with elevated levels of cytochrome d

Respiratory mutants of Azotobacter vinelandii with elevated levels of cytochrome d

Respiration‐linked proton translocation in Azotobacter vinelandii

Effect of dissolved oxygen on nitrogen fixation by A. vinelandii. I. Free cell cultures

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