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. 1977 Jun;59(6):1021–1025. doi: 10.1104/pp.59.6.1021

Azolla-Anabaena azollae Relationship

V. 15N2 Fixation, Acetylene Reduction, and H2 Production 1,2

Gerald A Peters a, Robert E Toia Jr a, Samuel M Lough a
PMCID: PMC542497  PMID: 16659984

Abstract

In order to characterize the reactions catalyzed by nitrogenase in the Azolla-Anabaena association, 15N2 fixation, C2H2 reduction, and ATP-dependent H2 production were measured in both the Azolla-Anabaena complex and in the alga isolated from the complex.

The rate of reduction of substrates and of ATP-dependent H2 evolution was determined at various partial pressures of C2H2 and N2. A pC2H2 of 0.1 atm was nearly optimal for C2H4 production and inhibited H2 production by 95%. The ratio of C2H2 reduced to N2 fixed was determined as a function of constant pC2H2 (0.1 atm) and variable pN2. This ratio decreased with increasing pN2 and the decrease was correlated with less H2 production. Ratios obtained at N2 partial pressures of approximately 0.3, 0.6, and 0.8 atm, respectively, were 3.2, 2.0, and 1.7 for the association and 4.4, 3.0, and 2.5 for the isolated symbiont. Rates obtained for C2H2 reduction, N2 fixation, and H2 production were used to obtain an expression of the electron balance in vivo.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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