Plant and Soil

, Volume 35, Issue 1, pp 551–559 | Cite as

Biochemical and physiological studies with free-living, nitrogen-fixing bacteria

  • John Postgate


1. Rumen fluid from four sheep, one on a low nitrogen diet, showed slight acetylene reduction.Desulfotomaculum ruminis, a rumen anaerobe, fixes N2 but the effective organisms in rumen samples seem to resembleClostridium pasteurianum; this organism can persist in the sheep rumen. In domestic sheep the contribution of rumen fixation to the animal's N-nutrition is probably negligible; other ruminants on various diets require study.

2. Respiration inAzotobacter species functions partly to protect nitrogenase from interference by oxygen. When such ‘respiratory protection’ of nitrogenase fails, the organisms reversibly ‘switch off’ nitrogenase activity, a process attributed to a change in the conformation of the nitrogenase components. When this ‘conformational protection’ fails, irreversible damage to the oxygen-sensitive protein 2 (Fe protein) of nitrogenase occurs and can be demonstrated with cell-free extracts.

3. Protein 1 (Mo-Fe protein) and protein 2 (Fe protein) ofKlebsiella pneumoniae nitrogenase, labelled with Fe57, show Mössbauer resonances tentatively assigned to ferrous and ferric iron. In mixtures, these are additive unless both ATP and Na2S2O4 (the components necessary for enzymic activity) are present, when changes take place, including the appearance of a new doublet at −0.85 and +2.2 mm/sec. Permutation of labelled and unlabelled proteins indicates that the major change occurs in protein 1. N2, C2H2, CN or CO altered the intensity of an absorption at +2.8 mm/sec attributable to protein 2. Hence activation of the N2-ase complex involves changes in the environment of Fe but no resonances assignable to Fe-substrate binding appear.


Acetylene Reduction Azotobacter Rumen Fluid Mossbauer Spectrum Rumen Content 
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  1. 1.
    Bergersen, F. J. and Hipsley, E. H., J. Gen. Microbiol. 60, 61–65 (1970).PubMedCrossRefGoogle Scholar
  2. 2.
    Hillson, S. et al., J. Applied Bacteriol 33, 270–273 (1970).CrossRefGoogle Scholar
  3. 3.
    Bulen, W. A. et al., Proc. Natl. Acad. Sci. U.S.A. 53, 532–539 (1965).PubMedCentralPubMedCrossRefGoogle Scholar
  4. 4.
    Burns, R. C. et al., Biochem. Biophys. Research Comm. 39, 90–99 (1970).CrossRefGoogle Scholar
  5. 5.
    Coleman, G. S., J. Gen. Microbiol. 22, 423–436 (1960).PubMedCrossRefGoogle Scholar
  6. 6.
    Dalton, H. and Postgate, J. R., J. Gen. Microbiol. 54, 463–473 (1969).CrossRefGoogle Scholar
  7. 7.
    Dalton, H. and Postgate, J. R., J. Gen. Microbiol. 56, 307–319 (1969).PubMedCrossRefGoogle Scholar
  8. 8.
    Drozd, J. and Postgate, J. R., J. Gen. Microbiol. 60, 427–429 (1970).PubMedCrossRefGoogle Scholar
  9. 9.
    Drozd, J. and Postgate, J. R., J. Gen. Microbiol. 63, 63–73 (1970).PubMedCrossRefGoogle Scholar
  10. 9a.
    Hardy, R. W. F. et al., Plant Physiol., 43, 1185–1207 (1968).PubMedCentralPubMedCrossRefGoogle Scholar
  11. 10.
    Hino, S. and Wilson, P. W., J. Bacteriol. 75, 403–408 (1958).PubMedCentralPubMedGoogle Scholar
  12. 11.
    Ivanov, I. D. et al., Mikrobiologiya 37, 330–333 (1968).Google Scholar
  13. 12.
    Kelly, M., Biochim. Biophys. Acta 171, 9–22 (1969).PubMedCrossRefGoogle Scholar
  14. 13.
    Kelly, M., Biochim. Biophys. Acta 191, 527–540 (1969).PubMedCrossRefGoogle Scholar
  15. 14.
    Kelly, M. and Lang, G., Biochim. Biophys. Acta 223, 86–104 (1970).PubMedCrossRefGoogle Scholar
  16. 15.
    Moisio, T. et al., Suomen Kemintlehti B 42, 432–433 (1969).Google Scholar
  17. 16.
    Novikov, G. V. et al., C.R. Acad. Sci. U.S.S.R. 181, 1170–1173 (1969).Google Scholar
  18. 17.
    Oppenheim, J. et al., J. Bacteriol. 101, 292–296 (1970).PubMedCentralPubMedGoogle Scholar
  19. 18.
    Postgate, J. R., J. Gen. Microbiol. 63, 137–139 (1970).PubMedCrossRefGoogle Scholar
  20. 19.
    Smith, D. D. and Wyss, O., Antonie van Leeuwenhoek 35, 84–96 (1969).PubMedCrossRefGoogle Scholar
  21. 20.
    Stewart, W. D. P., Proc. Roy. Soc. B. 172, 367–388 (1969).CrossRefGoogle Scholar
  22. 21.
    Yates, M. G., J. Gen. Microbiol. 60, 393–401 (1970).PubMedCrossRefGoogle Scholar

Copyright information

© Martinus Nijhoff 1971

Authors and Affiliations

  • John Postgate
    • 1
  1. 1.A.R.C. Unit of Nitrogen FixationUniversity of SussexBrightonUK

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