Abstract
Azotobacter vinelandii growing in oxygen controlled chemostat culture was subjected to sudden increases of ambient oxygen concentrations (oxygen stress) after adaptation to different oxygen concentrations adjustable with air (100% air saturation corresponds to 225±14 μM O2). Inactivations of cellular nitrogenase during stress (switch off) as well as after release of stress (switch on) were evaluated in vivo as depending on stress duration and stress height (ΔpO2). Switch off was at its final extent within 1 min of stress. The extent of switch off, however, increased with stress height and was complete at ΔpO2 between 8–10% air saturation irrespective of different oxygen concentrations the organisms were adapted to before stress, indicating that switch off is adaptable. Inactivation of nitrogenase measurable after switch on represents irreversible loss of activity. Irreversible inactivation was at its characteristic level within less than 3 min of stess and at a ΔpO2 of less than 1% air saturation. The level of irreversible inactivation increased linearly with the oxygen concentration the organisms were adapted to before stress. Thus adaptation of cells to increased oxygen concentrations did not prevent increased susceptibility of nitrogenase to irreversible inhibition during oxygen stress. The fast response of irreversible inactivation at low stress heights suggests that it takes place already during stress. Thus switch off comprised both a reversible and an irreversible phase. The data showed that reversible inactivation of nitrogenase was less susceptible to oxygen stress than irreversible inactivation. A basic pre-requisite of the hypothesis of respiratory protection of nitrogenase, i.e. the proposed relationship between respiratory activities and the protection of nitrogenase from irreversible inhibition by oxygen, was not supported by the results of this report.
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References
Dalton H, Postgate JR (1969) Effect of oxygen on growth of Azotobacter chroococcum in batch and continuous cultures. J Gen Microbiol 54:463–473
Drozd J, Postgate JR (1970) Effects of oxygen on acetylene reduction, cytochrome content and respiratory activity in Azotobacter chroococcum. J Gen Microbiol 63:63–73
Haaker H, Veeger C (1977) Involvement of the cytoplasmic membrane in nitrogen fixation by Azotobacter vinelandii. Eur J Biochem 77:1–10
Post E, Kleiner D, Oelze J (1983) Whole cell respiration and nitrogenase activities in Azotobacter vinelandii growing in oxygen controlled continuous culture. Arch Microbiol 134:68–72
Postgate JR (1982) The fundamentals of nitrogen fixation. University Press, Cambridge
Robson RL, Postgate JR (1980) Oxygen and hydrogen in biological nitrogen fixation. Ann Rev Microbiol 34:183–207
Scherings G, Haaker H, Veeger C (1977) Regulation of nitrogen fixation by the FeS protein II in Azotobacter vinelandii. Eur J Biochem 77:621–630
Scherings G, Haaker H, Veeger C (1983) On the formation of an oxygen-tolerant three-component nitrogenase complex from Azotobacter vinelandii. Eur J Biochem 135:591–599
Veeger C, Laane C, Scherings G, Haaker H, Van Zeeland-Wolbers L (1980) Membrane energization and nitrogen fixation in Azotobacter vinelandii and Rhizobium leguminosarum. In: Newton WE, Orme-Johnson WH (eds) Nitrogen fixation, vol I. University Press, Baltimore, pp 111–137
Yates MC, Eady RR (1980) The physiology and regulation of nitrogen fixation. In: Subba Rao NS (ed) Recent advances in biological nitrogen fixation. Edward Arnold Ltd, London, pp 88–120
Yates MG, Jones CW (1974) Respiration and nitrogen fixation in Azotobacter. Adv Microb Physiol 11:97–135
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Dingler, C., Oelze, J. Reversible and irreversible inactivation of cellular nitrogenase upon oxygen stress in Azotobacter vinelandii growing in oxygen controlled continuous culture. Arch. Microbiol. 141, 80–84 (1985). https://doi.org/10.1007/BF00446744
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DOI: https://doi.org/10.1007/BF00446744