Archives of Microbiology

, Volume 138, Issue 1, pp 26–30 | Cite as

The relationship between the state of adenylylation of glutamine synthetase I and the export of ammonium in free-living, N2-fixing Rhizobium

  • William R. Evans
  • Deborah K. Crist
Original Papers


The relationship between ammonium assimilation and ammonium export has been studied in free-living, N2-fixing Rhizobium sp. 32H1. After 55 to 67 h of microaerobic growth under a gas phase of 0.2% O2 – 1.0% CO2 – 98.8% Ar high levels of nitrogenase were observed concomitant with a slightly adenylylated glutamine synthetase (GSI) and some glutamine synthetase (GSII) activity. However, after growth of 89 h, or longer, GSI became adenylylated and the level of GSII had decreased. When the gas phase was shifted to 0.2% O2 – 1.0% CO2 – 98.8% N2, a lag was observed before ammonium export could be detected in the 55 to 67 h cultures. No lag in ammonium export was observed in the cultures previously grown for 89 h. The onset of ammonium export in the 55 to 67 h cultures was found to correlate with the adenylylation state of GSI. There appeared to be no correlation between the level of GSII and the export of ammonium. Neither an increase in the adenylylation level of GSI nor ammonium export was observed when the 55 to 67 h cultures were maintained under the Ar gas mixture.

Key words

Ammonium export Ammonium assimilation Glutamine synthetase Nitrogen fixation Rhizobium sp. 32H1 



Glutamate synthase


glutamine synthetase


[N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid]


cetyltrimethylammonium bromide


[2-(N-morpholino)-ethane sulfonic acid]


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Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • William R. Evans
    • 1
  • Deborah K. Crist
    • 1
  1. 1.Charles F. Kettering Research LaboratoryYellow SpringsUSA

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