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Nitrite and ammonia assimilation by anaerobic continuous cultures of Escherichia coli

Nitrite and ammonia assimilation by anaerobic continuous cultures of Escherichia coli
Nitrite and ammonia assimilation by anaerobic continuous cultures of Escherichia coli

Anaerobic continuous cultures of E. coli strains HfrC and K12 OR75 assimilated nitrite to produce 63.7 g dry mass/g atom N. Washout occurred when these cultures were aerated, or when the dilution rate was above 0.05 hr-1. Nitrite reductase, glutamate dehydrogenase and glutamine synthetase activities and cytochrome C552 synthesis were depressed when growth of strain OR75 was limited by concentration of either nitrite or ammonia in the reservoir. Glutamate synthase activity was far less than glutamate dehydrogenase, but was highest when nitrite limited growth. These results indicate that enzymes which catalyse glutamate synthesis from inorganic nitrogen compounds are regulated in an interdependent manner, but that glutamine synthetase protein is unlikely to be the aporepressor for glutamate dehydrogenase synthesis in this organism. Possible reasons for apparently opposite regulatory mechanisms in E. coli and Klebsiella aerogenes are discussed in the context of the selective pressures which are applied to bacteria in continuous culture. It is concluded that E. coli K12 has alternative pathways for synthesizing glutamate, and because the Km of glutamate dehydrogenase for NH3 is 1.6 mM, a growth limiting concentration of an inorganic nitrogen compound in the reservoir would be assimilated predominantly by the glutamine synthetase glutamate synthase pathway.

0022-1287
11-22
Cole, J. A.
1669d303-23e9-4e51-8d29-a83b58f91bbc
Coleman, K. J.
92b937f4-d354-4aab-871b-b0e8b6018a1d
Compton, B. E.
e4fd8c43-968f-43f8-8d5c-64733298b28a
Kavanagh, B. M.
19d0bc2c-cf7b-4884-bbc3-61659b2e0364
Keevil, C. W.
cb7de0a7-ce33-4cfa-af52-07f99e5650eb
Cole, J. A.
1669d303-23e9-4e51-8d29-a83b58f91bbc
Coleman, K. J.
92b937f4-d354-4aab-871b-b0e8b6018a1d
Compton, B. E.
e4fd8c43-968f-43f8-8d5c-64733298b28a
Kavanagh, B. M.
19d0bc2c-cf7b-4884-bbc3-61659b2e0364
Keevil, C. W.
cb7de0a7-ce33-4cfa-af52-07f99e5650eb

Cole, J. A., Coleman, K. J., Compton, B. E., Kavanagh, B. M. and Keevil, C. W. (1974) Nitrite and ammonia assimilation by anaerobic continuous cultures of Escherichia coli. Journal of General Microbiology, 85 (1), 11-22. (doi:10.1099/00221287-85-1-11).

Record type: Article

Abstract

Anaerobic continuous cultures of E. coli strains HfrC and K12 OR75 assimilated nitrite to produce 63.7 g dry mass/g atom N. Washout occurred when these cultures were aerated, or when the dilution rate was above 0.05 hr-1. Nitrite reductase, glutamate dehydrogenase and glutamine synthetase activities and cytochrome C552 synthesis were depressed when growth of strain OR75 was limited by concentration of either nitrite or ammonia in the reservoir. Glutamate synthase activity was far less than glutamate dehydrogenase, but was highest when nitrite limited growth. These results indicate that enzymes which catalyse glutamate synthesis from inorganic nitrogen compounds are regulated in an interdependent manner, but that glutamine synthetase protein is unlikely to be the aporepressor for glutamate dehydrogenase synthesis in this organism. Possible reasons for apparently opposite regulatory mechanisms in E. coli and Klebsiella aerogenes are discussed in the context of the selective pressures which are applied to bacteria in continuous culture. It is concluded that E. coli K12 has alternative pathways for synthesizing glutamate, and because the Km of glutamate dehydrogenase for NH3 is 1.6 mM, a growth limiting concentration of an inorganic nitrogen compound in the reservoir would be assimilated predominantly by the glutamine synthetase glutamate synthase pathway.

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Published date: 1 November 1974

Identifiers

Local EPrints ID: 437268
URI: http://eprints.soton.ac.uk/id/eprint/437268
ISSN: 0022-1287
PURE UUID: d56b831c-46ce-470b-8766-4a9930de0306
ORCID for C. W. Keevil: ORCID iD orcid.org/0000-0003-1917-7706

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Date deposited: 23 Jan 2020 17:34
Last modified: 10 Nov 2021 03:04

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Contributors

Author: J. A. Cole
Author: K. J. Coleman
Author: B. E. Compton
Author: B. M. Kavanagh
Author: C. W. Keevil ORCID iD

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