Nitrogen metabolism inRhodopseudomonas globiformis |
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Authors: | Michael Madigan Sharon S Cox |
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Institution: | (1) Department of Microbiology, Southern Illinois University, 62901 Carbondale, Illinois, USA |
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Abstract: | Rhodopseudomonas globiformis strain 7950 grew with a variety of amino acids, urea, or N2 as sole nitrogen sources. Cultures grown on N2 reduced acetylene to ethylene; this activity was absent from cells grown on nonlimiting NH
4
+
. Glutamate dehydrogenase could not be detected in extracts of cells of strain 7950, although low levels of an alanine dehydrogenase were present. Growth ofR. globiformis on NH
4
+
was severely inhibited by the glutamate analogue and glutamine synthetase inhibitor, methionine sulfoximine. High levels of glutamine synthetase (as measured in the -glutamyl transferase assay) were observed in cell extracts of strain 7950 regardless of the nitrogen source, although N2 and amino acid grown cells contained somewhat higher glutamine synthetase contents than cells grown on excess NH
4
+
. Levels of glutamate synthase inR. globiformis were consistent with that reported from other phototrophic bacteria. Both glutamate synthase and alanine dehydrogenase were linked to NADH as coenzyme. We conclude thatR. globiformis is capable of fixing N2, and assimilates NH
4
+
primarily via the glutamine synthetase/glutamate synthase pathway.Abbreviations GS
glutamine synthetase
- GOGAT
Glutamineoxoglutarate aminotransferase
- GDH
Glutamate dehydrogenase
- ADH
Alanine dehydrogenase
- MSO
Methionine sulfoximine |
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Keywords: | Rhodospirillaceae Rhodopseudomonas globiformis Nitrogen metabolism Nitrogen fixation Glutamine synthetase |
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