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. 1980 Sep;143(3):1234–1240. doi: 10.1128/jb.143.3.1234-1240.1980

Ammonium assimilation in Rhizobium meliloti.

M S Osburne, E R Signer
PMCID: PMC294485  PMID: 6106011

Abstract

We have characterized a mutant of Rhizobium meliloti strain 2011 which cannot use ammonium as a nitrogen source. This mutant, RTm2620, was found to have significantly altered glutamate synthase activity. Both the mutant and the wild-type strains had glutamate dehydrogenase activity, which, although stimulated in the presence of glutamate and ammonium, was apparently insufficient to allow ammonium assimmilation. We conclude that the glutamine synthetase-glutamate synthase pathway may be the normal mode of ammonium assimilation by this strain in the free-living state. Independent revertants of Rm2620 were isolated and fell into two classes. Class I revertants regained partial glutamate synthase activity and had the same levels of glutamate dehydrogenase activity as Rm2620. Class II revertants retained the altered glutamate synthase activity but acquired a very high level of assimilatory glutamate dehydrogenase activity. Both classes were found to be altered in their symbiotic properties, although the original Rm2620 mutant was normal in this regard.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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