The genus Erwinia is heterogeneous with respect to the presence of the ammonia assimilating enzymes glutamine synthetase (GS), NADP-linked glutamate synthase (GOGAT) and NADP-linked glutamate dehydrogenase. Three major groups were distinguished; one showed activity of all three enzymes, the second only GS and GOGAT activity and the third only GS activity. Aspartase did not appear to be significant in ammonia assimilation in any group.

No abstract

~ ~~~~~The influence of specific growth rate on the ammonia-assimilating enzymes glutamine synthetase, NADP-linked glutamate synthase and NADP-linked glutamate dehydrogenase was studied in ammonia-limited and glucose-limited chemostat cultures of Erwinia carotovora var. carotovora, E. nigrijluens and E. amylovora. The response of these organisms, representatives of various ' enzyme groups' within the genus Erwinia, showed considerable variation and confirmed the heterogeneity of the genus with respect to ammonia-assimilating enzymes. The overall significance of the glutamine synthetase/glutamate synthase pathway in any organism where the synthesis of these enzymes is not constitutive is questioned.