Regulation of glutamate metabolism in the cyanobiont Nostoc ANTH by nitrogen sources
✍ Scribed by Dr. Surendra Singh
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 304 KB
- Volume
- 33
- Category
- Article
- ISSN
- 0233-111X
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✦ Synopsis
Growth, heterocyst differentiation, nitrogenase activity and glutamate uptake were studied in the cyanobiont Nostoc ANTH, a free-living isolate of the liverwort Anthoceros punctatus. Nostoc ANTH grew well in N,-medium and produced heterocyst and nitrogenase activity whereas NO;-and NHf -grown cultures did not show heterocyst differentiation and nitrogenase activity. Also, glutamate inhibited the diazotrophic growth, heterocyst differentiation and nitrogenase activity. However, the availability of NO; and N H f to the glutamate-medium resulted in the recovery of growth. NO; and NH2-grown cells showed reduced levels of glutamate uptake which further reduced by the supplementation of NO; and NHf in the reaction mixture during experimentation. These results suggest that in Nostoc ANTH glutamate acts as an inhibitor of heterocyst differentiation and nitrogenase activity rather than as a nitrogen source and that availability of NO; and NHf alleviates the glutamate toxicity by inhibiting its uptake. This glutamate toxicity may be the reason for the localization of glutamate forming enzyme, glutamate synthase (GOGAT) within vegetative cells and not within heterocysts.