Inorganic nitrogen regulation of glutamate uptake in the cyanobacterium Nostoc muscorum |
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Authors: | R Prakasham A K Singh H N Singh A N Rai |
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Institution: | Dept of Biochemistry, North-Eastern Hill Univ., Shillong-793014, India.;School of Life Sciences, Univ. of Hyderabad, Hyderabad-500134, India |
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Abstract: | In Nostoc muscorum (Anabaena ATCC 27893) glutamate was not metabolised as a fixed nitrogen source, rather it functioned as an inhibitor of growth. The latter effect was nitrogen source specific and occurred in N2-fixing cultures but not in cultures assimilating nitrate or ammonium. NO3--grown cultures lacked heterocysts and nitrogenase activity and showed a nearly 50% reduction in glutamate uptake rates, as well as in the final extent of glutamate taken up, compared to N2-fixing or nitrogen-limited control cultures. NH4+-grown cultures showed a similar response, except that the reduction in glutamate uptake rates and the final exten of glutamate taken up was over 80%. The present results suggest a relation between nitrate/ammounium nitrogen-dependent inhibition of glutamate uptake, probably via repression of the glutamate transport system, and glutamate toxicity. |
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Keywords: | Anabaena ATCC 27893 cyanobacteria glutamate uptake growth NH4+-grown N2-fixation NO3--grown Nostoc muscorum |
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