Effect of nitrogen starvation on ammonium-inhibition of nitrogenase activity in Azotobacter chroococcum |
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Authors: | Francisco J Cejudo Antonio Paneque |
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Institution: | (1) Instituto de Bioquímica Vegetal v Fotosíntesis, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas, Facultad de Biología, Apartado 1113, E-41080 Sevilla, Spain |
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Abstract: | When Azotobacter chroococcum cells grown in batch culture under N2-fixing conditions were transferred to a medium lacking a nitrogen source, the cellular C/N ratio, the amount of alginic acid released into the external medium and the rate of endogenous respiration increased appreciably after 6 h to the exclusion of dinitrogen, whereas nitrogenase activity did not undergo any significant change. Nitrogen deficiency caused a decrease in the ammonium inhibition of nitrogenase activity from 95% inhibition at zero time to 14% after 6 h incubation under dinitrogen starvation, with no difference in the rate of ammonium utilization by N2-fixing and N2-starved cells being observed. This suggests that a balance of nitrogen and carbon assimilation is necessary for the ammonium inhibition of nitrogenase activity in A. chroococcum to take place. |
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Keywords: | Ammonium Azotobacter chroococcum Nitrogen starvation Nitrogenase activity |
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