Mutants of Azotobacter vinelandii altered in the regulation of nitrate assimilation |
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| Authors: | F Luque E Santero J R Medina M Tortolero |
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| Institution: | (1) Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, E-41080 Sevilla, Spain;(2) Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, E-41080 Sevilla, Spain |
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| Abstract: | The two enzymes involved in the assimilatory pathway of nitrate in Azotobacter vinelandii are corregulated. Nitrate reductase and nitrite reductase are inducible by nitrate and nitrite. Ammonium represses induction by nitrate of both reductases. Repression by ammonium is higher in media containing 2-oxo-glutarate as carbon source than in media containing sucrose. Mutants in the gene ntrC lost nitrate and nitrite reductase simultaneously. Ten chlorate-resistant mutants with a new phenotype were isolated. In media without ammonium they had a normal phenotype, being sensitive to the toxic effect of chlorate. In media containing low ammonium concentrations they were resistant to chlorate. These mutants seem to be affected in the repression of nitrate and nitrite reductases by ammonium. |
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| Keywords: | Nitrate reductase Nitrite reductase Ntr system Chlorate-resistant mutants Azotobacter vinelandii |
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