1991/07/01 by H. B. Machado, Hidevaldo B. Machado, S. Funayama +2
Agricultural and Biological Sciences · Engineering · Environmental Science · #Plant nutrient uptake and metabolism #Biofuel production and bioconversion #Wastewater Treatment and Nitrogen Removal
paper · doi:10.1139/m91-092
Several spontaneous ethylenediamine-resistant mutants of Azospirillum brasilense strain FP2 (Sp7, Nal R Sm R ) were isolated. Four mutants, HM053, HM14, HM26, and HM210, were found to fix nitrogen constitutively in the presence of high concentration of NH 4 + and to excrete NH 4 + derived from nitrogen fixation. They also showed lower rates of NH 4 + uptake than the wild-type strain, FP2. All of the mutants were prototrophic for glutamine or glutamate. Their glutamate synthase and glutamate dehydrogenase activities were similar to those of the wild-type strain. However, they presented different patterns of glutamine synthetase activity. Mutant HM14 showed low levels of normally regulated glutamine synthetase activity, while the other mutants showed low levels (HM053) or wild-type levels (HM26 and HM210) of constitutively adenylylated glutamine synthetase activity. The mutants are probably defective in the adenylylation system. Key words: Azospirillum brasilense, ammonium excretion, ethylenediamine resistance, glutamine synthetase.