Molecular analysis of the chromosomal region encoding the nifA and nifB genes of Acetobacter diazotrophicus |
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Authors: | Kátia RS Teixeira Manuela Wülling Theodore Morgan Ricardo Galler Eva-Maria Zellermann José I Baldani Christina Kennedy Dietmar Meletzus |
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Institution: | University of Arizona, Department of Plant Pathology, Tucson, AZ 85721, USA;EMBRAPA-Centro Nacional de Pesquisa de Agrobiologia, Km47 antiga Rio-Sao Paulo, ItaguaéRio de Janeiro, Brazil;FIOCRUZ-Departamento Bioquémica e Biologia Molecular, Av. Brasil 4365, Rio de Janeiro, Brazil;Universität Bielefeld, Fakultät für Biologie, Lehrstuhl Gentechnologie/Mikrobiologie, D-33615 Bielefeld, Germany |
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Abstract: | The Acetobacter diazotrophicus nifA gene was isolated by its ability to restore a Nif+ phenotype to a nifA mutant of Azotobacter vinelandii. Sequencing revealed that the nifA gene was upstream and adjacent to the nifB gene and both are transcribed in the same direction but independently from different promoters. The 3′ end of the nifB gene was located approximately 2.5 kb upstream of the nitrogenase structural gene cluster, nifHDK. The deduced amino acid sequences of the A. diazotrophicus nifA and nifB gene products were most similar to the NifA and NifB proteins of Azorhizobium caulinodans and Rhodobacter capsulatus, respectively. A. diazotrophicus nifA expression was repressed in cultures exposed to high levels of ammonium while oxygen apparently had no influence. Both oxygen and ammonium prevented expression of a nifB-reporter strain, consistent with the observation that ammonium repressed nifA expression, and indicating that A. diazotrophicus NifA activity is inhibited by oxygen as in other Proteobacterial α group diazotrophs. |
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Keywords: | nif gene Amino acid sequence Acetobacter diazotrophicus |
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