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Regulation of Azospirillum brasilense nifA gene expression by ammonium and oxygen
C M Fadel-Picheth1, E M Souza, L U Rigo
1Department of Medical Pathology, UFPR, C. Postal 19046, CEP 81531-990, Curitiba, Brazil.
Abstract:
The structure and activity of the nifA promoter of Azospirillum brasilense was studied using deletion analysis. An essential region for nifA promoter activity was identified between nucleotides -67 and -47 from the identified transcription start site. A sequence resembling a sigma(70) recognition site occurs in this region and may constitute the nifA gene promoter. The regulation of the nifA gene was studied in plasmid and chromosomal nifA::lacZ fusions. Full expression was obtained under low oxygen levels and in the absence of ammonium ions. Repression of nifA expression involves a synergistic effect between oxygen and ammonium.
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