CONTROL OF NIFH TRANSCRIPTION IN AZOSPIRILLUM-BRASILENSE - INVOLVEMENT OF NIFA AND OF CIS-ACTING SEQUENCES

The regulatory sequences of Azospirillum brasilense Sp7 nifH gene were fused with the cam reporter gene and used for studying the factors co ntrolling nifH transcription. A DNA sequence, downstream the ATG codon of nifH, that could be involved in the negative regulation of nifH tr anscription, was identified. The effect of 1 and 2 mM of ammonium on t he transcription of the A, brasilense nifH gene and on the nitrogenase activity, in the presence of the Klebsiella pneumoniae NifA protein, was examined.