Regulation of nitrogen fixation in Azospirillum brasilense
1997
Zhang, Y. | Burris, R.H. | Ludden, P.W. | Roberts, G.P.
The regulation of nitrogen fixation in Azospirillum brasilense is very complicated, and it responds to exogenous fixed nitrogen or a change of oxygen concentration. This regulation occurs at both transcriptional and posttranslational levels. Unlike regulation seen in Klebsiella pneumoniae, transcription of nifA does not require NTRB/NTRC in A. brasilense and the expression of nifHDK is controlled by posttranslational regulation of NIFA activity. Addition of NH4(+) or a shift from microaerobic to anaerobic conditions also causes a rapid loss of nitrogenase activity in A. brasilense. This posttranslational regulation of nitrogenase activity involves the DRAT/DRAG regulatory system which is similar to that of Rhodospirillum rubrum. Both DRAT and DRAG activities are regulated in vivo but the mechanisms for their regulation are unknown.
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