The rpoN region of Pseudomonas
stutzeri was cloned, and an rpoN null mutant was
constructed.
RpoN was not essential for denitrification in this bacterium but
affected
the expression levels and enzymatic activities of cytochrome
cd1
nitrite reductase and nitric oxide reductase, whereas those of
respiratory
nitrate reductase and nitrous oxide reductase were comparable to
wild-type
levels. Since the transcription of the structural genes nirS
and
norCB,
coding for nitrite reductase and the nitric oxide reductase complex,
respectively,
proceeded unabated, our data indicate a posttranslational process for
the
two key enzymes of denitrification depending on RpoN.