Cleavage of chromosomal DNA from
Pseudomonas
aeruginosa PAO by SpeI and DpnI has been used
together
with PFGE and Southern hybridization to establish the map location of
the
following principal denitrification genes: narGH (encoding the
large
and small subunits of respiratory nitrate reductase),
nirS (cytochrome-cd1
nitrite reductase), nirE (uroporphyrinogen-III
methyltransferase
for haem d1 biosynthesis), norCB
(nitric-oxide
reductase complex), nosZ (nitrous-oxide reductase) and nosA
(an outer-membrane protein and OprC homologue). The study also included
several genes related to anaerobic or microaerophilic metabolism: napA
(encoding the catalytic subunit of the periplasmic nitrate reductase),
ccoN
(catalytic subunit of the cytochrome-cbb3 oxidase),
hemN
(oxygen-independent coproporphyrinogen-III oxidase), an fnr-like
regulatory gene, and azu and fdxA (electron carriers
azurin
and ferredoxin, respectively). Genes necessary for denitrification are
concentrated at 20 to 36 min on the P. aeruginosa chromosome,
where
they form three separate loci, the nir-nor, nar and nos
gene clusters. Genomic DNA of Pseudomonas stutzeri ZoBell was
also
subjected to SpeI restriction and Southern analysis to assign
denitrification
genes to individual fragments. A homologue of nosA encoding a
putative
component of the Cu-processing apparatus for nitrous-oxide reductase
was
identified. In both P. aeruginosa and P. stutzeri there
is
evidence for the linkage of anr (fnrA) with hemN
and
ccoN
and for the presence of a napA gene.