LOCALIZATION OF DENITRIFICATION GENES ON THE CHROMOSOMAL MAP OF PSEUDOMONAS-AERUGINOSA

Cleavage of chromosomal DNA from Pseudomonas aeruginosa PAO by SpeI an d 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 nit rate reductase), nirS (cytochrome-cd(1) nitrite reductase), nirE (urop orphyrinogen-III methyltransferase for haem d(1) biosynthesis), norCB (nitric-oxide reductase complex), nosZ (nitrous-oxide reductase) and n osA (an outer-membrane protein and OprC homologue). The study also inc luded several genes related to anaerobic or microaerophilic metabolism : napA (encoding the catalytic subunit of the periplasmic nitrate redu ctase), ccoN (catalytic subunit of the cytochrome-cbb(3) oxidase), hem N (oxygen-independent coproporphyrinogen-III oxidase), an fnr-like reg ulatory gene, and azu and fdxA (electron carriers azurin and ferredoxi n, respectively), Genes necessary for denitrification are concentrated at 20 to 36 min on the P. aeruginosa chromosome, where they form thre e separate loci, the nir-nor, nar and nos gene clusters. Genomic DNA o f Pseudomonas stutzeri ZoBell was also subjected to SpeI restriction a nd Southern analysis to assign denitrification genes to individual fra gments. A homologue of nosA encoding a putative component of the Cu-pr ocessing apparatus for nitrous-oxide reductase was identified. In both P. aeruginosa and P. stutzeri there is evidence for the linkage of an r (fnrA) with hemN and ccoN; and for the presence of a napA gene.