title: Nitric oxide reductase (norB) gene sequence analysis reveals discrepancies with nitrite reductase (nir) gene phylogeny in cultivated denitrifiers.
abstract: Gene sequence analysis of cnorB and qnorB, both encoding nitric oxide reductases, was performed on pure cultures of denitrifiers, for which previously nir genes were analysed. Only 30% of the 227 denitrifying strains rendered a norB amplicon. The cnorB gene was dominant in Alphaproteobacteria, and dominantly coexisted with the nirK gene, coding for the copper-containing nitrite reductase. Both norB genes were equally present in Betaproteobacteria but no linked distributional pattern of nir and norB genes could be observed. The overall cnorB phylogeny was not congruent with the widely accepted organism phylogeny based on 16S rRNA gene sequence analysis, with strains from different bacterial classes having identical cnorB sequences. Denitrifiers and non-denitrifiers could be distinguished through qnorB gene phylogeny, without further grouping at a higher taxonomic resolution. Comparison of nir and norB phylogeny revealed that genetic linkage of both genes is not widespread among denitrifiers. Thus, independent evolution of the genes for both nitrogen oxide reductases does also occur.
authors.affiliation: Laboratory of Microbiology, Department of Biochemistry, Physiology and Microbiology, Ghent University, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium. Kim.Heylen@UGent.be
authors.forename: Kim
authors.initials: K
authors.lastname: Heylen
authors.forename: Bram
authors.initials: B
authors.lastname: Vanparys
authors.forename: Dirk
authors.initials: D
authors.lastname: Gevers
authors.forename: Lieven
authors.initials: L
authors.lastname: Wittebolle
authors.forename: Nico
authors.initials: N
authors.lastname: Boon
authors.forename: Paul
authors.initials: P
authors.lastname: De Vos
mesh_terms: D001105:Archaea / Q000145:classification; D008040:Genetic Linkage / Q000235:genetics; D006094:Gram-Positive Bacteria / Q000145:classification; D009572:Nitrite Reductases / Q000235:genetics*; D010088:Oxidoreductases / Q000235:genetics*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000145:classification*; D017422:Sequence Analysis, DNA
chemical_list: D012336:RNA, Ribosomal, 16S; D010088:Oxidoreductases; D009572:Nitrite Reductases; C034747:nitric-oxide reductase