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The incidence of nirS and nirK and their genetic heterogeneity in cultivated denitrifiers
Author(s) -
Heylen Kim,
Gevers Dirk,
Vanparys Bram,
Wittebolle Lieven,
Geets Joke,
Boon Nico,
De Vos Paul
Publication year - 2006
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2006.01081.x
Subject(s) - biology , gammaproteobacteria , betaproteobacteria , alphaproteobacteria , phylogenetic tree , denitrifying bacteria , phylogenetics , 16s ribosomal rna , bacteroidetes , genetics , firmicutes , proteobacteria , gene , denitrification , actinobacteria , physics , quantum mechanics , nitrogen
Summary Gene sequence analysis of nirS and nirK , both encoding nitrite reductases, was performed on cultivated denitrifiers to assess their incidence in different bacterial taxa and their taxonomical value. Almost half of the 227 investigated denitrifying strains did not render an nir amplicon with any of five previously described primers. NirK and nirS were found to be prevalent in Alphaproteobacteria and Betaproteobacteria , respectively, nirK was detected in the Firmicutes and Bacteroidetes and nirS and nirK with equal frequency in the Gammaproteobacteria . These observations deviated from the hitherto reported incidence of nir genes in bacterial taxa. NirS gene phylogeny was congruent with the 16S rRNA gene phylogeny on family or genus level, although some strains did group within clusters of other bacterial classes. Phylogenetic nirK gene sequence analysis was incongruent with the 16S rRNA gene phylogeny. NirK sequences were also found to be significantly more similar to nirK sequences from the same habitat than to nirK sequences retrieved from highly related taxa. This study supports the hypothesis that horizontal gene transfer events of denitrification genes have occurred and underlines that denitrification genes should not be linked with organism diversity of denitrifiers in cultivation‐independent studies.