Partial and complete denitrification in Thermus thermophilus: lessons from genome drafts

We have obtained draft genomic sequences of PD (partial denitrificant) and CD (complete denitrificant) strains of Thermus thermophilus . Their genomes are similar in size to that of the aerobic strains sequenced to date and probably contain a similar megaplasmid. In the CD strain, the genes encoding a putative cytochrome cd 1 Nir (nitrite reductase) and ancillary proteins were clustered with a cytochrome c -dependent Nor (nitric oxide reductase), and with genes that are probably implicated in their regulation. The Nar (nitrate reductase) and associated genes were also clustered and located 7 kb downstream of the genes coding for the Nir. The whole nar – nir – nor denitrification supercluster was identified as part of a variable region of a megaplasmid. No homologues of NosZ were found despite nitrogen balance supports the idea that such activity actually exists.