Quantification of denitrifier genes population size and its relationship with environmental factors.

The objectives of this study were to use real-time PCR for culture-independent quantification of the copy numbers of 16S rRNA and denitrification functional genes, and also the relationships between gene copy numbers and soil physicochemical properties. In this study, qPCR analysis of the soil samples showed 16S rRNA, nirS, nirK, nosZI and nosZII average densities of 3.0 × 108, 2.25 × 107, 2.9 × 105, 4.0 × 106 and 1.75 × 107 copies per gram of dry soil, respectively. In addition, the abundances of (nirS + nirK), nosZI and nosZII relative to 16S rRNA genes were 1.4-34.1%, 0.06-3.95% and 1.3-39%, respectively, confirming the low proportion of denitrifiers to total bacteria in soil. This showed that the non-denitrifying nosZII-type bacteria may contribute significantly to N2O consumption in the soil. Furthermore, the shifts in abundance and diversity of the total bacteria and denitrification functional gene copy numbers correlated significantly with the various soil factors. It is the first study in Turkey about the population size of denitrification functional genes in different soil samples. It also aims to draw attention to nitrous oxide-associated global warming.