Environmental pH effects on denitrification and the related genes of transcription denitrification

Lubna Ahmed Abdulkarim


 The pH effect on denitrification in soil bacteria of environmental samples was investigated.Norwegian environmental soil samples (Torp rejion) was investigated, to explore the control of pH on the regulation of denitrification, quantified the functional genes nosZ (encoding for nitrous oxide reductase) and nirS (encoding for nitrite oxide reductase) and their transcripts during transition from oxic to anoxic conditions. Soil samples from field experiments from treated Norwegian soil (pH 7.5) were compared, environmental samples was investigated, adapted in to two different pH levels (pH 6 and pH 7). The results were interpreted in relation to the kinetics of NO, N2O and N2 production and compared with external data, obtained from similar experiment. The kinetic of gas transformations (O2, NO, N2O and N2) were monitored using a robotic incubation system. The number of bacteria that were recovered on the Nycodenz cushion was estimated and compared with the total number of bacteria / g soil (using SYBR-green I). RNA was purified and converted to cDNA and quantified to indicate the transcriptional activity of the functional genes at the time of sampling.

PCR-DGGE used to study the complex bacterial community of the denitrification genes and the composition of their transcripts.

The experiment showing that denitrification is affected by acidic pH environments. The transcription levels of the nirS and nosZ genes, the expression of nirS and nosZ genes, were notably lower at pH 6 than at pH 7. Study shows  that at low transcription levels, nirS can produce NO but nosZ not able to produce N2. The result showing that the production of a functional nosZ enzyme is extremely affected by the pH of the environment.


pH, denitrification process, genes, transcription, PCR-DGGE

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