Bacterial shifts associated with known inhibitors for nitrification process

Biobio river is one of the most larger in Chile recieving through its transit from the Andes towards the Pacific Ocean the influence of agricultural, pulp and mill activities, affecting the water quality of the river and organic matter composition. At the last portion of the river a higher organic matter degradation and green house gases production, such as nitrous oxide fluxes towards the atmosphere were reported compared with the river origin or middle part. Herein, we determine shifts of bacterial community structure using T-RFLP associated with the last portion of the river during dry periods (september and november 2014). Also, changes in active bacterial composition using 16S rRNA sequencing were determined in-situ and experimentally in order to evaluate the potential role of nitrification using ATU and Azide. The results indicates that bacteria presented shifts associated with the proximity to the river mouth and nutrients. The most representative phyla were Proteobacteria, Bacteroidetes, Cyanobacteria and Actinobacteria. Incubation generated changes in the active bacterial community, reducing their richness and diversity mostly associated with Proteobacteria phyla, including nitrifying groups, whereas Cyanobacteria and Bacteroidetes phyla were stimulated during the incubation. In total, our results indicates that a diverse microbial community is active at the river mouth, showing a spatial variability linked with the high hydrodynamic of the river mouth also showing nitrification potential linked to previously found high nitrous oxide production.