Dynamics of occurrence and metabolic activity of microorganisms involved in the removal of nutrients in urban sequential sedimentation-biofiltration systems
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Urban areas are important sources for river contamination with nitrogen and phosphorus compounds (nutrients). Their extensive amount in urban surface waters promote the proliferation of cyanobacterial harmful algal blooms (CyanoHABs) which could harm biodiversity and human health. Therefore, sequential sedimentation-biofiltration systems (SSBSs) were implemented to collect polluted water from urban rivers to reduce the nutrient load. Microbial communities play an important role in nutrient cycling in the environment, thus, the present study focused on the investigation of such communities in sediments from three SSBSs, two in Lodz city and one in Gniezno city (Poland). Two publications described how the differences in the system design, season, and physico-chemical parameters, influenced the functional metabolic activity of microbial communities (using community level physiological profile approach), and the abundance of nitrifying and denitrifying bacteria (using qPCR to estimate the gene abundance of amoA and nosZ, respectively). The results indicated that SSBS’s geochemical zones containing limestone presented the highest metabolic activity in summer, and the highest abundance of nitrifying bacteria in spring, while denitrifying zones containing brown coal were more abundant with denitrifying bacteria in summer. Moreover, 16S rRNA High throughput sequencing suggested that Commamonadaceae, Flavobacteriaceae, and Crenotrichaceae were the most representative families containing nitrogen-transforming bacteria, while the Rhodocyclaceae with polyphosphate accumulating bacteria. Finally, a third publication described the isolation and characterization of ten nitrogen-transforming bacterial strains from SSBSs sediments, from which two presented the most promising results in the removal of nitrogen compounds in controlled assays: Citrobacter fruendii Bzr02 and Pseudomonas mandelii Str21.