Molecular insights into enhanced nitrogen removal induced by trace fluoroquinolone antibiotics in an anammox system

It has been widely reported that fluoroquinolones (FQs) can affect the anaerobic ammonium oxidization (anammox) microorganisms, which interferes with the performance of nitrogen removal from wastewater. However, the metabolic mechanism of anammox microorganisms responding to FQs has rarely been explored. In this study, it was found that 20 mu g/L FQs promoted the nitrogen removal performance of anammox microor-ganisms in batch exposure assays, and 36-51% of FQs were removed simultaneously. Combined metabolomics and genome-resolved metagenomic analysis revealed up-regulated carbon fixation in anammox bacteria (AnAOB) , while purine and pyrimidine metabolism, protein generation and transmembrane transport were enhanced in AnAOB and symbiotic bacteria by 20 mu g/L FQs. Consequently, hydrazine dehydrogenation, nitrite reduction, and ammonium assimilation were bolstered, improving the nitrogen removal efficiency of the anammox system. These results revealed the potential roles of specific microorganisms in response to emerging FQs and provided further information for practical application of anammox technology in wastewater treatment.

Automated summary

It was found that 20 μg/L of fluoroquinolones promoted the nitrogen removal performance of anammox microorganisms and removed 36-51% of the drugs. Metabolomics and genome-resolved metagenomic analysis revealed enhanced carbon fixation, purine and pyrimidine metabolism, protein generation, and transmembrane transport in anammox bacteria and symbiotic bacteria in response to 20 μg/L of fluoroquinolones. Consequently, hydrazine dehydrogenation, nitrite reduction, and ammonium assimilation were bolstered, improving the nitrogen removal efficiency of the anammox system.