Virus-prokaryote interactions assist pollutant removal in constructed wetlands

As a vital part of microbial communities, viruses in constructed wetlands (CWs) remain poorly explored, yet they could significantly affect pollutant removal. Here, two pilot-scale CWs were built to investigate the viral community under different hydraulic loading rates (HLRs) using in-depth metagenomic analysis. Gene-sharing networks suggested that the CWs were pools of unexplored viruses. A higher abundance of prokaryotic functional genes related to sulfur cycling and denitrification was observed in the higher HLR condition, which was associated with greater removal of total nitrogen and nitrate nitrogen compared to the lower HLR condition. Viruses also affect nitrogen pollutant removal by potentially infecting functional prokaryotes, such as denitrification bacteria and ammonia-oxidizing bacteria, and by providing auxiliary metabolic genes involved in sulfur and nitrogen cycling. These findings reveal the significance of viruses in pollutant removal in CWs and enhance the understanding of the relationship between engineering design parameters and performance from microbial perspectives.