Viral community dynamics and virus-prokaryote interactions in a full-scale constructed wetland

Microorganisms are key drivers of nutrient and pollutant removal in constructed wetlands (CWs). Viruses are increasingly recognized for their role in regulating microbial communities through interactions with their hosts. However, their specific roles within CW biofilms have not yet been elucidated. In this study, samples were collected from a full-scale CW employed for tertiary treatment. The viral community, prokaryotic community, and extracellular polymeric substances (EPS) composition were analyzed to elucidate the ecological roles of viruses and the dynamics of virus-prokaryote interactions. Our results revealed that viral and prokaryotic communities in CWs exhibited seasonal dynamics and were closely interconnected. The abundance ratio of lytic to lysogenic phages showed a significant negative correlation with prokaryotic α-diversity (Shannon R² = 0.35, p < 0.05; Richness R² = 0.34, p < 0.05), suggesting an association between shifts in viral infection strategies and prokaryotic community diversity. Phages infected both bacteria and archaea in CWs, and virus-host patterns in core bacterial taxa were broadly consistent with the "Kill-the-Winner" model. Moreover, phage-encoded auxiliary metabolic genes (AMGs) related to C, N, P, and S metabolism showed seasonal shifts in functional composition, indicating season-dependent variation in viral functional potential that may be associated with biogeochemical cycling in CWs. Overall, this study provides a comprehensive profile of viral communities in CWs and highlights the potential role of phages in shaping microbial community structure and function, offering new insights into virus-host interactions within biofilms in nature-based wastewater treatment technology.