The hidden influence of protozoa on hydrophyte-epiphytic bacterial communities

Plants and their epiphytic microorganisms synergistically participate in biogeochemical cycling and pollutant removal in wetlands, but the assembly mechanisms of epiphytic microbial communities remain unclear. In this study, we use high-throughput sequencing to investigate the epiphytic bacterial communities of two hydrophytes, Vallisneria natans and Nymphaea tetragona and planktonic one in the Yuguqiao Wetland of the Fenhe River, China. We observed differences in composition and diversity among these three microbial environments. The α-diversity of the epiphytic bacterial communities was significantly higher than that of the planktonic one ( p < 0.05), with the composition of protozoa community was the main predictors of V. natans and planktonic bacterial communities. Neutral and null model analyses indicated that dispersal limitation dominated the assembly of the V. natans epiphytic bacterial community, whereas homogeneous selection had the most important influence on that of N. tetragona (53.3 %) and the planktonic (54.2 %) bacterial communities. As ascertained by a network analysis, the bacteria-protozoa bipartite network was more robust and less complex than the bacterial co-occurrence network in all three habitats. In additional, the relative abundance of carbon and nitrogen metabolism-related functional bacterial taxa was found to be negatively related to the |βNTI| of bacterial communities, thus indicating that the assembly processes of bacterial communities were closely associated with community function. According to these findings, we conclude that protozoa have an important impact on the assembly processes and stability of hydrophytes-epiphytic bacterial communities which can inform future strategies for enhancing wetland ecosystem health and improving bioremediation efforts by leveraging the interactions between microorganisms and hydrophytes.