Plant species dominance over PFAAs in structuring bacterial communities and their functional profiles in treatment wetlands

This study investigates the impact of different plant species (Iris pseudacorus L., Phragmites australis (Cav.) Trin. Ex Steud., Typha latifolia L.) and solutions containing increasing perfluoroalkyl acids (PFAAs) concentrations (11 perfluorocarboxylic acids and three perfluorosulfonic acids, 500, 2500, and 5000 ng L−1, each) on bacterial communities in treatment wetland (TW) mesocosm systems. The aim was to rank the respective importance of plant species and pollutant concentration in shaping the structure of the selected bacterial communities. While microbial community structure was mainly a function of plant species, PFAAs had some effect on the predictable bacterial functional profiles. Among the tested species, Typha demonstrated exceptional versatility in supporting bacterial communities with enhanced nitrogen, sulfur, and organic compound metabolism, outperforming Iris and Phragmites. Different PFAA concentrations did not modify the overall taxonomical community structure, although they significantly altered the relative abundances of single functional groups. The observed variations in taxonomy-predictable functional groups highlighted the impact of PFAAs on specific plant bacteria, with potential implications also for the metabolism of other specific compounds. The study also identified distinct bacterial functional profiles associated with specific plant species, revealing that bacteria linked to Typha exhibited more specialized functions, while those associated with Phragmites qualified more within the generalist category. This suggests that Typha may be particularly suitable for TWs under PFAA-rich wastewaters, due to its ability to support the metabolism of organic compounds. Additionally, results indicated that phylum diversity may be used as a reliable proxy of functional diversity patterns. Overall, this study contributes to cast light on the intricate relationships between plant species, PFAA concentrations, and bacterial communities and their catabolic functions, which provides an exploitable advancement of knowledge for the optimization of treatment wetlands.