Salinity levels influence treatment performance and the activity of electroactive microorganisms in a microbial fuel cell system for wastewater treatment Castellano-Hinojosa, Antonio Gallardo Altamirano, Manuel Jesús Pozo Llorente, Clementina González Martínez, Alejandro González López, Jesús Juan Marshall, Ian P.G. Wastewater Anode biofilm Electroactive microorganisms Current production Metagenomics Metatranscriptomics Agua residual Metagenómica Metatranscriptómica This research was financially supported by the Marie Skłodowska-Curie Postdoctoral European Fellowship (101108081) from HORIZON-MSCA-2022-PF-01 (Horizon Europe, 2022). There is growing interest in developing effective treatment technologies to mitigate the environmental impact of saline wastewater while also potentially recovering valuable resources from it. However, it remains largely unknown how different salinity levels impact treatment performance, energy generation, and the diversity and composition of electroactive microorganisms in MFCs treating real effluents such as urban wastewater. This study explores the impact of three salinity levels (3.5, 7, and 15 g/L NaCl) on current production, organic removal rates, and bacterial community dynamics in a continuous-flow microbial fuel cell (MFC) fed with urban wastewater. Using metagenomics and metatranscriptomics, we explored variations in the abundance and expression of extracellular electron transfer (EET) genes and those involved in other general metabolisms. We found that low salinity (3.5 g/L NaCl) enhanced both current production and organic removal efficiency compared to higher salinity levels. This improvement was linked to an increased abundance and activity of electroactive microorganisms, particularly taxa within the Ignavibacteria class, which possess genes coding for outer membrane cytochromes and porin cytochromes. Additionally, salinity influenced general metabolic genes and microbial community composition, with higher salinity levels limiting bacterial growth and diversity. This research provides valuable insights into the interplay between salinity stress and microbial adaptation, contributing to the optimization of MFC technologies for enhanced environmental and bioengineering applications. 2025-03-19T09:35:08Z 2025-03-19T09:35:08Z 2025-04 journal article A. Castellano-Hinojosa et al. Salinity levels influence treatment performance and the activity of electroactive microorganisms in a microbial fuel cell system for wastewater treatment. Journal of Environmental Management 379 (2025) 124858. https://doi.org/10.1016/j.jenvman.2025.124858 https://hdl.handle.net/10481/103172 10.1016/j.jenvman.2025.124858 eng info:eu-repo/grantAgreement/EC/H2020/101108081 http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Elsevier