Modulación mediada por hierro de sistemas Anammox: Perspectivas mecanicistas sobre interacciones microbianas e...

Anaerobic ammonium oxidation (anammox) has emerged as a key energy-efficient and cost-effective biological nitrogen removal process, yet its full-scale implementation remains hampered by the intrinsic slow growth of anammox bacteria, high environmental sensitivity, and strict nitrite dependence. Increasing evidence identifies iron as a crucial but double-edged modulator of anammox systems, with roles acting across enzymatic, microbial, and engineering scales. The impacts of iron are highly dependent on its speciation, i.e. soluble species act as indispensable enzyme cofactors and electron shuttles; solid-phase forms facilitate extracellular electron transfer and reconfigure microbial interactions; and engineered iron-based materials accelerate reactor start-up and enhance stability, but at the risk of introduction of oxidative stress. At molecular and community levels, iron governs uptake and homeostasis, regulates enzymatic nitrogen transformations, and restructures microbial consortia, thereby shaping syntrophic networks and competitive dynamics with nitrifiers and heterotrophs. While iron modulation has yielded gains in nitrogen removal efficiency, resilience, and start-up time, critical uncertainties remain regarding long-term stability, ecological safety, and economic viability. Therefore, this review critically examines the divergent roles of iron in anammox systems, integrating mechanistic, ecological, and engineering insights. We argue that future progress demands predictive models of iron-microbe interactions, real-time monitoring of iron speciation, and the rational design of multi-functional iron-based materials to move beyond empirical optimization toward resilient, scalable, and sustainable anammox-based wastewater treatment.