From capability to deployment: closing the translational gap in extremophile-mediated bioremediation

Abstract Extremophiles are a recurring answer to a recurring problem in environmental biotechnology: many waste streams most in need of treatment are too saline, hot, acidic, or alkaline for conventional microorganisms to treat effectively. Organisms that not only tolerate but require those conditions can, in principle, act on such streams directly, and their extreme niche doubles as a barrier against contamination, the premise for open, non-sterile processing. The literature cataloging which extremophile degrades which pollutant is now large and, in places, mature. Far less settled is whether any of it works outside the laboratory. This minireview surveys the demonstrated degradative capabilities of extremophiles and then concentrates on the translational gap separating a capable strain from a deployable process. Six problems recur: the scarcity of field and pilot validation, especially for halophilic and engineered systems; performance on the multi-contaminant, multi-stressor matrices real waste presents, and the open question of whether managed or designed consortia outperform single isolates; activity against recalcitrant contaminants such as per- and polyfluoroalkyl substances (PFAS), where we identified no halophilic reports; immature genetic toolkits that constrain engineering and biocontainment; the little-explored combination of treatment with resource recovery; and the scarcity of techno-economic and life-cycle evidence. For each, we identify the experiments and analyses that would close it, and we distinguish, throughout, between what is genuinely absent from the literature and what may simply be underreported. Key points • Extremophile-mediated bioremediation is demonstrated in the laboratory but rarely validated in the field. • No halophilic PFAS defluorination was identified in the literature searched, unlike acidophiles and mesophiles. • Coupling treatment with resource recovery is a promising but unproven route.