Ponente
Descripción
Hypersaline ecosystems are among the most physicochemically extreme habitats on Earth, where high ionic strength, low water activity, and nutrient limitation impose energetic constraints on microbial metabolism. Despite these conditions, hypersaline lakes sustain stable microbial communities in which haloarchaea frequently dominate carbon turnover and energy fluxes. Understanding how microbial metabolism operates under such physicochemical constraints is therefore essential for explaining carbon processing in these ecosystems. Here, we reconstruct the first genome-scale metabolic model (GSMM) of the haloarchaeon Haloquadratum walsbyi, a globally distributed microorganism that dominates NaCl-saturated thalassohaline microbial communities. Owing to its known global dominance, metabolic processes in this organism are likely to exert a strong influence on nutrient processing in hypersaline systems. We hypothesize that physicochemical constraints of hypersaline environments restrict the set of energetically feasible metabolic states available to this organism, thereby shaping carbon assimilation strategies in these ecosystems. The reconstruction integrates genome reannotation, sequence homology, structural inference, and extensive manual curation, resolving functional assignments for 212 previously uncharacterized proteins. The resulting network comprises 1,323 metabolites and 1,820 reactions. Model simulations indicate that glycerol-and pyruvate-supported metabolism remain energetically feasible under hypersaline physicochemical conditions, and comparison with independent transcriptomic datasets shows that these predicted pathways are transcriptionally active in vivo, supporting the hypothesis that physicochemical constraints filter the set of metabolic states realized in hypersaline ecosystems. By extending the GSMM with a non-ideal, energy-dependent thermokinetic model, this study provides a mechanistic link between genomic potential, environmental constraints, and the formation of metabolic niches in hypersaline microbial ecosystems.