Abstract EANA2025-115

Understanding how extremophilic microorganisms might adapt to extraterrestrial environments is central to astrobiology. Acidithiobacillus ferrooxidans, a chemolithoautotrophic acidophile capable of iron and sulfur oxidation, is a promising analog for hypothesized microbial life in the Venusian cloud layer. This study presents a genome-scale metabolic model (GSM) reconstruction of A. ferrooxidans using a constraint-based framework and flux balance analysis (FBA) to evaluate its metabolic feasibility under Venus-analog atmospheric conditions.

The model includes 408 genes, 817 reactions, and 640 metabolites, and was manually curated using the merlin platform and validated using COBRApy and MEWpy toolkits. Simulated environments incorporated physicochemical constraints derived from Venus cloud data, including low pH, high sulfuric acid concentration, minimal oxygen, and redox potential consistent with H₂, Fe²⁺, and reduced sulfur species.

Our findings demonstrate that A. ferrooxidans retains a viable core metabolism under such conditions, particularly via sulfur oxidation pathways (e.g., tetrathionate and thiosulfate metabolism) coupled with iron redox cycling. We identified key metabolic bottlenecks, including limitations in carbon fixation efficiency under low CO₂ partial pressures and ATP yield under redox-constrained scenarios. Additionally, metabolic robustness was observed across variations in H₂ and Fe²⁺ availability, supporting its adaptability.

This work establishes a detailed metabolic map of A. ferrooxidans as a model Venusian extremophile and lays the groundwork for testing metabolic plasticity in cloud-like environments. The results provide insights both into the boundaries of microbial habitability, and into bio-signature prediction and experimental setups in atmospheric simulation chambers.