Exploring the biotechnological potential of terrestrial hot spring microbiomes for CO₂utilisation

<b>Background.</b> Terrestrial hot springs are extreme environments shaped by geothermal heat, geogenic gases and extremes of pH and temperatures. Their gas fluxes, which include CO₂, CO, H₂S and SO₂, mirror the chemical composition of CO₂-rich waste streams. Microbial communities inhabiting these environments are typically thermotolerant or thermophilic and sustained by CO₂ fixation and chemolithotrophic metabolism. Such communities may therefore provide a natural starting point for developing <i>ex-situ</i>, consortium-based biotechnologies capable of operating under elevated temperatures and chemically harsh conditions. Here, we assess the metabolic capabilities of hot spring microbiomes systematically through a biotechnological lens.<br/><br/><b>Results.</b> We conducted comparative analysis of 73 worldwide hot spring metagenomes, spanning a wide range of environmental conditions (pH 1.5–10.0, temperatures 25–98°C). By taking a gene-centric approach to whole communities, we show that hot spring microbiomes ubiquitously encoded carbon fixation pathways and biosynthetic genes (and gene clusters) for the synthesis of value-added products, regardless of geographical location and pH-temperature conditions. Candidate value-added products include platform chemicals such as acetone, lactic acid, and 1,2-propanediol, as well as high-value biomolecules including B vitamins and alginate.<br/><br/><b>Conclusions.</b> This first biotechnology-focused assessment of hot spring microbiomes demonstrates that these communities encode the genomic potential to support novel,<i> ex situ </i>microbial platforms for upgrading CO₂and transforming chemically complex gas mixtures.<br/><br/><b>Significance.</b> Industrial CO₂ waste streams pose both an environmental challenge and an unutilised resource. Harnessing microbial consortia to valorise CO₂, through a circular bioeconomy, remains underexplored and could offer an alternative to energy-intensive chemical methods. By reanalysing predominantly publicly available metagenomic data, we demonstrate how hot spring microbiomes can be mined for traits pre-adapted to CO₂-rich, high-temperature, and chemically extreme conditions. In doing so, we provide proof-of-concept for their future biotechnological application and establish a blueprint for other microbiome-scale bioprospecting surveys.<br/><br/>