Metagenomes and metatranscriptomes in  poly-extreme high-altitude desert ecosystem within the Atacama Desert
The Barrancas Blancas (BB) plain, situated in the high-altitude Puna de Atacama, serves as a unique natural laboratory for studying microbial metabolic strategies under poly-extreme desert conditions. Using a metatranscriptomic approach, we characterized microbial communities along a 70-meter moisture gradient created by a temporary freshwater lake. A clear functional transition was observed—from trace gas-based metabolism in arid zones to light-driven primary production in wetter regions . The highest microbial activity and RNA content were detected 8 to 23 meters from the lake, where transcriptional profiles revealed abundant photosynthetic microalgae (Diatomea) with active oxygenic phototrophy (psaA, psbA), active proteobacterial anoxygenic phototrophy (pufL, pufM), and genes involved in carbon (rbcL) and nitrogen (nifH) fixation, despite limited organic carbon and nitrogen availability. In contrast, the driest site was dominated by Actinobacteriota with metabolic signatures of hydrogen oxidation (hyaB) and hydrogenotrophic carbon fixation. These findings highlight a moisture-driven transition in microbial energy acquisition strategies and underscore the ecological importance of both photoautotrophy and chemolithotrophy. The BB plain and its temporary lake thus provide a powerful model for understanding microbial resilience, functional plasticity, community assembly, and trophic interactions in extreme environments, offering novel insights into life at the edge of habitability.