199 / 2025-04-14 20:54:34

Unveiling Cryptic Life: Chemolithoautotrophic and Heterotrophic Microbes Drives Biogeochemical Cycling in Tibetan Plateau Subglacial Ecosystems

Tibetan Plateau Glaciers,Subglacial Ecosystem,Metagenome-Assembled Genome,Biogeochemistry Cycle,Microbial Metabolisms

Theme 4: Microbial and Biogeochemical Evolution through Time > Session 4b: Roles of Microbes in Shaping Our Habitable Earth

Subglacial ecosystems, located at ice-bedrock interface, release bedrock substrates via rock comminution for microbial availability and drive biogeochemical cycles of C, N, S, H and Fe through microbially mediated redox reaction, yet their functional interactions and dynamics across diverse glacial environments remain underexplored. This study investigated microbial-mediated elemental cycling in subglacial ice and sediments, regarded as main habitats of microorganisms, from the Tibetan Plateau (TP) glaciers using metagenome sequencing associated with geochemical profiling. Due to low nutrient retention in oligotrophic subglacial environment , resulting from low concentration of bioavailable organic carbon and nitrogen, microbes are oligotrophic bacteria and required unique metabolisms to survive. Nevertheless, enriched iron, carbonate and sulfate in minerals is potential energy source for heterotrophic and chemoautotrophic microbes. Proteobacteria (90%-96% relative abundance) prevailed in subglacial microbiomes, with high intra-habitat alpha-diversity but inter-habitat beta-diversity divergence, collectively shaping a low-biodiversity ecosystem. Metagenome-assembled genomes (MAGs) indicated that 82% MAGs are unclassified species, suggesting subglacial species are required to be discovered. Metagenomic functional annotation of MAGs revealed that Tibetan Plateau subglacial communities harbor diverse metabolic adaptations, with Bacterial communities undergoing redox-driven elemental cycling, serving as biogeochemical cycle of C-N-S-H-Fe in diverse ecosystems. For autotrophs performing carbon fixation and providing organic matters to oligotrophic environment, Proteobacteria and Chloroflexota participated in both photosynthesis via penetrated light from glacier surface and chemosynthesis, coupling with sulfide oxidation (Proteobacteria), ferrous iron oxidation (Desulfobacterota), nitrification (Proteobacteria) and hydrogen oxidation (Desulfobacterota, Chloroflexota, Proteobacteria). In contrast, heterotrophs undergo processes such as sulfate reduction (Proteobacteria), dissimilarity nitrate reduction (Proteobacteria), ferric iron reduction (Desulfobacterota) to facilitate the assimilation of carbon skeletons and energy harvest via oxidative phosphorylation. Our findings suggests that subglacial environments are ignored microorganism habitats with plenty of unclassified bacteria, utilizing inorganic compounds to maintain microbial activities. Our finding uncovered a previously unclassified microorganisms within alpine subglacial environments, sustaining metabolic activity through redox-driven chemolithoautotrophic and heterotrophic pathways under oligotrophic conditions and enhancing critical biogeochemical cycling. This finding provided empirical evidence for life persistence strategies during Snowball Earth era and informed the search for cryosphere-hosted biospheres on icy moons and extraterrestial planet within subglacial liquid water reservoirs.