Fossilized anaerobic and possibly methanogenesis-fueling fungi identified deep within the Siljan impact structure, Sweden

Abstract Recent discoveries of extant and fossilized communities indicate that eukaryotes, including fungi, inhabit energy-poor anoxic environments deep within the fractured igneous crust. This subterranean biosphere may constitute largest fungal habitat on our planet, but knowledge abyssal fungi their syntrophic interactions with prokaryotes concomitant metabolisms is scarce. Here we report findings fossilized, chitin-bearing hyphae at ~540 m depth in bedrock Siljan impact structure, crater Europe. Strong 13 C-enrichment calcite precipitated suggests formation following methanogenesis, anaerobic decomposed dispersed organic matter producing for example H 2 have fueled autotrophic methanogens. An Eocene age determined infers first timing constraint continental Fungi be widespread decomposers overlooked providers to autotrophs vast rock-hosted biosphere.