Meta-Analysis of Fungal Community Structure and Cyanide-Related Metabolic Potential in Geothermal Hot Springs

Hot springs are extreme environments characterized by high temperatures, variable pH, and the presence of toxic compounds such as cyanide, which act as selective pressures on microbial communities. Although prokaryotes have been widely studied in these systems, fungal diversity and its functional roles remain poorly understood. Herein, a meta-analysis of fungal communities in continental hot springs was conducted using 43 publicly available shotgun metagenomic and ITS metabarcoding datasets. Taxonomic and ecological analyses revealed that fungal communities were predominantly dominated by Ascomycota (64.2%), followed by Basidiomycota (17.7%) and other minor phyla, with significant site-specific differences. Ecological analyses demonstrated that Shannon diversity index ranged from low to moderate (1.74–3.22). Furthermore, Hill numbers (q1, q2) indicated that communities were characterized by a few abundant taxa, such as Acidomyces acidothermus , Emericellopsis glabra or Epicoccum thailandicum and a large proportion of rare species. Distance-based redundancy analysis showed that environmental variables (temperature, pH and dissolved oxygen) explained 47% of the variation in community composition across sites, with pH and temperature as the statistically significant factors. Functional genomic analyses of representative taxa revealed widespread genetic potential for cyanide degradation, mainly through rhodanese-mediated sulfurtransferase activity, as well as oxidative (via cyanase) and hydrolytic (via cyanide hydratase) pathways. However, some taxa (e.g. yeast and saprobes such as Mucor lusitanicus ) lacked key genes for hydrolytic or oxidative pathways in cyanide degradation, suggesting ecological specialization or alternative nitrogen metabolism strategies. These findings highlight the ecological relevance and metabolic potential of fungi in hydrothermal systems.