Microbial diversity of high-elevated fumarole fields, low-biomass communities on the boundary between ice and fire.

Fumarole fields on active volcanoes are habitats that host unique microbial ecosystems. However, DNA extraction from them for further analysis is rather challenging. In this study, we compared two different ways of sample homogenization for DNA extraction to further profile the microbial communities of active fumarolic fields from Elbrus and Ushkovsky volcanoes and the frozen fumarole deposits of Fujiyama. Vertical homogenizer gave significantly higher DNA concentrations for the Elbrus samples, and more archaeal amplicon sequence variants for Elbrus and Ushkovsky samples compared to the horizontal one. This suggests that vertical homogenizer might be preferable for DNA extraction from sandy and rocky soils. Independent of the homogenizer type, the dominant phyla for Elbrus were Acidobacteriota and Pseudomonadota, and Crenarchaeota for Ushkovsky. The bacterial community of Fuji was less diverse, with Actinomycetota, Pseudomonadota and Bacillota being the dominant phyla. Thus, the studied fumaroles showed distinct microbial profiles, revealing unique adaptations to their respective extreme environments. Within the fungal community, Ascomycota, Basidiomycota and Chytridiomycota were the most dominant phyla for all three volcanoes, but their abundance varied. This study offers the first comprehensive analysis of microbial and fungal communities of active and frozen fumarolic fields, and demonstrates that the choice of methodology can significantly influence the understanding of microbial diversity in extreme environments.