Microbiomes in an acidic rock–water cave system

Abstract

Belowground ecosystems are accessible by mining, where a specific microbial community can be discovered. The biodiversity of a former alum mine rich in carbon, but with a low pH of 2.6–3.7, was evaluated by DNA- and cultivation-dependent methods using samples of the black slate rock material, secondary mineralization phases and seepage water. Pyrite oxidation within the low-grade metamorphic Silurian black slate established high concentrations of Fe and $\rm{SO}_4^{2-}$ forming the extreme conditions visible with acidophilic and Fe-oxidizing microorganisms. In addition, an unexpected predominance of fungi in this C-rich and acidic cave ecosystem, including high numbers of Mucoromycota and Mortierellomycota, was detected. Therefore, fungal cultures were obtained, mainly from the secondary mineral phases that are iron phosphates. Hence, the fungi might well have been involved in phosphate mobilization there. The rock material itself is rich in organic carbon that can be used by oxidase activity. The cultivation setup mimicked the cave conditions (low temperature, low pH, oxic conditions), with one oligotrophic and one medium rich in nutrients that allowed for isolation of different fungal (and eutrophic bacterial) groups. The acidic conditions prevented the occurrence of many basidiomycetes, while the isolated fungi could survive these adverse conditions.

Diversity of Microfungi in a High Radon Cave Ecosystem

“…The saprotrophic fungus Leptobacillium leptobactrum was detected in French and German caves ( Bastian et al, 2009 ; Porca et al, 2011 ; Burow et al, 2019 ). In Spanish caves, the abundance of Leptobacillium leptobactrum and Leptobacillium symbioticum amounted 100% of the fungi isolated from the air in some halls ( Dominguez-Moñino et al, 2021 ).…”

Heat Shock Response of the Active Microbiome From Perennial Cave Ice

“…At the genus level ( Supplementary Figure 1 ), the potentially active fungal reads from the T0 sample could be assigned to the Rhizophydium (Chytridiomycota), Geoglossum (Ascomycota), and Ochroconis (Ascomycota) taxa, with relatively similar representation. Rhizophydium species belonging to Rhysophydiales are parasites of invertebrates, chytrids, and algae, assuming a possible role in the control of aquatic populations, and are also common in soil, primarily as saprobes, with a possible role in nutrient recycling ( Powell, 1993 ; Nieves-Rivera, 2003 ; Ibelings et al, 2004 ; van der Wal et al, 2013 ; Burow et al, 2019 ). Ochroconis is a fungal genus reported in caves ( Novakova, 2009 ; Martin-Sanchez et al, 2012b ; Martinez-Avila et al, 2021 ), guano, and bats ( Cunha et al, 2020 ).…”

Biomineralization by Extremely Halophilic and Metal-Tolerant Community Members from a Sulfate-Dominated Metal-Rich Environment

“…Fungi are described to be mainly influenced by the plant population of a site as well as water availability and other abiotic factors such as N-richness, carbon content, or soil quality [46][47][48][49]. Mortierellomycota are often found in heavy-metal-and radionuclide-contaminated, disturbed soil and they are known for accumulation of heavy metals such as Cd, Co, Hg, Ni, Zn, and U [6,50,51] Here, we could show Mortierellomycota in high abundances correlated with Sr and Cs gradients in a saline environment. Rozellomycota (Basidiomycota) were found enriched in the most contaminated samples confirming their occurrence in (saline) wetlands, including the vicinity of a uranium mine [52].…”

“…Environments with high salt concentrations such as brines, salty soils, or sediments drive adaptation of the microbial community present at such sites [1][2][3][4]. Specific contaminants include not only NaCl, but specifically due to mining operations of sulfidic ores, high sulfate concentrations may lead to halophilic communities establishing on such sites [5][6][7]. Usually, high salinity is observed concomitantly with high pH [1,8,9].…”