Metabolically Active Eukaryotic Communities in Extremely Acidic Mine Drainage

Abstract

Acid mine drainage (AMD) microbial communities contain microbial eukaryotes (both fungi and protists) that confer a biofilm structure and impact the abundance of bacteria and archaea and the community composition via grazing and other mechanisms. Since prokaryotes impact iron oxidation rates and thus regulate AMD generation rates, it is important to analyze the fungal and protistan populations. We utilized 18S rRNA and beta-tubulin gene phylogenies and fluorescent rRNA-specific probes to characterize the eukaryotic diversity and distribution in extremely acidic (pHs 0.8 to 1.38), warm (30 to 50°C), metal-rich (up to 269 mM Fe 2؉ , 16.8 mM Zn, 8.5 mM As, and 4.1 mM Cu) AMD solutions from the Richmond Mine at Iron Mountain, Calif. A Rhodophyta (red algae) lineage and organisms from the Vahlkampfiidae family were identified. The fungal 18S rRNA and tubulin gene sequences formed two distinct phylogenetic groups associated with the classes Dothideomycetes and Eurotiomycetes. Three fungal isolates that were closely related to the Dothideomycetes clones were obtained. We suggest the name "Acidomyces richmondensis" for these isolates. Since these ascomycete fungi were morphologically indistinguishable, rRNA-specific oligonucleotide probes were designed to target the Dothideomycetes and Eurotiomycetes via fluorescent in situ hybridization (FISH). FISH analyses indicated that Eurotiomycetes are generally more abundant than Dothideomycetes in all of the seven locations studied within the Richmond Mine system. This is the first study to combine the culture-independent detection of fungi with in situ detection and a demonstration of activity in an acidic environment. The results expand our understanding of the subsurface AMD microbial community structure.The Richmond Mine at Iron Mountain, which is near the city of Redding in northern California, is a subsurface mine that contains chemolithotrophic microbial communities that are sustained by energy derived from pyrite (FeS 2 ) oxidation (4). The dissolution of pyrite from the Richmond Mine ore body yields warm (35 to 57°C), extremely acidic (typically pHs 0.5 to 0.9), metal-rich (for a review, see reference 4) fluids referred to as acid mine drainage (AMD). At the Richmond Mine it is possible to access, via mining tunnels, several environments that harbor these extremely acidophilic communities.Microbial eukaryotes likely play critical, but as yet only partially determined, roles in AMD communities. Fungal hyphae comprise a significant but variable portion of the total biomass in many biofilm communities in the Richmond Mine, particularly in those growing in flowing solutions. The hyphae may contribute to the anchoring of biofilms to pyrite sediments and may confer structure, especially to "slime streamers" (4). Relatively large fungal filaments also provide surfaces for the attachment of prokaryotes (see Fig. 3C in reference 4). In addition, they keep organic carbon levels low and produce dissolved carbonate ions, which are likely important for the growth of chemolithoautot...

Generation of Acid Mine Lakes Associated with Abandoned Coal Mines in Northwest Turkey

“…Similarly, Hackley and Anderson (1986) showed a huge variation in the d 34 S value of pyrite (-52.6 to ?34.6 %) in coal from the Rocky Mountain region. Sulfur isotope fractionation of 2 % for S 0 oxidation with A. ferrooxidans has been reported by Balci et al (2012), which encompasses the value determined in this study, thus indicating that biological oxidation of sulfur, particularly in AML 2, cannot be neglected because numerous sulfur-oxidizing bacteria were determined in the lake as suggested by various studies (McGuire et al 2001;Druschel et al 2003Druschel et al , 2004Baker et al 2004). …”

Fungal Iron Biomineralization in Río Tinto

“…All major microbial groups are capable of immobilizing metal ions and carrying out mineralization processes through organic and inorganic precipitation of secondary associated minerals as well as depositing crystalline material on and within cell walls [31,34,35]. Also, fungi have been reported as an important part of the microbial community of Río Tinto, as well as other mine drainage systems with similar characteristics (e.g., [7,[36][37][38]) So, in a scenario like Río Tinto, it is not unreasonable that fungi may be involved in different geochemical cycles, such as the dissolution of certain minerals and the formation of new ones.…”

“…Río Tinto, as well as other mine drainage systems with similar characteristics (e.g., [7,[36][37][38]) So, in a scenario like Río Tinto, it is not unreasonable that fungi may be involved in different geochemical cycles, such as the dissolution of certain minerals and the formation of new ones. Our TEM and HAADF-STEM analyses of the M13 sediments showed fungal cells involved in biomineralization processes with minerals nucleated on fungal cell walls (Figure 4).…”

In situ proteo-metabolomics reveals metabolite secretion by the acid mine drainage bio-indicator, Euglena mutabilis

“…AMDs exposed environments are usually considered very toxic to biota as they are characterized, besides low pH values, by very high concentrations of metallic compounds (Leblanc et al, 1996). Such drainages are observed in ancient mining exploitations where oxidation of the extruded rocks leads to the production of sulfuric acid and mobilization of elements such as iron, copper, aluminum and arsenic into the percolating waters (Leblanc et al, 1996;Baker et al, 2004;Canovas et al, 2008). This process leads to a persistent contamination of downstream aquatic environments and is a major concern for environmental and public health in many countries.…”