Profiling extremophile bacterial communities recovered from a mining tailing against soil ecosystems through comparative genome-resolved metagenomics and evolutionary analysis
Microbial communities inhabiting mining environments harbor a diverse array of bacteria with specialized metabolic capacities adapted to extreme conditions. Here, we utilized comparative genome-resolved metagenomics of a high-quality Illumina-sequenced sample from the Cauquenes copper tailing in central Chile. We investigate the metabolic roles and evolutionary behaviors of the resident microorganisms, focusing on capacities related to copper, iron, and sulfur metabolism. We recovered 44 medium and high-quality metagenome-assembled genomes (MAGs), primarily classified belonging to phylum Actinobacteriota (21), Proteobacteria (10), and Acidobacteriota (6). These MAGs were compared to the Global Soil MAGs project (SMAG catalog), which includes bacteria from conventional or natural ecosystems, to uncover specialized properties of mining bacteria. Notably, we discovered a new phylum, Nitrospirota_A, and provided insights into the unexplored taxonomic classifications at the lowest ranks such as genus and species. Functional potential analysis revealed that the mining community has enhanced molecular capabilities associated with sulfur and copper metabolism. Evolutionary analysis revealed that mining genes involved in targeted metabolism are under strong negative selection, indicating conservative evolutionary pressure within the mining environment. In particular, it was possible to identify a MAG from the genus Acidithrix with a global dN/dS ratio greater than 1, suggesting positive selection. Additionally, core proteins essential for bacterial survival, such as flagellar motors, cell cycle regulators, and biogenesis proteins, were also under positive selection. The latter points to the need for enhanced mobility in these microorganisms to locate resources efficiently. We demonstrate that copper mining communities are diverse and possess a significant metabolic repertoire under extreme conditions in sulfur and copper proteins. Those specialized genes appear to be in a conservative state rather than undergoing adaptive evolution. This study enhances our understanding of extremophile mining microbiomes, highlighting their high variability in classification, metabolic functions, evolution, and adaptation, which can be leveraged for further biotechnological applications.