Structural and functional diversity of microbial communities in ancient mining sites from San Luis Potosí, México

Abstract

The purpose of this study was to evaluate the effects of potentially toxic elements (PTEs) on soil microbial community functionality and structure. Charcas and Cedral in San Luis Potosí, Mexico, are sites with ancient mining activity. This activity has generated heavy metals (HMs) polluted soils that provoke deleterious effects on microbial community. Sampling was conducted in sites with and without aged mining activity. The parameters analysed were physicochemical properties and PTE concentrations. Functional diversity was evaluated with a community-level physiological profiling (CLPP) analysis, diversity was evaluated using the richness (S), and the indices of Shannon's diversity (H), Simpson's dominance (D) and Pielou's evenness (J) were for the structure evaluation, based on relative substrate utilisation. CLPP results of set of soils indicated the following substrate utilisation pattern: carbohydrates > polymers (POL) > carboxylic/ketonic acids > amino acids (AmA) > amine/amides (A/A). In Cedral, the AmA utilisation favoured the increase of J value. In addition, it was observed that the utilisation of these compounds decreases at a higher concentration of Al and organic matter (OM) but increases at a higher concentration of Cu, Pb, Zn, Fe, Mn, and Ni, a phenomenon opposite to that was observed in Charcas. The results of set of soil indicated that AmA utilisation increases the values of S, J, D, and H. These results indicate that the microorganisms in soil are resistant to high PTE concentrations, in that condition they need accessible carbon sources as energy and as nutrients, however, they adapted to use complex carbon sources (POL). Furthermore, it presented low OM mineralisation despite high values of H, or J, then some metabolic processes could be compromised. Therefore, an intervention for soil conservation and monitoring is required.