Early ecological succession and functional persistence of chemolithoautotrophic bacterial communities of mine tailings

Mine tailings, resulting from industrial processes, constitute extreme environments due to toxic heavy metals, metalloids, and low concentrations of inorganic nitrogen, phosphorus, and organic carbon. Despite these selective pressures, pioneer microorganisms colonize these substrates, utilize limited resources, alter environmental conditions, and initiate ecological succession. This study compared the bacterial community diversity in mine tailings of different ages (1.5 and 5 years) from Durango, Mexico. Metagenomic DNA was extracted from the tailings, and the V4-V5 region of the bacterial 16S rRNA gene was amplified and sequenced using a metabarcoding approach. No metagenomic DNA was recovered from recently deposited samples; however, 127 bacterial genera were identified across both mine tailings, with 47 genera shared. The 1.5-year-old tailings exhibited greater genus richness than the 5-year-old samples. Proteobacteria dominated both communities, followed by actinomycetes. The chemolithoautotrophic genus Thiobacillus , capable of oxidizing sulfide, sulfur, and thiosulfate, was most abundant. Chemolithoheterotrophic thiosulfate-oxidizing Limnobacter and Sulfurifustis were prevalent in young and old tailings, respectively. Chemoorganoheterotrophic bacteria, including Nocardioides and Kribella (Actinobacteria), as well as Hydrogenophaga and Pseudomonas (Betaproteobacteria), were also detected. The relative abundance of chemolithoautotrophic bacteria corresponded with the environmental conditions of the mine tailings, which lack organic carbon and contain abundant reduced inorganic sulfur compounds as energy sources. Early ecological succession at the bacterial genus level was evident, primarily involving Sulfurifustis , Nocardioides , and Kribella .