Geomicrobiology of Mine Tailings from Malanjkhand Copper Project, India

Abstract

Geomicrobiology of mine tailing from Asia’s largest open-cast Cu mine at Malanjkhand was established, emphasizing the roles of microorganisms in acidification process using 16S rRNA gene amplicon and shotgun metagenomics. Mine tailings collected from five different locations portrayed the characteristic oligotrophic geochemical nature, with varying pH (pH 1.9–7.2), high heavy metals (Fe, Cu, Zn, Ni) and sulfate, but reduced, carbon, nitrogen and phosphate content. Iron-oxides and sulfate mineral phases were detected. Highly acidophilic, iron- and sulfur-oxidizing microorganisms including Sulfobacillus, Acidithiobacillus, Leptospirillium, Ferrimicrobium, Ferrithrix, etc. encoding the genes necessary for chemolithoautotrophic metabolism (sqr, sox, cbbL, cox, cyc1, etc.), resistance to low pH (sqh, kdp, gadB, etc.) and heavy metal stress (cop, cus, czc, chr, etc.) predominated the oxidized tailings. A markedly different microbial community represented by Thiobacillus, Sphingomonas, Meiothermus, Sulfurifustis, and members of Hydrogenophilaceae, Acidiferrobacteraceae, Gaiellales, Gemmatimonadetes, Ignavibacteriales, KD4-96, etc. predominated the fresh tailings. Metagenome of the fresh tailings confirmed presence of similar sets of genes as found in oxidized tailings, however, taxonomic affiliations of most of these functional genes vary between the two habitats, indicating differential taxa recruitment under the two contrasting ecological conditions. The study provided an in-depth understanding of Cu mine tailings microbial community and their role in acidification process.