Isolation and Characterization of Soil Bacteria from an Abandoned Coal Mine in Southeast Kansas

Acid mine drainage (AMD) is found in areas of abandoned coal mines in southeast Kansas as a result of mine waste and tailings from century old mining events. Soil bacterial population acts as a reliable indicator of ecosystem health in these human-perturbed areas. The goals of the present study were to isolate and characterize soil bacteria from an abandoned coal mine land that included an AMD site in southeast Kansas and to isolate acid-tolerant bacterial species for bioremediation purpose. Soil samples were collected seasonally from five topographically diverse locations at the mine land. Soil texture was evaluated and soil chemistry was analyzed using inductively-coupled plasma optical emission spectroscopy. Up to sixty morphologically different colonies were isolated by dilution plating of soil samples on nutrient rich media, characterized using physiological and biochemical tests, checked for their growth on selective acid media, and identified at species-level using 16S rRNA gene sequencing. Data showed that soil pH ranged from 2.4-6.8 and contained varied concentrations of arsenic, manganese, and iron. Total bacterial concentration was 102-106 CFU/g of soil. Biochemical tests revealed a diverse metabolic potential of the bacterial population. A total of 13 acid-tolerant bacterial strains were recovered. Majority of bacterial species belonged to phylum Firmicutes, followed by Actinobacteria, and Proteobacteria. Baseline measurements of culturable bacterial diversity as well as soil chemistry at AMD sites in this region are novel and the findings would have potential use in bioremediation of AMD sites.