Arsenic release from gold mine rocks mediated by the activity of indigenous bacteria

The ancient gold mine at Zloty Stok is a source of serious arsenic contamination of underground and ground water, and soil. The objectives of this study were to investigate the impact of arsenic-metabolizing bacteria on arsenic mobilization from natural minerals and to estimate their potential role in the arsenic biogeochemical cycle in Zloty Stok gold mine. Using simple cultivation methods it was found that bacteria isolated from this gold mine could directly and indirectly influence arsenic mobilization from primary and secondary minerals. The dissimilatory arsenate reducers Shewanella sp. O23S and Aeromonas sp.O23A were particularly active in direct mobilization of the arsenic. Siderophores produced by Pseudomonas spp. isolated from a mine rock biofilm were shown to play a significant role in indirect arsenic mobilization. A potential mechanism of arsenic release from arsenate minerals, mediated by arsenite oxidizers, dissimilatory arsenate reducers and arsenic-resistant bacteria is proposed.