Arsenic-Hypertolerant Pseudomonads Isolated from Ancient Gold and Copper-Bearing Black Shale Deposits

This report describes the comparative characteristics of Pseudomonas strains isolated from Lubin copper mine and Zloty Stok gold mine in SW Poland. The 9 isolates exhibited huge resistance to arsenic, being able to grow in the presence of 500 mM arsenate and 15 mM arsenite. All strains have evolved strong resistance mechanisms supported by arsenate reduction, but none could utilize arsenite or arsenate in respiratory processes. In addition, these Pseudomonads produced siderophores during growth on medium lacking free iron, which could promote mineral dissolution and mobilization of the more toxic As(III) species in the environment.