Isolation and characterization of Acidithiobacillus ferrooxidans strain QXS-1 capable of unusual ferrous iron and sulfur utilization

• Acidithiobacillus ferrooxidans strain QXS-1 was isolated from a Pb–Zn–Ag mine area.
• QXS-1 exhibited an unusual trait on the utilization of ferrous iron and sulfur.
• S-domesticated QXS-1only oxidizes sulfur when both Fe2 + and sulfur are available.
• Fe2 +-domesticated QXS-1 cells simultaneously oxidize both Fe2 + and sulfur.
• QXS-1 cells accumulated intracellular sulfur in S8 ring and polysulfide forms.

A novel Acidithiobacillus ferrooxidans strain QXS-1 was isolated from the acid mine drainage of Qixiashan Pb–Zn–Ag mine area in China. The isolate QXS-1 is a motile, rod-shaped Gram-negative bacterium with an optimum growth at 30 °C and pH 2.0. The phylogenetic analysis has demonstrated that QXS-1 is a new strain of A. ferrooxidans. The strain QXS-1 exhibited an unusual trait on the utilization of ferrous iron and sulfur as energy sources. The sulfur-domesticated QXS-1 cells only utilized sulfur as energy source for growth when both ferrous iron and sulfur are available, whereas ferrous-domesticated QXS-1 cells prefer to simultaneously utilize both ferrous iron and sulfur as energy source for growth in the presence of both substrates. The QXS-1 cells accumulated intracellular hydrophilic sulfur during growth. Based on the ultrastructure study, we deduced that the accumulated sulfur in QXS-1 exists in both octasulfur ring form and polysulfide form. The strain QXS-1 exhibited remarkable marmatite-bioleaching capacity. It is able to extract 6585 mg/L zinc from marmatite within 18 days in shake flask.