Comparative Study of Fluoride-Tolerance of Five Typical Bioleaching Microorganisms

In the bioleaching of uranium ore, fluoride that ever accreted with the ore floats into solution, inhibiting the growth and metabolic processes of microorganism or even killing them, further reducing the efficiency of uranium leaching. In order to study the fluoride tolerance of the bioleaching microorganisms, five typical bioleaching strains including Acidithiobacillus ferrooxidans ATCC 23270, Leptospirillum ferriphilum YSK, Sulfobacillus thermosulfidooxidans ST, Acidithiobacills thiooxidans A01, Acidithiobacills caldus S1 were selected to compare their growth fluctuation and their oxidation rate of iron or sulfur in the presence of different concentration of fluoride. The results showed that At. ferrooxidans ATCC 23270 held the best fluoride tolerance, while S. thermosulfidooxidans ST took the worst. In order to explore the mechanism of microbial resistance to fluoride, whole-genome array (WGA) was used to analyze the genome-wide expression profiling of At. ferrooxidans ATCC 23270 upon 4.8 mM fluoride stress. The results showed that gene categories closely related to fluoride tolerance include cell membrane, energy metabolism, transport and binding functions of proteins, DNA metabolism, cell processing, synthesis and transportation of protein and other functional and metabolic pathways. Most of the genes associated with iron-sulfur metabolic system of At. ferrooxidans were highly expressed during 10 to 120 minutes, while in the long-term stress for 4 hours, the gene expression returned to normal level or even were down regulated. All these results provide useful information for further research on domesticating bacteria and increasing the efficiency of uranium leaching.