en تخصصي Special Original articles <div style="text-align: justify;"><strong><em>Introduction:</em></strong> Mutations are the most popular way to increase the efficiency of mineral waste bioleaching. <em>Acidithiobacillus ferrooxidans</em> are used as an important microorganism in <a href="http://scholar.google.com/scholar?q=biohydrometallurgy&hl=en&as_sdt=0&as_vis=1&oi=scholart&sa=X&ved=0ahUKEwiT7bax8cfVAhUEfFAKHcdxBCUQgQMIJzAA">biohydrometallurgy</a>. Arsenate is one of the toxic elements in mines, which reduces the efficiency of <em>A. ferrooxidans</em> leaching. The purpose of this research was to increase the resistance of <em>A. ferrooxidans</em> to high concentrations of arsenate.<br> <strong><em>Materials and Methods:</em></strong> This research was an analytical &ndash; descriptive study. The studied population was isolated <em>A. ferrooxidans</em> bacterium from the Sarcheshmeh copper mine in Kerman. The highest tolerable concentration of arsenate was determined by successive cultures of this bacterium at increasing concentrations of arsenate. The bacteria were exposed to UV radiation at different times and then cultured in higher concentrations of arsenate.<br> <strong><em>Results:</em></strong> The results showed that the wild strain was able to grow in the medium containing 20 mM of arsenate. With adaptation, this bacterial strain could grow in medium containing increasing concentrations (40, 60, 80, 100, 120, and 140 mM) of arsenate. When the bacterium was exposed to UV ray for 60 minutes, it was able to grow at a concentration of 120 mM of arsenate.<br> <strong><em>Conclusion:</em></strong> The results indicated a very good effect of UV ray on increasing the arsenate resistance of <em>A. ferrooxidans</em>. It is suggested that this modified strain can be used in real environments for bioleaching.<br> &nbsp;</div> Acidithiobacillus Ferrooxidans, Ultraviolet Rays, Mutation, Copper. 710 716 http://jehsd.ssu.ac.ir/browse.php?a_code=A-10-1-102&slc_lang=en&sid=1 Abdolrahman Dehghani 0000-0003-3925-6962 No Medical Biotechnology Research Center, Ashkezar Branch, Islamic Azad University, Ashkezar, Yazd, Iran. Behrooz Dousti 0000-0001-7287-2674 No Department of Biology, Khoramabad Branch, Islamic Azad University, Khoramabad, Iran. Farhad Gilavand 0000-0002-1459-0078 No Department of Biology, Khoramabad Branch, Islamic Azad University, Khoramabad, Iran. Amirarsalan Kavyanifard 0000-0001-9619-8768 No Department of Biology, Payam Noor University, Tehran, Iran. Samaneh Sedighi – Khavidak sedighi.samaneh@yahoo.com 0000-0002-2177-7340 Yes Medical Biotechnology Research Center, Ashkezar Branch, Islamic Azad University, Ashkezar, Yazd, Iran.