Gene expression response of mutagenic breeding of Acidithiobacillus sp. FJ2 to different concentrations of uranium low grade ore

Abstract

<em>Acidithiobacillus ferrooxidans </em>(<em>At. f</em>) is a bacterium involved in the bioleaching process<em>_.</em>In the present study, we investigated the effects of <em>Acidithiobacillus </em>sp. FJ2 induced with diethyl sulfate (DES) as mutagen on the bioleaching of low grade uranium ore. The comparison was carried out within 5, 10, 15, 25 and 50% uranium ore pulp densities in the bioleaching system. The impact of the induction of <em>Acidithiobacillus </em>sp. FJ2 was determined by Eh and pH values, concentrations of Fe²⁺ and uranium extraction rates at 24 h intervals. The results showed that DES with 0.8% may lead to an obvious change on bacteria leading to improvement of bioleaching capability in 5, 10, 15% pulp densities. However, the bioleaching activity of the original bacteria was more efficient than DES-induced bacteria at 25 and 50% pulp densities. The gene expression results in 0.8% DES treated bacteria indicated that the bacteria attempt to adjust in the bioleaching systems (with different pulp densities) through decreased<em> cyc2</em> and increased <em>rus</em>, <em>cyc1</em> and <em>coxB </em>levels. These results suggest that uranium may induce oxidative stress in the wild and treated strains in the high pulp density, while the bacteria tried to survive and gain more energy from the iron oxidation. However, when the amount of uranium increased, the mutants couldn’t cope up woth the enhanced stress in 25 and 50% pulp densities. It may be due to inhibitory effect of uranium toxicity on adaptive processes which may change the trends.