| Acidithiobacillus ferrooxidans, an important microorganism in bioleaching, is also one of the most studied organisms in the bioleaching microbial community. While Acidiphilium cryptum is an assistant bioleaching bacterium, which can reduce Fe(â…¢) and utilize organic matter formed by A. ferrooxidans. In this way, it can eliminate the inhibition and toxicity effect of these organic matters and produce Fe(â…¡) as energy for A. ferrooxidans. Because of the rude living environment, they are resistant to many heavy metals including arsenite and copper. Both of them have arsH gene, which is not common and its function is not very clear so far. The aim of this paper is to investigate the influence of Acidiphilium cryptum DX1-1on As resistance gene arsH expression of A. ferrooxidans.In this paper, the tolerance on two heavy metal ions Cu2+,As3+ of A. ferrooxidans CMS and Acidiphilium cryptum DX1-1 was studied. The results showed that strain CMS's tolerance on Cu2+ was higher than strain DX1-1, while strain DX1-1's tolerance on As3+ was higher than strain CMS. Meanwhile strain DX1-1 can promote the living activity and As resistance of strain CMS.Bioleaching research of A. ferrooxidans CMS and Acidiphilium cryptum DX1-1 showed that the leaching efficiency of strain DX1-1 was worse than strain CMS, but when mixed culture together the leaching efficiency of strain CMS is much better. Adding heavey metal caused the leaching efficiency decline. And the higher concentration of heavey metal, the lower leaching efficiency.Real-time PCR was used to detect the differential expression of arsH in A. ferrooxidans ATCC23270 in different concentrations of As3+ and differential expression of arsH when culture with Acidiphilium cryptum DX1-1 or not. The results showed that arsH gene expression was sensitive to As3+, and it may have important role in As resistance. The arsH gene expression was enhanced while the As3+ concentration increased. When strain ATCC23270 was cultured with strain DX1-1, the arsH gene expression was lower than that when strain ATCC23270 was cultured itself. To some extent, strain DX1-1 influenced the arsH gene expression of strain ATCC23270.Bioinformatic analysis of the diversity of arsH genes in arsenic-resistant bacteria revealed that the horizontal gene transfer (HGT) is occurred not only among the species within the same phyla but also among the species of different phyla. Rarefaction curves indicate that current efforts on arsenic resistant bacteria isolation and sampling are largely inadequate. Researches indicate that arsH plays an important role in bacteria resistance to arsenite, but there is still much work to do to make clear its exact function. Among these arsH containing species, many have special functions like infecting pathogens, plant symbiosis, macromolecular polymer degradation, chlorophyll production, and heavy metal resistance.All of these results confirmed that arsH plays an important role in As resistance. Acidiphilium cryptum DX1-1 can enhance the living activity and As resistance of A. ferrooxidans. These results lead us to a further step for understanding the mechanism of As resistance in this extremophilic microorganism, and interrelationship of Acidiphilium cryptum DX1-1 and A. ferrooxidans.
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