title: Use of Walnut Shell Powder to Inhibit Expression of Fe(2+)-Oxidizing Genes of Acidithiobacillus Ferrooxidans.
abstract: Acidithiobacillus ferrooxidans is a Gram-negative bacterium that obtains energy by oxidizing Fe(2+) or reduced sulfur compounds. This bacterium contributes to the formation of acid mine drainage (AMD). This study determined whether walnut shell powder inhibits the growth of A. ferrooxidans. First, the effects of walnut shell powder on Fe(2+) oxidization and H⁺ production were evaluated. Second, the chemical constituents of walnut shell were isolated to determine the active ingredient(s). Third, the expression of Fe(2+)-oxidizing genes and rus operon genes was investigated using real-time polymerase chain reaction. Finally, growth curves were plotted, and a bioleaching experiment was performed to confirm the active ingredient(s) in walnut shells. The results indicated that both walnut shell powder and the phenolic fraction exert high inhibitory effects on Fe(2+) oxidation and H⁺ production by A. ferrooxidans cultured in standard 9K medium. The phenolic components exert their inhibitory effects by down-regulating the expression of Fe(2+)-oxidizing genes and rus operon genes, which significantly decreased the growth of A. ferrooxidans. This study revealed walnut shell powder to be a promising substance for controlling AMD.
authors.affiliation: Department of Biological and Environmental Engineering, Hefei University, Hefei 230601, China. yuhuili112@163.com.
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Public Health, Anhui Medical University, Hefei 230032, China. liuyehao@ahmu.edu.cn.
authors.forename: Yehao
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Biological and Environmental Engineering, Hefei University, Hefei 230601, China. 15805699883@139.com.
authors.forename: Huifang
authors.initials: H
authors.lastname: Tan
authors.affiliation: Department of Biological and Environmental Engineering, Hefei University, Hefei 230601, China. 13485672396@139.com.
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Biological and Environmental Engineering, Hefei University, Hefei 230601, China. hfyuemei@163.com.
authors.forename: Mei
authors.initials: M
authors.lastname: Yue
mesh_terms: D042763:Acidithiobacillus / Q000235:genetics* / Q000378:metabolism*; D001673:Biodegradation, Environmental; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000378:metabolism*; D031324:Juglans / Q000737:chemistry*; D008906:Mining; D009876:Operon; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000378:metabolism*
chemical_list: D010936:Plant Extracts; D007501:Iron
keywords: Acidithiobacillus ferrooxidans; acid mine drainage; rus operon; walnut shell powder