Isolation and Identification of Mercury-Tolerant Bacteria LBA119 from Molybdenum-Lead Mining Soils and Their Removal of Hg2

Hanyue Yao; Hui Wang; Jiangtao Ji; Aobo Tan; Yang Song; Zhi Chen

doi:10.3390/toxics11030261

Isolation and Identification of Mercury-Tolerant Bacteria LBA119 from Molybdenum-Lead Mining Soils and Their Removal of Hg²

Toxics. 2023 Mar 12;11(3):261. doi: 10.3390/toxics11030261.

Authors

Hanyue Yao¹, Hui Wang¹, Jiangtao Ji², Aobo Tan¹, Yang Song², Zhi Chen³

Affiliations

¹ School of Chemical Engineering and Pharmacy, Henan University of Science and Technology, Luoyang 471023, China.
² College of Agricultural Equipment Engineering, Henan University of Science and Technology, Luoyang 471023, China.
³ Department of Building, Civil and Environmental, Concordia University, Montreal, QC H3G 1M8, Canada.

Abstract

Aims: To screen heavy metal-tolerant strains from heavy metal-contaminated soil in mining areas and determine the tolerance of the strains to different heavy metals and their removal rates through experiments.

Methods: Mercury-resistant strain LBA119 was isolated from mercury-contaminated soil samples in Luanchuan County, Henan Province, China. The strain was identified by Gram staining, physiological and biochemical tests, and 16S rDNA sequences. The LBA119 strain showed good resistance and removal rates to heavy metals such as Pb²⁺, Hg²⁺, Mn²⁺, Zn²⁺, and Cd²⁺ using tolerance tests under optimal growth conditions. The mercury-resistant strain LBA119 was applied to mercury-contaminated soil to determine the ability of the strain to remove mercury from the soil compared to mercury-contaminated soil without bacterial biomass.

Results: Mercury-resistant strain LBA119 is a Gram-positive bacterium that appears as a short rod under scanning electron microscopy, with a single bacterium measuring approximately 0.8 × 1.3 μm. The strain was identified as a Bacillus by Gram staining, physiological and biochemical tests, and 16S rDNA sequence analysis. The strain was highly resistant to mercury, with a minimum inhibitory concentration (MIC) of 32 mg/L for mercury. Under a 10 mg/L mercury environment, the optimal inoculation amount, pH, temperature, and salt concentration of the LBA119 strain were 2%, 7, 30 °C, and 20 g/L, respectively. In the 10 mg/L Hg²⁺ LB medium, the total removal rate, volatilization rate, and adsorption rate at 36 h were 97.32%, 89.08%, and 8.24%, respectively. According to tolerance tests, the strain showed good resistance to Pb²⁺, Mn²⁺, Zn²⁺, Cd²⁺, and other heavy metals. When the initial mercury concentration was 50 mg/L and 100 mg/L, compared with the mercury-contaminated soil that contained an LB medium without bacterial biomass, LBA119 inoculation increased 15.54-37.67% after 30 days of culture.

Conclusion: This strain shows high bioremediation potential for mercury-contaminated soil.

Keywords: 16S rDNA; Bacillus; heavy metal mercury; soil.

Grants and funding

This work was supported by the National Natural Science Foundation of China [No.41471256]; Project for the Training of Young Backbone Teachers of Higher Education Institutions in Henan Province (2018GGJS047); Henan Province Science and Technology Research Project (192102110050).