Screening of Heavy Metal-Immobilizing Bacteria and Its Effect on Reducing Cd2+ and Pb2+ Concentrations in Water Spinach (Ipomoea aquatic Forsk.)

Tiejun Wang; Xiaoyu Wang; Wei Tian; Lunguang Yao; Yadong Li; Zhaojin Chen; Hui Han

doi:10.3390/ijerph17093122

Screening of Heavy Metal-Immobilizing Bacteria and Its Effect on Reducing Cd²⁺ and Pb²⁺ Concentrations in Water Spinach (Ipomoea aquatic Forsk.)

Int J Environ Res Public Health. 2020 Apr 30;17(9):3122. doi: 10.3390/ijerph17093122.

Authors

Tiejun Wang^{1

2}, Xiaoyu Wang¹, Wei Tian³, Lunguang Yao¹, Yadong Li², Zhaojin Chen¹, Hui Han¹

Affiliations

¹ Collaborative Innovation of Water Security for the Water Source Region of Mid-line of the South-to-North Diversion Project of Henan Province, College of Agricultural Engineering, Nanyang Normal University, Nanyang 473061, China.
² State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan 430062, China.
³ Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China.

Abstract

Microbial immobilization is considered as a novel and environmentally friendly technology that uses microbes to reduce heavy metals accumulation in plants. To explore microbial resources which are useful in these applications, three water spinach rhizosphere soils polluted by different levels of heavy metals (heavy pollution (CQ), medium pollution (JZ), and relative clean (NF)) were collected. The community composition of heavy metal-immobilizing bacteria in rhizosphere soils and its effects on reducing the Cd²⁺ and Pb²⁺ concentrations in water spinach were evaluated. Four hundred strains were isolated from the CQ (belonging to 3 phyla and 14 genera), JZ (belonging to 4 phyla and 25 genera) and NF (belonged to 6 phyla and 34 genera) samples, respectively. In the CQ sample, 137 strains showed a strong ability to immobilize Cd²⁺ and Pb²⁺, giving Cd²⁺ and Pb²⁺ removal rates of greater than 80% in solution; Brevundimonas, Serratia, and Pseudoarthrobacter were the main genera. In total, 62 strains showed a strong ability to immobilize Cd²⁺ and Pb²⁺ in the JZ sample and Bacillus and Serratia were the main genera. A total of 22 strains showed a strong ability to immobilize Cd²⁺ and Pb²⁺ in the NF sample, and Bacillus was the main genus. Compared to the control, Enterobacter bugandensis CQ-7, Bacillus thuringensis CQ-33, and Klebsiella michiganensis CQ-169 significantly increased the dry weight (17.16-148%) of water spinach and reduced the contents of Cd²⁺ (59.78-72.41%) and Pb²⁺ (43.36-74.21%) in water spinach. Moreover, the soluble protein and Vc contents in the shoots of water spinach were also significantly increased (72.1-193%) in the presence of strains CQ-7, CQ-33 and CQ-169 compared to the control. In addition, the contents of Cd and Pb in the shoots of water spinach meet the standard for limit of Cd²⁺ and Pb²⁺ in vegetables in the presence of strains CQ-7, CQ-33 and CQ-169. Thus, the results provide strains as resources and a theoretical basis for the remediation of Cd- and Pb-contaminated farmlands for the safe production of vegetables.

Keywords: Cd2+ and Pb2+; community composition; heavy metal-immobilizing bacteria; immobilization; water spinach.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Bacillus thuringiensis
Bacteria
Cadmium
Enterobacter
Ipomoea* / chemistry
Klebsiella
Lead
Metals, Heavy* / metabolism
Soil
Soil Pollutants*
Water

Substances

Metals, Heavy
Soil
Soil Pollutants
Cadmium
Water
Lead

Supplementary concepts

Enterobacter bugandensis
Klebsiella michiganensis