Screening of Heavy Metal-Immobilizing Bacteria and Its Effect on Reducing Cd 2+ and Pb 2+ Concentrations in Water Spinach ( Ipomoea aquatic Forsk.)

Tiejun Wang, Xiaoyu Wang, Wei Tian, Lunguang Yao, Yadong Li, Zhaojin Chen and Hui Han
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Tiejun Wang: 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
Xiaoyu Wang: 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
Wei Tian: Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China
Lunguang Yao: 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
Yadong Li: State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan 430062, China
Zhaojin Chen: 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
Hui Han: 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

IJERPH, 2020, vol. 17, issue 9, 1-16

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 Cd 2+ and Pb 2+ 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 Cd 2+ and Pb 2+ , giving Cd 2+ and Pb 2+ 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 Cd 2+ and Pb 2+ in the JZ sample and Bacillus and Serratia were the main genera. A total of 22 strains showed a strong ability to immobilize Cd 2+ and Pb 2+ 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 Cd 2+ (59.78–72.41%) and Pb 2+ (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 Cd 2+ and Pb 2+ 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: heavy metal-immobilizing bacteria; Cd 2+ and Pb 2+; water spinach; immobilization; community composition (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
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