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

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.

Raoultella ornithinolytica as a Potential Candidate for Bioremediation of Heavy Metal from Contaminated Environments

“…The presence of lead had little impact on the growth rate of R. ornithinolytica , which might be due to a well-developed lead tolerance mechanism occurring as a result of high Pb concentrations in the Tanjaro River. The lower concentration of Cd in the water samples, meanwhile, resulted in a lower tolerance rate for this metal ion and a slower growth rate than in the absence of heavy metal, similar to findings observed by [ 56 ].…”

Isolation and characterization of potential indigenous bacteria from the former bauxite mining area for heavy metal reduction

“…Numerous studies investigated the potential of bacteria in nature as heavy metal bioremediation agents (Pambudiono et al 2018;Anno et al 2020;Wang et al 2020;Oziegbe et al 2021). Only limited data presently exist on indigenous bacteria from former bauxite mining areas that possess the ability to bio-remove Pb and Cr.…”

Caracterização de bactérias resistentes a metais pesados e o potencial para biorremediação

“…Kamala-Kannan e Lee (2008) encontraram semelhante resultados. Das amostras sedimentos de um ecossistema de água salobra na Coreia do Sul, todas as cepas bactérias que pertenciam ao gênero Bacillus, apresentaram alta tolerância a altas concentrações de Mn e resistência aos antibióticos ampicilina, tetraciclina, canamicina e estreptomicina Wang et al (2020),. a partir de amostras de solo contaminado com metais pesados, isolaram cepas bacterianas onde o gênero Bacillus era dominante, com alta resistência ao metais Cd e Pb e capacidade de fixação dos metais.…”