Integrated mechanism of heavy metal bioremediation from soil to rice (Oryza sativa L.) mediated by Enterococcus faecium

• Published in: Plant growth regulation 2022-07, Vol.97 (3), p.523-535
• Main Authors: Cheng, Xin, Sheng, Luo, Peng, Shuaiying, Thorley, Elizabeth, Cao, Huansheng, Li, Kuntai
• Format: Article
• Language: English
• Subjects: Agriculture; Aqueous solutions; Biomedical and Life Sciences; Bioremediation; Cadmium; Calcium chloride; Chromium; Copper; Crops; Cultivation; DNA sequencing; Efficiency; Enterococcus faecium; Food safety; Grain cultivation; Growth rate; Heavy metals; Inoculation; Life Sciences; Metal ions; Microorganisms; Original Paper; Oryza sativa; Plant Anatomy/Development; Plant Physiology; Plant Sciences; Probiotics; Ribosomal DNA; Rice; Soil contamination; Soil pollution; Soils; Toxicity
• ISSN: 0167-6903; 1573-5087
• DOI: 10.1007/s10725-022-00811-2

The growth and physiological metabolism of plants have been shown to be strongly inhibited by the presence of high levels of heavy metals. Among all heavy metal elements, cadmium (Cd) has been considered to be one of the heavy metals that poses the greatest threat to agriculture and human health. In this study, a Cd-resistant bacterial strain 2–6 was isolated. The strain was later assigned to the species Enterococcus faecium by 16 S ribosomal DNA sequencing. The removal efficiency of this Cd-resistant strain E. faecium 2–6 on three heavy metal ions (Cd, Cu and Cr) was investigated, and this experimental setup was used again to observe the effects of E. faecium 2–6 inoculation upon the growth rate and Cd accumulation patterns of cultivated rice. It was found that E. faecium 2–6 demonstrated varying metal ion removal ability in aqueous solution when exposed to Cd, Cu and Cr ions. Growth of rice was severely inhibited under the stress imposed by exposure to Cd, but this inhibition was alleviated under the addition of E. faecium 2–6. Most significantly, soil CaCl 2 -extractable Cd and soluble Cd concentrations also declined by the inoculation of E. faecium 2–6, thereby reducing the toxicity of Cd to rice. At the same time, inoculation of E. faecium 2–6 dramatically decreased detectable Cd concentrations in rice roots, stems and leaves. In conclusion, results from this study showed that Cd-resistant probiotics can not only affect the biological activities of Cd in soil, they can also be used to regulate the absorption and distribution efficiency of Cd in crops. These results provide new workable notions for the application of Cd-resistant microorganisms in heavy metal contaminated soil, for the purposes of improving production efficiency and food safety of crops.