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| Isolation and Cd adsorption mechanisms of Delftia sp. M6 strain |
| Received:April 28, 2022 |
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| KeyWord:soil;bacteria;Delftia sp.;cadmium;adsorption;mechanism |
| Author Name | Affiliation | E-mail | | SHI Yangyang | College of Environment, Sichuan Agricultural University, Chengdu 611130, China
Danjiangkou Tobacco Monopoly Bureau, Hubei Province, Danjiangkou 442700, China | | | XU Min | College of Environment, Sichuan Agricultural University, Chengdu 611130, China | | | WAN Qin | College of Environment, Sichuan Agricultural University, Chengdu 611130, China | | | XIE Daimin | College of Environment, Sichuan Agricultural University, Chengdu 611130, China | | | XIAO Xiao | College of Environment, Sichuan Agricultural University, Chengdu 611130, China | | | WU Jun | College of Environment, Sichuan Agricultural University, Chengdu 611130, China | wuj1962@163.com |
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| Abstract: |
| The key to Cd bioremediation technology is obtaining Cd-resistant strains with high tolerance and strong fixation to Cd. The bioremediation effectivity is closely related to the mechanism of Cd fixation used by microorganisms. In this study, we isolated a Cd-resistant bacterial strain M6 from heavy metals contaminated soil. We employed batch adsorption experiments, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectrometry, and other techniques to explore the Cd fixation capacity and mechanism of the M6 strain. It was found that M6 had the highest adsorption rate（71.8%）for Cd at pH 7, temperature of 35 ℃, and after 48 h of incubation with 10 mg·L-1 of initial Cd concentration. Adsorption capacity of Cd increased with concentration of Cd from 10 mg·L-1 to 100 mg·L-1, and the maximum adsorption capacity was 36.73 mg·L-1. The mechanism of Cd fixation by M6 included intracellular accumulation and extracellular adsorption. Scanning electron microscopy indicated precipitates on the cell surface of M6 after Cd adsorption. The Fourier-transform infrared spectra showed that various functional groups on the cell surface were involved in the adsorption of Cd by M6. X-ray photoelectron spectroscopy analysis revealed that Cd may existed on the surface of cells in the form of Cd（OH）2 and CdCO3. The results of 16S rRNA gene sequence analysis showed that M6 was 100% homologous to Delftia sp.12, and was preliminarily identified as Delftia sp.. In conclusion, M6 has strong resistance to Cd and high fixation effect on Cd, and its fixation mechanism include intracellular accumulation, extracellular adsorption and extracellular precipitation. |
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