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| Cadmium adsorption characteristics and mechanisms of cadmium-resistant strains |
| Received:January 05, 2024 |
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| KeyWord:heavy metal;cadmium;adsorption;microbial remediation;transcriptome |
| Author Name | Affiliation | E-mail | | XIE Weixia | School of Biological Science & Engineering, North Minzu University, Yinchuan 750021, China | | | ZHU Mengke | School of Biological Science & Engineering, North Minzu University, Yinchuan 750021, China | | | FAN Ruijuan | School of Biological Science & Engineering, North Minzu University, Yinchuan 750021, China
Key Laboratory of Ecological Protection of Agro-pastoral Ecotones in the Yellow River Basin, National Ethnic Affairs Commission of the People's Republic of China, Yinchuan 750021, China | fanruijuan@163.com | | YAN Xingfu | School of Biological Science & Engineering, North Minzu University, Yinchuan 750021, China
Key Laboratory of Ecological Protection of Agro-pastoral Ecotones in the Yellow River Basin, National Ethnic Affairs Commission of the People's Republic of China, Yinchuan 750021, China | |
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| Abstract: |
| The focus of this study was the mechanism of cadmium resistance of three previously screened bacterial strains, i. e., Stenotrophomonas sp. Cd-2, Achromobacter sp. Cd-3, and Staphylococcus sp. Cd-7. The characteristics of bacterial adsorbents for Cd2+ and the secretion of extracellular polymeric substances（EPS）of the three strains under Cd2+ stress were investigated. The gene expression profile of strain Cd-3 was examined using transcriptome sequencing technology after exposure to Cd2+ stress, with the aim of investigating the mechanisms underlying the resistance to Cd. The results showed that the strains exhibited the highest adsorption rate of Cd 2+, reaching over 90%, under the following conditions：pH, 7; temperature, 30 ℃; contact time, 120 min; Cd2+ concentrations, 20~100 mg·L-1; bacterial biosorbent concentrations, 1 g·L-1（Cd-7）and 8 g·L-1（Cd-2, Cd-3）. The adsorption processes followed the Langmuir model and pseudosecond-order kinetic model, indicating that the adsorption of Cd2+ by these three strains is via a single molecular layer, with the adsorption rate mainly limited by chemical adsorption. The EPS assay revealed that, under conditions of Cd2+ stress, the three strains primarily inhibited the entry of Cd2+ into cells through extracellular protein complexation. The transcriptome sequencing results showed that strain Cd-3 exhibited a response to Cd2+ stress by upregulating genes associated with growth metabolism, redox reactions, and transmembrane transport, indicating that strain Cd-3 was resistant to Cd2+ stress by regulating the expression of these genes. |
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