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Limited Role of Rhamnolipids on Cadmium Resistance for an Endogenous-Secretion Bacterium

Author

Listed:
  • Sufang Xing

    (Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China)

  • Zhen Yan

    (Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China)

  • Chao Song

    (Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China)

  • Huifang Tian

    (Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China)

  • Shuguang Wang

    (Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
    Sino-French Research Institute for Ecology and Environment (ISFREE), School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China)

Abstract

Rhamnolipids, a type of biosurfactant, represent a potential strategy for both enhancing organismic resistance and in situ remediation of heavy metals contaminations. In-depth study of the mechanism of rhamnolipids synthesis in response to heavy metals stress, is indispensable for a wide use of biosurfactant-secreting microbes in bioremediation. In this study, we employed the wild-type and the rhlAB deficient strain (Δ rhlAB ) of Pseudomonas aeruginosa , a prototypal rhamnolipids-producing soil microorganism, to investigate its responses to cadmium resistance based on its physicochemical, and physiological properties. Compared with the wild-type strain, the Δ rhlAB were more sensitive to Cd-stress at low Cd concentration (<50 mg/L), whereas there was little difference in sensitivity at higher Cd concentrations, as shown by spot titers and cell viability assays. Secreted rhamnolipids reduced intracellular Cd 2+ accumulation to alleviate Cd 2+ stress, whereas endogenous rhamnolipids played a limited role in alleviating Cd 2+ stress. Synthesized rhamnolipids exhibited a higher critical micelle concentration (CMC) (674.1 mg/L) and lower emulsification index (4.7%) under high Cd-stress, while these parameters showed no obvious changes. High Cd-stress resulted in high hydrophilic wild-type bacterial surface and lower bioremediation ability. This study could advance a deeper understanding of the mechanism of cadmium resistance and provide a theoretical foundation for the application of biosurfactant and biosurfactant-secreted bacterium in contaminant bioremediation.

Suggested Citation

  • Sufang Xing & Zhen Yan & Chao Song & Huifang Tian & Shuguang Wang, 2022. "Limited Role of Rhamnolipids on Cadmium Resistance for an Endogenous-Secretion Bacterium," IJERPH, MDPI, vol. 19(19), pages 1-14, October.
    • Handle: RePEc:gam:jijerp:v:19:y:2022:i:19:p:12555-:d:931405
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    References listed on IDEAS

    as
    1. Yanfeng Zhu & Jing Ma & Fu Chen & Ruilian Yu & Gongren Hu & Shaoliang Zhang, 2020. "Remediation of Soil Polluted with Cd in a Postmining Area Using Thiourea-Modified Biochar," IJERPH, MDPI, vol. 17(20), pages 1-13, October.
    2. Qiuye Zhang & Hongyan Liu & Fang Liu & Xianhang Ju & Faustino Dinis & Enjiang Yu & Zhi Yu, 2022. "Source Identification and Superposition Effect of Heavy Metals (HMs) in Agricultural Soils at a High Geological Background Area of Karst: A Case Study in a Typical Watershed," IJERPH, MDPI, vol. 19(18), pages 1-17, September.
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