Zhou Zijie, Yu Hongbo, Liu Jiahui, Zhu Lin, Wang Gejiao, Shi Kaixiang
National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China.
Appl Environ Microbiol. 2025 Jan 31;91(1):e0209724. doi: 10.1128/aem.02097-24. Epub 2024 Dec 4.
Cadmium (Cd) and chromium (Cr) are frequently encountered toxicants, while iron (Fe) plays a crucial role in bacterial survival under conditions of heavy metal stress. However, intracellular Fe ion depletion by heavy metals leads to a state of Fe starvation. Therefore, it is imperative to investigate the mechanism through which bacteria maintain a balance between heavy metal detoxification and Fe homeostasis. This study demonstrates Cd(II) immobilization and Cr(VI) reduction abilities of sp. SY1, while proteomics reveals the upregulation of heme metabolism in response to Cd(II) and Cr(VI) exposure. The expression of the heme-uptake system in can enhance Cd(II) immobilization and facilitate Cr(VI) reduction. The ferruginous hemeprotein HhuH exhibits the ability to chelate Cd(II) and reduce Cr(VI). The presence of Cd(II) and Cr(VI) in strain SY1 initially led to Fe starvation. Subsequently, the hemeprotein HhuH facilitated Cd(II) adsorption and Cr(VI) reduction, thereby restoring normal cellular Fe homeostasis. Our findings explain the hemeprotein-mediated mechanism for Cd(II) adsorption and Cr(VI) reduction, providing further insights into the correlation between heavy metal and Fe metabolism.IMPORTANCEIron (Fe) is an indispensable trace element for many organisms, and virtually, all bacteria require Fe as a cofactor in enzymes to facilitate redox reactions involved in fundamental cellular processes during periods of heavy metal stress. Understanding bacterial response to Fe in heavy metal contamination is essential. Therefore, our study elucidates Cd(II) adsorption and Cr(VI) reduction processes mediated by the Fe-bearing hemeprotein HhuH. It is a unique trifunctional protein capable of chelating Cd(II) and reducing Cr(VI), demonstrating significant potential in the environmental remediation of heavy metals.
镉（Cd）和铬（Cr）是常见的有毒物质，而铁（Fe）在细菌于重金属胁迫条件下的存活中起着关键作用。然而，重金属导致的细胞内铁离子耗竭会引发铁饥饿状态。因此，研究细菌在重金属解毒与铁稳态之间维持平衡的机制势在必行。本研究展示了sp. SY1对Cd(II)的固定和Cr(VI)的还原能力，而蛋白质组学揭示了响应Cd(II)和Cr(VI)暴露时血红素代谢的上调。中血红素摄取系统的表达可增强Cd(II)的固定并促进Cr(VI)的还原。含铁血红素蛋白HhuH具有螯合Cd(II)和还原Cr(VI)的能力。菌株SY1中Cd(II)和Cr(VI)的存在最初导致铁饥饿。随后，血红素蛋白HhuH促进了Cd(II)的吸附和Cr(VI)的还原，从而恢复了正常的细胞铁稳态。我们的研究结果解释了血红素蛋白介导的Cd(II)吸附和Cr(VI)还原机制，为重金属与铁代谢之间的相关性提供了进一步的见解。重要性铁（Fe）是许多生物体不可或缺的微量元素，实际上，所有细菌在重金属胁迫期间都需要Fe作为酶中的辅因子，以促进参与基本细胞过程的氧化还原反应。了解细菌在重金属污染中对铁的反应至关重要。因此，我们的研究阐明了含铁血红素蛋白HhuH介导的Cd(II)吸附和Cr(VI)还原过程。它是一种独特的三功能蛋白，能够螯合Cd(II)并还原Cr(VI)，在重金属的环境修复中显示出巨大潜力。
