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Abstract <p>Hexavalent chromium [Cr(VI)] is a highly mobile and toxic metal species that poses serious environmental risks. Microbial Cr(VI) reduction is a potential remediation approach to reduce the mobility and toxicity of this metal in the environment. However, the diversity and metabolic mechanisms of Cr(VI)-reducing bacteria (CrRBs) remain insufficiently understood in long-term Cr-contaminated anaerobic environments. In this study, anaerobic enrichment cultures were established using Cr-contaminated sediment from Xikuangshan (XKS) and paddy soil from Wanshan (WS) as inocula, with acetate as the electron donor and Cr(VI) as the electron acceptor. 16S rRNA gene sequencing and genome-resolved metagenomic analysis were used to identify putative CrRBs and their metabolic potential. After three enrichment cycles, Cr(VI) was completely removed within 6&#xa0;days in the XKS cultures and 12&#xa0;days in the WS cultures, whereas sterile controls showed only limited Cr(VI) loss. <i>Cellulomonas, Enterobacter, Rikenellaceae</i>, and <i>Citrifermentans</i> were enriched and identified as putative CrRBs. Reconstructed metagenome-assembled genomes (MAGs) harbored genes potentially involved in chromate transport/reduction, electron transfer, and metal resistance, including <i>chrA</i>, <i>chrR</i>, <i>ribF</i>, <i>nfsA</i>, <i>nemA</i>, <i>nrfA</i>, and <i>modA</i>. These results provide genomic evidence for indigenous microorganisms potentially involved in Cr(VI) detoxification, although metagenomic predictions do not confirm gene expression or enzymatic activity.</p>

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Deciphering Microbial Mechanisms for Hexavalent Chromium Reduction in Contaminated Sediment and Paddy Soil

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Xin Zhang,
  • Zexin Wang,
  • uhammad Usman Ghani,
  • Tianle Kong,
  • Weimin Sun,
  • Xiaoxu Sun,
  • Baoqin Li,
  • Zewen Tan,
  • Geng Yan

摘要

Abstract

Hexavalent chromium [Cr(VI)] is a highly mobile and toxic metal species that poses serious environmental risks. Microbial Cr(VI) reduction is a potential remediation approach to reduce the mobility and toxicity of this metal in the environment. However, the diversity and metabolic mechanisms of Cr(VI)-reducing bacteria (CrRBs) remain insufficiently understood in long-term Cr-contaminated anaerobic environments. In this study, anaerobic enrichment cultures were established using Cr-contaminated sediment from Xikuangshan (XKS) and paddy soil from Wanshan (WS) as inocula, with acetate as the electron donor and Cr(VI) as the electron acceptor. 16S rRNA gene sequencing and genome-resolved metagenomic analysis were used to identify putative CrRBs and their metabolic potential. After three enrichment cycles, Cr(VI) was completely removed within 6 days in the XKS cultures and 12 days in the WS cultures, whereas sterile controls showed only limited Cr(VI) loss. Cellulomonas, Enterobacter, Rikenellaceae, and Citrifermentans were enriched and identified as putative CrRBs. Reconstructed metagenome-assembled genomes (MAGs) harbored genes potentially involved in chromate transport/reduction, electron transfer, and metal resistance, including chrA, chrR, ribF, nfsA, nemA, nrfA, and modA. These results provide genomic evidence for indigenous microorganisms potentially involved in Cr(VI) detoxification, although metagenomic predictions do not confirm gene expression or enzymatic activity.