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<p>A Gram positive strain of <i>Alkalihalobacillus clausii</i> ABF28, indigenous to environment contaminated by Cr(VI) was identified by applying molecular imaging and <i>de novo</i> genomic profiling. This study investigates the potential of <i>Alkalihalobacillus clausii</i> ABF28 for the bioremediation of hexavalent chromium in a batch column reactor. We assess both immobilized and free bacterial cell systems to evaluate their efficiency in reducing chromium contamination. Bacterial strain grew well in marine broth media despite being stressed with 700&#xa0;mg/l and 1500&#xa0;mg/l chromate. Furthermore, the MIC found was 2500&#xa0;mg/l. The XPS confirmed that the bacterial strain reduced Cr(VI) to a + 3 oxidation state. The strain was grown in free and immobilized state and later was analyzed with SEM, STEM, XPS and FTIR. A similar observation was made in elemental mapping of EDX. In addition, we conduct whole genome profiling of the bacterial strain to uncover the underlying genetic mechanisms that facilitate chromium detoxification. The chromate transporter ChrA is acknowledged as a crucial component in the expulsion of chromium, which aids in maintaining low intracellular levels. A collection of reductive enzymes, including MdaB (NADPH-dependent quinone reductase), Fpr (ferredoxin-NADP⁺ reductase), Qor (quinone oxidoreductase), and CypX (cytochrome P450 oxidoreductase), collaborate within complementary pathways to channel electrons from NADPH and ferredoxin for the reduction of Cr(VI), simultaneously contributing to the alleviation of oxidative stress. These genes collaborate with antioxidant mechanisms such as superoxide dismutase and catalase, establishing a dual strategy that integrates efflux and enzymatic reduction. Collectively, these findings underscore <i>A. clausii</i> ABF28 as a remarkably versatile bacterium proficient in detoxifying Cr(VI), indicating its potential role in the remediation of chromium-contaminated marine ecosystems.</p> Graphical Abstract <p></p>

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Revealing the Chromium Detoxification Mechanisms in the Highly Tolerant Alkalihalobacillus Clausii ABF28 via Genomic and Functional Analyses

  • 期刊论文

  • 发表日期：

    2026年2月24日

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  • Swati Sonker,
  • Abhay B. Fulke,
  • Siddant Ratanpal,
  • Aashna Monga,
  • Ashlesha S. Mhatre,
  • Praveen Valsalan

摘要

A Gram positive strain of Alkalihalobacillus clausii ABF28, indigenous to environment contaminated by Cr(VI) was identified by applying molecular imaging and de novo genomic profiling. This study investigates the potential of Alkalihalobacillus clausii ABF28 for the bioremediation of hexavalent chromium in a batch column reactor. We assess both immobilized and free bacterial cell systems to evaluate their efficiency in reducing chromium contamination. Bacterial strain grew well in marine broth media despite being stressed with 700 mg/l and 1500 mg/l chromate. Furthermore, the MIC found was 2500 mg/l. The XPS confirmed that the bacterial strain reduced Cr(VI) to a + 3 oxidation state. The strain was grown in free and immobilized state and later was analyzed with SEM, STEM, XPS and FTIR. A similar observation was made in elemental mapping of EDX. In addition, we conduct whole genome profiling of the bacterial strain to uncover the underlying genetic mechanisms that facilitate chromium detoxification. The chromate transporter ChrA is acknowledged as a crucial component in the expulsion of chromium, which aids in maintaining low intracellular levels. A collection of reductive enzymes, including MdaB (NADPH-dependent quinone reductase), Fpr (ferredoxin-NADP⁺ reductase), Qor (quinone oxidoreductase), and CypX (cytochrome P450 oxidoreductase), collaborate within complementary pathways to channel electrons from NADPH and ferredoxin for the reduction of Cr(VI), simultaneously contributing to the alleviation of oxidative stress. These genes collaborate with antioxidant mechanisms such as superoxide dismutase and catalase, establishing a dual strategy that integrates efflux and enzymatic reduction. Collectively, these findings underscore A. clausii ABF28 as a remarkably versatile bacterium proficient in detoxifying Cr(VI), indicating its potential role in the remediation of chromium-contaminated marine ecosystems.

Graphical Abstract