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Issues on microbial soil remediation: a case of Cd detoxification by Bacillus strains for alleviating heavy metal stress in crop plants

Summary

This research paper identifies critical problems in how scientists are using bacteria to clean up cadmium-contaminated soil for farming. The authors found that researchers often incorrectly identify which species of Bacillus bacteria they are using, don’t properly check if the bacteria are safe for humans and animals, and use unrealistically high levels of contamination in experiments that don’t reflect real-world conditions. The paper calls for better standards in this research to ensure that microbial remediation techniques are accurate, safe, and actually applicable to real contaminated farmland.

Background

Cadmium (Cd) is a persistent environmental pollutant that accumulates in crop plants and poses significant risks to human health and ecosystems. Microbial remediation using Cd-tolerant bacteria, particularly Bacillus strains, has emerged as a promising green and cost-effective approach for addressing Cd-contaminated soils.

Objective

To critically examine and highlight key issues in microbial soil remediation studies using Bacillus strains for Cd detoxification, including inaccurate species identification, safety concerns, inadequate reporting of cell numbers and delivery methods, and unrealistic Cd concentrations in experimental settings.

Results

The survey identified that 50% of reviewed articles (10 of 20) misidentified Bacillus isolates based solely on 16S rRNA gene alignment. Most studies failed to conduct safety assessments before application, particularly for B. cereus strains with known pathogenic potential. Cell numbers, delivery methods, and Cd concentrations were frequently under-reported or unrealistically high (10,000-fold above natural soil levels).

Conclusion

Critical standardization is needed in microbial remediation research including: multi-locus sequencing for accurate Bacillus identification, comprehensive biosafety evaluation frameworks, detailed reporting of inoculum size and delivery methods, and use of realistic Cd concentrations representative of actual contaminated soils.
  • Published in:Frontiers in Microbiology,
  • Study Type:Review,
  • Source: 10.3389/fmicb.2025.1665354; PMID: 41048489
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