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Background <p>Thiamethoxam (TMX) has been frequently used in mango orchards for protecting the fruit from insects and pests. However, its high water solubility, persistence, and ecotoxicity, presents a potential threat to ecosystems and living beings. Nevertheless, the full impact of TMX residue in soil environments remains insufficiently explored. Therefore the present study aims to restore TMX contaminated soils in eco-friendly and cost effective manner by utilizing the TMX degrading microbes.</p> Methods <p>To isolate TMX-resistant bacteria the soil samples collected from mango orchard at ICAR-CISH, Lucknow, a culture enrichment technique was employed. The resistance potential of these bacterial isolates to TMX was assessed in both liquid mineral salt medium (MSM) and soil. TMX residues in MSM samples were quantified using Ultra fast liquid chromatography (UFLC), with further validation by Ultra high-performance liquid chromatography (UHPLC). To identify the localization of TMX-degrading enzymes in the selected bacterial isolates, their presence was evaluated as extracellular, intracellular, or membrane-bound.</p> Results <p>Two <i>Pseudomonas</i> strains (A2 and C1), isolated from the rhizospheric soil of a mango orchard, exhibited significant TMX degradation by utilizing the pesticide as their sole carbon source. Their degradation efficiency was assessed at varying TMX concentrations of two considerable lower doses (0.2 and 0.5 g kg<sup>−1</sup>) and one higher dose (1.0 g kg<sup>−1</sup>) in broth, sterile soil, and non-sterile soil over 210 days. Results showed that degradation efficiency decreased with increasing TMX concentration, with the highest degradation efficiency observed in broth (89.60–98.29%), followed by sterile soil (55.34–96.97%) and non-sterile soil (52.22–99.04%). Optimal degradation occurred at 32 °C and pH 7.0 for both strains. Enzyme localization studies revealed that TMX degradation was primarily mediated by membrane-bound enzymes (both outer and inner membranes), with limited extracellular activity, likely due to reduced enzyme-substrate interaction outside the cell. Additionally, soil health assessments, including dehydrogenase activity (DHA) and fluorescein diacetate (FDA) hydrolysis, demonstrated the strain’s positive influence on soil biochemical functioning.</p> Conclusion <p>This research contributes to the development of novel approaches for efficient TMX degradation, with strains <i>viz</i>., <i>Pseudomonas aeruginosa</i> strain A2 and <i>Pseudomonas sp</i>. Strain C1 showing promise as biological agents for <i>in situ</i> remediation of TMX-contaminated environments.</p> Clinical trial number <p>Not applicable.</p>

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Biodegradation of thiamethoxam in mango orchards by Pseudomonas spp.: a study on soil health and sustainability

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年10月1日

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  • Pradeep Kumar Shukla,
  • Govind Kumar,
  • Sumit K. Soni,
  • Shatrohan Lal,
  • Ningthoujam Samarendra Singh,
  • A. K. Bhattacherjee,
  • Rishi Kumar Saxena

摘要

Background

Thiamethoxam (TMX) has been frequently used in mango orchards for protecting the fruit from insects and pests. However, its high water solubility, persistence, and ecotoxicity, presents a potential threat to ecosystems and living beings. Nevertheless, the full impact of TMX residue in soil environments remains insufficiently explored. Therefore the present study aims to restore TMX contaminated soils in eco-friendly and cost effective manner by utilizing the TMX degrading microbes.

Methods

To isolate TMX-resistant bacteria the soil samples collected from mango orchard at ICAR-CISH, Lucknow, a culture enrichment technique was employed. The resistance potential of these bacterial isolates to TMX was assessed in both liquid mineral salt medium (MSM) and soil. TMX residues in MSM samples were quantified using Ultra fast liquid chromatography (UFLC), with further validation by Ultra high-performance liquid chromatography (UHPLC). To identify the localization of TMX-degrading enzymes in the selected bacterial isolates, their presence was evaluated as extracellular, intracellular, or membrane-bound.

Results

Two Pseudomonas strains (A2 and C1), isolated from the rhizospheric soil of a mango orchard, exhibited significant TMX degradation by utilizing the pesticide as their sole carbon source. Their degradation efficiency was assessed at varying TMX concentrations of two considerable lower doses (0.2 and 0.5 g kg−1) and one higher dose (1.0 g kg−1) in broth, sterile soil, and non-sterile soil over 210 days. Results showed that degradation efficiency decreased with increasing TMX concentration, with the highest degradation efficiency observed in broth (89.60–98.29%), followed by sterile soil (55.34–96.97%) and non-sterile soil (52.22–99.04%). Optimal degradation occurred at 32 °C and pH 7.0 for both strains. Enzyme localization studies revealed that TMX degradation was primarily mediated by membrane-bound enzymes (both outer and inner membranes), with limited extracellular activity, likely due to reduced enzyme-substrate interaction outside the cell. Additionally, soil health assessments, including dehydrogenase activity (DHA) and fluorescein diacetate (FDA) hydrolysis, demonstrated the strain’s positive influence on soil biochemical functioning.

Conclusion

This research contributes to the development of novel approaches for efficient TMX degradation, with strains viz., Pseudomonas aeruginosa strain A2 and Pseudomonas sp. Strain C1 showing promise as biological agents for in situ remediation of TMX-contaminated environments.

Clinical trial number

Not applicable.