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<p>Extracellular polymeric substances (EPS) constitute a significant component of soil organic matter (SOM), but the processes by which EPS are transformed and further retained by soil minerals remain poorly understood. This study investigated the chemical speciation of biogenic elements and mineral-SOM associations after EPS adsorption and turnover in typical clay minerals and three soils. Synchrotron-based X-ray absorption near-edge structure (XANES) analysis revealed that incubation induced approximately twice the changes in C and S speciation compared to EPS surface adsorption alone, suggesting that stimulated microbial activity is a more important pathway for EPS to participate in SOM turnover. Incubation with EPS significantly increased carboxylic carbon by 15.9%, while decreasing aromatics by 30.0% across the three studied soils. <i>In-situ</i> Fourier-transform infrared (μ-FTIR) spectroscopy showed enhanced spatial correlation between Fe oxides and organic functional groups (with an average increase in <i>R</i><sup>2</sup> of 90%) after incubation, whereas phyllosilicate-EPS associations were less stable and underwent disintegration in the Fe-rich, low-pH conditions of Mollisol and Alfisol. The differential preservation patterns for various molecules arise from molecular fractionation, with carboxylic-rich compounds preferentially enriched on iron oxides, while aromatic and aliphatic carbon are enriched on phyllosilicates. Overall, EPS stabilizes SOM by stimulating the microbial carbon pump to assimilate native SOM and facilitating its association with iron oxides.</p> Graphical Abstract <p></p>

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Adsorption and incubation show iron (oxyhydr)oxides control the persistence of bacterial extracellular polymeric substances in soils

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月6日

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  • Chenchen Qu,
  • Jiaxin Zhao,
  • Shanshan Yang,
  • Mohammad Bahadori,
  • Chengrong Chen,
  • Xueqi Song,
  • Ke Dai,
  • Ming Zhang,
  • Yichao Wu,
  • Peng Cai,
  • Wenli Chen,
  • Qiaoyun Huang

摘要

Extracellular polymeric substances (EPS) constitute a significant component of soil organic matter (SOM), but the processes by which EPS are transformed and further retained by soil minerals remain poorly understood. This study investigated the chemical speciation of biogenic elements and mineral-SOM associations after EPS adsorption and turnover in typical clay minerals and three soils. Synchrotron-based X-ray absorption near-edge structure (XANES) analysis revealed that incubation induced approximately twice the changes in C and S speciation compared to EPS surface adsorption alone, suggesting that stimulated microbial activity is a more important pathway for EPS to participate in SOM turnover. Incubation with EPS significantly increased carboxylic carbon by 15.9%, while decreasing aromatics by 30.0% across the three studied soils. In-situ Fourier-transform infrared (μ-FTIR) spectroscopy showed enhanced spatial correlation between Fe oxides and organic functional groups (with an average increase in R2 of 90%) after incubation, whereas phyllosilicate-EPS associations were less stable and underwent disintegration in the Fe-rich, low-pH conditions of Mollisol and Alfisol. The differential preservation patterns for various molecules arise from molecular fractionation, with carboxylic-rich compounds preferentially enriched on iron oxides, while aromatic and aliphatic carbon are enriched on phyllosilicates. Overall, EPS stabilizes SOM by stimulating the microbial carbon pump to assimilate native SOM and facilitating its association with iron oxides.

Graphical Abstract