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Aims <p>Microbe-assisted phytoremediation is a promising strategy for remediating heavy metal-contaminated soils. However, the contrasting mechanisms by which immobilizing and mobilizing microbes enhance phytoremediation in leguminous plants remain poorly understood.</p> Methods <p>This study systematically investigated the effects of inoculating an immobilizing strain (<i>Enterococcus casseliflavus</i> WZ13) and a mobilizing strain (<i>Serratia marcescens</i> WG20) on cadmium (Cd) and lead (Pb) bioavailability, soil microbial community structure, and phytoextraction efficiency of <i>Robinia pseudoacacia</i> L. through integrated pot and soil culture experiments.</p> Results <p>WZ13 inoculation decreased bioavailable Cd and Pb fractions in soil by 36.77% and 21.76%, respectively, whereas WG20 inoculation increased them by 22.93% and 36.98%, respectively. These contrasting effects on metal bioavailability led to two distinct phytoextraction mechanisms by <i>R. pseudoacacia</i> L. Specifically, WZ13 enhanced plant metal uptake primarily by increasing plant biomass by 63.41%, despite lowering Cd and Pb concentrations in the plant tissues. Conversely, WG20 significantly increased Cd and Pb concentrations in the plant by 23.19% and 13.52%, respectively, without significantly affecting biomass. Both strains reshaped the soil bacterial community, enriched beneficial taxa (e.g., <i>Bacteroidetes</i>, <i>Chloroflexi</i>, and <i>Firmicutes</i>), and promoted more stable co-occurrence networks. WG20 exhibited a stronger recruitment capacity. Linear discriminant analysis effect size (LEfSe) identified <i>Sphingomonas</i> and <i>Paenibacillus</i> as the key biomarkers associated with WZ13 and WG20, respectively.</p> Conclusions <p>This study proposes a targeted microbial application strategy for Cd- and Pb-contaminated soils. WZ13 mitigates heavy metal mobility in soil and restricts metal transfer to adjacent edible crops through soil leaching or runoff, thereby indirectly ensuring crop safety during agricultural production. WG20 is recommended for maximizing extraction efficiency during dedicated remediation.</p> Graphical Abstract <p></p>

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Contrasting mechanisms of immobilizing and mobilizing bacterial strains in Robinia pseudoacacia L.-mediated phytoremediation of cadmium- and lead-contaminated soils

  • 期刊论文

  • 发表日期：

    2026年3月30日

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  • Zexun Liu,
  • Xinyan Lv,
  • Tong Zhao,
  • Jie Lu,
  • Zaien Xu,
  • Yiping Yu,
  • Jiayao Zhuang

摘要

Aims

Microbe-assisted phytoremediation is a promising strategy for remediating heavy metal-contaminated soils. However, the contrasting mechanisms by which immobilizing and mobilizing microbes enhance phytoremediation in leguminous plants remain poorly understood.

Methods

This study systematically investigated the effects of inoculating an immobilizing strain (Enterococcus casseliflavus WZ13) and a mobilizing strain (Serratia marcescens WG20) on cadmium (Cd) and lead (Pb) bioavailability, soil microbial community structure, and phytoextraction efficiency of Robinia pseudoacacia L. through integrated pot and soil culture experiments.

Results

WZ13 inoculation decreased bioavailable Cd and Pb fractions in soil by 36.77% and 21.76%, respectively, whereas WG20 inoculation increased them by 22.93% and 36.98%, respectively. These contrasting effects on metal bioavailability led to two distinct phytoextraction mechanisms by R. pseudoacacia L. Specifically, WZ13 enhanced plant metal uptake primarily by increasing plant biomass by 63.41%, despite lowering Cd and Pb concentrations in the plant tissues. Conversely, WG20 significantly increased Cd and Pb concentrations in the plant by 23.19% and 13.52%, respectively, without significantly affecting biomass. Both strains reshaped the soil bacterial community, enriched beneficial taxa (e.g., Bacteroidetes, Chloroflexi, and Firmicutes), and promoted more stable co-occurrence networks. WG20 exhibited a stronger recruitment capacity. Linear discriminant analysis effect size (LEfSe) identified Sphingomonas and Paenibacillus as the key biomarkers associated with WZ13 and WG20, respectively.

Conclusions

This study proposes a targeted microbial application strategy for Cd- and Pb-contaminated soils. WZ13 mitigates heavy metal mobility in soil and restricts metal transfer to adjacent edible crops through soil leaching or runoff, thereby indirectly ensuring crop safety during agricultural production. WG20 is recommended for maximizing extraction efficiency during dedicated remediation.

Graphical Abstract