Exopolysaccharide-producing strains alter heavy metal fates and bacterial communities in soil aggregates to reduce metal uptake by pakchoi

作者：Heyun Zhang, Junqing Zhang, Shixiong Tang, ZhongYan Deng, Randa S. Makar, Lunguang Yao, Hui Han · 发表于：Frontiers in Microbiology · 年份：2025 · DOI：10.3389/fmicb.2025.1595142 · 被引用次数：16 · 研究领域：Chromium effects and bioremediation、Heavy metals in environment、Microbial Fuel Cells and Bioremediation

The characteristics of heavy metals in soil aggregates represent critical factors influencing the uptake of heavy metals by crops. However, the mechanisms underlying the immobilization of Cd and Pb by soil aggregates of different particle sizes mediated by exopolysaccharide (EPS)-producing bacteria have remained poorly understood. In this study, a selective medium was employed to isolate and screen EPS-producing bacteria from the heavy metal-contaminated soil, with their mechanisms of Cd and Pb immobilization investigated through solution adsorption experiments. Pot experiments combined with high-throughput sequencing technology were conducted to examine the effects of these strains on heavy metal uptake by pakchoi and to elucidate the underlying microbiological mechanisms. Two high-EPS-yielding bacterial strains, Pseudomonas sp. H7 and Agrobacterium sp. Z22, were successfully isolated from heavy metal-contaminated farmland. These strains effectively facilitated the formation of Fe 2 Pb(PO 4 ) 2 , CdCO 3 , and Pb 2 O 3 precipitates, thereby immobilizing Cd and Pb in aqueous solutions. Compared to the CK group, inoculation with Pseudomonas sp. H7 and Agrobacterium sp. Z22 reduced the Cd (30.7–81.8%) and Pb (8.1–57%) contents in the pakchoi tissues. Notably, Pseudomonas sp. H7 and Agrobacterium sp. Z22 enhanced EPS production and promoted the specific formation of CdCO 3 , PbCO 3 , Cd 2 (OH) 2 CO 3 , and 2PbCO 3 ·Pb(OH) 2 within microaggregates (< 250 μm), which signific...