State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Ministry of Water Resources, Yangling, 712100, China; CAS Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xian, 710061, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ, Groningen, the Netherlands.
Chemosphere. 2020 Sep;254:126724. doi: 10.1016/j.chemosphere.2020.126724. Epub 2020 Apr 8.
Chelants application can increase the bioavailability of metals, subsequently limiting plant growth and reducing the efficiency of phytoremediation. Plant growth-promoting rhizobacteria (PGPRs) and rhizobium have substantial potential to improve plant growth and plant tolerance to metal stress. We evaluated the effects of co-inoculation with a PGPR strain (Paenibacillus mucilaginosus) and a Cu-resistant rhizobium strain (Sinorhizobium meliloti) on the efficiency of biodegradable chelant (S,S-ethylenediaminedisuccinic acid; EDDS) assisted phytoremediation of a Cu contaminated soil using alfalfa. The highest total Cu extraction by alfalfa was observed in the EDDS-treated soil upon co-inoculation with the PGPR and rhizobium strains, which was 1.2 times higher than that without co-inoculation. Partial least squares path modeling identified plant oxidative damage and soil microbial biomass as the key variables influencing Cu uptake by alfalfa roots. Co-inoculation significantly reduced the oxidative damage to alfalfa by mitigating the accumulation of malondialdehyde and reactive oxygen species, and improving the antioxidation capacity of the plant in the presence of EDDS. EDDS application decreased microbial diversity in the rhizosphere, whereas co-inoculation increased microbial biomass carbon and nitrogen, and microbial community diversity. Increased relative abundances of Actinobacteria and Bacillus and the presence of Firmicutes taxa as potential biomarkers demonstrated that co-inoculation increased soil nutrient content, and improved plant growth. Co-inoculation with PGPR and rhizobium can be useful for altering plant-soil biochemical responses during EDDS-enhanced phytoremediation to alleviate phytotoxicity of heavy metals and improve soil biochemical activities. This study provides an effective strategy for improving phytoremediation efficiency and soil quality during chelant assisted phytoremediation of metal-contaminated soils.
螯合剂的应用可以增加金属的生物利用度，从而限制植物的生长，降低植物修复的效率。植物促生根际细菌（PGPR）和根瘤菌具有显著提高植物生长和植物耐受金属胁迫的潜力。我们评估了与 PGPR 菌株（粘质沙雷氏菌）和铜抗性根瘤菌菌株（苜蓿中华根瘤菌）共接种对生物可降解螯合剂（S，S-乙二胺二琥珀酸；EDDS）辅助修复苜蓿污染土壤中铜的效率的影响。在 PGPR 和根瘤菌共接种的 EDDS 处理土壤中，苜蓿对总铜的提取量最高，是未共接种的 1.2 倍。偏最小二乘路径模型确定植物氧化损伤和土壤微生物生物量是影响苜蓿根系铜吸收的关键变量。共接种通过减轻丙二醛和活性氧的积累，以及在 EDDS 存在下提高植物的抗氧化能力，显著降低了 EDDS 对苜蓿的氧化损伤。EDDS 应用降低了根际微生物多样性，而共接种增加了微生物生物量碳和氮，以及微生物群落多样性。放线菌和芽孢杆菌的相对丰度增加以及厚壁菌门的存在表明，共接种增加了土壤养分含量，改善了植物生长。PGPR 和根瘤菌的共接种可以改变 EDDS 增强植物修复过程中的植物-土壤生化反应，减轻重金属的植物毒性，提高土壤生化活性。这项研究为螯合剂辅助修复污染土壤中提高植物修复效率和土壤质量提供了一种有效的策略。
