制备了一种具有镉活化功能的包裹型根际促生菌剂,用于强化镉超累积植物龙葵对镉污染农田土壤的植物修复作用.结果表明:包裹型菌剂Z16的多腔室结构适合菌株的生存,菌剂Z16的释菌浓度在24h孵育后达到106CFU·g-1;与菌液组EC相比,菌剂Z16组的龙葵地上部鲜重提高了 19.81％,地上部和根部镉的富集系数分别提高了 20.98％和168.97％,根际土壤碳酸盐结合态镉的浓度得到活化,龙葵对钙、锰和铁元素的吸收能力也得到增强.因此,与施用菌液EC相比,包裹型根际促生菌剂Z16通过在根际土壤持续释放菌株,可提高难溶性镉的活化效果及提高植物修复效率.本研究可为强化超累积植物-根际促生菌联用技术对镉污染农田的植物修复效率提供参考.

Microbe-assisted phytoremediation for Cd-polluted soil is being regarded increasingly. However, the availability of microbes that can collaborate with Cd-hyperaccumulators effectively has become one of bottlenecks restricting the remediation efficiency. A siderophore-producing bacterium (Y16; Enterobacter cloacae) isolated from the rhizospheric soil of Cd-hyperaccumulator Solanum nigrum L. was identified by 16S rRNA gene sequencing and biochemical analysis, and then used for analyzing microbial chemotaxis, carbon source utilization, and insoluble P/Cd mobilization capacities. Besides, a soil-pot trial was performed to underlie the phytoremediation mechanism of Cd-polluted soil assisted by D-gluconate-enhanced Enterobacter cloacae colonization (DEYC) in the Solanum nigrum L. rhizosphere. Results displayed that D-gluconate was an effective chemoattractant and carbon source strengthening Y16 colonization, and Y16 exhibited strong abilities to mobilize insoluble P/Cd in shake flask by extracellular acidification (p < 0.05). In the soil-pot trial, DEYC observably enhanced soil Cd phytoextraction by Solanum nigrum L., and increased microbial diversity according to alpha- and beta-diversity analysis (p < 0.05). Taxonomic distribution and co-occurrence network analysis suggested that DEYC increased relative abundances of dominant microbial taxa associated with soil acidification (Acidobacteria-6), indoleacetic acid secretion (Ensifer adhaerens), soil fertility improvement (Flavisolibacter, Bdellovibrio bacteriovorus, and Candidatus nitrososphaera), and insoluble Cd mobilization (Massilia timonae) at different classification levels. Importantly, COGs analysis further shown that DEYC aroused the up-regulation of key genes related to chemotactic motility, carbon fixation, TCA cycle, and propanoate metabolism. These results indicated that DEYC drove the rhizospheric enrichment of pivotal microbial taxa directly or indirectly involved in soil Cd mobilization, meanwhile distinctly promoted plant growth for accumulating more mobilizable Cd. Therefore, Y16 could be used as bio-inoculants for assisting phytoremediation of Cd-polluted soil.