Enhanced dimethyl phthalate phytoremediation efficiency by C4-HSL-assisted Bacillus sp. YT2: Roles of rhizosphere microbiome-plant interaction

The widespread accumulation of organic pollutants in agricultural soils, such as dimethyl phthalate (DMP), poses serious risks to human health and ecological safety. The application of plant growth-promoting rhizobacteria (PGPR) to improve phytoremediation efficiency for organic pollutant-contaminated soils has gained increasing attention. However, synergistic PGPR-plant signaling and competitive root colonization of PGPR directly affect the remedial efficiency of the PGPR-plant system for soil organic pollutants. Acyl-homoserine lactones (AHLs), one of the quorum sensing (QS) signals, can enhance microbial cooperation and promote plant growth, thereby probably facilitating phytoremediation processes for pollutant degradation. In this study, the potential capacity of AHLs to assist PGPR in the phytoremediation of DMP-polluted soils was explored, with a focus on their effects on DMP removal, plant physiological functions, and rhizosphere microbial community structure. The results showed that AHLs (C 4 -HSL)-assisted PGPR ( Bacillus YT2) treatment significantly increased DMP removal to 92.60 % and improved plant growth. Compared to the individual AHLs or PGPR treatments, the AHLs-assisted PGPR more effectively enhanced plant photosynthesis, osmoregulation, and antioxidant capacity, reduced oxidative damage, and improved soil enzyme activity and nutrient availability. Additionally, the AHLs-assisted PGPR treatment modulated microbial community in the rhizosphere, increasing the richness of pivotal functional taxa such as Xanthomonadaceae and Acidobacteriota. AHLs might directly promote DMP degradation by regulating the QS system and enhancing plant-bacterial communication, while also indirectly supporting plant growth through stress tolerance enhancement. In conclusion, AHLs-mediated enhancement of PGPR functionality provides a promising approach for remediating DMP-contaminated soils and offers a theoretical basis for developing composite microbial formulations.