Bacteria Sphingobium yanoikuyae Sy310 enhances accumulation capacity and tolerance of cadmium in Salix matsudana Koidz roots.

Phytoremediation assisted by plant growth-promoting bacteria (PGPB) is considered an effective strategy for cadmium (Cd) removal in contaminated sites. This study uses a hydroponic experiment to investigate how Sphingobium yanoikuyae Sy310 affects Cd accumulation capacity and tolerance of Salix matsudana Koidz (S. matsudana) roots. The results showed that Cd induced growth change and physiological response on S. matsudana roots, displaying with reduced root length, increased antioxidant enzyme activities, and most importantly, enhanced cell wall polysaccharide contents. The Sy310 inoculation enhanced Cd accumulation in roots and alleviated the Cd toxic effects by regulating root growth, antioxidant enzyme system, and cell wall polysaccharide remodeling. Under Cd stress, Sy310 significantly induced increased root length and biomass, as well as higher root IAA level and Cd retention in cell walls. The Sy310 inoculation enhanced root pectin and hemicellulose 1 content, and pectin methylesterase activity, indicating that more amount of -COOH and -OH in cell walls for binding Cd. With Sy310-regulated extensive Cd regional sequestration in root cell walls and enhanced catalase activity, the root H₂O₂ and malondialdehyde content decreased, which contributes to improve Cd tolerance of S. matsudana roots. Furthermore, the Sy310 inoculation did not affect root cell wall structure and oxidative stress in the absence of Cd, representing a well-symbiotic relationship between Sy310 and S. matsudana. Therefore, Sy310 plays an important role in expediting the phytoremediation process of Cd with S. matsudana and has practical application potential.