Newly Isolated Bacterium and Arbuscular Mycorrhizal Fungus Effectively Reduce the Root Cadmium Concentration and Increase the Root Biomass of Ophiopogon japonicus

Abstract

Soil cadmium (Cd) contamination is one of the major challenges in food production. This has led to above-maximum threshold accumulation of Cd in O. japonicus roots. This research identifies Pseudomonas tianjinensis S2 (PL), a newly isolated bacterium, and Corymbiglomus tortuosum (Ct), an arbuscular mycorrhizal fungus (AMF), as effective agents for reducing Cd concentration in the roots of O. japonicus. Compared to the control (CK) treatment, the root Cd levels decreased by 62.27% and 46.13%, respectively, significantly enhancing root biomass. We also noticed the involvement of –OH, –CH, and CC functional groups in Cd chelation in both treatments, and the formation of precipitates, including C₂H₂CdO₄, C₄H₆CdO₄, Cd(OH)₂, and Cd₃(PO₄)₂, in both PL and Ct treatments. Moreover, the proportion of residual Cd in soil increased by 21.21% and 10.61% for the PL and Ct treatments, respectively, compared to the CK. The findings suggest that P. tianjinensis S2 is more effective than C. tortuosum for high Cd-contaminated fields, while the fungal inoculant is suitable for lower contamination levels, offering valuable strategies for bioremediation. Therefore, we suggest further research to focus on elucidating the effect of a P. tianjinensis S2 and C. tortuosum combination on O. japonicus root growth and Cd accumulation.