Bacterial-assisted cadmium phytoremediation by Ocimum gratissimum L. in polluted agricultural soil: a field trial experiment

A field study of cadmium phytoremediation by Ocimum gratissimum L. and the potential enhancement by two cadmium-resistant bacteria, Ralstonia sp. TISTR 2219 and Arthrobacter sp. TISTR 2220, were explored in a cadmium-polluted agricultural area. The results demonstrated the ability of one of the bacterial strains to promote cadmium accumulation in O. gratissimum L. planted in soil with cadmium concentrations till 65.2 mg kg⁻¹. After transplantation in contaminated soil for 2 months, soil inoculation with Arthrobacter sp. enhanced cadmium accumulation in the roots, above-ground tissues, and whole plant of O. gratissimum L. by 1.2-fold, 1.4-fold, and 1.1-fold, respectively, compared with the untreated control. The presence of Arthrobacter sp. in soil facilitated cadmium phytoremediation in O. gratissimum L. similar to that of an EDTA application. Seeds of O. gratissimum L. grown in polluted soil contained undetectable to negligible concentrations of cadmium. Significant increases in the bioconcentration and translocation factors of O. gratissimum L. were observed in Arthrobacter sp.-inoculated plants at only 2 months post-transplant compared with the uninoculated control. The highest percentage of cadmium removal was found in soil used to cultivate EDTA-treated O. gratissimum L., followed by an Arthrobacter sp.-inoculated plant. Our findings suggest that the synergistic use of Arthrobacter sp. with O. gratissimum L., an essential oil-producing crop, could be a feasible economic and environmental option for the reclamation of cadmium-polluted areas.