Reducing cadmium bioavailability and accumulation in vegetable by an alkalizing bacterial strain

Highlights: • A Cd-resistant and alkalizing bacterium was isolated from a Cd-contaminated soil. • Strain XT-4 effectively increased the rhizosphere soil pH. • Strain XT-4 decreased the CaCl₂ extractable Cd concentration in the soil. • Strain XT-4 reduced Cd accumulation in the edible part of Brassica rapa vegetable. Cadmium (Cd) contamination in agricultural soils is a widespread environmental problem that can affect food safety and human health. Effective remediation methods are needed to reduce Cd bioavailability in soil and Cd accumulation in food crops. In the present study, we isolated a Cd-resistant and alkalizing bacterium strain XT-4 from a Cd-contaminated soil and evaluated its potential application in Cd bioremediation. Based on its morphological, physiological and biochemical characteristics, together with 16S rRNA gene sequence analysis, strain XT-4 was identified as a member of the Bacillus genus. Strain XT-4 showed a strong ability to increase the pH and decrease Cd solubility in the medium. A greenhouse-based pot experiment with a Cd-contaminated soil was conducted to evaluate the effect of strain XT-4 inoculation on the growth and Cd accumulation of the vegetable Pak choi (Brassica rapa ssp. chinensis). Inoculation increased the rhizosphere pH, decreased CaCl₂-extractable Cd in the soil and decreased Cd concentration in the edible part of Pak choi by 28–40%. The results suggest that inoculation with alkalizing bacterial strain XT-4 represents an effective solution to increase rhizosphere pH and decrease Cd uptake by vegetable crops in Cd-contaminated acid soils.