Reducing cadmium in rice using metallothionein surface-engineered bacteria WH16-1-MT

Area of Science:

• Environmental Microbiology
• Agricultural Science
• Biotechnology

Background:

• Cadmium (Cd) accumulation in rice grains presents a significant human health risk.
• Developing effective strategies to mitigate Cd contamination in staple crops like rice is crucial.

Purpose of the Study:

• To engineer a bacterium, Alishewanella sp. WH16-1-MT, for enhanced cadmium adsorption.
• To evaluate the efficacy of WH16-1-MT in reducing Cd uptake and accumulation in rice grown in contaminated soil.

Main Methods:

• Engineered Alishewanella sp. WH16-1-MT to express metallothionein on its cell surface for increased Cd adsorption.
• Inoculated rice with WH16-1-MT in moderately Cd-contaminated paddy soil and compared with the parental strain.
• Assessed plant growth parameters, Cd concentrations in various plant parts and soil, and soil microbiome composition.

Main Results:

• WH16-1-MT demonstrated significantly higher Cd2+ adsorption efficiency compared to the parental strain.
• Inoculation with WH16-1-MT improved rice plant growth metrics and reduced oxidative stress indicators.
• WH16-1-MT inoculation substantially decreased Cd concentrations in brown rice (by 44.0%) and other plant tissues, and altered soil Cd bioavailability.
• Microbiome analysis confirmed that WH16-1-MT did not significantly disrupt the native soil bacterial community.

Conclusions:

• Engineered Alishewanella sp. WH16-1-MT is a promising microbial agent for reducing cadmium accumulation in rice.
• This approach offers a novel and effective strategy for mitigating cadmium contamination in agricultural produce.
• The use of WH16-1-MT can contribute to safer rice production in Cd-polluted environments without negatively impacting soil microbial ecosystems.