Microplastic shift the microbial community and the functional taxa in the cadmium contamination wheat rhizosphere soil

Microplastic (MP) and heavy metals are contaminants that pose a threat to soil health and food security. The synergy of these two contaminants on functional microbial communities in the agricultural soil is illuminated in this study. We observed that single or combined addition of polyethylene (PE) MP (1% w/w) and cadmium (Cd; 1.5 mg/kg, 5 mg/kg) enhanced the wheat biomass, especially in the high Cd contaminated soil. Combined addition of MP and Cd decreased the bacterial alpha diversity in wheat bulk soil. The addition of MP reduces the relative abundance of Proteobacteria that beneficial for nitrogen fixation, while Cd increases the relative abundance of Proteobacteria and Actinobaciota that related to N cycling. FAPROTAX analysis revealed that increasing Cd concentration promotes the abundance of bacterial functional communities, such as nitrification denitrification, nitrate and nitrite respiration in rhizosphere soil. The FunGuild analysis showed that synergy of PE and Cd stimulated the community abundance of saprophytic fungi, indicating an increase of degradation ability under pollutant stimulation.