Responses of abundant and rare subcommunities to bioremediation conducted by Pseudomonas chenduensis in cadmium contaminated paddy soil

Crops cultivation in the cadmium (Cd)-contaminated paddy soil causes great risk for food safety. In situ soil bioremediation conducted by functional microorganisms has been increasingly applied. However, how local microbiota responded to bioremediation processes accompanying with crop cultivation, and its effect on uptake of Cd by rice is rarely discussed. Here, Pseudomonas chenduensis strain MBR was applied to remedy Cd-contaminated paddy soil, during which microbial community dynamics were investigated. The results showed that bioremediation by strain MBR significantly lessened Cd accumulation in rice grains and root, and meanwhile caused great dynamics of microbial communities in rhizosphere soil but less dynamics in bulk soil. Although both abundant and rare subcommunities showed great variations during bioremediation, they exhibited distinct temporal trajectories. Mantel and partial mantel tests showed that microbial communities in paddy soil without bioremediation tended to be structured by stochastic processes, while bioremediation caused important roles of edaphic factors and cadmium pressure in regulating microbial communities, which worked only in rhizosphere soil. Consequently, effects of bioremediation by strain MBR on local communities depended on types of subcommunities (abundant and rare) and soils (rhizosphere and bulk). This study shed light on microecological processes during bioremediation accompanying with crop cultivation in situ.