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Responses of Sorghum Growth and Rhizosphere–Plastisphere Microbiomes to Cadmium and Polypropylene Microplastic Co-Contamination

Agronomy 2026
Zong-Hua Wang, Shanshan Gao, Lei Yang, Lei Yang, Yue-Liang Meng, Meng Wang, Meng Wang, Bai-Lian Larry Li, Bai-Lian Larry Li, Zhao-Jin Chen

Summary

Researchers examined how combined cadmium and polypropylene microplastic contamination affects sorghum growth and the bacterial communities in both rhizosphere soil and on the plastic surfaces. They found that co-contamination inhibited sorghum development more severely than either pollutant alone, and the bacterial community on the plastic surface was structurally simpler with lower diversity than in surrounding soil. The study suggests that microplastics in contaminated soils can serve as distinct microbial habitats that differ significantly from the native soil environment.

Polymers

Microplastics (MPs) can serve as bearers of microorganisms and additional contaminants. However, the functional composition and assembly processes of plastisphere bacteria in co-contaminated soil–plant systems are not yet well understood. Using a pot experiment, we examined the effects of both individual and combined cadmium (Cd) and polypropylene (PP) MP contamination on the development of the bioenergy plant sorghum. The bacterial community, co-occurrence networks, and assembly processes in the rhizosphere soil and PP plastisphere were investigated using high-throughput sequencing. Compared with contamination by a single compound, combined contamination with Cd and PP had a more potent inhibitory effect on the development of sorghum. PCoA and diversity indices indicate that the bacterial community on PP plastics is structurally simpler than that in rhizosphere soil. The PP plastisphere could recruit bacteria from the genera Sphingomonas, Rhizobium, and Bacillus. The bacterial communities in the soil and the PP plastisphere were mostly formed by stochastic processes, with diffusion limitation playing a greater role in the bacterial community in the PP plastisphere. Co-occurrence network analysis revealed differences between the bacterial communities in the soil and in the PP plastisphere, with the network in the PP plastisphere showing lower complexity and connectivity. Functional prediction revealed that the prevalence of nitrogen cycling genes was greater in the PP plastisphere than in the dirt and that the PP plastisphere presented greater metabolic activity. The relative prevalence of metabolic pathways associated with human diseases was markedly elevated in the PP plastisphere, which may be correlated with the dissemination of pathogenic microorganisms. These findings indicate that the PP plastisphere, as a distinct microbial niche, might attract certain bacteria, consequently affecting the functional characteristics of cocontaminated soil–plant systems.

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