The combined pollution of microplastics and heavy metals can potentially interact. This may have an important impact on the growth and development of plants and the rhizosphere microbial community and function. In this study, the effects of heavy metal cadmium combined with different types of microplastics(PE and PS), different particle sizes(13 μm and 550 μm), and different concentrations(0.1% and 1%) on Pennisetum hydridum growth were studied under pot conditions. The results showed that the effects of the combined pollution of MPs and Cd on plant dry weight and Cd accumulation varied with different types, concentrations, and particle sizes of MPs, and the combined pollution stress increased, whereas the Cd content and Cd accumulation decreased. Metagenomic analysis showed that the combined contamination of MPs and Cd could change the composition of the bacterial community and reduce bacterial diversity, among which the ACE index and Chao1 index in the 550 μm 0.1% PE+Cd treatment group were the most significant. Metagenomic analysis of microbial species function showed that the main functional groups were metabolism, amino acid transport and metabolism, energy generation and conversion, and signal transduction mechanisms. Compared with that under single Cd pollution, the addition of MPs could change the gene abundance of functional groups such as metabolism, amino acid transport and metabolism, and energy generation and conversion, and the effects of different MPs types, concentrations, and particle sizes varied. In this study, metagenomics and amplification sequencing were used to analyze the effects of the combined pollution of MPs and Cd on the bacterial community and function in P. hydridum in order to provide basic data and scientific basis for the ecotoxicological effects of the combined heavy metal pollution of MPs and its biological remediation.
Keywords: Pennisetum hydridum; cadmium(Cd); community structure and function; metagenome; microplastics(MPs).