Effects of combined microplastic and cadmium pollution on sorghum growth, Cd accumulation, and rhizosphere microbial functions.

The interaction between microplastics (MPs) and cadmium (Cd) poses a threat to agricultural soil environments, and their effects on plant growth and rhizosphere microbial community functions are not yet clear. In this study, energy sorghum was used as a test plant to investigate the effects of two types of MPs, polystyrene (PS) and polyethylene (PE), at different particle sizes (13 µm, 550 µm) and concentrations (0.1%, 1% w/w), and Cd, as well as their interactions, on the growth of sorghum in a soil-cultivation pot experiment. The results showed that the combined effects of MP and Cd pollution on the dry weight and Cd accumulation rate in sorghum varied depending on the type, concentration, and particle size of the MPs, with an overall trend of increasing stress from combined pollution with increasing Cd content and accumulation. High-throughput sequencing analysis revealed that combined MP and Cd pollution increased bacterial diversity, and the most significant increase was observed in the abundance-based coverage estimator (ACE), Shannon, and Sobs indices in the 13 µm 1% PS+Cd treatment group. Metagenomic analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways revealed that 19 groups of metabolic pathways, including microbial metabolism and methane metabolism, differed significantly under combined MP and Cd pollution. Hierarchical clustering results indicated that Cd treatment and combined MP and Cd treatment affected the abundances of sorghum rhizosphere soil nitrogen (N) and phosphorus (P) cycling genes and that the type of MP present was an important factor affecting N and P cycling genes. The results of this study provide a basis for exploring the toxic effects of combined MP and Cd pollution and for conducting soil environmental risk assessments.

[Effects of Combined Pollution of Microplastics and Cadmium on Microbial Community Structure and Function of Pennisetum hydridum Rhizosphere Soil].

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.

[High-Throughput Sequencing Combined with Metabonomics to Analyze the Effect of Heavy Metal Contamination on Farmland Soil Microbial Community and Function].

Heavy metal contamination affects microbial composition and diversity. The interaction between heavy metal contamination and soil microorganisms has been a hot topic in ecological research. Battery manufacturing has been going on for over six decades in Xinxiang City, resulting in severe soil heavy metal contamination due to battery wastewater runoff. Few studies have investigated the effect of heavy metal contamination due to long-term battery wastewater runoff on microbial diversity and metabolomics in Xinxiang City. In this study, we collected samples from three heavy metal contaminated sites in Xinxiang City and found that Cd and Pb exceeded the recommended thresholds by 34-66 fold and 1.5-2.32 fold, respectively. High-throughput sequencing showed that Bacillus, Arthrobacter, Sphingomonas, and Streptomyces were the dominant bacteria genera, while Olpidium, Plectosphaerella, and Gibellulopsis were the dominant fungi genera, indicating that heavy metal contaminated soil in Xinxiang City was rich in heavy metal tolerant bacteria and fungi due to the long-term heavy metal stress. Correlation analysis showed that total Cu, DTPA extract Cu, and water soluble Pb were significant factors in bacterial diversity, while total Cd, total Ni, total Pb, total Zn, DTPA extract Cu, and water soluble Pb were significant factors in fungal diversity. To better understand the effect of heavy metal contamination on the metabolism of soil microorganisms, we conducted non-targeted metabolomic profiling, which showed significant differences in metabolites across the samples. Pathway enrichment analysis showed that these differential metabolites were involved in pathways such as metabolism, environmental information processing, and genetic Information Processing, which may play a role in heavy metal stress mitigation and environmental adaptation.