Effects of biochar amendment on bacterial communities and their function predictions in a microplastic-contaminated Capsicum annuum L. soil

Abstract

Microplastics (MPs) have been confirmed as a novel type of environmental pollutant. They have long-term existence in the soil environment and threaten the soil ecological environment system. Biochar soil amendment is capable of enhancing the water and nutrient holding capacity and improving the soil structure and quality of terrestrial ecosystems. However, the effect of biochar amendment on bacterial community in MPs-contaminated soil–plant system remain unclear, in particular the prediction of bacterial function of these systems. In this study, the effects of biochar amendment on the bacterial community structure of MPs-contaminated soil were investigated through different treatments at three pepper growth stages, and the bacterial function of MPs-contaminated soil was predicted. As indicated by the results of this study, biochar amendment led to the increased species evenness and richness of bacterial community in MPs-contaminated soil, the enhanced relative abundance of MPs-contaminated tolerant bacteria (e.g., Proteobacteria, Acidobacteria, Actinobacteria, and Bacteroidetes), as well as the improved relative abundance of Massilia, Lysobacter, and Terrimonas. Furthermore, soil total phosphorus (TP), soil organic carbon (SOC), NH4+-N, NO3−-N, and pH served as the main factors for the composition of soil bacterial community, as revealed by the result of Pearson correlation analysis and redundancy analysis. Bacterial genera Massilia, Lysobacter, and Terrimonas significantly affected the growth indicator of pepper. PICRUSt functional prediction suggested that the bacterial community of MPs-contaminated soil primarily comprised four level-1 functional layers and 16 level-2 functional layers, and the active soil bacterial community was identified in Metabolism, Genetic information processing, as well as Cellular processes. Biochar amendment enhanced the abundance of genes correlated with Amino acid metabolism and Carbohydrate metabolism of bacteria in MPs-contaminated soil, thus facilitating the nitrogen and phosphorus metabolism cycle of MPs-contaminated soil plants. Our results confirmed that biochar amendment increase the beneficial bacteria in MPs-contaminated soil, more significantly facilitate the nitrogen and phosphorus metabolism cycle within MPs-contaminated soil plants, while effectively expediting the growth of plants in MPs-contaminated soil. This study provides more insights into the correlation of plant and bacterial communities in response to biochar amendment in MPs-contaminated soil system.