Metabolism of Penicillium oxalicum-mediated microbial community reconstructed by nitrogen improves stable aggregates formation in bauxite residue: A field-scale demonstration

Abstract

Microbially-driven stable aggregate formation plays a crucial role during the soil formation process in alkaline bauxite residue. However, the interacting mechanisms between microbial community assembly and aggregate formation remain poorly understood. In this study, we conducted a field-scale experiment and laboratory validations, coupled with multi-omics analysis, to investigate microbially-driven aggregate fraction turnover and its microbial driving mechanisms in bauxite residue. Field-based results demonstrated that Penicillium oxalicum (P. oxalicum) significantly increased the proportions of microaggregates (250-53 μm) and macroaggregates (>250 μm) by 20.98% and 22.19%, respectively. Moreover, nitrogen input was more strongly associated with the formation of microaggregates, increasing the proportion by 23.13% during the incubation. Microbial taxonomic analysis revealed that aggregate fraction turnover was regulated by functional trait-based community assembly and significantly correlated with Actinobacteria and Proteobacteria. Untargeted metabolomic analyses further confirmed that nitrogen input stimulated carbohydrate and nitrogen metabolism, with key metabolites (e.g., c-di-GMP, saccharopine, and arginine) involved in polysaccharide and protein biosynthesis, thus positively influencing aggregate formation. Furthermore, laboratory validations demonstrated that exogenous application of key metabolites significantly increased particle size and corrosion resistance. These findings highlighted the enhancement of nitrogen on P. oxalicum-mediated aggregate fraction turnover and advanced our understanding of microbially-driven soil formation processes in bauxite residue.