Functional redundancy enables a simplified consortium to match the lignocellulose degradation capacity of the original consortium

The relationship between structure and function in microbial communities is intriguing and complex. In this study, we used single-carbon source domestication to derive consortium YL from the straw-degrading consortium Y. Y and YL exhibited similar straw degradation capabilities, yet YL harbored only half the species diversity of Y, with distinct dominant species. The most enriched microorganisms in Y were Ureibacillus, Acetanaerobacterium, and Hungateiclostridiaceae, whereas Bacillaceae, Bacillus, and Peptostreptococcales-Tissierellales were most enriched in YL. In-depth analysis revealed that Y and YL had comparable abundances of core lignocellulose-degrading genes, as validated by lignocellulolytic enzyme activity assays. However, the number of species harboring these key lignocellulose-degrading genes (K01179, K01181, K00432) in YL was reduced by over 50%, suggesting that functional redundancy enabled YL to maintain similar degradation capabilities to Y despite reduced diversity. Further analyses of key degradative species and co-occurrence networks highlighted the critical functional roles of dominant degradative species within these communities. An analysis of the overall functional pathways in the two microbial consortia revealed distinct metabolic characteristics between them. Pathways such as polycyclic aromatic hydrocarbon degradation and fluorobenzoate degradation were down-regulated in YL compared to Y, a finding corroborated by the metabolomic data. These results suggest a coupling between community structure and functional capacities within these microbial consortia. Overall, our findings deepen our understanding of the structure-function relationship in microbial communities and provide valuable insights for the design of lignocellulose-degrading consortia.