Deterministic assembly processes shaping habitat-specific glycoside hydrolase composition

Aim: Glycoside hydrolases (GHs) encoded by prokaryotes play a crucial role in the degradation of carbohydrates, which is a key step in the carbon cycle. However, their global distribution remains poorly understood. Here, we conducted a comprehensive investigation of the global biogeographic patterns of prokaryotic-encoded GHs. Location: Global. Time Period: Present. Major Taxa Studied: Prokaryotes. Methods: We conducted a global survey of GH distribution based on 10,000 samples from the Earth Microbiome Project (EMP) and 17,923 completely sequenced prokaryotic genomes. The samples were retrieved from 7 continents, covering all 17 EMP Ontology environments. We evaluated the assembly process and influencing factors of GH functional genes within prokaryotic communities, and analyzed the rank abundance distributions (RADs), occupancy frequency distributions (OFDs), and taxonomic sources of GH families across various environments. Results: The median number of GH genes per thousand genes encoded by global prokaryotic communities was 9.11 (7.16-11.58), with a higher GH abundance in host-associated communities than in free-living communities. The median number of GH families in prokaryotic communities was 105 (86-121), with fewer families but tighter functional connections between families in host-associated communities compared to free-living communities. In any environment, the RAD of GH families followed a lognormal model, and their OFD was bimodal, with a strong positive correlation between the two. In addition, most GH families had complex and diverse taxonomic sources across different environments. Main Conclusions: This study provides a panoramic view of the functional potentials for carbohydrate degradation across prokaryotic communities under diverse environmental conditions. The composition of GHs encoded by prokaryotic communities exhibits clear habitat specificity, which is driven by a combination of biotic and abiotic factors and generated through highly deterministic assembly processes