Abstract Description

Understanding the biogeographic patterns of understudied microbial communities remains a major ecological endeavour. Acidobacteriota are one of the most biodiverse and widespread bacterial phyla in soils. Recent studies have shown that several families within this phylum possess plant-growth promoting traits. However, global trends related to their: 1) spatial clustering, 2) niche differentiation and 3) niche breadth remain poorly understood. This limitation, combined with the generally difficult-to-culture nature of members of this phylum, remains a major bottleneck which limits their application as potential bioinoculants. Here, we used SingleM and Sandpiper to characterize the distributions of the plant-growth promoting Acidobacteriota, namely, Acidobacteriaceae, Bryobacteraceae, Korobacteraceae, Pyrinomonadaceae across a global set of soil metagenomes. We then linked these distributions to a biogeographic framework (i.e., realm- and biome-level) and publicly available environmental data including soil texture, pH, nitrogen, soil organic carbon and cation exchange capacity. Spatial clustering of these families was first determined using the Ward algorithm applied to biogeography and soil texture data. Using the Mann-Whitney U test, the soil habitats associated with the resultant clusters were then compared based on pH, nitrogen, soil organic carbon and cation exchange capacity. Finally, using the abovementioned chemical data, the niche breadths of the clusters were then quantified using a bootstrapped inter-quartile range analysis (1,000 replicates; 95% confidence intervals). Overall, we identified two clusters: Cluster 1 (Acidobacteriaceae and Korobacteraceae) and Cluster 2 (Bryobacteraceae and Pyrinomonadaceae). These clusters exhibited niche differentiation (p < 0.001), with Cluster 2 demonstrating a broader pH niche breadth and a greater prevalence in arid biogeographic units. Overall, Bryobacteraceae and Pyrinomonadaceae are the most ecologically versatile plant-growth promoting Acidobacteriota globally, supporting their prioritization in bioinoculant development.