Contrasting edaphic and land-use signatures of microbial phosphorus mobilisation and accumulation genes

Abstract

Phosphorus (P) is an essential nutrient that constrains productivity across many terrestrial ecosystems. Soil microorganisms regulate P transformation through distinct functional strategies, yet how these strategies vary with land use and environmental conditions across chronically P-impoverished landscapes remains poorly understood. Here, we combined 268 soil metagenomes from natural, pasture, and cropland systems across Australia with genome-resolved analyses of 1,077 metagenome-assembled genomes (MAGs). Results revealed contrasting genomic distributions among P-cycling strategies. P accumulation genes were widely distributed across bacterial phylogeny, whereas mineralization gene and solubilisation gene were concentrated within specific lineages. Land-use-associated differences were most evident in the relative abundances of mineralisation and solubilisation genes, whereas accumulation genes showed comparatively little variation. Soil properties were stronger predictors of relative P-cycling gene abundance than climatic variables. Among these variables, soil pH was the strongest predictor of both the combined relative abundance of P-cycling genes and mineralisation genes, whereas accumulation genes were negatively associated with the mineral-associated organic carbon fraction. Continental predictions further suggested higher combined relative P-cycling gene abundance in wetter south-western and coastal eastern regions. These analyses reveal contrasting microbial P-cycling gene strategies across Australian soils and provide a genome-resolved framework for understanding their phylogenetic distributions and environmental associations at the continental scale.