Unraveling plasmid contributions to phosphorus acquisition in soil microbiomes

Phosphorus (P) is a fundamental macronutrient for plant and microbial growth, but its availability in soils is often constrained by strong interactions with minerals and organic matter. While the role of bacteriophages in P cycling has gained attention, plasmids remain comparatively underexplored despite their central role in horizontal gene transfer. This study aimed to investigate the occurrence, diversity, and ecological relevance of plasmid-borne genes involved in P acquisition across soils with contrasting P availability.

Using curated plasmid databases and soil metagenomes from diverse biomes, we identified a broad repertoire of plasmid-encoded P-acquisition genes. These genes encompassed regulatory pathways, transport systems, organic P mineralization, and inorganic P solubilization. Regulatory and transporter genes were the most abundant categories, with phoB, phoP, and ugpC among the most frequently detected. When additional analyses were performed using habitat-specific P classifications and continuous P gradients, these associations appeared weak and were not significant after multiple-testing correction. These results suggest that plasmid-encoded P-acquisition genes are broadly distributed across environments rather than tightly constrained by measured soil P levels, while taxonomic assignment revealed that Pseudomonadota were the predominant plasmid hosts, followed by Bacillota and Actinobacteriota, suggesting broad host diversity.

This study provides a genomic overview of plasmid-borne genes associated with P acquisition in soils. Our results show that these genes are widespread across plasmids from diverse environments and host taxa, suggesting that the soil mobilome may represent an important reservoir of functions related to microbial P metabolism. While the presence and relative abundance of these genes indicate their potential ecological relevance, functional expression and ecological impact remain to be experimentally validated. These findings expand current knowledge of plasmid contributions to nutrient cycling and highlight the mobilome as a potential target for future studies aiming to better understand microbial strategies for P acquisition in soil ecosystems.