Phosphate Solubilization by the Gut Microbiota of Earthworms

Phosphorus is an essential macronutrient for plant growth and development, commonly present in soils but often unavailable to plants due to its low solubility and strong fixation with soil particles. Various soil microorganisms-including fungi, bacteria, and actinomycetes-play a crucial role in mobilizing this nutrient through phosphate solubilization mechanisms. Earthworms, well-known for enhancing soil structure and fertility, may also contribute to phosphorus transformation, either directly through their physiological activity or indirectly via their associated gut microbiota. However, limited information is available regarding the phosphate-solubilizing capabilities of earthworm gut microflora. In the present study, the potential of earthworm gut microbiota to solubilize phosphate was evaluated using dicalcium and tricalcium phosphate as substrates. The results demonstrated effective solubilization by several gut-associated microbes, predominantly actinomycetes. Notably, the efficiency of phosphate solubilization varied among the different microbial isolates, indicating species-specific functional capabilities within the earthworm gut ecosystem.