Microbial energetic costs of phosphorus mining and uptake

Phosphorus (P) is a growth-limiting nutrient for plants and microorganisms in many natural and agricultural ecosystems. Microbial transformations of P in soils play a crucial role in increasing its availability to plants. Once taken up by microorganisms, P contributes to the energy and nutrient metabolism of microbial cells and often becomes plant-available only after microbial cell death (i.e., through the mineralization of microbial necromass).

The processes of P acquisition and microbial activation require cellular energy, which is often transferred by P-containing substances with high-energy phosphoester bonds, most commonly adenosine triphosphate (ATP). Microbial phosphorus mining from organic phosphorus compounds demands energy for the production of phosphatases. The type and combination of phosphatases required depend on the complexity of the P-containing compound, as these enzymes hydrolyze P into a plant-available form.

This talk will present measurements of the energetic costs microorganisms invest in producing various enzymes to solubilize P from compounds of increasing complexity. Additionally, the energetic costs of microbial P uptake from inorganic sources will be compared to those associated with the enzymatic hydrolysis of organic sources.

Results from incubation experiments revealed that the heat released during organic P hydrolysis increased with the complexity of the substrate, ranging from phosphomonoester bonds in sugar phosphate to six ester bonds in phytate. Furthermore, microorganisms expended significantly more energy on enzyme production than on phosphorus uptake via active cellular transport alone.

These findings provide valuable insights into predicting the hydrolysis of organic P compounds in soil, based on potential enzymatic activities and the energy balance of microorganism-mediated processes.

Acknowledgments and Funding: This work was funded by the German Research Foundation (DFG, BI 2570/1-1), project number 525137622.