AP1: EnzymeCosts

Metabolic and energetic costs of microbial substrate degradation to mine phosphorus

AP1 is a project funded by the DFG within the Walter Benjamin Programme and is affiliated to the SPP 2322 SoilSystems.

Transformation of matter and energy in soils depends on the activity state of microorganisms and their metabolism. Microbial mining of phosphorus (P) may be driven not only by P, but also carbon (C) and energy limitation, as high-energy phosphoester bondings serve as major energy-transfer and storage molecules in cells. In this project we will deepen the thermodynamic-metabolic approach developed within ‘EcoEnergeticS’ towards the bioenergetics of P mining from organic sources. We aim to evaluate the energy costs of enzyme production for P mining to acquire C, energy and nutrients from substrates of contrasting complexity. We aim to combine the parameters of microbial P immobilization (Pmic formation), ATP level, dynamics of storage compound (PHBs), PLFA and DNA contents and ratios and enzyme activity with heat dissipation and CO2 emission as proxies of metabolic activity. We hypothesize that energy costs of P-hydrolyzing enzyme production by microorganisms increase with increasing substrate complexity. Besides, at either C or P limitation, microorganisms utilize compounds with high-energetic phosphoester bonds (e.g. ATP) rather as a source of either C or P, respectively. In the absence of P limitation, C from ATP can be accumulated to storage compounds (i.e. PHB) to save the energy, while hydrolyzed P is released to the soil. In WP1, we will assess the investment of microorganisms into enzyme production to mine energy and nutrients from organic P substances of various complexity, that requires hydrolysis by one or several phosphatases (phosphomono- and phosphodiesterases, phytases). Further in WP2, we will disentangle the energy costs of i) inorganic P uptake and anabolic use, ii) mineralization of organic P compounds of increasing complexity. The fate of high energy, C and P-containing organo-phosphoesters used by microorganisms with nutrient and/or energy limitation will be investigated in WP3. Specifically, we aim to define ATP incorporation into cell components as an indicator of the metabolic state of cell being able to differentiate i) energy limited, ii) C limited or iii) P limited microbial communities in soils. Overall, this project will investigate how nutrient deficiencies and the requirement of phosphatase formation is interfering with energy and C storage and how the microbial activity state of microorganisms affects the control of these P and C pathways. The understanding of these mechanisms will help to increase the microbial efficiency in P transformation from SOM especially considering the future P crisis.

Link to English scientific abstract
Link to German scientific abstract