Summary

The lack of iron in the soil can be a significant challenge in agriculture. Microbes have the potential to make this essential micronutrient bioavailable, because they synthesize as secondary metabolites so-called siderophores capable of chelating insoluble Fe³⁺. In recent studies, it could be demonstrated that microbial siderophores provide Fe-nutrition when the bioavailability of iron in the soil is limited, thereby enhancing plant growth. Therefore, siderophores have tremendous application potential in agriculture as ingredient to alternative fertilizers. However, their native biosynthesis in bacteria is controlled by complex regulatory networks, which hampers functional analysis and biotechnological production. Thus, the efficient synthesis of siderophores in engineered microbial hosts is of high interest to gain access to this class of valuable compounds. Therefore, in the planned interdisciplinary project, we will (i) construct a novel Pseudomonas putida chassis to produce siderophores by targeting the well-characterized, water-soluble compound pyoverdine. Alongside, we will (ii) evaluate if outer membrane vesicles (OMV) can be used as extracellular microcompartments for siderophore encapsulation. In parallel, we will (iii) characterize free and encapsulated pyoverdine as plant growth-promoting agents. To this end, we will evaluate if OMV encapsulation of pyoverdine can enhance its stability and uptake by plants as essential characteristics for root and leaf fertilization.