The decline of bee populations threatens ecosystems and agriculture and is driven by factors like habitat loss, pesticide use, climate change, and pathogens. All are linked to floral resources and bee nutrition. This project aims to clarify the link between bee health and nutrition at a molecular level, focusing on pollen as a key nutritional source. We will investigate the impact of different pollen molecules on bee health and their role in pathogen interactions. One of the approaches will be to identify metabolic pathways in bee-pathogen interactions, initially focusing on Bombus and Osmia species.