Complex carbohydrates are important biopolymers fulfilling a myriad of different biochemical and structural functions across all kingdoms of life. Chitin is one of the two most abundant biopolymers on earth and is an essential polymer in the cell wall of fungi and the exoskeleton of arthropods. Chitin is a linear polysaccharide of N-acetyl glucosamine that is prone to self-associate into semi-crystalline fibrillar structures that can be integrated with other polymers to create specialized biomaterials.

Because chitin is both absent in humans and physiologically essential for many pathogens, chitin biosynthesis and assembly qualify as attractive targets for the development of novel pesticides and antimicrobial agents. Despite many years of study, the molecular and cellular pathways leading to assembled cell walls and cuticles are still unknown.

In collaborative effort between Simone Mattei in EMBL and Luca Bertinetti and Yael Politi in TU Dresden, we seek to characterize chitin biosynthesis and organization on a molecular and mechanistic level across scales in two of the most important chitin-producing groups, yeast and insects. To this end we will (1) determine the molecular structure of chitin synthase (CHS) from yeast and insects using cryo-electron microscopy; (2) determine the dynamic of CHS in vivo in insect cells and tissues using super-resolution live imaging methodologies; (3) determine the cellular pathway of chitin-protein fiber co-assembly and orientation using volume imaging with nanometer resolution; (4) establish methodological workflows that allow determination of molecular structure of chitin synthase and assembly in their native environment using in situ cryo-electron tomography. Determining the molecular and mechanistic basis underlying the different modes of chitin fibre assembly will provide the molecular basis to target this Achilles’ heel in the development of many pathogens.