Aspergillus fumigatus is a human pathogenic mold that causes life-threatening diseases in immunocompromised patients. In contrast to mammalian cells, fungi have a tough cell wall that consists of chitin and other polysaccharides. The cell wall defines the organisms shape, protects it from physical stress and is essential to withstand the mammalian immune system. Due to its essential function in fungi and its absence in mammals the cell wall is an important antifungal drug target. We study the molecular mechanisms that regulate the biogenesis of the fungal cellwall. In addition, we develop and evaluate new diagnostic testsfor fungal and bacterial infections.