During my PhD project I am working with Legionella pneumophila. L. pneumophila encodes more than 300 effector proteins that are injected into the host cell by the Dot/Icm type IV b secretion system (T4SS) during infection. I am interested in the secretion mechanism of the hydrophobic transmembrane domain (TMD)-containing effector proteins (TMEs) through the Legionella T4SS. We showed previously that, depending on the TMD hydrophobicity, TMEs either use a two-step secretion pathway with an inner membrane intermediate or are targeted directly to the T4SS. I am investigating whether the hydrophobicity of the TMEs is the only factor affecting the pathway of secretion or if other non-T4SS or T4SS components are involved in the process. Furthermore, I will investigate the functional mechanism of TME secretion through the T4SS.