Deciphering Legionella effector delivery by Icm/Dot secretion system reveals a new role for c-di-GMP signaling

•The dynamics of multi-effector secretion is addressed in the paradigm Legionella Icm/Dot T4SS.•A kinetic translocation assay allowing a fine monitoring of the T4SS activity is set up.•Specific secretion patterns consistent with sequential functions in the host are reported.•T4SS-dependent translocation is promoted by a diguanylate cyclase.•Unreported control of Type 4 secretion by the second messenger c-di-GMP signaling is revealed.