Updated publication reference for PubMed record(s): 29636436. Tyrosine phosphorylation is key for signal transduction from exogeneous stimuli, including the defence against pathogenic microbes. Pathogens have acquired mechanisms to subvert protein phosphorylation as a means to control host immune responses and facilitate invasion and dissemination. The bacterial effector protein EspJ is injected into host cells by pathogenic strains of Escherichia coli, Salmonella and Citrobacter rodentium where it can prevent phagocytosis via the inhibitory amidation and ADP ribosylation of Src kinase E310. Here, we found that EspJ can ADP ribosylate members of the Src, Abl, Csk, Tec and Syk kinase families. ADP ribosylation of Csk inhibits its kinase activity, giving EspJ ultimate control over the Src/Csk signalling axis.