Many bacterial pathogens use specialised protein secretion systems to inject virulence “effector” proteins into eukaryotic host cells. In the last 10 years, it has emerged that bacterial effector proteins are typically enzymes that mediate sometimes highly novel post-translational modifications of eukaryotic proteins. Recent examples include arginine glycosylation, phosphoribosyl-linked ubiquitination and ADP-riboxanation. As such, bacterial effectors are unique tools to explore fundamental aspects of cell biology and biochemistry. In addition, the identification of the targets of effector activity in host cells provides valuable insight into host mechanisms of cell intrinsic immunity, since effector proteins have evolved to block these pathways. While it is well established that bacterial effectors target host eukaryotic proteins, the possibilty that bacterial effectors modify host RNA is not commonly explored. We recently discovered that an effector protein from Legionella pneumophila degrades host glycolytic mRNAs to inhibit host cell metabolism during infection. We demonstrated that the effector protein is a bone fide RNA binding protein that preferentially binds to host mRNA by recognising a guanine rich motif. This finding reinforces the prospect that effector proteins not only mediate post translational modifications of host proteins but also may target the host epitranscriptome.