The bacterium P. aeruginosa causes the most common secondary infection in hospital patients with influenza, COVID-19 or cystic fibrosis and it is resistant to antibiotics. Another bacterial pathogen, Vibrio vulnificus, is found in raw seafood and brackish waters and can have rare, but deadly consequences for human beings. To poison the cells, both pathogens use toxins called ExoY that are almost inactive inside the bacteria. Once injected into cells, however, ExoY takes a turning point as it becomes ten thousand times more active. Yet, the exact mechanism that leads to this ten thousand fold activity was until recently unknown.