Colin Kleanthous is Professor of Microbial Biochemistry at the University of Oxford. He is a microbial biochemist whose discoveries using bacteriocins have fundamentally changed our understanding of the Gram-negative bacterial cell envelope. How bacteriocins kill cells and how they navigate through the many layers of the cell envelope have been largely unknown, until Kleanthous’ work. He demonstrated how nuclease bacteriocins transport through the outer membrane, laying the foundations for exploitation of these pathways for future antibiotics. These discoveries explain how bacteria tune the composition of their outer membrane to a changing environment and have major implications for our understanding of antibiotic resistance and bacterial pathogenicity mechanisms.