The pyocins of P. aeruginosa target several different outer membrane receptors involved in uptake of the essential nutrient iron and pyocin L1 has also been shown to bind to the common polysaccharide antigen (CPA), which is the major surface antigen produced by P. aeruginosa when growing in the lungs of CF patients14, 22, 23, 24. Here, CPA1 is linked to cystic fibrosis.