Title: R type pyocins in Pseudomonas aeruginosa cystic fibrosis lung infection biofilms

Abstract: Pseudomonas aeruginosa (Pa) is a prevalent Gram-negative opportunistic pathogen found in a number of infections; however, it is a major problem in lung infections of individuals with cystic fibrosis (CF). It is believed that one strain of Pa takes over and diversifies over the course of these chronic lung infections, however the mechanism for this is poorly understood. Studies suggest intra-species competition of Pa can be mediated via production of bacteriocins known as pyocins. Pyocins are considered narrow spectrum antimicrobials, specifically produced by Pa to kill other strains of Pa. Current studies have focused on showing that R-type pyocins play a role in intra-species competition due to the production of various types (types 1-5) of R-pyocins, as each strain produces only one of the five R-pyocin types. To investigate the impact of Pa population diversity on intra-species competition in CF lungs, we have collected a “biobank” of whole populations of Pa from CF patients. We primarily focused on several Pa populations that produce different types of R-pyocins collected from patients with chronic lung infections. We found (i) populations collected from a single sputum sample produce the same R-pyocin type and this does not change over a period of months; (ii) populations from the same sputum sample exhibit diversity in susceptibility to pyocins of other isolates of Pa; (iii) the different R-pyocin types are found in isolates from various environments. Our work is a step towards understanding how intra-strain competition via pyocins can affect the dynamics of evolved, diverse Pa populations. These data suggest that R-pyocins may play a role in shaping the Pa population of chronic CF lung infections.