Loss of O-specific antigen shapes <i>Pseudomonas aeruginosa</i> population microbiogeography in murine preclinical pulmonary infection model

Abstract Chronic Pseudomonas aeruginosa infections are the hallmark of late-stage lung disease in individuals with cystic fibrosis. During chronic infection P. aeruginosa becomes the dominant bacteria in the airway. Within-host adaptation of P. aeruginosa leads to vast phenotypic and genetic population heterogeneity. In vitro studies show mutations in lipopolysaccharide (LPS) O-specific antigen changes the aggregate formation in P. aeruginosa , however role of these changes in aggregate assembly in vivo is not understood. Using a synthetic CF sputum media and a preclinical murine infection model we assessed how the PAO1 wildtype and O-specific antigen mutants interact with each other, and if P. aeruginosa population heterogeneity affects the colonization of the murine lungs. Our findings suggest that the presence of variants lacking O-specific antigen does not impact the population fitness and size in both in vitro and in vivo , however it can influence the aggregate volume in vivo .