Pseudomonas aeruginosa adaptation, pathogenicity, and persistence in the environment and cystic fibrosis airway.

Abstract

Pseudomonas aeruginosa is an opportunistic Gram-negative bacterium associated with airway infections of patients with cystic fibrosis (CF). Lipid A is the membrane anchor of lipopolysaccharide, the dominant component of the outer leaflet of the outer membrane of Gram-negative bacteria. Lipid A structure can be modified via a number of biosynthetic enzymes. Here, we describe two -hydroxylase enzymes, LpxO1 and LpxO2, capable of catalyzing 2-hydroxylation of lipid A in P. aeruginosa. We additionally characterize their role in persistence and infectivity. Phylogenetic analysis suggests at least one lpxO originated from lateral gene transfer and the gene duplication is a recurring feature in Pseudomonas evolution. To determine the roles of LpxO1/2 in vivo, we used a rapid extraction from lavage fluid to describe the structure of P. aeruginosa lipid A isolated from the lungs of mice after intranasal infection. Lipid A is also known to be altered during adaptation to the lungs of CF patients, where P. aeruginosa can colonize and cause infection throughout a patient’s lifetime. This is a leading contributor of morbidity and mortality in this patient population, and thus the genetic and phenotypic adaptations that P. aeruginosa undergoes during CF airway infection are of interest. We used whole-genome sequencing of 130 P. aeruginosa isolates, including 81 from young children with CF, to define early-stage genetic adaptation events, including lipid A modification. We additionally investigate the influence of patient region of residence on such adaptation. With these data, we provide the first longitudinal analysis of P. aeruginosa genetics in young patients with CF in the United States. We additionally analyzed ten sublines of laboratory-adapted strain PAO1 to determine the level of microevolution experienced by this set of isolates. In total, our analyses contribute to our understanding of lipid A structure, synthesis, and modification in P. aeruginosa, and our sequencing data will serve as a resource for the entire CF and Pseudomonas community.