Genome-wide survey ofPseudomonas aeruginosaPA14 reveals a role for the glyoxylate pathway and extracellular proteases in the limited utilization of mucin

Abstract

ABSTRACTChronic airway infections by the opportunistic pathogenPseudomonas aeruginosaare major cause of mortality in cystic fibrosis (CF) patients. While this bacterium has been extensively studied for its virulence mechanisms, biofilm growth and immune evasion within the CF airways, comparatively little is known about the nutrient sources that sustain its growthin vivo. Respiratory mucins represent a potentially abundant bioavailable nutrient source, though we have recently shown that canonical pathogens inefficiently use these host glycoproteins as a growth substrate. Yet, given thatP. aeruginosa, particularly in its biofilm mode of growth is thought to grow slowlyin vivo, the inefficient use of mucin glycoproteins may have relevance to its persistence within the CF airways. To this end, here we use whole genome fitness analysis combining transposon mutagenesis with high throughput sequencing (TnSeq) to identify genetic determinants required forP. aeruginosagrowth using intact purified mucins as a sole carbon source. Our analysis reveals a biphasic growth phenotype, during which the glyoxylate pathway and amino acid biosynthetic machinery are required for mucin utilization. Secondary analyses confirmed the simultaneous liberation and consumption of acetate during mucin degradation and revealed a central role for the extracellular proteases LasB and AprA. Together, these studies identified theP. aeruginosagenes required for mucin-based nutrient acquisition and reveal a host-pathogen dynamic that may contribute to its persistence within the CF airways.