Chronic airway infections by the opportunistic pathogen Pseudomonas aeruginosa are a major cause of mortality in cystic fibrosis (CF) patients. Although this bacterium has been extensively studied for its virulence determinants, biofilm growth, and immune evasion mechanisms, comparatively little is known about the nutrient sources that sustain its growth in vivo. Respiratory mucins represent a potentially abundant bioavailable nutrient source, although we have recently shown that canonical pathogens inefficiently use these host glycoproteins as a growth substrate. However, given that P. aeruginosa, particularly in its biofilm mode of growth, is thought to grow slowly in vivo, the inefficient use of mucin glycoproteins may be relevant to its persistence within the CF airways. To this end, we used whole-genome fitness analysis, combining transposon mutagenesis with high-throughput sequencing, to identify genetic determinants required for P. aeruginosa growth 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 describe a molecular basis for mucin-based nutrient acquisition by P. aeruginosa and reveal a host-pathogen dynamic that may contribute to its persistence within the CF airways.
Bibliographical noteFunding Information:
We acknowledge Caleb Levar and Chi-Ho Chan (BioTechnology Institute, University of Minnesota) for their assistance with TnSeq, and we acknowledge the Minnesota Supercomputing Institute. This study was supported by a Pathway to Independence Award from the National Heart, Lung, and Blood Institute (NHLBI) to R.C.H. (R00HL114862) and by the National Center for Advancing Translational Sciences (UL1TR000114). J.M.F. was supported by a National Institutes of Health Lung Sciences T32 fellowship (2T32HL007741-21) awarded through the NHLBI and by a Cystic Fibrosis Foundation Postdoctoral Fellowship (FLYNN16F0).
© 2017 American Society for Microbiology.
- Cystic fibrosis
- Glyoxylate pathway
- Pseudomonas aeruginosa