Elevated exopolysaccharide levels in Pseudomonas aeruginosa flagellar mutants have implications for biofilm growth and chronic infections

• DOI: 10.1371/journal.pgen.1008848
• Publication Date: 2020-06-12T17:40:48Z
• Authors: Joe J. Harrison; Henrik Almblad; Yasuhiko Irie; Daniel J. Wolter; Heather C. Eggleston; Trevor E. Randall; Jacob O. Kitzman; Bethany Stackhouse; Julia C. Emerson; Sharon Mcnamara; Tyler J. Larsen; Jay Shendure; Lucas R. Hoffman; Daniel J. Wozniak; Matthew R. Parsek
• Keywords: Transposon mutagenesis; Genetic screen

Pseudomonas aeruginosa colonizes the airways of cystic fibrosis (CF) patients, causing infections that can last for decades. During course these infections, P. undergoes a number genetic adaptations. One such adaptation is loss swimming motility functions. Another involves formation rugose small colony variant (RSCV) phenotype, which characterized by overproduction exopolysaccharides Pel and Psl. Here, we provide evidence two adaptations are linked. Using random transposon mutagenesis, discovered flagellar mutations linked to RSCV phenotype. We found mutants overexpressed Psl in surface-contact dependent manner. Genetic analyses revealed were selected at high frequencies biofilms, expression provided primary fitness benefit this environment. Suppressor mutagenesis RSCVs indicated overexpression required mot genes, suggesting flagellum stator proteins function surface-dependent regulatory pathway exopolysaccharide biosynthesis. Finally, identified mutant among CF isolates. The environment has long been known select mutants, with classic interpretation being gained relates an impairment host immune system target bacterium lacking flagellum. Our new findings lead us propose production key gain-of-function phenotype offers way interpret benefits mutations.