Abstract
Polymorphonuclear neutrophils are the most important mammalian host defence cells against infections with Pseudomonas aeruginosa. Screening of a signature tagged mutagenesis library of the non-piliated P. aeruginosa strain TBCF10839 uncovered that transposon inactivation of its pilY1 gene rendered the bacterium more resistant against killing by neutrophils than the wild type and any other of the more than 3000 tested mutants. Inactivation of pilY1 led to the loss of twitching motility in twitching-proficient wild-type PA14 and PAO1 strains, predisposed to autolysis and impaired the secretion of quinolones and pyocyanin, but on the other hand promoted growth in stationary phase and bacterial survival in murine airway infection models. The PilY1 population consisted of a major full-length and a minor shorter PilY1* isoform. PilY1* was detectable in small extracellular quinolone-positive aggregates, but not in the pilus. P. aeruginosa PilY1 is not an adhesin on the pilus tip, but assists in pilus biogenesis, twitching motility, secretion of secondary metabolites and in the control of cell density in the bacterial population.
Highlights
Pseudomonas aeruginosa is a metabolically versatile Gram-negative bacterium, which inhabits terrestrial and aquatic as well as animal, human and plant host associated environments (Ramos, 2004)
The PilC proteins whose expression can be switched on and off by phase variation (Rytkönen et al, 2004), are major adhesins and regulate PilTmediated T4P retraction in Neisseria (Morand et al, 2004). This datum indicates that the 3.5 kb P. aeruginosa pilY1 homologue may encode a protein with multiple functions including, but not restricted to, pilus biogenesis
A mini-Tn5 plasposon library of the cystic fibrosis (CF) airway isolate TBCF10839 carrying variable V40 (V = A, G, C) oligonucleotide signature tags were screened for survival in freshly prepared human Polymorphonuclear neutrophils (PMNs) in phagocytosis assays
Summary
Polymorphonuclear neutrophils are the most important mammalian host defence cells against infections with Pseudomonas aeruginosa. Screening of a signature tagged mutagenesis library of the non-piliated P. aeruginosa strain TBCF10839 uncovered that transposon inactivation of its pilY1 gene rendered
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