Swimming motility and type IV pili modulate phagocytosis by shaping physical interactions between Pseudomonas aeruginosa and macrophages.

Swimming motility and type IV pili in Pseudomonas aeruginosa shape physical contact with macrophages, reducing phagocytic uptake when motility or T4P function is disrupted.

• Why it matters: Chronic lung infection involves diverse P. aeruginosa populations, but how bacterial heterogeneity alters macrophage processing is not well defined.
• What they did: Using an attenuated T3SS-deficient mutant to isolate phagocytosis susceptibility, the authors applied Tn-seq to find fitness factors under phagocytic selection, then used live-cell imaging to test attachment and surface accumulation.
• The result: Motility gene disruptions lowered macrophage uptake by destabilizing bacterial attachment and surface accumulation; clinical isolates with reduced swimming or twitching showed similar uptake defects, and restoring T3SS revealed an attenuated killing phenotype for the non-flagellated, hyper-piliated ΔfliC ΔpilT mutant.

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