The susceptibility of Tfp extension and retraction mutants to SP-A-mediated opsonization. a, b RAW 264.7 macrophages were infected with PAO1, ΔpilA and the extension or retraction mutants in the presence or absence of hSP-A. The ratio of ingested bacteria between those exposed to hSP-A to those unexposed was expressed as fold increase in phagocytosis. a Phagocytosis of PAO1, ΔpilA and extension mutants ΔchpA, ΔpilG and ΔpilB. b Phagocytosis of PAO1, ΔpilA and retraction mutants ΔpilH, ΔpilT and ΔpilU. * p < 0.05 when comparing phagocytosis of PAO1 to the ΔpilA mutant. # p < 0.05 when comparing phagocytosis of PAO1 to the ΔpilT and ΔpilU mutants. All experiments were independently performed in triplicate. The mean ± standard deviation from 1 representative experiment is shown. c, d Membrane permeabilization of PA strains by hSP-A. c Membrane permeabilization of PAO1, ΔpilA and extension mutants ΔchpA, ΔpilG and ΔpilB. d Membrane permeability of PAO1, ΔpilA and retraction mutants ΔpilH, ΔpilT and ΔpilU. All experiments were independently performed in triplicate. The mean ± standard deviation from 1 representative experiment is shown.