Figure 5. Flagellar motility enhances both the association and the uptake of bacteria by phagocytes.

(A) P. aeruginosa PA14 WT, flgK, or motABmotCD that were incubated in parallel with adherent macrophages at 4°C exhibited similar binding (assessed by CFUs following washing and lysis of the macrophages) (left). However, the difference in relative bacterial association with macrophages dramatically changed when, following washing, the bound bacteria and cells were warmed to 37°C (middle); and this differential was even more substantial when assessed on the basis of phagocytosed (gentamicin-resistant) bacteria (right). Plots show total mean recovered CFUs accounting for input bacteria (left panel) and the number of recovered CFUs plotted relative to WT (right panel). (B) Murine peritoneal macrophages were treated with cytochalasin D prior to co-incubation with PA14 WT, flgK, or motABmotCD and were assayed for bacterial association and protection from gentamicin. (C) Fluorescence microscopy of cytochalasin D-treated macrophages co-incubated with GFP-expressing PA14 WT, GFP-expressing flgK, or GFP-expressing motABmotCD and subsequently stained with wheat germ agglutinin-conjugated Alexa647. 65x magnification. N≥5, *p<0.05.