(A) Percentage of minicells attached to the host membrane via needle-membrane contact. Data were compared using a chi-squared test. (B, C) Central slices from tomograms showing the ΔsipBCD injectisomes interacting with the host PM. (E, F) Central slices from tomograms showing the ΔsipB injectisomes interacting with the host PM. (H, I) Central slices from tomograms showing the ΔsipD injectisomes interacting with the host PM. Blue arrows indicate needles attached to the host PM. Red arrows indicate unattached needles. (D, G, J) Schematic models depicting needle-attachment patterns from three mutants, respectively.