Figure 3.

Structure of BcpA pili lacking the CNA₂ and CNA₃ isopeptide bonds. (A, E) Immuno TEM of B. anthracis Sterne (pJB61 or pJB107) in which K¹⁷⁴A and E⁴⁷²A pili are labeled using rabbit anti-BcpA followed by goat anti-rabbit IgG-10 nm gold conjugate. (B, F) Similar as panels (A, E), however cells were incubated with goat anti-rabbit IgG-10 nm gold conjugate alone (bar = 100 nm). (C+G) High resolution negative-staining TEM micrographs of pili released and purified from B. anthracis Sterne srtA (pJB61 or pJB107). Single pili, double pili, and higher order assemblies of pili are observed (bar = 50 nm). (D+H) Flattened AFM images of B. anthracis Sterne (pJB61 or pJB107) elaborating either K¹⁷⁴A or E⁴⁷²A pili on their surface with varying diameters (bar = 100 nm). Insets, close-ups of double filaments.