Fig. 1.

Electron microscopic analysis of pneumococcal pili. (A) Negative staining of S. pneumoniae strain T4 showing abundant pili on the bacterial surface. (B) Negative staining of mutant strain T4Δ(rrgA-srtD) showing no pili. (C) Negative staining of the T4Δ(mgrA) mutant showing abundant pili. (D) Negative staining of the T4Δ(rrgA-srtD, mgrA) mutant showing no pili on the bacterial surface. (E) Immunogold labeling of T4 by using anti-RrgA. Anti-RrgA was shown to label the bacterial cell surface, suggesting that RrgA anchors the pilus structure to the cell wall. (F) Immunogold labeling of T4 with anti-RrgB (5 nm) and anti-RrgC (10 nm). Anti-RrgB was shown to decorate the entire pili. (Bar, 200 nm.) (G) High magnification of T4 pili double-labeled with anti-RrgB (5 nm) and anti-RrgC (10 nm). It shows specific labeling of a pilus tip by anti-RrgC as indicated by arrows. (Bar, 100 nm.) (H) Immunogold labeling of the deletion mutant S. pneumoniae T4Δ(rrgA-srtD) with no visible pili on the surface detectable by anti-RrgB and anti-RrgC. (Bar, 200 nm.)