FIG. 3.

(a) Thin section of C. difficile VPI 10463 after exposure of the bacterium to compound 1 for 10 min and viewed by TEM. Electron-dense bismuth is found inside the cell, often in association with the cytoplasmic membrane. Bar, 300 nm. (b) Thin section control; distilled water replaced compound 1. Bar, 600 nm. (c) Thin section of bacteria from a 2-h culture of C. difficile incubated anaerobically with compound 1 for a further 4 h. Note the large amount of intracellular bismuth. Bar, 600 nm. (d) Thin section of bacteria from the culture described in the legend for panel c but incubated for a total of 18 h. Note the healthy looking bacteria containing little or no bismuth as well as lysed cells containing large amounts of bismuth. Bar, 600 nm. (e) Thin section of a spore-containing cell of C. difficile from the culture described in the legend for panel c after 3 h of growth in the presence of compound 1. Bar, 600 nm.