Fig. 9.

Transmission electron microscopy appearance of an E. coli cells from a 10-mL, 5-min exposure treatment combination. At the low magnification (a) (20,000 ×, scale bar is 2 μm), the numbers of obviously damaged and apparently intact cells are about the same, with visually intact cells dominating. Similar to unexposed controls (Fig. 6), in cells retaining electron-dense cytoplasm, less dense regions (pili) are associated with the cell wall. Other cells are partially or almost entirely lacking cytoplasm. At the higher magnification (b, c) (40,000 ×, scale bar is 1 μm), damaged cells have a vacuolated appearance (b); the arrow in (c) points to a region of a cell in which the cell wall has invaginated. The surviving fraction associated with this treatment combination was 0.51 ± 0.16.