FIG. 3.

Transmission electron micrographs showing B. pertussis within HTE cells after 1 or 3 h of coincubation. Panels: A, adherent parental strain B. pertussis Tohama I; B and C, intracellular B. pertussis Tohama I; D, adherent AC-Hly-deficient mutant B. pertussis 348; E and F, intracellular AC-Hly-deficient mutant B. pertussis 348. The lack of AC-Hly expression did not appear to render these bacteria more susceptible to damage by lysosomal enzymes. In panels C and F, note the close proximity of the bacterial outer membrane to the membrane of the endocytic vacuole. For panels A and D, the coincubation period was 1 h. For panels B, C, E, and F, the coincubation period was 3 h.