Fig 4.

Sal4 causes distortion of the bacterial envelope. S. Typhimurium strain 14028 was treated with PBS (A and B) or Sal4 (5 μg/ml) for 15 min (C and D) or 60 min (E and F) and then collected by centrifugation, fixed with glutaraldehyde, and processed for TEM, as described in Materials and Methods. The OM of control cells (arrows [A] or arrowheads [B]) were uniformly smooth. In contrast, cells treated with Sal4 for 15 min were surrounded by a fuzzy coat (arrows [C] or arrowheads [D]). The fuzzy coat was more pronounced after 60 min incubation with Sal4 (arrows [E] or arrowheads [F]). The boxed areas in panels A, C and E are enlarged in panels B, D, and F, respectively.