Shiga toxins (Stx) comprise a family of potent cytotoxins that are involved in severe human
disease. Stx are mainly produced by Escherichia coli isolated from human and nonhuman
sources, and by Shigella dysenteriae type 1. The genes encoding Stx are thought to be
generally encoded in the genome of lambdoid prophages (Stx-converting bacteriophages;
Stx phages). They share a unique position in the late region of the phage genome
downstream of the late promoter pR′. This location suggests that expression of stx is …