Final answer:
The enterohemorrhagic E. coli (EHEC), particularly the strain O157:H7, produces both SLT I and SLT II, which are Shiga-like toxins. These toxins were likely acquired through horizontal gene transfer, possibly from Shigella dysenteriae.
Step-by-step explanation:
The E. coli strain that makes SLT I (Shiga-like toxin I) and SLT II (Shiga-like toxin II) is known as the enterohemorrhagic E. coli (EHEC). These toxins are very similar to the Shiga toxin originally found in Shigella dysenteriae. The most notorious of the EHEC strains is E. coli O157:H7, which can cause severe outbreaks. The presence of both toxins is attributed to horizontal gene transfer, likely through a bacteriophage that transferred the Shiga toxin genes from Shigella dysenteriae to E. coli. This strain also has a locus of enterocyte effacement (LEE), which is responsible for the formation of pedestals on intestinal cells but does not produce the enterotoxins associated with enterotoxigenic E. coli (ETEC).