FIG. 2.

Nucleotide sequences used to define the ends of the fragilysin pathogenicity islet. The nontoxigenic sequence was from B. fragilis VPI 2553. Toxigenic sequences across the left and right ends of the pathogenicity islet were from enterotoxigenic B. fragilis strain VPI 13784. Lowercase letters represent where the sequence from the nontoxigenic strain varied from the sequence flanking the ends of the islet. A 17-bp sequence present only in DNA from the nontoxigenic strain is boxed. Arrows indicate the ends of the islet and corresponding nucleotide number. Direct repeats (DR) are underlined.