FIG. 2.

(A) Western blot (with anti-Stx 2 A subunit) of crude concentrated supernatants of cultures of E. coli O157:H7 ATCC 43888 infected with: 10, 1, and 0.1 ml of sewage that had been centrifuged, filtered, and DNase treated (lanes 2, 3, and 4, respectively); sonically derived lysates of E. coli O157:H7 ATCC 43889 (lane 1) and ATCC 43888 (lane 5); sewage that had been centrifuged, filtered, and DNase treated (lane 6); and prestained protein size standards in kDa (lane M). (B) Lanes are as in panel A, after cutting a strip of the SDS-PAGE slab gel of the zone to which the A subunit migrates, eluting the strips electrophoretically, and concentrating the eluates by passage through 10K cutoff filtration membrane microconcentrators (Microsep) by centrifugation at 16,000 × g at 4°C.