John G. Bruno and Jeffery C. Sivils
Western blot-like analyses using DNA aptamers raised against the surfaces of general nonpathogenic Escherichia coli (ATCC No. 8739) as well as alpha and gamma intimins and Shiga-like toxin 2 (SLT-2) B subunit verified that the aptamers bound proteins of the correct molecular weights for intact outer membrane proteins (OMPs), intimins and SLT-2. Some bands on the aptamer Western blots were shared between the “Big 6” non-O157 Shiga toxin-producing E. coli (STEC), E. coli O157 and related Gram negative bacteria. However, unrelated Gram positive bacteria exhibited very few, if any, bands in common with those identified on the E. coli Western aptamer blots, thus attesting to the specificity of these aptamers. In general, the use of aptamers in Western blot formats is advantageous for validation of aptamer binding and specificity based on molecular weight matching of detected electrophoretic bands across a spectrum of related and unrelated bacteria.