Figure 2

McrBC-mediated blocking of establishment of an epigenetic genome methylation system. (a) Quantitative transformation. Varying amounts of pUC19 (2 pg, 20 pg, 200 pg, 2 ng, 20 ng, and 200 ng) were used to transform E. coli DH5α by electroporation. Experiments were conducted in triplicate. (b) Transformation of plasmids carrying the PvuII methyltransferase gene. Plasmids (100 ng) carrying one of several modification methyltransferase genes were used to transform E. coli ER1562 (mcrB1) and ER1563 (mcrBC⁺). The relative transformation efficiency was calculated as the ratio of the transformation efficiency of the test plasmid to that of the empty vector. M.PvuII (ColE1) indicates pEF43, while M.PvuII (pPvu1) indicates pEF65 (Table 1). The empty vector for the latter is pEF67, while that for the former is pEF33. The vector for the remaining plasmids is pBR322. The measurements from two separate experiments conducted in duplicate are shown. All (20/20) of the rare transformants of mcrBC⁺ by pEF43 examined were found to have lost McrBC activity.