FIG. 2.

Role of an unlinked suppressor in the low efficiency and two-hit kinetics of transformation of the wild type to ΔclpX::erm. (A) Transformation of wild-type CP1250 with the indicated amounts of CP1500 genomic DNA carrying a Nov^r marker (—▪—) or of genomic DNA from Em^r strain CP1361 (—▴—). Theoretical slopes are shown for linear (dotted; y = ax, for a = 10 or 1,000) and quadratic (dashed; y = bx², for b = 1 or 100) kinetics. (B) Transformation of the ClpX⁺Em^s strain CP1973, using the same donor DNAs as those represented in panel A. Theoretical slope is shown for linear kinetics (dotted; y = 12,000×). (C) Interpretation of transformation kinetics. The hypothetical suppressor of lethality of ΔclpX (slx) is sufficiently distant from clpX that it is carried on a distinct DNA fragment and transferred independently from clpX. CP1973, retaining the slx suppressor, is transformed by CP1361 DNA via a single recombination event.