Figure 1.

(A) Apparent stability of psk⁺ and psk⁻ plasmids measured in RR1 in the absence of selection. The fraction of cells carrying a plasmid was measured at ≈20 generation intervals as described in Materials and Methods. RR1 containing psk⁻_p-empty symbols, ○, □, and ▵; psk⁺_p-filled symbols, ●, ■, and ▴. Each line represents a single experiment. (B) Realized stability of psk⁺ and psk⁻ plasmids in the absence of selection. The total number of psk⁺ and psk⁻ plasmids inherited in A was estimated by extrapolating the number of plasmid generations between each dilution time point. Shown is the average ratio (and SD) of psk⁺:psk⁻ plasmid generations.