FIG. 1.

The effect of the loss of the plasmids pGB2ts and pGB2ts::phd-doc on the growth of MC4100 and its ΔmazEF derivative. (A) Growth on LB plates with spectinomycin. E. coli MC4100 (wild type) and its ΔmazE derivative, both harboring either plasmid pGB2ts or pGB2ts::phd-doc, were plated on LB plates with 100 μg of spectinomycin/ml. The plates were incubated at 30 or at 42°C overnight. (B) Bacterial growth curves at 42°C in liquid LB medium without any added antibiotic. The bacteria were grown to an OD₆₀₀ of 0.7 and then diluted to an OD₆₀₀ of 0.07. This step was repeated twice in order to cure the cells from the plasmids. The curves represent the values after the second dilution. Results for MC4100 are illustrated by black lines, and those for its ΔmazEF derivative are illustrated by gray lines. Results with MC4100/pGB2ts (■), MC4100/pGB2ts::phd-doc (▴), ΔmazEF/pGB2ts ( ), and ΔmazEF/pGB2ts::phd-doc (□) are shown.