FIG. 4.

Effect of growth phase on lysis of E. coli by overexpression of dd-carboxypeptidases. E. coli CS109 was transformed with the following plasmids carrying the indicated PBPs under control of the arabinose promoter: (A) pPJ5C, PBP 5; (B) pPJ4, PBP4; (C) pPJ6, PBP 6; and (D) pPJDacD, DacD. Overnight cultures were diluted 1:500 into fresh LB broth and incubated at 37°C in a Bioscreen C Microbiology Reader. PBP expression was induced at three different times in the growth cycle by adding arabinose to a final concentration of 0.1% (wt/vol). No arabinose, ●; arabinose added at an A₆₀₀ of 0.15, ■; arabinose added at an A₆₀₀ of 0.30, ▴; arabinose added at an A₆₀₀ of 0.60, ▾.