FIG. 4.

Dot blot analysis of mdtJI mRNA in E. coli CAG2242 cells cultured with or without spermidine (SPD). Dot blot analysis was performed as described in Materials and Methods. The radioactivity of each spot was quantified using a Fujix Bas 2000II imaging analyzer, and the averages for four dots are shown as relative amounts. Results were reproducible in two separate experiments. (A) Levels of mdtJI mRNA in E. coli CAG2242 cells transformed with pUCmdtJI or pUC119 and cultured for 12 or 36 h in the presence and absence of 2 mM spermidine. (B) Levels of mdtJI mRNA in E. coli CAG2242 cells transformed with pMWmdtJI, pMW119, or pUCmdtJI and cultured for 2 or 4 h in the presence and absence of 12 mM spermidine. Cell growth was started at an A₅₄₀ of 0.05.