FIGURE 2.

Levels of RpoS (σ³⁸), OmpC, and RMF in E. coli MA261 cultured in the presence and absence of putrescine. A, Western blot analysis was performed using 5 μg of protein for RpoS (σ³⁸) and OmpC, and 25 μg of protein for RMF. Percentage of acrylamide used in SDS-polyacrylamide gel electrophoresis was 10.5% for RpoS (σ³⁸) and OmpC, and 15% for RMF. B, dot blot analysis of rmf mRNA in E. coli MA261 harvested at A₅₄₀ = 0.2 or 24 h after the onset of cell culture was performed using various amounts of RNA shown in the figure. C, immunoprecipitation of [³⁵S]methionine-labeled RMF was performed using E. coli MA261 cells incubated with [³⁵S]methionine for 5 min as described under “Experimental Procedures.” Values shown in A–C are means ± S.E. of triplicate determinations. D, ribosomal profiles were analyzed by sucrose density gradient centrifugation using the cell lysate of E. coli MA261 cells harvested at A₅₄₀ = 0.2 or 24 h after the onset of cell culture. Student's t test was performed for the value obtained in the presence of putrescine versus in the absence of putrescine. ns, p > 0.05; **, p ≤ 0.01.