FIGURE 1.

Northern analysis of RNA from MG1655* I⁻ and mutant derivatives lacking RNase R, PNPase, and the RNase R helicase. Cultures of the indicated strains were grown in LB medium to an A₆₀₀ = 0.6. Total RNA was isolated and resolved in a 1.2% agarose gel. A, cultures were grown at 37 °C; gels were stained with ethidium bromide. L denotes RNA ladder. B, cultures were grown at 37 °C to an A₆₀₀ = 0.6, and then shifted to 31 °C for 4 h; gels were stained with ethidium bromide. C, Northern analysis using probes specific for 16S and 23S rRNA of the gel shown in panel A. D, Northern analysis using probes specific for 16S and 23S rRNA of the gel shown in panel B. Arrows indicate the positions of the major rRNA fragments. Lines and numbers above the gels indicate the positions of the probes on the 16S and 23S RNA sequences.