Fig 1.

Accumulation of mRNA degradation fragments in strains lacking phosphorolytic exonucleases. (A) Total RNA was isolated from MG1655* (wild type), MG1655*Δrph, MG1655*Δpnp, or MG1655*Δrph Δpnp strains following growth in LB medium at 37°C and was analyzed by Northern blotting using probes to rpsO, trxA, lpp, or ompA mRNA. The positions of the full-length RNAs and the degradation products that accumulate in the absence of the phosphorolytic RNases are indicated by arrows and brackets, respectively. (B) Strains MG1655* or derivatives that contain Δrnr, pnp(Ts), or Δrnr pnp(Ts) mutations were grown to saturation in LB medium at 30°C, diluted 1,000-fold into fresh medium, transferred to 44°C, and harvested for RNA preparation upon reaching mid-log phase. RNA samples were analyzed by Northern blotting with an ompA mRNA probe. RNA derived from MG1655*Δrph Δpnp was loaded as a control.