FIG. 1.

(A) RNase II can complement the cold-sensitive phenotype of the Δpnp cells at 15°C. The E. coli wild-type cells were transformed with the pINIII plasmid as a control, and the Δpnp cells were transformed with the pINIII plasmid alone (control) or containing pnp, rnb, or rnr. The cells were streaked on LB plates containing ampicillin (50 μg ml⁻¹) and incubated at 37°C and 15°C. Results with plates incubated at 37°C for 24 h or at 15°C for 96 h are presented. (B) RNase II or RNase R is not essential for cell growth at 15°C. E. coli wild-type, Δpnp, Δrnb, Δrnr, and Δrnb Δrnr cells were streaked on LB plates and grown at 37 or 15°C. Results with plates incubated at 37°C for 24 h or at 15°C for 96 h are presented.