Growth of various polA and ypcP mutants on LB plates at 37°C (A) or 56.5°C (B). Relevant genotypes are shown: ΔpolA, polA deletion strain NBS5004; ΔypcP, ypcP deletion strain NBS4070; ΔpolAC, polA Klenow fragment deletion strain NBS183; ΔpolAN, polA 5′-3′ exonuclease domain deletion strain NBS184; ΔypcP, ΔpolAC, Klenow fragment and ypcP deletion strain NBS185. (C) Alternatively, the polA deletion strain NBS182 and its derivatives were examined on LB plates containing 1 mM IPTG at 56.5°C. Two independent transformants (each) of NBS247 (amyE::polA) (a and b), NBS248 (amyE::polAN) (c and d), and NBS249 (amyE::ypcP) (e and f) are shown.