TABLE 3.

Ability of β⁺ and β^148–152 to complement the temperature sensitive growth phenotype of various dnaN159 mutant strains deficient in specialized Pols.

E. coli straina	Relevant genotypeb:			Ratio (42°C/30°C) of colony forming units/ml for dnaN159 strain transformed withc:
	polB	dinB	umuDC	control plasmid	dnaN+	dnaN148–152
MS120	+	+	+	< 4.2 (±1.1) × 10−5	1.1 (±0.09)	0.67 (±0.53) × 10−3
MS134 d	Δ	+	+	0.73 (±0.45) × 10−5	0.93 (±0.09)	0.66 (±0.49) × 10−1
MS123	+	Δ	+	0.80 (±0.1) × 10−5	1.0 (±0.09)	0.62 (±0.04) × 10−2
MS122	+	+	Δ	1.2 (±1.6) × 10−5	0.87 (±0.04)	2.8 (±1.4) × 10−4
MS135	Δ	Δ	+	< 5.6 (±0.31) × 10−5	1.1 (±0.17)	0.25 (±0.27)
MS136	Δ	+	Δ	< 2.9 (±5.5) × 10−5	0.81 (±0.35)	2.6 (±3.9) × 10−2
MS124	+	Δ	Δ	< 2.5 (±0.10) × 10−5	1.2 (±0.05)	2.0 (±0.02) × 10−2
MS137	Δ	Δ	Δ	< 2.3 (±0.11) × 10−5	1.2 (±0.40)	1.1 (±0.63)

^aE. coli strains are described in Table 4.

^bAbbreviations: +, wild type; Δ, deletion. Specific alleles used include: polB (Pol II), ΔpolB::Ω; dinB (Pol IV), Δ(dinB-yafN)::kan; and umuDC (Pol V), ΔumuDC595::cat.

^cRepresentative transformants of the indicated strain bearing either the control plasmid (pSU38 [Kan^R], pACM [Cam^R], or pAMP [Amp^R]), the β⁺- (pACYCdnaN⁺ [Kan^R], pACMdnaN⁺ [Cam^R], or pAMPdnaN⁺ [Amp^R]) or the β^148–152-expressing plasmid (pACYCβ5A [Kan^R], pACMβ5A [Cam^R], or pAMPβ5A [Amp^R]) were cultured overnight, and serial dilutions of each were plated onto LB-agar containing appropriate antibiotics. Results shown represent the average of duplicates. Values in parentheses represent the range. Cell titers were on the order of ~10⁹ cells/ml for all strains except MS134 bearing pACYCβ5A (see footnote d below). Kan^R plasmids were used with strains MS120, MS134, MS122, and MS136, Cam^R plasmids were used with strains MS123 and MS135, and Amp^R plasmids were used with strains MS124 and MS137. All plasmids were derived from pSU38, and their salient features are described in Table 4.

^dTiters of cultures for strain MS134 bearing the β^148–152-expressing plasmid (pACYCβ5A) were on the order of ~10⁶ cells/ml, which corresponds to ~1,000-fold fewer viable cells than observed for the same strain bearing either the control plasmid (pSU38) at 30°C, or the β^+-expressing plasmid (pACYCdnaN⁺) at both 30° and 42°C.