TABLE 8.

Synthesis of DNA by dnaE(Ts) strains incubated at 40°C^a

Genotype of strain	Dilution	Vol (ml)	Total amt of DNA (μg) in culture after incubation at 40°C for:						N/N0b
			0 h	1.5 h	2.5 h	3 h	4 h	4.5 h
dnaE74	1:10	50	279				1,250
	1:10	10	80.7	221	324		417		3.6
	1:1,000	25	1.06				7.4		0.0063
	1:1,000	100	4.25				32.6		0.0044
dnaE486	1:10	10	463				834		1.08
	1:100	50	46				247		0.0058
	1:1,000	100	4.6				38.9		0.001
dnaE74 cydA	1:10	10	25.8				211		5
	1:100	50	12.9				143		5.7
	1:1,000	100	2.6				25.0		5.7
	1:100	50	9.8	31.6		45		86.6	5.7c

^aCultures were grown overnight to a concentration of ≈5 × 10⁹ cells/ml for the dnaE74 strain or 2 × 10⁹ to 3 × 10⁹ cells/ml for the dnaE74 cydA strain, collected, resuspended in LB medium, diluted, and incubated in different volumes of prewarmed medium for different times. Cultures were harvested, washed with 1× SSC, and extracted first with cold perchloric acid and then with hot perchloric acid. The perchloric acid extracts were analyzed by the diphenylamine method of Burton (9).

^bN, viable count after incubation for 4 h, unless indicated otherwise; N₀, viable count at zero time.

^cThe viable count after incubation was determined after incubation for 4.5 h.