TABLE 4.

Free phage titer of λprm240 lysogen^a

Medium	Temp (°C)	Doubling timeb for λJL163 lysogen (min)	Free phage/cellb for λ prm240 lysogen	37°C/30°Cc
M9 glucose	30	160	5.4 × 10−6	11
	37	110	5.9 × 10−5
M9 glucose +	30	127	0.012	18
Casamino Acids	37	73	0.21
Tryptone broth	30	80	0.08	16
	37	54	1.3
LB	30	72	1.8	10
	37	44	17

^aStrain JL6112 was grown overnight in tryptone broth at 30°C and then grown as follows. For growth in M9 glucose with or without Casamino Acids, an aliquot was grown exponentially for many generations in M9 glucose at 30°C, followed by exponential growth for at least five generations under the indicated conditions. For growth in tryptone or LB, an aliquot was diluted into tryptone and grown for three generations at 30°C, followed by exponential growth for at least five generations in the indicated conditions and sampling for free phage as described in Materials and Methods.

^bFor calculation of doubling time and phage/cell, cell growth and cell numbers were determined on cultures of JL5904 growing in parallel. Titers given for minimal medium are likely underestimated by a factor of 2 to 5, since λ virions were somewhat unstable in minimal medium (see text). To test for readsorption of free phage in tryptone broth (which lacks glucose), in a separate experiment strain JL6112 and its λ-resistant derivative JL5024 were grown in parallel in tryptone broth, at both 30 and 37°C. At each temperature, free phage levels for both cultures were the same within experimental error. Hence, readsorption is not significant under our conditions.

^cRatio of titer of free phage at 37°C to that of free phage at 30°C.