Table 1.

Effect of hfl mutations on lysogenization of λ

Exp.	Strain	Relevant genotype	Plasmid carried	Lysogenization frequency, %	λc17 propagation†
1	AD16	WT	—	2.4	+
2	AK990	ΔhflKC	—	40.6	−
3	AK863	hflC9	—	1.7	+
4	AK865	hflK13	—	1.5	+
5	AK525	zgj-525::IS1A	—	81.9	−
6	AD16	WT	pBAD18 (vector)	3.0	+
7	AD16	WT	pKH178 (hflK+C+)	42.8	−
8	AK1127	hflC::tet	pMW119 (vector)	31.3	−
9	AK1127	hflC::tet	pKH146 (hflC+)	4.5	+
10	AK1127	hflC::tet	pKH339 (hflCΔ165–200)	6.7	+

Cells were pregrown either at 30°C (for experiments 1–5) or at 37°C (for experiments 6–10), but lysogenization frequencies were all measured at 37°C. See Materials and Methods for further details about the media and other growth conditions before infection. 

^†Cells were cross-streaked with λc17 on TB agar and cell lysis/plaque formation was scored after overnight incubation at 37°C. This phage cannot propagate in cells in which lysogenization is preferred (8, 10). WT, wild type.