TABLE 5.

Environmental regulation with σ^SΔ1-50^a

Variable(s)	Culture condition	β-Galactosidase sp act for lac fusion with the following promoter in the indicated strain:
		proU P1		katE
		rpoS+	ΔrpoS/pHYD408	rpoS+	ΔrpoS/pHYD408
Temp and growth phase	30°C, log	63	27	110	50
	30°C, stationary	536	263	772	586
	10°C, log	279	263	1,686	645
Osmolarity	No NaCl	63	21	297	65
	0.3 M NaCl	275	193	576	333

^aCultures for β-galactosidase assays were grown in LB medium for experiments involving growth phase (log or mid-exponential phase and 1 h after entry into stationary phase) and temperature as variables and in K-tryptone medium (to mid-exponential phase at 30°C) for those involving osmolarity as the variable. For strain derivatives with the proU P1-lac fusion (on plasmid pHYD275), the medium was supplemented with trimethoprim; for derivatives with plasmid pHYD408, it was supplemented with ampicillin and Ara. Enzyme specific activities are reported in Miller units (22). Strains used were as follows (in the order rpoS⁺ and ΔrpoS): for proU P1-lac, GJ862 and GJ2778 (each with pHYD275); and for katE-lac, GJ2770 and GJ2782.