TABLE 4.

Effects of H-NS, RfaH, and SlyA on expression from PR3 at 37°C and 20°C

Strain	Mean β-Galactosidase activity (Miller units) ± SEMa
	37°C	20°C
P90C(pRS415)	124 ± 17	100 ± 7
P90C(pRSA)	1,028 ± 125	26 ± 7
P90Chns(pRSA)	496 ± 20	857 ± 90
P90CslyA(pRSA)	186 ± 51	25 ± 5
P90Chns slyA(pRSA)	95 ± 25	24 ± 4
P90CrfaH(pRSA)	523 ± 24	89 ± 12

^aβ-Galactosidase activity of P90C and mutants bearing either the promoter probe plasmid pRS415 or derivatives was assayed at 37°C and 20°C. Plasmid pRSA is described in Fig. 2 and Table 1. Neither the hns nor the slyA mutation had any effect on the level of β-galactosidase activity expressed by pRS415 (data not shown). Data are the means of three independent experiments performed in triplicate.