Table 2.

PhoPQ regulation of ivi genes

ivi-lac fusion*	β-Galactosidase, units†
	phoP+Q+	phoP102::Tn10d-Cm	phoQ24
phoP	110	11	132
spvB	118	14	294
pmrB	122	31	187
mgtB	48	9	35
iviVI-A	236	5	563
ndk	18	21	21

^*Wild-type, PhoP⁻ [phoP102::Tn10d-Cm (7)], and PhoQ^c [phoQ24, which constitutively activates PhoP-activated genes (8)] strains were grown in Mops media (15), where Mops [3-(N-morpholino)propanesulfonic acid] was replaced with Mes [2-(N-morpholino)ethanesulfonic acid] and buffered to pH 5.5 (50 μM Mg²⁺). The defects observed in phoP102::Tn10d-Cm may also be attributed to the lack of phoQ. 

^†Numbers given indicate β-galactosidase activities assayed according to Slauch and Silhavy (14). Units are given as (units per OD₆₀₀ unit × ml of cell suspension) × 10³, where 1 unit = 1 μmol of o-nitrophenol formed per min (n = 3, SD < 10%).