TABLE 3.

Influence of the 5′ upstream region and TraR on expression of a repA::lacZ fusion

Test plasmid	TraRa	AAI production	β-Galactosidase activity (U/108 CFU)b		Ratio of enzyme activitiesc
			−AAI	+AAId
pPLrep4	−	−	106	NTe
	+	+++	150	NT	1.42 (1.42–2.53)
pPLrep5	−	−	183	211	1.15 (0.79–1.15)
	+	−	173	237	1.37 (1.09–2.68)
pPLrep6	−	−	78	96	1.23 (1.23–1.26)
	+	−	89	74	0.83 (0.64–0.83)

^aTraR was provided by introducing pSVB33 in trans to the test plasmid. 

^bValues shown are from a representative experiment in which all strains were tested in parallel. 

^cActivity ratios for pPLrep5 and pPLrep6 were calculated by dividing the β-galactosidase activity in cells incubated with AAI by the activity in cells grown in the absence of AAI, using the data shown. Values for pPLrep4 were calculated by dividing the β-galactosidase activity in cells expressing TraR by the activity in cells lacking traR. Numbers in parentheses show the range in calculated ratios obtained in four or five repetitions of the experiment. 

^dSynthetic AAI was added at a concentration of 40 nM, and the cultures were incubated for 6 h. 

^eNT, not tested.