Table 1. Effect of mlc and nagC mutations on expression of nagE–lacZ fusions.

		w.t.	mlc		nagC		nagC mlc
		Units	Units	Ind	Units	Ind	Units	Ind
nagBE–lacZ	looped	47	45	1.0	1590	34	1200	25
nagE–lacZ	single site	1620	2040	1.3	1650	1.0	1430	0.9
nagE–lacZ s.o.	single site with super-operator	7.5	6.5	0.9	580	77	550	73

JM101 was lysogenised with bacteriophage λ carrying the three nagE–lacZ fusions and the nagC and mlc mutations introduced by P1 transduction. Bacteria were grown in MOPS medium containing 0.4% glycerol and 0.5% cas amino acids at 30°C. β-galactosidase activities were measured at several points throughout the exponential growth phase. Ind (induction) gives the fold increase in expression caused by the mutations compared to the expression of the same fusion in the wild-type strain.