TABLE 6.

β-Lactamase inducibility in E. cloacae 8009 and various transformants

Expt. no. and strain	Phenotype	Inducera	β-Lactamase activityb		Inducibility and inducibility ratioc
			μM/min · mg of protein	Ratiod
Expt 1
E. cloacae 8009	AmpA AmpR	−	340	1.0	Inducible
		+	2,400	7.1	7.1
E. coli DH10B		−	<1	<0.003	Constitutive
		+	<1	<0.003	1.0e
E. coli DH10B/pFCX300L (TF-L)	AmpA AmpR	−	22	0.064	Inducible
		+	210	0.64	9.6
E. coli DH10B/pFCX300M (TF-M)	AmpA AmpR	−	119	0.35	Inducible
		+	1,720	5.1	14.5
E. coli DH10B/pFCX301 (TF-L7)	AmpA AmpR	−	700	2.1	Inducible
		+	6,500	19	9.2
E. coli DH10B/pFCX302 (TF-M4)	AmpA AmpR	−	620	1.9	Inducible
		+	7,400	22	11.9
Expt 2
E. cloacae 8009	AmpA AmpR	−	260	1.0	Inducible
		+	2,500	9.6	9.3
E. coli DH10B/pFCX310 (TF2-2)	AmpA	−	280	1.1	Constitutive
		+	280	1.1	1.0
E. coli DH10B/pFCX320 (TF2-3)	AmpA	−	350	1.3	Constitutive
		+	350	1.3	1.0

^aThe inducer was imipenem-cilastatin at 0.1 μg/ml. 

^bCefotaxime (100 μM) was used as a substrate. 

^cInduced activity/uninduced activity for each set. 

^dActivity of extract/uninduced activity of E. cloacae 8009. 

^eNitrocefin was used as the substrate for calculation of the inducibility ratio for this strain.