TABLE 4.

Development of blue color on plates containing X-Gluc, and β-glucuronidase activity detected for L. lactis strains harboring gal-lac promoter fusion plasmids

Plasmid	Putative promoter	Growth medium carbohydrate	Color development ata:		β-Glucuronidase activityb
			48 h	72 h
pCRN24	galT	Glucose	−	−
		Lactose	+	++	NDc
		Galactose	−	+
		Glucose-lactose	−	−
pCRN21	lacA	Glucose	−	−
		Lactose	−	+	ND
		Galactose	−	−
		Glucose-lactose	−	−
pCRN20	galE	Glucose	++++		459
		Lactose	++++		935
		Galactose	++++		492

^a−, no blue color; increasing numbers of + signs indicate more-intense blue color. 

^bIn micromoles per minute per milligram of protein. 

^cND, not detectable.