TABLE 2.

Regulation of β-galactosidase expression directed by the vegII promoter and cre-containing vegII promoter derivatives in S. xylosus wild-type and mutant strains altered in catabolite repression

cre operatora	Strain	Genotypeb	β-Galactosidase activity (nmol of nitrophenol produced/ min/mg of protein)c
			B medium	B medium + glucose	Glucose repression ratiod
None	TX302	Wild type	139	150	0.9
	TX602	ccpA::ermB	125	131	0.9
	TX402	ΔglkA	120	127	0.9
	TX502	ΔglcU	110	122	0.9
	TX702	hprK::ermB	124	97	1.3
malRA	TX313	Wild type	82	26	3.2
	TX613	ccpA::ermB	97	90	1.1
	TX413	ΔglkA	89	53	1.7
	TX513	ΔglcU	87	42	2.1
	TX713	hprK::ermB	81	70	1.1
xylAB	TX314	Wild type	38	5	7.6
	TX614	ccpA::ermB	68	62	1.1
	TX414	ΔglkA	33	9	3.7
	TX514	ΔglcU	36	11	3.2
	TX714	hprK::ermB	55	47	1.2
ccpA	TX315	Wild type	104	25	4.1
	TX615	ccpA::ermB	114	110	1.0
	TX415	ΔglkA	110	57	1.9
	TX515	ΔglcU	106	55	1.9
	TX715	hprK::ermB	98	91	1.1
lacPH	TX316	Wild type	38	16	2.4
	TX616	ccpA::ermB	51	53	1.0
	TX416	ΔglkA	36	24	1.5
	TX516	ΔglcU	38	25	1.5
	TX716	hprK::ermB	56	50	1.1
scrA	TX320	Wild type	128	71	1.8
	TX620	ccpA::ermB	118	115	1.0
	TX420	ΔglkA	124	116	1.1
	TX520	ΔglcU	108	94	1.2
	TX720	hprK::ermB	103	91	1.2

^aThe sequences of the integrated cre operators are listed in Fig. 2; cre sequences were designated according to their corresponding genes. 

^bOnly the genotype relevant for regulation is shown. In all strains, the lac region is modified (′lacR ΔlacP P-lacH). 

^cMean values of three independent cultures are presented. The standard deviations did not exceed ±15%. Strains were grown in complex B medium to an OD₅₇₈ of 1; 25 mM glucose was added as indicated. After 1 h of further growth, the OD₅₇₈ was determined, and the cells were harvested and disrupted with glass beads. Extracts prepared from 30 ml of cells adjusted to an OD₅₇₈ of 2 were used for the determination of β-galactosidase activities. 

^dThe glucose repression ratio was calculated by dividing the enzyme activity found in cultures in B medium by the enzyme activity detected in glucose-containing cultures.