CLONING, EXPRESSION, AND CATABOLITE REPRESSION OF A GENE ENCODING BETA-GALACTOSIDASE OF BACILLUS-MEGATERIUM ATCC-14581

A gene encoding beta-galactosidase, designated mbgA, was isolated from Bacillus megaterium ATCC 14581, Chromosomal beta-galactosidase produc tion could be dramatically induced by lactose but not by isopropyl-bet a-D-thiogalactopyranoside (IPTG) and was subject to catabolite repress ion by glucose. Disruption of mbgA in the B. megaterium chromosome res ulted in loss of lactose-inducible beta-galactosidase production. A 27 -bp inverted repeat was found to overlap the mbgA promoter sequence. T wo partially overlapping catabolite-responsive elements (CREs) were id entified within the inverted repeat. Base substitutions within CRE-I a nd/or CRE-II caused partial relief from catabolite repression. The res ults suggest that the 27-bp inverted repeat may serve as a target for a catabolite repressor(s).