A gal region mutant that requires cAMP for growth on galactose in an adenyl cyclase negative (cya delta) background

Strains of Escherichia coli K12 that contain a deletion of the adenyl cyclase gen (cya delta), required for the synthesis of cyclic adenosine-3';5' monophosphate (cAMP), grow on galactose-containing minimal medium. A mutant was isolated that grows on this medium only if cAMP is added. The mutation (designated galP20) is linked to the gal operon region as determined by both generalized transduction with bacteriophage P1 and specialized transduction with bacteriophage lambda. Studies with galP20 cya delta strains as well as gal delta (deletions of the gal operon) cya delta strains indicate that synthesis of the physiologically important transport mechanism for galactose (galactose permease) requires either cAMP or a function mission from both the galdelta strains and the galP20 strain.