Agal region mutant that requires cAMP for growth on galactose in an adenyl cyclase negative (cyaΔ) background

Abstract
Strains ofEscherichia coli K12 that contain a deletion of the adenyl cyclase gene (cyaΔ), 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 (designatedgalP20) is linked to thegal operon region as determined by both generalized transduction with bacteriophage P1 and specialized transduction with bacteriophage λ. Studies withgalP20 cyaΔ strains as well asgalΔ (deletions of thegal operon)cyaΔ strains indicate that synthesis of the physiologically important transport mechanism for galactose (galactose permease) requires either cAMP or a function missing from both thegalΔ strains and thegalP20 strain.