Expression of the Bacillus subtilis sacB gene leads to sucrose sensitivity in the gram-positive bacterium Corynebacterium glutamicum but not in Streptomyces lividans.

The expression of the structural gene (sacB) encoding Bacillus subtilis levansucrase in two gram-positive soil bacteria, Corynebacterium glutamicum ATCC 13032 and Streptomyces lividans 1326, was investigated. sacB expression in the presence of sucrose is lethal to C. glutamicum but not to S. lividans. While S. lividans secretes levansucrase into the medium, we could show that the enzyme is retained by C. glutamicum cells. Our results imply that the sacB gene can be used as a positive selection system in coryneform bacteria.