Genetic analysis of sacB, the structural gene of a secreted enzyme, levansucrase of Bacillus subtilis Marburg

The structural gene sacB encoding B. subtilis levansucrase, a secreted enzyme, expresses in E. coli. E. coli hosts of the sacB gene are poisoned by sucrose. This property allowed a powerful selection of mutants affected in the cloned gene. The plasmidic mutations were readily introduced in the B. subtilis chromosome. Using a collection of plasmids bearing various deletions extending in sacB we developed a technique of deletion mapping based on plasmid integration in the chromosome of B. subtilis. A generalization of this technique is discussed.