P119: Development of a counter-selectable marker system for genome mutation in Bacillus subtilis

Genome mutation without remaining any foreign DNA behind requires an efficient counter-selectable marker system. Here we developed a genome mutation method in Bacillus subtilis by using a transcriptional repressor gene under the control of inducible promoter as a counter-selectable marker system. The repressor gene can be functioned as a counter-selectable marker only under the presence of the inducer. The system has been proved highly efficient for genome mutation and minimal generation of false positive clones. Using this method, we successfully carried out base insertion, deletion, and point mutation of B. subtilis genome without remaining any foreign DNA behind. This method may be useful to construct designer Bacillus strains for various industrial applications. [This study was supported by the Export Promotion Technology Development Program, Ministry for Agriculture, Forestry, and Fisheries, and the KRIBB Research Initiative Program, Republic of Korea.]