Figure 1
From: Current development in genetic engineering strategies of Bacillus species
Operator-repressor system-based genetic engineering strategy. (A) In the presence of the R gene, the constitutively expressed R protein specifically binds to the Pr promoter and represses promoter activity. (B) When the R gene is excised from the genome, the Pr promoter is activated and mutants can be selected by antibiotic resistance. (C) Diagrams of selection and counter-selection marker cassettes. R: Repressor, AR: Antibiotic resistance, Pr: Promoter. [AR1R], [AR1S], [AR2R], and [AR2S] are AR1-resistant, AR1-sensitive, AR2-resistant, and AR2-sensitive bacterial phenotypes, respectively.