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Fig. 1 | Microbial Cell Factories

Fig. 1

From: TECS: a toxin expression control strategy as a tool for optimization of inducible promoters

Fig. 1

Scheme of TECS concept and two-step selection protocol. a TECS is based on the two-step selection process in order to select inducible promoter variants. An inducible promoter is placed upstream of sacB gene and used as the template for subsequent mutagenesis or randomization (the library of mutants). In the first step, the transformed library of promoter mutants is plated on 5% sucrose plates, on which only mutants with low or no expression of sacB will grow. Next, colonies are inoculated in a 96-well plate, grown over night and replica plated on trays with LA, sucrose or sucrose plus inducer media. b Phenotypes of cells producing SacB can be easily distinguished from non-producing colonies (marked by white triangles). High level of SacB results in lysis of cells and characteristic colony morphology. In addition, the presence of active SacB is manifested by white halo surrounding colonies

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