Construction of the control system of target molecule expression in Escherichia coli: application to a validation platform for bactericidal and bacteriostatic profiles due to suppression of a target molecule.

Validation of bactericidal profiles owing to a deficiency of target bacterial molecule provides opportunities to discover antimicrobial drug candidates. In this study, we constructed genetic-engineered Escherichia coli strains, in which the target gene expression is conditionally regulated by a tryptophan promoter, while the target protein expression is regulated by N-end rule-based proteolysis. Among 10 genes, whose correspondent proteins are target candidates of antibiotics for community acquired respiratory tract infection, it was clearly demonstrated that the suppression of DnaB, GlmU, or DnaX results in a bactericidal profile, while the suppression of FabB, PyrG, DnaG, Der, PyrH, Era, or IspA leads to a bacteriostatic profile. This study is the first to predict the antibacterial inhibition profiles of Der, DnaG, DnaX, Era, GlmU, IspA, PyrG, and PyrH, and confirms previous findings for DnaB and FabB. The results suggested that the system constructed in this study is a novel and useful tool to validate whether the target bacterial molecule has appropriate properties as a target of antimicrobial agents.