Butanol as a regulatory factor of ompC gene expression in E. coli cells

The influence of butanol on the expression of ompC gene encoding synthesis of OmpC porin in the MG1655 strain of E. coli and butanol-tolerant mutant ButR was studied. It was shown that in the case of wild bacteria, the addition of butanol to the growth medium results in an increased level of ompC transcription. However, OmpC porin is not detected in the membrane fraction of cells. ButR mutant exhibits a higher level of ompC gene expression. A direct correlation is observed between the level of OmpC porin expression and its content in the membrane fraction of ButR mutant cells. In the regulatory region of the ompC gene of the ButR mutant, three nucleotide substitutions located in the binding sites of OmpR and CpxR activator proteins were identified. It was shown that mutations in the regulatory region of the ompC gene in the ButR mutant are responsible for the decreased level of OmpC porin expression under normal growth conditions. However, these mutations lead to an increased level of OmpC porin synthesis in the presence of butanol. These data suggest an additional mechanism of ompC gene regulation with the participation of butanol as a positive transcription effector.