Engineered fumarate sensing Escherichia coli based on novel chimeric two-component system

DcuS/DcuR two component system (TCS) was firstly employed for the expression of the gfp gene under the dcuB gene promoter in aerobic condition to develop high throughput screening system able to screen microorganisms producing high amount of fumarate. However, the DcuS/DcuR TCS could not produce a signal strong enough to mediate the expression of the gfp gene responding fumarate concentration. Thus, DcuS/DucR TCS was engineered by recruiting the EnvZ/OmpR system, the most-studied TCS in E. coli. A chimeric DcuS/EnvZ (DcuSZ) TCS was constructed by fusing the sensor histidine kinase of DcuS with the cytoplasmic catalytic domain of EnvZ, in which the expression of the gfp gene or the ompC gene was mediated by the ompC gene promoter through the cognate response regulator, OmpR. The output signals produced by the chimeric DcuSZ TCS were enough to detect fumarate concentration quantatively, in which the expressions of the gfp gene and the ompC gene were proportional to the fumarate concentration in the medium. Moreover, principal component analysis of C₄-dicarboxylates showed that DcuSZ chimera was highly specific to fumarate but could also respond to other C₄-dicarboxylates, which strongly suggests that TCS-based high throughput screening system able to screen microorganisms producing target chemicals can be developed.