Bacterial

Whole-cell biosensors represent one of the tools used for assessing the effects of various agents on living cells. Here we have constructed and tested whole-cell lux-biosensors to detect membrane damage in both Gram-negative and Gram-positive bacteria using the stress-inducible promoter of the pspA gene from Escherichia coli and Bacillus subtilis fused to the lux genes from Photorhabdus luminescens. These biosensors increase their luminescence in response to treatment with a number of known membrane-damaging compounds, such as ethanol, Triton X-100, polymyxin B, dimethylsulfoxide (DMSO) and melittin. E. coli- and B. subtilis-based biosensors demonstrated differences in response to the action of the same membrane-damaging agent. Thus, ethanol and polymyxin B specifically induced the pspA promoter in both lux-biosensors, but the induction amplitude was higher in the E. coli. Triton X-100 and melittin specifically induced the pspA promoter exclusively in B. subtilis cells, while DMSO induced it only in E. coli cells. This indicates a difference in the stress response of the Psp system to membrane-damaging agents in E. coli and B. subtilis cells. Thus, we demonstrated the functionality and efficiency of the constructed lux-biosensors and, using them, showed that some of the tested compounds are able to specifically activate Psp stress response systems in case of membrane damage.