Bacterial lux-Biosensors for Detecting Specific Cell Responses to Membrane Damage

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 <i>lux</i>-biosensors to detect membrane damage in both Gram-negative and Gram-positive bacteria using the stress-inducible promoter of the <i>pspA</i> gene from <i>Escherichia coli</i> and <i>Bacillus subtilis</i> fused to the <i>lux</i> genes from <i>Photorhabdus luminescens</i>. 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. <i>E. coli-</i> and <i>B. subtilis</i>-based biosensors demonstrated differences in response to the action of the same membrane-damaging agent. Thus, ethanol and polymyxin B specifically induced the <i>pspA</i> promoter in both <i>lux</i>-biosensors, but the induction amplitude was higher in the <i>E. coli</i>. Triton X-100 and melittin specifically induced the <i>pspA</i> promoter exclusively in <i>B. subtilis</i> cells, while DMSO induced it only in <i>E. coli</i> cells. This indicates a difference in the stress response of the Psp system to membrane-damaging agents in <i>E. coli</i> and <i>B. subtilis</i> cells. Thus, we demonstrated the functionality and efficiency of the constructed <i>lux</i>-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.