FIGURE 1.

Previous and further improved antimicrobial engineered probiotics through quorum sensing. The left part shows the schematic of the “sense-and-kill” system. 3OC12HSL, the quorum-sensing molecule released by P. aeruginosa, binds with LasR to form LasR–3OC12HSL complex. This complex thereafter activates the production of E7 lysis protein and S5 pyocin. When the accumulation of E7 protein is enough to lead to the cell lysis, Pyocin S5 is released into the exogenous environment and kills P. aeruginosa. The right part shows the improvement of this system. The chromosomal deletion of alr and dadX genes in E. coli Nissle promotes the retention of plasmid carrying alr gene. An evident difference of the killing part is the addition of dspB, which encodes an anti-biofilm enzyme with enhanced inhibition efficacy.