Design and Application of an Artificial Hybrid PromoterP_luxI-lacOin Genetic Circuit to Achieve Lower Basal Expression...

Quorum quenching (QQ) enzymes, which degrade signaling molecules so as to disrupt the quorum sensing signaling process, have drawn much attention as alternative antimicrobial agents. However, the screening methods for evolution of such enzymes through constructing genetic circuits remain a challenge for its relatively high false positive rates caused by the higher basal expression level of the naturally acquired promoter. Thus, we presented an improved genetic circuit by introducing an artificial hybrid promoter P_luxI-lacO combining P_lacO originated from lactose promoter with QS regulatory promoter P_luxI to control the expression of reporter gene rfp. Herein, we investigated the effect of various expression strengths of suppressive protein LacI and signaling molecule AHL on the expression of rfp. We found that the effect AHL exerted on the expression of rfp outweighed that from IPTG. The results also demonstrated that our genetic circuit could achieve the lower basal expression level of reporter gene and could respond to the expression of AiiA. The resulting circuits show the potential for screening the evolved AiiA more efficiently by virtue of inherent low basal expression level.