Influence of the Regulatory Gene Dosage and Expression Level on the Sensitivity of the Whole-Cell Biosensor to Acyl-Homoserine Lactone.

LuxR and LuxR1 and LuxR2 regulatory proteins are quorum sensing transcriptional (QS) activators, inducing promoters of genes in the presence of an autoinducer (3-oxo-hexanoyl-l-homoserine lactone). In the cells, genes are regulated by HNS, CRP, LitR, etc. Here we investigated the role of the expression level in LuxI/R QS system functionality and improved the whole-cell biosensor for autoinducer detection. -based bacterial -biosensors were used, in which genes were controlled by LuxR-dependent promoters and , , or regulatory genes. We varied either the dosage of the regulatory gene in the cells using additional plasmids, or the level of the regulatory gene expression using the lactose operon promoter. It was shown that an increase in expression level, as well as dosage of the regulatory gene in biosensor cells, leads to an increase in sensitivity (the threshold concentration of AI is reduced by one order of magnitude) and to a two to threefold reduction in response time. The best parameters were obtained for a biosensor with an increased dosage of (sensitivity to 3-oxo-hexanoyl-l-homoserine lactone reached 30-100 pM).