Figure 2.

In vivo effect of synthetic pheromone variants.A, dose response of P_comS activity upon addition of synthetic (8 aa) XIP_Sth WT (blue), XIP-A5M (purple), or XIP-L1V-A5M (fuchsia). Maximum specific luciferase activity (% RLU × OD₆₀₀⁻¹) was monitored by using a S. thermophilus ΔcomS reporter strain (P_comS-luxAB). The value obtained in the presence of 100 nM XIP_Sth was used as reference. Plots were fitted with the Hill equation to calculate the EC₅₀ values that are indicated in the graphs. B, kinetics of luciferase activation (solid lines) and growth curves (dotted lines) of the reporter strain upon addition (100 nM) of synthetic XIP_Sth WT (blue), XIP-A5M (purple), or XIP-L1V-A5M (fuchsia), or in absence of peptide (black). C, dose response of P_comS activity upon addition of synthetic XIP_Sth WT (blue), or XIP-5 variants: XIP-A5T (light blue), XIP-A5V (red), XIP-A5I (green), or XIP-A5M (purple). The monitoring of luciferase activity and estimation of EC₅₀ were performed as in panel A. The inset represents the fold change (FC) in EC₅₀ of each XIP-5 variant using as reference the EC₅₀ of XIP_Sth WT. Increase in fold change is representative of a decrease in EC₅₀ compared with XIP_Sth WT fixed at 1. D, maximum specific luciferase activity (% RLU × OD₆₀₀⁻¹; gray bars) and transformation efficiency (transformants × ml⁻¹; blue bars) of S. thermophilus reporter strains producing the full-length precursor ComS-24aa WT, ComS-24aa-A5M or ComS-24aa-L1V-A5M. S. thermophilus WT in the presence of 100 nM XIP_Sth and a ΔcomS mutant strain were included as positive and negative control, respectively. The WT strain in the presence of XIP_Sth is used as reference to normalize the maximum specific luciferase activity. In A, C, and D, experimental values represent the mean ± SD of at least three independent replicates.